PPC 2021: XIV International Workshop on Interconnections between Particle Physics and Cosmology

17 May 2021, 08:30 → 21 May 2021, 13:00 US/Central

University of Oklahoma

The 14th International Conference on Interconnections between Particle Physics and Cosmology, organized by the physics department at the University of Oklahoma, Norman, Oklahoma, will take place over Zoom. 

Plenary talks are 25+5 minutes, and parallel talks are 12+3 minutes.

Plenary speakers and topics:

• Mustafa Amin (Rice) - The End of Inflation
• K.S. Babu (Oklahoma State) - Neutrino Theory
• Kyu Jung Bae (Kyungpook National University) - Feebly-Interacting and Decaying Dark Matter
• Yang Bai (Wisconsin) - Macroscopic Dark Matter
• Kimberly Boddy (UT Austin) - Cosmological Signatures of Dark Matter Interactions
• Anadi Canepa (Fermilab) - SUSY at the LHC
• Michele Cicoli (Bologna) - Statistical predictions for low-energy physics from the string landscape
• Bhupal Dev (U. Washington St. Louis) - Current Anomalies: From Muon g-2 to B-physics and Neutrinos
• Keith Dienes (U. Arizona) - Cosmological Imprints of Non-Minimal Dark Sectors
• Bhaskar Dutta (Texas A&M) - Light Mediators
• Cora Dvorkin (Harvard) - Discovering New Physics with Cosmological Data Sets
• Adrienne Erickcek (UNC Chapel Hill) - Cosmology of Early Matter Domination
• Rouven Essig (Stony Brook) - Dark Matter: New Frontiers
• Gabriel Facini (University of Warwick) - Searches for Exotic Physics with ATLAS and CMS
• Jiji Fan (Brown) - New Developments in Axion Physics
• Stefania Gori (UC Santa Cruz) - Dark Sectors
• André De Gouvea (Northwestern) - Topics in Neutrino Physics
• Tao Han (U. Pittsburgh) - Higgs at the HL-LHC
• Steven Harris (U. Washington) - BSM Physics with Magnetars and Neutron Star Mergers
• Gordon Kane (U. Michigan) - The Visible Sector
• Doojin Kim (TAMU) - New Ideas in Lab-based Axion Searches
• Gordan Krnjaic (Fermilab) - Light Dark Matter Cosmology
• Rafael Lang (Purdue) - Dark Matter Direct Detection - Experiment
• Liam McAllister (Cornell) - Axions and String Vacua
• Irina Mocioiu (Penn State) - Flavor Physics and Light Mediators
• Simona Murgia (UC Irvine) - Fermi-LAT
• Keith Olive (U. Minnesota) - Dark Matter Candidates in Supersymmetric Models
• Pavel Fileviez Perez (Case Western) - New Gauge Theories and the TeV Scale
• Alexey Petrov (Wayne State) - Rare Processes and Precision Measurements
• Stefano Profumo (UCSC) - Primordial Black Holes and Dark Matter
• Fernando Quevedo (Cambridge) - Type IIB String Phenomenology
• Laura Reina (Florida State) - New physics and precision at the energy frontier
• Dean Robinson (LBNL) - Challenges in Flavor Physics
• Pearl Sandick (Utah) - Topics in Primordial Black Hole Physics
• Kate Scholberg (Duke) - Status of Neutrino Experiments
• Dibyashree Sengupta (NTU) - Supersymmetry, naturalness and the landscape
• Sarah Shandera (Penn State) - Dissipative dark matter and black holes
• Gary Shiu (U. Wisconsin) - Quantum Information in de Sitter Space
• Sheldon Stone (Syracuse) - Physics at LHCb
• Tim Tait (UC Irvine) - Dark Matter Theory
• Cumrun Vafa (Harvard) - Strings, Early Universe and Topological Gravity
• Lian-Tao Wang (U. Chicago) - Signals of new dynamics during inflation
• Andrew Whitbeck (Texas Tech) - Accelerator-based Searches for Dark Matter: An Overview
• Graham White - Phase Transitions and Gravitational Waves: The Precision Frontier
• Yue Zhao (Utah) - Astrophysical probes to new physics beyond the Standard Model - EHT and GW experiments

International Advisory Committee Ben Allanach (Cambridge) John Ellis (King’s College London/CERN) Vernon Barger (Wisconsin) V.A. Bednyakov (JINR) Wim de Boer (Karlsruhe) Joel Butler (FNAL/CERN) Tiziano Camporesi (CERN) Johnathan Ellis (CERN) JoAnne Hewett (SLAC) Ian Hinchliffe (LBL) Fabio Iocco (ICTP-SAIFR & IFT-UNESP) Karl Jakobs (U. Freiburg) Gordon Kane (Michigan) Dmitri I. Kazakov (JINR, Dubna) Robert Kirshner (Harvard) Tomio Kobayashi (Tokyo) Pran Nath (NEU) Mihoko Nojiri (KEK) Saul Perlmutter (LBNL) Michael Peskin (SLAC) Adam Riess (Johns Hopkins) Graham Ross (Oxford) Paul Shapiro (UT Austin) Melvyn Shochet (Chicago) George F. Smoot (UC Berkeley) David Spergel (Princeton) Paris Sphicas (CERN & Athens U.) S.C.C. Ting (MIT) Steven Weinberg (UT Austin)

Local Organizing Committee Brad Abbott Howie Baer Dorival Gonçalves (OSU) Huaike Guo Phillip Gutierrez Ahmed Ismail (OSU) Chung Kao Ferah Munshi Amber Roepe Kuver Sinha Michael Strauss John Stupak

Parallel-and-Video-Links.html

Plenary-and-Video-Links.html

PPC-2021-Schedule-Zoom.pdf

Monday, 17 May

08:30 → 09:00 Introduction

09:00 → 10:30 Plenary: Neutrino

Convener: Irina Mocioiu (Pennsylvania State University)

09:00 Status of Neutrino Experiments

Speaker: Kate Scholberg (Duke University)

ppc21.pdf

09:30 Topics in Neutrino Physics

Speaker: Andre De Gouvea (Northwestern University)

PPC_2021.pdf

10:00 Neutrino Theory

Speaker: Kaladi Babu (Oklahoma State University)

PPC_2021_Babu.pdf

10:30 → 11:00 Break

11:00 → 12:30 Plenary: Neutrino/Models

Convener: Kaladi Babu (Oklahoma State University)

11:00 Flavor Physics and Light Mediators

Speaker: Irina Mocioiu (Pennsylvania State University)

PPC21_mocioiu.pdf

11:30 New Gauge Theories and the TeV Scale

Speaker: Pavel Fileviez Perez (Case Western Reserve University)

PPC-2021 final.key.pdf

12:00 Fermi-LAT

Speaker: Simona Murgia (University of California, Irvine)

PPC21MurgiaS.pdf

12:30 → 14:00 Lunch

14:00 → 15:30 Plenary: Dark Matter

Convener: Yang Bai (University of Wisconsin, Madison)

14:00 Dark Matter Direct Detection - Experiment

Speaker: Rafael Lang

rafael_directdetection.pdf

14:30 Dark Matter Theory

Speaker: Tim M.P. Tait (University of California, Irvine)

Tait-PPC21.pdf

15:00 Current Anomalies: From Muon g-2 to B-physics and Neutrinos

Speaker: Bhupal Dev (Washington University in St. Louis)

dev_ppc21.pdf

15:30 → 16:00 Break

16:00 → 17:30 Plenary

Convener: JiJi Fan (Brown University)

16:00 Macroscopic Dark Matter

Speaker: Yang Bai (University of Wisconsin, Madison)

MDM_PPC2021.pdf

16:30 Dark Sectors

Speaker: stefania gori (UC Santa Cruz)

TalkOklahoma.pdf

17:00 Phase Transitions and Gravitational Waves: The Precision Frontier

Speaker: Graham White (TRIUMF)

precision_GWs.pdf

Tuesday, 18 May

08:30 → 10:30 Plenary: Supersymmetry

Convener: Liam McAllister (Cornell University)

08:30 SUSY at the LHC

Speaker: Anadi Canepa (Fermi National Accelerator Lab. (US))

canepa.pdf

09:00 Dark Matter Candidates in Supersymmetric Models

Speaker: Keith Olive

PPC21.pdf

09:30 Supersymmetry, naturalness and the landscape

While the ATLAS/CMS experiments discovered a Standard Model-like Higgs boson at LHC, no compelling new physics signal has been seen yet. Lack of experimental evidence of $sparticles$ has pushed the lower limit on their masses in the multi-TeV regime. LHC searches for Weak scale supersymmetry (SUSY) show that gluinos should lie beyond 2.2 TeV and top squarks should lie beyond 1.1 TeV. Such high mass limits are well beyond early upper limits from naturalness and gives rise to the question whether SUSY is now unnatural. We critique the older notions of naturalness and suggest an update based on the more conservative electroweak naturalness measure. In that case, SUSY with light higgsinos and highly mixed TeV-scale top squarks is still quite natural. The emergence of the string landscape within the setting of eternal inflation adds substance to the naturalness debate. In this case, a statistical pull to large soft terms must be balanced by the requirement that the derived weak scale lie within the narrow ABDS anthropic window. Then the landscape predicts $m_h \sim $ 125 GeV with $sparticles$, except light higgsinos, generally beyond LHC reach. We outline consequences of this ``stringy naturalness" for future collider and dark matter searches.

Speaker: Dibyashree Sengupta (University of Oklahoma)

PPC_2021.pdf

10:00 Statistical predictions for low-energy physics from the string landscape

Speaker: Michele Cicoli (Università di Bologna)

PPC2021_Cicoli_new.pdf

10:30 → 11:00 Break

11:00 → 12:30 Plenary: String Phenomenology

Convener: Michele Cicoli (Università di Bologna)

11:00 Type IIB String Phenomenology

Speaker: Fernando Quevedo (University of Cambridge)

11:30 Axions and String Vacua

Speaker: Liam McAllister (Cornell University)

McAllister_PPC2021.pdf

12:00 Strings, Early Universe and Topological Gravity

Speaker: Cumrun Vafa (Harvard University)

Top.Grav.PPCtalk.pdf

12:30 → 14:00 Lunch

14:00 → 15:30 Plenary: Cosmology

Convener: Adrienne Erickcek (University of North Carolina at Chapel Hill)

14:00 Discovering New Physics with Cosmological Data Sets

Speaker: Prof. Cora Dvorkin (Harvard)

Dvorkin_PPC_Conference_May_2021.pdf

14:30 Quantum Information in de Sitter Space

Speaker: Gary Shiu

PPC2021.pdf

15:00 The End of Inflation

Speaker: Mustafa Amin (Rice University)

Amin_InflationEnd_PPC21.pdf

15:30 → 16:00 Break

16:00 → 17:00 Plenary

Convener: Gary Shiu (University of Wisconsin & HKUST)

16:00 Cosmology of Early Matter Domination

Speaker: Adrienne Erickcek (University of North Carolina at Chapel Hill)

PPC_Erickcek.pdf

16:30 Signals of new dynamics during inflation

Speaker: LianTao Wang (University of Chicago)

Inlfation_ppc_LianTaoWang.pdf

Wednesday, 19 May

08:30 → 10:30 Plenary: Dark Matter

Convener: Pearl Sandick (University of Utah)

08:30 Feebly-Interacting and Decaying Dark Matter

Speaker: Kyu Jung Bae (Korea Advanced Institute of Science and Technology)

ppc_210519.pdf

09:00 Light Dark Matter Cosmology

Speaker: Gordan Krnjaic (Fermilab)

09:30 Cosmological Imprints of Non-Minimal Dark Sectors

Speaker: Keith Dienes (University of Arizona)

talk_PPC.pdf

10:00 Cosmological Signatures of Dark Matter Interactions

Speaker: Kimberly Boddy (University of Texas at Austin)

10:30 → 11:00 Break

11:00 → 12:30 Plenary: Black Holes

Convener: Keith Dienes (University of Arizona)

11:00 Topics in Primordial Black Hole Physics

Speaker: Pearl Sandick (University of Utah)

PBH4PPC.pdf

11:30 Primordial Black Holes and Dark Matter

Speaker: Stefano Profumo (University of California, Santa Cruz)

Profumo_PPC2021_210519.pdf

12:00 Dark Black Holes

Speaker: Sarah Shandera

PPCMay2021.pdf

12:30 → 14:00 Lunch

14:00 → 15:30 Cosmology 1

Convener: Rouzbeh Allahverdi (University of New Mexico)

14:00 UV completing Higgs inflation

A minimal model allowing for the stage of accelerated expansion in the early Universe is inlation driven by the Standard model Higgs field. However, this model requires large non-minimal coupling between the Higgs field and gravity. This leads to quite low energy scale after which the model becomes strongly coupled and non-predictive. In particular, UV completion of Higgs inflation is required for the description of reheating and connection between low and high energy parameters. I will discuss the possibilities to build UV completion for Higgs inflation by adding the quadratic in curvature term for gravity and the scenario allowing for completing the model without introducing new degrees of freedom which exploits non-local propagator for the Higgs field. It is shown that the predictions for inflationary parameters are not sensitive to the details of UV completion while the reheating stage crucially depends on these details.

Speaker: Anna Tokareva (University of Jyvaskyla)

UV.pdf

14:15 Higgs-Sparticle Inflation In The MSSM

Without any extension of the MSSM, we build the model of inflation in which the inflaton field is a scalar component of the MSSM state(s).
The inflaton protential involves only MSSM Yukawa superpotential couplings, which make considered model very predictive, establishing close connection between the cosmology and particle physics.
The values of the scalar spectral index and the tensor-to-scalar ratio are predicted to be ns≃0.966 and r=0.00118. The postinflation reheating of the Universe proceeds by the decay of the inflaton with the reheating temperature around 10^7 GeV.
Some phenomenological implications will be also discussed.

Speaker: Zurab Tavartkiladze (Ilia State University)

2021.05.19-Tavartkiladze-PPC2021.pdf

14:30 Multi-field inflation in the extreme-turning limit

Models of inflation with multiple scalar fields are well-motivated from supergravity and string theory. However, the steep potential gradients often seen in these models naively violate the slow-roll criteria employed in single-field inflation. Multi-field solutions that rapidly turn in field space can achieve sustained slow-roll inflation in such models, but criteria for turning trajectories only exist for the case of two fields. In this talk, I will generalize these criteria to an arbitrary number of fields and quantify the extreme turning limit, in which rapid-turn solutions may be found efficiently via a variety of newly-developed methods. These methods reproduce the inflationary solutions in known rapid-turn models and can be used to search string constructions for rapid-turn trajectories. For the first time, we are able to efficiently search for these solutions and even exclude slow-roll, rapid-turn inflation from one string-derived potential.

Speaker: Vikas Aragam (The University of Texas at Austin)

extreme.pdf

14:45 Quintessential Inflation in Palatini Gravity

Quintessential inflation aims to explain both inflation and dark energy using a single degree of freedom in a common theoretical framework. This economic proposal explains away the coincidence problem of quintessence by means of the inflationary attractor. Model building quintessential inflation is rather difficult because a successful model must account for both inflation and dark energy observations. An effort to achieve quintessential inflation in the context of modified gravity in the Palatini formulation is presented. The model is shown to satisfy CMB observations and generate definite predictions for the running of the dark energy barotropic parameter as well as a spike in primordial gravitational waves, soon to be observable.

Speaker: Dr Konstantinos Dimopoulos

Oklahoma.pptx

15:00 Is Our Universe the Remnant of Chiral Anomaly in Inflation?

Modern cosmology has been remarkably successful in describing the Universe from a second after the Big Bang until today. However, its physics before that time is still much less certain. It profoundly involves particle theory beyond the Standard Model to explain long-standing puzzles: the origin of the observed matter asymmetry, nature of dark matter, massive neutrinos, and cosmic inflation. In this talk, I will explain that a new framework based on embedding axion-inflation in left-right symmetric gauge extensions of the SM can possibly solve and relate these seemingly unrelated mysteries of modern cosmology. Thus, it can naturally explain the observed coincidences among cosmological parameters. The baryon asymmetry and dark matter today are remnants of a pure quantum effect (chiral anomaly) in inflation which is the source of CP violation in inflation. As a smoking gun, this setup has robust observable signatures for the GW background to be probed by future CMB missions and laser interferometer detectors.

Speaker: Dr Azadeh Maleknejad (CERN)

PPC-2021.pdf

15:15 A Real Time Approach to Quantum Tunneling

Recently there has been increasing interest in alternate methods to compute quantum tunneling in field theory. Of particular interest is a stochastic approach which involves (i) sampling from the free theory Gaussian approximation to the Wigner distribution in order to obtain stochastic initial conditions for the field and momentum conjugate, then (ii) evolving under the classical field equations of motion, which leads to random bubble formation. Previous work showed parametric agreement between the logarithm of the tunneling rate in this stochastic approach and the usual instanton approximation. However, recent work claimed excellent agreement between these methods. Here we show that this approach does not in fact match precisely; the stochastic method tends to overpredict the instanton tunneling rate. To quantify this, we parameterize the standard deviations in the initial stochastic fluctuations by $\epsilon*\sigma$, where $\sigma$ is the actual standard deviation of the Gaussian distribution and $\epsilon$ is a fudge factor; $\epsilon$ = 1 is the physical value. We numerically implement the stochastic approach to obtain the bubble formation rate for a range of potentials in 1+1-dimensions, finding that $\epsilon$ always needs to be somewhat smaller than unity to suppress the otherwise much larger stochastic rates towards the instanton rates; for example, in the potential of Braden, et. al. one needs $\epsilon$ ~ 1/2. We find that a mismatch in predictions also occurs when sampling from other Wigner distributions, and in single particle quantum mechanics even when the initial quantum system is prepared in an exact Gaussian state. If the goal is to obtain agreement between the two methods, our results show that the stochastic approach would be useful if a prescription to specify optimal fudge factors for fluctuations can be developed.

Speaker: Neil Shah (Tufts University)

Neil_Shah_PPC_2021_Stochastic_Tunneling_Talk.pdf

14:00 → 15:30 Dark Sectors: Cosmological Aspects 1

Convener: Malte Buschmann (Princeton University)

14:00 Deciphering the Archaeological Record: Cosmological Imprints of Non-Minimal Dark Sectors

Many proposals for physics beyond the Standard Model give rise to a dark sector containing many degrees of freedom. In this talk, we discuss the cosmological implications of non-trivial dynamics that may arise within such dark sectors, focusing on decay processes which take place entirely among the dark constituents. First, we demonstrate that such decays can leave dramatic imprints on the resulting dark-matter phase-space distribution. In particular, this distribution need not be thermal---it can even be multi-modal, exhibiting a non-trivial pattern of peaks and troughs as a function of momentum. We then proceed to show how these features can induce modifications to the matter power spectrum. Finally, we assess the extent to which one can approach the archaeological inverse problem of deciphering the properties of an underlying dark sector from the matter power spectrum. Indeed, one of our main results is a remarkably simple conjectured analytic expression which permits the reconstruction of many of the important features of the dark-matter phase-space distribution directly from the matter power spectrum. Our results therefore provide an interesting toolbox of methods for learning about, and potentially constraining, the features of non-minimal dark sectors and their dynamics in the early universe.

Speaker: Jeff Kost (University of Sussex)

KOSTtalk.pdf

14:15 Extracting Primordial Dark-Matter Velocity Distribution from Halo Masses: A Reconstruction Conjecture

In many scenarios beyond the traditional thermal paradigm, dark matter could be produced with a non-thermal (and sometimes highly nontrivial) primordial velocity distribution. The distribution of primordial dark-matter velocities can significantly influence the growth of cosmological structure. In principle, one can therefore exploit the halo-mass distribution in order to learn about the dark sector. In practice, however, this task is both theoretically and computationally intractable. In this talk, we present a simple one-line conjecture which can be used to “reconstruct” the primordial dark-matter velocity distribution directly from the shape of the halo-mass function. Although our conjecture is completely heuristic, we show that it successfully reproduces the salient features of the underlying dark-matter velocity distribution — even for non-trivial distributions which are highly non-thermal and/or multi-modal, such as might occur for non-minimal dark sectors. Our conjecture therefore provides an operational tool for probing the dark sector which does not rely on the existence of non-gravitational couplings between dark and visible states.

Speaker: Fei Huang (ITP CAS and UC Irvine)

PPC 2021.pdf

14:30 Enlarging the Space of Viable Inflation Models: A Slingshot Mechanism

The viability of a given model for inflation is determined not only by the form of the inflaton potential, but also by the initial inflaton field configuration. In many models, field configurations which are otherwise well-motivated nevertheless fail to induce inflation, or fail to produce an inflationary epoch of duration sufficient to solve the horizon and flatness problems. In this talk, I describe a mechanism which enables inflation to occur even with such initial conditions. This mechanism involves multiple scalar fields which experience a time-dependent mixing. This in turn leads to a "re-overdamping" phase as well as a parametric resonance which together "slingshot" the inflaton field from regions of parameter space that do not induce inflation to regions that do. This mechanism is flexible, dynamical, and capable of yielding an inflationary epoch of sufficiently long duration. This slingshot mechanism can therefore be utilized in a variety of settings and thereby enlarge the space of potentially viable inflation models.

Speaker: Brooks Thomas (Lafayette College)

PPC-2021 (15 minutes).pdf

14:45 Cosmological constraints on light (but massive) relics

In this talk I will show how to leverage cosmological data sets to search for new light–but not necessarily massless–degrees of freedom. These light relics arise ubiquitous in BSM theories, and their feeble interactions with the visible sector make them decouple in the early universe, and thus conserve significant number densities. Due to their small couplings, and large cosmic abundances, these BSM degrees of freedom are most powerfully searched with cosmological datasets. Massless relics act as a simple change in the number N_eff of effective neutrinos. Light but Massive Relics (LiMRs), however, also affect the clustering of matter, in a manner similar to that of massive neutrinos. I will show how current CMB+LSS data covers a large part of the relic parameter space, and in particular how they set the tightest constraints on the gravitino mass at 3 eV (95% CL).

Speaker: Julian Munoz (Harvard-Smithsonian Center for Astrophysics)

15:00 Cosmological constraints on multi-interacting dark matter

Despite its remarkable success, the standard $\Lambda$CDM paradigm has been challenged lately by significant tensions between different datasets. This has boosted interest in non-minimal dark sectors, which are theoretically well-motivated and inspire new search strategies for DM. With this in mind, we have developed a new and efficient version of the Boltzmann code CLASS that allows for one DM species to have multiple interactions with photons, baryons, and dark radiation simultaneously. In this talk I will present our new results obtained using this framework, where we have reassessed existing cosmological bounds on the various interaction coefficients in multi-interacting DM scenarios, as well as investigating the possibility of these models to alleviate the cosmological tensions. The upcoming public release of our code will pave the way for the study of various rich dark sectors.

Speaker: Dr Deanna C. Hooper (ULB (Université libre de Bruxelles))

HOOPER_ppc21.pdf

15:15 Electroweak Confinement and $SU(2)_L$ Dark Matter

We consider how a modified cosmological history with a period of electroweak confinement could allow a WIMP dark matter candidate to escape current exclusion bounds. We consider an $SU(2)_L$ vector doublet fermionic dark matter candidate which confines with standard model fermions during this era. These composite particles interact, depleting the dark matter abundance. After these processes freeze out, the electroweak period deconfines and proceeds according to the typical cosmological timeline. We find that this scenario naturally leads to a WIMP dark matter candidate while avoiding current exclusion bounds.

Speakers: Jessica N. Howard (University of California Irvine (US)), Jessica N. Howard (Department of Physics & Astronomy, UC Irvine)

Howard_Jessica_PPC2021_final.pdf

14:00 → 15:30 Light DM Detection 1

Convener: Jeff Dror (Lawrence Berkeley National Laboratory)

14:00 Sub-GeV Dark Matter and $U(1)_{T3R}$

Recently, there has been much theoretical and experimental focus on dark matter with a mass in the MeV-GeV range. We propose a scenario which not only accommodates this mass scale, but which naturally leads to such a light dark matter candidate. We consider a scenario in which 1st/2nd generation right-handed fermions are charged under a new gauge group, $U(1)_{T3R}$, which is spontaneously broken to a $Z_2$ subgroup. In this scenario, a Majorana fermion which is odd under the surviving parity is a dark matter candidate. Moreover, the mass of the dark matter particle is tied to the mass of the Standard Model fermions charged under the new $U(1)$, leading to a natural sub-GeV dark matter candidate. This scenario is tightly constrained by direct detection, collider, astrophysical and cosmological data, but there is open parameter space. We comment on the prospects for future experiments to probe this remaining parameter space, and on the implications for $g-2$ and for flavor anomalies.

Speaker: Jason Kumar

PPC2021a.pdf

14:15 Looking for elusive dark sectors in the lab and sky

In this talk, I will present the theoretical framework to probe dark sectors that have portal interactions with the standard model mediated by irrelevant operators. The focus is to develop a model-independent approach, without any specific model biases. I will focus on dark sectors with approximate conformal dynamics, and elucidate how this allows model-independent bounds to be derived. I will present the constraints from the various class of experiments and explain the procedures and assumptions involved.
The general picture that emerges is that these sectors are poorly constrained at the moment and points to the kind of future experimental facilities that will improve the reach on such dark sectors.

Speaker: Rashmish Mishra (Harvard University)

PPC_DS.pdf

14:30 Phenomenology of Minimal Leptophilic dark-matter models

In this talk, we discuss the phenomenology of a minimal model for GeV-scale Majorana dark matter (DM) coupled to the standard model lepton sector via a charged scalar singlet. The theoretical framework extends the Standard Model by two $SU(2)_L$ singlets: one charged Higgs boson and a singlet right-handed fermion. The latter plays the role of the DM candidate. We show that there is an anti-correlation between the spin-independent DM-Nucleus scattering cross-section $\sigma_{\rm SI}$ and the DM relic density for parameter values allowed by various theoretical and experimental constraints. Moreover, we find that even when DM couplings are of order unity, $\sigma_{\rm SI}$ is below the current experimental bound but above the neutrino floor. Furthermore, we show that the considered model can be probed at High Energy lepton colliders using e.g. the mono-Higgs production and same-sign charged Higgs pair production while hadron colliders provide an extra complementary role. We discuss the potential of embedding this model into grand-unified theories and comment on the astrophysical implications.

Speaker: Dr Adil Jueid (Konkuk University)

PPC2021_AJ.pdf

14:45 Light Dark Matter through Resonance Scanning

We propose a new out-of-equilibrium production mechanism of light dark matter: resonance scanning. If the dark matter mass evolved in the early Universe, resonant production may have occurred for a wide range of light dark matter masses today. We show that the dark matter relic abundance may be produced through the Higgs portal, in a manner consistent with current experimental constraints.

Speaker: Rachel Houtz (IPPP Durham)

Resonance_Scanning_PPC.pdf

15:00 Integral X-ray constraints on sub-GeV dark matter

Dark matter (DM) in cosmic structures is expected to produce signals originating from its particle physics nature, among which the electromagnetic emission represents a relevant opportunity. One of the major candidates for DM are weak-scale particles, however no convincing signal of them has been observed so far. For this reason, alternative candidates are getting increasing attention, notably sub-GeV particles, which are the subject of our work. The challenge in indirect detection of sub-GeV DM is that there is scarcity of competitive experiments in the energy range between 1 MeV and hundreds of MeV, hence we need to find alternative ways to study DM candidates with mass in this energy window. In our work we proposed to look at energies much lower than the mass of the sub-GeV DM particles by including the contribution from Inverse-Compton scattering in the total flux. In particular, the electrons and positrons produced by DM particles give rise to X-rays by upscattering the low-energy photons of the radiation fields in the Galaxy (CMB, infrared from dust, optical starlight). These X-rays fall in the energy range covered by the INTEGRAL data, which we used to determine conservative bounds on the DM annihilation cross-section. We considered three annihilation channels: electron, muon and pion. As a result, we derived competitive constraints for DM particles with a mass between 150 MeV and 1.5 GeV.

Speaker: Elena Pinetti

talk_Pinetti.pdf

15:15 Probing light dark matter particles with astrophysical experiments

Strong bounds from direct detection experiment put stringent
limit on the dark matter mass which forces us to go beyond WIMP model of dark matter. In recent years the light mass dark matter particles gain lots of attention among the particle physicists. In this talk I will discuss about light gauge bosons motivated from U(1) extension of standard model and axions which can be a possible dark matter candidates and its
detection in several astrophysical experiments.

Speaker: Tanmay Poddar (Physical Research Laboratory)

ppc2021.pdf

14:00 → 15:30 Neutrinos 1

Convener: Julia Gehrlein

14:00 keV Sterile Neutrino Dark Matter Terrestrial Searches: Alive and Well

What if the dark matter content of the universe was made up of sterile neutrinos with a mass of the order of keV?
Currently, constraints from the measured relic abundance of dark matter and from observations in the X-ray band threaten the possibility of finding in terrestrial experiments a signal of such sterile neutrinos produced through oscillation and collisions in the early universe.
We look at two scenarios in which the simple hypothesis of

• a low reheating temperature
• a new contribution to the sterile neutrino decay process

naturally relax these constraints and give new vigor to the hope of getting in the near future a proof of the existence of these elusive Dark Matter candidates in experiments such as KATRIN and ECHo.

Speaker: Ms Cristina Benso (Max Planck Institute for Nuclear Physics in Heidelberg)

PPC_2021_Benso.pdf

14:15 Unified framework for B-anomalies, muon g-2 and neutrino masses

We present a model of radiative neutrino masses which also resolves anomalies reported in $B$-meson decays, $R_{D^{(\star)}}$ and $R_{K^{(\star)}}$, as well as in muon $g-2$ measurement, $\Delta a_\mu$. Neutrino masses arise in the model through loop diagrams involving TeV-scale leptoquark (LQ) scalars $R_2$ and $S_3$. Fits to neutrino oscillation parameters are obtained satisfying all flavor constraints which also explain the anomalies in $R_{D^{(\star)}}$, $R_{K^{(\star)}}$ and $\Delta a_\mu$ within $1\, \sigma$. An isospin-3/2 Higgs quadruplet plays a crucial role in generating neutrino masses; we point out that the doubly-charged scalar contained therein can be produced in the decays of the $S_3$ LQ, which enhances its reach to 1.1 (6.2) TeV at $\sqrt s=14$ TeV high-luminosity LHC ($\sqrt s=100$ TeV FCC-hh). We also find that the same Yukawa couplings responsible for the chirally-enhanced contribution to $\Delta a_\mu$ give rise to new contributions to the SM Higgs decays to muon and tau pairs, with the modifications to the corresponding branching ratios being at (2--6)\% level, which could be tested at future hadron colliders, such as HL-LHC and FCC-hh.

Speaker: Anil Thapa

PPC_2021.pdf

14:30 Muon g−2 Anomaly and Neutrino Magnetic Moments

We present a novel framework based on $SU(2)_H$ horizontal symmetry, which generates a naturally large neutrino transition magnetic moment and explains the XENON1T electron recoil excess also predicts a positive shift in the muon anomalous magnetic moment. This shift is of the right magnitude to be consistent with the Brookhaven measurement as well as the recent Fermilab measurement of the muon $g-2$. A relatively light neutral scalar from a Higgs doublet with a mass near 100 GeV contributes to muon $g-2$, while its charged partner induces the neutrino magnetic moment. We also discuss the LHC phenomenology of these models.

Speaker: Vishnu Padmanabhan Kovilakam (Oklahoma State University)

gm2_NMM_PPC21.pdf

14:45 Hidden Photons in light of g-2

Recently, the Muon g-2 collaboration released their first result of the muon anomalous magnetic moment $(g-2)_\mu$ measured with the E989 experiment at Fermilab. When combined with previous data this result confirms a 4.2 $\sigma$ excess over the Standard Model prediction. In light of this exciting news an anomaly-free $U(1)_{L_\mu-L_\tau}$ allows for an explanation of $(g-2)_\mu$ with a novel MeV-mass hidden photon. Focussing on neutrino interactions, I will present a dedicated strategy of how to combine measurements from muon beam, coherent neutrino-nucleus scattering and direct detection experiments to independently confirm $U(1)_{L_\mu-L_\tau}$ as a solution to $(g-2)_\mu$ and discriminate it from a simplified muon-coupled $U(1)_{L_\mu}$ mediator.

Speaker: Patrick Foldenauer

ppc_foldenauer.pdf

15:00 Probing Baryogenesis using Neutron-Anti-Neutron Oscillation

Neutron-Anti-neutron ($n$-$\bar{n}$) oscillation is a baryon number violating process that requires New Physics beyond the Standard model, and will be probed in future experiments at ESS and DUNE. We study the potential consequences of a future $n$-$\bar{n}$ oscillation signal for baryogenesis, in an effective field theory framework and for one of the two possible UV complete topologies. We also present a comprehensive prescription for the Boltzmann equation treatment of different baryogenesis scenarios that have a connection to $n$-$\bar{n}$ oscillation, and compare them to other low-scale observables such as meson oscillation, as well as the LHC.

Speaker: Kare Fridell (Technical University of Munich (TUM))

fridell_nnbar_PPC.pdf

15:15 The Singly-Charged Scalar Singlet as the Origin of Neutrino Masses

We consider the generation of neutrino masses via a singly-charged scalar singlet. Under general assumptions we identify two distinct structures for the neutrino mass matrix. This yields a constraint for the antisymmetric Yukawa coupling of the singly-charged scalar singlet to two left-handed lepton doublets, irrespective of how the breaking of lepton-number conservation is achieved. The constraint disfavours large hierarchies among the Yukawa couplings. We study the implications for the phenomenology of lepton-flavour universality, measurements of the $W$-boson mass, flavour violation in the charged-lepton sector and decays of the singly-charged scalar singlet. We also discuss the parameter space that can address the Cabibbo Angle Anomaly.

Speaker: Tobias Felkl (University of New South Wales)

talk-ppc2021-felkl.pdf

14:00 → 15:30 Phase Transitions and GW

Convener: Soubhik Kumar (University of Maryland)

14:00 Probing Baryonic Dark Matter Models with Gravitational Waves

Gravitational waves provide a unique method of testing theories with extended gauge symmetries. In particular, spontaneous symmetry breaking can lead to a detectable stochastic gravitational wave background generated by cosmic strings and first order phase transitions in the early universe. I will discuss the unique gravitational wave signature of a simple model with gauged baryon and lepton numbers, in which a high scale of lepton number breaking is motivated by the seesaw mechanism for the neutrinos, whereas a low scale of baryon number breaking is required by the observed dark matter relic density. This novel signature can be searched for in near-future gravitational wave experiments.

Speaker: Bartosz Fornal (University of Utah)

B_Fornal.pdf

14:15 Implications for first-order cosmological phase transitions from the third LIGO-Virgo observing run

We place constraints on the normalised energy density in gravitational waves
from first-order strong phase transitions using data from Advanced LIGO and Virgo's first, second and third observing runs. First, adopting a broken power law model, we place $95 \%$ confidence level upper limits simultaneously on the gravitational-wave energy density at 25 Hz from unresolved compact binary mergers, $\Omega_{\rm cbc} < 6.1 \times 10^{-9}$ , and strong first-order phase transitions, $\Omega_{\rm bpl} < 4.4 \times 10^{-9}$. The inclusion of the former is necessary since we expect this astrophysical signal to be the foreground of any detected spectrum. We then consider two more complex phenomenological models, limiting at 25 Hz the gravitational-wave background due to bubble collisions to $\Omega_{\rm pt} < 5.0\times 10^{-9}$ and the background due to sound waves to $\Omega_{\rm pt} < 5.8\times10^{-9}$ at $95 \%$ confidence level for phase transitions occurring at temperatures above $10^8$~GeV.

Speaker: Ms Alba Romero (IFAE)

main.pdf

14:30 Searching for Cosmic Strings using data from the third Advanced LIGO-Virgo observing run

Cosmic string network generically appears in many natural extensions of particle SM. And cosmic strings are one-dimension topological defects which can be formed in grand unified theory scale phase transitions in the early universe and are also predicted to form in the context of string theory. The main mechanism for a network of Nambu-Goto cosmic strings to lose energy is through the production of loops and the subsequent emission of GW, thus offering an experimental signature for the existence of cosmic strings. And the unresolvable GW bursts produced by cosmic strings at different loop scale and cosmic time will overlap with each other and form a stochastic GW background (SGWB). We performed the parameter estimation in three cosmic string models using the third Advanced LIGO-Virgo observation run isotropic stochastic search results. We also consider a new source component in the model, i.e. kink-kink collision, using more realistic model parameters.

Speaker: Fengwei Yang (University of Utah)

Searching for Cosmic Strings using data from the third LIGO-Virgo observing run - v2.pdf

14:45 Gravity Gradient Noise from Asteroids

The gravitational coupling of nearby massive bodies to test masses in a gravitational wave (GW) detector cannot be shielded, and gives rise to ‘gravity gradient noise’ (GGN) in the detector. I will discuss how, for any GW detector using local test masses in the Inner Solar System, the GGN from the motion of the field of $\sim 10^5$ Inner Solar System asteroids presents an irreducible noise floor for the detection of GW that rises exponentially at low frequencies. This severely limits prospects for GW detection using local test masses for frequencies $f_{\text{gw}} < 􏰁 \text{(few)} \times 10^{-7}$ Hz. At higher frequencies, the asteroid GGN falls rapidly enough that detection may be possible; however, the incompleteness of existing asteroid catalogs with regard to small bodies makes this an open question around $f_{\text{gw}} \sim \mu$Hz. I'll discuss possible alternative detection approaches that could overcome the limitations of local test masses for GW detection in the $\sim 10\,\text{nHz}–\mu$Hz band.

Speaker: Dr Michael Fedderke (Johns Hopkins University)

Fedderke_PPC2021.pdf

15:00 Detecting new forces in the gravitational wave background

Supermassive black hole binaries generate a gravitational wave background that will soon be measured by pulsar timing arrays. While the amplitude of this background is uncertain, the shape of its spectrum is a robust prediction of general relativity. We show that the effects of new forces beyond the Standard Model can modify this prediction and introduce unique features into the spectral shape. As a benchmark scenario, we study the case in which the black holes themselves are charged under a new long-range force, which occurs naturally in many dark sector models. In this situation, we find that pulsar timing arrays can detect the effects of such a force on the spectral shape even if typical charges are small, making the shape a powerful new probe of fundamental physics.

Speaker: Benjamin Lehmann (UC Santa Cruz)

lehmann_slides.pdf

15:15 Gravitational Waves as a Big Bang Thermometer

There is a guaranteed background of stochastic gravitational waves produced in the thermal plasma in the early universe. Its energy density per logarithmic frequency interval scales with the maximum temperature $T_{\rm max}$ which the primordial plasma attained at the beginning of the standard hot big bang era. It peaks in the microwave range, at around $80$ GHz $[106.75/g_{*s}(T_{\rm max})]^{1/3}$, where $g_{*s}(T_{\rm max})$ is the effective number of entropy degrees of freedom in the primordial plasma at $T_{\rm max}$. We present a state-of-the-art prediction of this Cosmic Gravitational Microwave Background (CGMB) for general models, and carry out calculations for the case of the Standard Model (SM) as well as for several of its extensions. On the side of minimal extensions we consider the Neutrino Minimal SM (νMSM) and the SM-Axion-Seesaw-Higgs portal inflation model (SMASH), which provide a complete and consistent cosmological history including inflation. As an example of a non-minimal extension of the SM we consider the Minimal Supersymmetric Standard Model (MSSM). Furthermore, we discuss the current upper limits and the prospects to detect the CGMB in laboratory experiments and thus measure the maximum temperature and the effective number of degrees of freedom at the beginning of the hot big bang.

Speaker: Jan Schuette-Engel (University of Illinois at Urbana-Champaign)

GWs_as_HBB_Thermometer.pdf

14:00 → 15:30 Primordial Black Holes

Convener: Nicholas Orlofsky (University of Wisconsin-Madison)

14:00 Asymmetric Reheating by Primordial Black Holes

We investigate Hawking evaporation of a population of primordial black holes (PBHs) as a novel mechanism to populate a dark sector which consists of self-interacting scalar dark matter with pure gravitational coupling to the visible sector. We demonstrate that depending on initial abundance of PBHs and the dark matter mass, the dark sector can reach chemical equilibrium with a temperature above, below, or equal to the temperature of the visible sector at the same time. Due to the absence of non-gravitational mediators between two sectors, any temperature asymmetry between two sectors will persist and evolve to keep the entropy of each sector conserved during the expansion of the Universe. We show that an equilibrated dark sector populated by Hawking evaporation of PBHs in an early radiation-dominated Universe can explain the dark matter relic abundance today for dark matter in the MeV-TeV mass range. We also show that populating the dark sector by evaporation of PBHs, when they dominate the energy density of the Universe, leads to overproduction of dark matter.

Speaker: Dr Barmak Shams Es Haghi (Department of Physics and Astronomy, University of Utah)

PPC2021.pdf

14:15 Primordial Black Holes and warm dark matter constraints

Primordial Black Holes (PBHs) formed in the early universe could have an impact on all cosmological era from Big Bang Nucleosynthesis to the Cosmic Microwave Background and even galaxy formation, thus they are subject to a very stringent set of constraints over an extended mass range from $10^9$ to $10^{50}$ g. However, PBHs lighter than $10^9$ g are at present practically unconstrained, evaporating before BBN. An interesting possibility is that those light PBHs produce, on top of Standard Model radiation, some light dark matter (DM) particle -- warm DM. We will demonstrate how the modification of the public code BlackHawk to compute Hawking evaporation of light PBHs into warm DM, as well as the use of CLASS to implement structure formation constraints, allow us to place constraints on warm DM (of all spins) originating in PBH evaporation.

Speaker: Auffinger Jérémy (Institut de Physique des 2 Infinis - Lyon - FRANCE)

main.pdf

14:30 Interplay Between Dark Matter Freeze Out/In and Primordial Black Hole Evaporation

In this talk, I will present the phenomenology of dark-matter production in the case where it is both produced by a freeze-out or freeze-in mechanism and by the evaporation of primordial black holes. I will show that the presence of a vector mediator between the hidden and the visible sector affects the production of dark-matter particles as well as its phase space distribution. I will also show that the population of DM particles produced by evaporation may be warm enough to re-thermalize with the pre-existing DM relic abundance, leading to non-trivial imprints on the value of the relic abundance at later time.

Speaker: Dr Lucien Heurtier (IPPP, Durham, England)

PPC_Heurtier.pdf

14:45 Charting the Landscape in Our Neighborhood from the PBHs Mass Distribution and GWs

We explicitly construct a double field inflationary model, which satisfies the latest PLANCK constraints at the CMB scales and produces the whole dark matter energy density as primordial black holes (PBHs), in the mass range 10^{-17}~M_{\odot}\lesssim M_{{}{\rm PBH}}\lesssim 10^{-13}~M{\odot}. The PBHs can be produced after the end of slow-roll inflation from the bubbles of true vacuum that nucleate during the course of inflation. Obtaining PBHs in this mass range enforces the scale of inflation to be extremely low, 10^{-7}~{\rm GeV}\lesssim H \lesssim 10^{-3} ~{\rm GeV}, which makes the efforts to observe gravitational waves at the CMB scales futile, although it is high enough to allow for a successful Big Bang Nucleosynthesis (BBN). We will show that the shape of the mass distribution of the PBHs is dependent on how inflation ends and the universe settles from the metastable direction to the true one. In particular, if settling to the true vacuum occurs with a first-order phase transition (PT) happens a bit after the termination of inflation by the slow-roll violation, the subcritical bubbles find enough time to collapse to PBHs, and the first order PT leaves behind a stochastic gravitational wave background (SGWB), which is {\it potentially} observable by LISA. On the other hand, if exit from inflation and settling to the true vacuum both occur with a first order PT, all the bubbles collide before they find the chance to collapse to PBHs, but an SGWB typical of first order PT will be left as a signature. In the other extreme scenario, if exit from the false valley to the true one occurs through a second order instability, there will be only PBHs in both sub- and supercritical branches of the mass distribution, but there will be no SGWB typical of first order PT. We also show that PBHs produced during such a first-order PT from the collision of bubble walls contribute negligibly to the PBH mass spectrum. Examining the mass distribution of PBHs and possible SGWB from the end of inflation, we may be able to gain invaluable information about the topography of the landscape in our neighborhood.

Speaker: Dr Amjad Ashoorioon (Institute for Research in Fundamental Sciences (IPM))

PPC-2021-19-May-2021.pdf

15:00 Probing axion-like particle radiation from primordial black holes

We consider the axion flux emitted as Hawking radiation by primordial black holes (PBHs). If these axions are coupled with photons, they can convert into these particles in the cosmic magnetic fields. We explore the possible consequences of this mechanism on the cosmic X-ray background (CXB), the soft X-ray excess from galaxy clusters, and the reionization history of the Universe. We also briefly discuss the possibility of direct detection of this axionic radiation by Earth-based experiments such as IAXO.

Speaker: Francesco Schiavone (Università degli Studi di Bari (UNIBA))

PPC2021_Schiavone.pdf

15:15 Cosmological PBHs as dark matter

In the early universe, primordial black holes (PBHs) can no longer be described by the simple Schwarzschild metric-- we need a metric which is locally surrounded by the cosmological fluid and asymptotically FLRW. It turns out that the phenomenology of PBHs is very sensitive to the choice of such a metric. In particular, the Thakurta metric stands out as perhaps the most justifiable metric for the radiation-dominated universe. In this description, PBHs have an effective mass proportional to the cosmological scale factor.

We demonstrate two very significant effects of this choice of metric for the phenomenology of PBHs as dark matter (DM) candidates. Firstly, the binary abundance bounds which tightly constrain LIGO-size PBHs as DM candidates are entirely evaded. Secondly, these PBHs are significantly hotter and so evaporate very rapidly-- we show that the smallest black hole which actually survives until today is of order 10^21 g, which fully closes the asteroid-mass window for DM candidates, which was previously totally unconstrained.

Speaker: Zachary Picker (The University of Sydney)

PPC Talk 2021.pdf

15:30 → 16:00 Break

16:00 → 17:30 Cosmology 2

Convener: Brooks Thomas (Lafayette College)

16:00 COSMOLOGICAL PARTICLE PRODUCTION AND PAIRWISE SPOTS ON THE CMB

I will describe a scenario in which heavy particles are produced during inflation via their couplings to the inflaton. Following their production, these heavy particles propagate classically and can give rise to localized spots on the CMB. Momentum conservation during particle production dictates that these localized spots come in pairs. I will discuss the properties of such pairwise spots and the prospects of their detection in the presence of the thermal fluctuations of the CMB itself.

Speaker: Soubhik Kumar (UC Berkeley)

hotspot_soubhik_ppc.pdf

16:15 Gravitational growth of perturbations during reheating

Near-exponential growth during primordial inflation must eventually be followed by big bang nucleosynthesis. The reheating processes that occur in the transition between the two can affect the inflationary power spectrum and dark matter abundance. If the inflaton field is not disrupted by resonance or prompt reheating, perturbations growth gravitationally. I will present the first simulations of this gravitational growth of non-linear perturbations in the inflaton condensate at the end of inflation.

Speaker: Nathan Musoke (University of New Hampshire)

pres-ppc2021.pdf

16:30 Small Field Polynomial Inflation: Reheating, Radiative Stability and Lower Bound

We revisit the renormalizable polynomial inflection point model of inflation, focusing on the small field scenario which can be treated fully analytically. In particular, the running of the spectral index is predicted to be $\alpha = -1.43 \times 10^{-3} +5.56 \times 10^{-5} \left(N_{\rm CMB}-65 \right)$, which might be tested in future. We also analyze reheating through perturbative inflaton decays to either fermionic or bosonic final states via a trilinear coupling. The lower bound on the reheating temperature from successful Big Bang nucleosynthesis gives lower bounds for these couplings; on the other hand radiative stability of the inflaton potential leads to upper bounds. In combination this leads to a lower bound on the location $\phi_0$ of the near inflection point, $\phi_0 > 3 \cdot 10^{-5}$ in Planckian units. The Hubble parameter during inflation can be as low as $H_{\rm inf} \sim 1$ MeV, or as high as $\sim 10^{10}$ GeV. Similarly, the reheating temperature can lie between its lower bound of $\sim 4$ MeV and about $4 \cdot 10^8 \ (10^{11})$ GeV for fermionic (bosonic) inflaton decays. We finally speculate on the ``prehistory'' of the universe in this scenario, which might have included an epoch of eternal inflation.

Speaker: Mr Yong Xu (Bethe Center for Theoretical Physics, Universität Bonn)

PPC21_Xu.pdf

16:45 Spillway Preheating: an efficient particle production mechanism

In traditional models of preheating, only an order one fraction of energy is transferred from the inflaton to radiation through nonperturbative resonance production immediately after inflation, due to backreaction effects. We propose a particle production mechanism, "spillway preheating", that could improve the depletion of the inflaton energy density by up to four orders of magnitude. The improvement comes from the fast perturbative decays of resonantly produced daughter particles. They act as a "spillway" to drain these daughter particles, reducing their backreaction on the inflaton and keeping the resonant production effective for a longer period. We also show that the fraction of energy density remaining in the inflaton has a simple inverse power-law scaling in the scenario.

Speaker: Qianshu Lu

Spillway_preheating_2021PPC.pdf

17:00 The synergy between CMB spectral distortions and anisotropies

Despite their incredible precision, both concluded and upcoming CMB missions (such as Planck, CMB-S4, or LiteBIRD) still face several intrinsic limitations that can only be overcome with the help of complementary probes. One particularly interesting avenue to extract more information from the CMB is given by its spectral distortions (SDs). Since these distortions are created whenever the energy or number density of the CMB photons is modified, they are an ideal candidate to constrain both exotic and non-exotic energy injection scenarios. In this talk, following the novel CLASS implementation of SDs, I will provide a brief pedagogical introduction to the topic of SDs, and discuss their application to a selection of examples including inflation, primordial black holes and the Hubble tension. The presented results will show the far-reaching possibilities of combining CMB anisotropies and SDs.

Speaker: Matteo Lucca (IDP - ULB (Universite libre de Bruxelles))

Lucca_PPC2021_SDs.pdf

17:15 Cosmology with UV Galaxy Luminosity Functions

UV luminosity functions (LF), measured with the Hubble Space Telescope, provide a wealth of information on the state of the early Universe. This probe tracks the evolution of the mass function of dark-matter halos at earlier times (z=4-10) and lower masses than the local Universe, an interesting regime to constrain the nature of dark matter and primordial fluctuations at small scales. In this talk I will show how to use UVLF data to learn about cosmology, focusing on primordial non-Gaussianity and set constraints on the non-Gaussianity amplitude fNL at small scales, beyond the reach of the CMB.

Speaker: Nashwan Sabti

UVLF_fNL_19_05_2021.pdf

16:00 → 17:30 Dark Sector Models

Convener: Rachel Houtz (IPPP Durham)

16:00 Baryogenesis and Flavored Dark Matter from Broken Twin Color

The dark sector may be as rich and varied as the standard model. Twin Higgs models, which explain the little hierarchy problem, provide a compelling and predictive realization of such a dark sector, where the standard model field content is copied in a hidden sector. I show how the spontaneous breaking of twin color can naturally lead to asymmetric flavored dark matter and baryogenesis in addition to solving the hierarchy problem. I outline how this scenario can be tested at the LHC and future colliders.

Speaker: Christopher Verhaaren (University of California, Irvine)

TwinBaryMay2021.pdf

16:15 $Z'$ bosons at the P2 experiment

The weak mixing angle is to be measured in the P2 experiment with elastic electron-proton and eletron-$^{12}$C scattering. If there is a (light) $Z'$ boson with parity-violating couplings to the standard model (SM) fermions, it will contribute additional parity violation to the P2 measurements. For the non-chiral $Z'$ scenarios, it is found that the P2 experiment can probe a coupling as small as $10^{-5}$ for a light $Z'$, or an effective cutoff scale up to 90 TeV when $Z'$ is heavy. If the parity-violating couplings of $Z'$ are from mass mixings with the SM $Z$ boson, the P2 experiment is sensitive to a mass mixing angle smaller than roughly $10^{-4}$.

Speaker: Yongchao Zhang (Southeast University)

P2_Yongchao_Zhang.pdf

16:30 Probing dark matter and dark energy with strong gravitational lensing

Evidence from different cosmological probes have lead to the establishment of the dark matter and dark energy paradigm. The fundamental physical origin of these phenomena remain unknown to date. Challenging this model with high-precision measurements is key in guiding theoretical models.
In my talk, I will describe how we use the phenomena of strong gravitational to constrain the physical nature of dark matter and dark energy. I will describe the lensing observables and the analysis techniques we have developed to measure the small scale dark structure and the expansion rate of the Universe. I will present the recent results in both domains and look in the near future and highlight the prospects of this technique with increasing sample size, analysis techniques and advances in instrumentation.

Speaker: simon birrer (Stanford University)

ppc2021_birrer.pdf

16:45 Flavor anomalies from a split dark sector

We investigate solutions to the flavor anomalies in B decays and the anomalous magnetic moment of the muon based on loop diagrams of a "split" dark sector. This is characterized by the simultaneous presence of heavy particles at the TeV scale and light particles around and below the B-meson mass scale. We show that viable parameter space exists for solutions based on penguin diagrams with a vector mediator, while minimal constructions relying on box diagrams are in strong tension with the constraints from the LHC and LEP. We highlight a regime where the mediator lies close to the B-meson mass, naturally realising a resonance structure and a q2-dependent effective coupling. We perform a full fit to the relevant flavor observables and analyze the constraints from intensity frontier experiments. We find that decays of the B meson, Bs-mixing, missing energy searches at Belle-II, and LHC searches for top/bottom partners can robustly test these scenarios in the near future.

Speaker: Enrico Maria Sessolo (NCBJ, Warsaw)

Sessolo_PPC_2021.pdf

17:00 Indirect Detection Signatures of a Dark Glueball Spectrum

I report on an ongoing investigation of how a hidden ‘dark’ confining gauge sector, common in Hidden Valley models such as the Mirror Twin Higgs, could lead to novel signatures in indirect detection searches for dark matter. Dark matter annihilation can then lead to dark showers of multiple and various hadrons, distinct from particle pair production. If there are no light fermions charged under this force, the lightest hadrons are glueballs, a spectrum of a dozen metastable states that is reasonably well understood from lattice calculations. The lightest of these states, the $0^{++}$ glueball, can mix with the Higgs and decay through this portal into the Standard Model (SM). The decay of $0^{++}$ glueballs has been studied within the context of collider searches, as it is the shortest lived state, decaying on scales that can be observed as displaced vertices. However, since indirect detection methods probe astrophysical length and time scales, they are also sensitive to the decays of longer living glueball states that can decay into $0^{++}$ and SM particles; this leads to an increased multiplicity of particles such as positrons and antiprotons, but also possibly probes the properties of the entire glueball spectrum. Since the decays depend on the allowed operators, this may allow information on the UV completion of the sector to be determined. Understanding the possible indirect signatures and constraints of a pure glue gauge theory is especially relevant as the next generation of cosmic ray telescopes, such as GAPS, begin their searches.

Speaker: Caleb Gemmell (University of Toronto)

PPC2021_gemmell.pdf

17:15 Probing axion-like particles with 𝛾𝛾 final states from vector boson fusion processes at the LHC

Abstract: Axion-like particles (ALPs) are pseudo-Nambu-Goldstone bosons of spontaneously broken global symmetries in theories attempting to address the incompleteness of the Standard Model (SM). In particular, ALPs arise in theoretical resolutions to the strong CP problem, offer explanations for the dark matter (DM) relic abundance, and are ubiquitous in string theory. The ALP mass $m_a$ can range from eV to TeV scale, and thus the ALPs parameter space includes regions relevant to a variety of astronomical, high-precision low-energy, and high-energy collider experiments. The focus of this talk is a feasibility study searching for ALPs using vector boson fusion (VBF) processes at the Large Hadron Collider (LHC). We consider the $a \to \gamma\gamma$ decay mode to show that the requirement of an energetic diphoton pair combined with two forward jets with large dijet mass and pseudorapidity separation can significantly reduce the SM backgrounds, leading to a 5$\sigma$ discovery region spanning $m_a$ values from MeV scale to TeV scale and revealing LHC sensitivity to previously unstudied regions of the ALP parameter space.

Speaker: Elijah Sheridan (Vanderbilt University)

sheridan_ppc_slides.pdf

16:00 → 17:30 Dark Sectors: Cosmological Aspects 2

Convener: Barmak Shams Es Haghi (University of Utah Department of Physics & Astronomy)

16:00 Phenomenology of Magnetic Black Holes

Magnetically charged black holes are interesting solutions of the Standard Model and general relativity. They may possess a “hairy” electroweak-symmetric corona outside the event horizon, which speeds up their Hawking radiation and leads them to become nearly extremal on short timescales. Their masses could range from the Planck scale up to the Earth mass. I will present various methods to search for primordially produced magnetic black holes and provide estimated upper limits on their abundance.

Speaker: Dr Nicholas Orlofsky (Carleton University)

Orlofsky_PPC.pdf

16:15 The History and Fate of Dark Neutrons

I examine cosmological and astrophysical signatures of a “dark baryon,” a neutral fermion that mixes with the neutron, deriving new, powerful limits from primordial nucleosynthesis and the cosmic microwave background. Additionally, neutrons in a neutron star could decay slowly to dark baryons, providing a novel source of heat that is constrained by measurements of pulsar temperatures. I identify parameter space where the dark baryon can be a viable dark matter candidate and discuss promising avenues for probing it.

Talk based on https://arxiv.org/abs/2012.09865, https://arxiv.org/abs/2006.15140.

Speaker: Nirmal Raj (TRIUMF)

Raj-darkneutrons-PPC2021.pdf

16:30 Thermal Squeezeout of Dark Matter

I present a detailed study of the confinement phase transition in a dark sector with a SU(N) gauge group and a single generation of dark heavy quark. I focus on heavy enough quarks such that their abundance freezes out before the phase transition and the phase transition is of first-order. I show that during this phase transition the quarks are trapped inside contracting pockets of the deconfined phase and are compressed enough to interact at a significant rate, giving rise to a second stage of annihilation that can dramatically change the resulting dark matter abundance. As a result, the dark matter can be heavier than the often-quoted unitarity bound of ~100 TeV. These findings are almost completely independent of the details of the portal between the dark sector and the Standard Model.

Speaker: Pouya Asadi (Massachusetts Institute of Technology)

PPC_May_2021_DM.pdf

16:45 Baryogenesis and Dark Matter from Dark, 1st Order Phase Transitions

We present two distinct models which rely on 1st order phase transitions in a dark sector. The first is a minimal model for baryogenesis which employs a new dark SU(2) gauge group with two doublet Higgs bosons, two lepton doublets, and two singlets. The singlets act as a neutrino portal that transfers the generated baryon asymmetry to the Standard Model. The model predicts extra relativistic degrees of freedom, exotic decays of the Higgs and Z bosons, and stochastic gravitational waves detectable by future experiments.

The second model additionally produces (asymmetric) dark matter while the dark gauge group is expanded to SU(3)xSU(2)xU(1). Dark matter is comprised of dark neutrons or dark protons and pions.This model is highly discoverable at both dark matter direct detection and dark photon search experiments and the strong dark matter self interactions may ameliorate small-scale structure problems.

Speaker: Robert McGehee (University of Michigan)

Robert_McGehee_PPC2021_slides.pdf

17:00 Dark matter Relic Abundance beyond Kinetic Equilibrium

In the usual approach to the determination of dark matter thermal relic abundance an assumption of local thermal equilibrium is made. In this talk I will discuss how to go beyond this assumption and will introduce DRAKE — a numerical precision tool that can trace not only the DM relic density, but also its velocity dispersion and full phase space distribution function. I will review the general motivation for this approach and, for illustration, highlight three concrete classes of models where kinetic and chemical decoupling are intertwined in a way that can impact the value of the relic density by as much as an order of magnitude: i) dark matter annihilation via a narrow resonance, ii) Sommerfeld-enhanced annihilation and iii) `forbidden' annihilation to final states that are kinematically inaccessible at threshold.

Speaker: Andrzej Hryczuk (National Centre for Nuclear Research, Poland)

PPPC2021.pdf

17:15 A Dark Sector to Restore Cosmological Concordance

Observations of the early Universe indicate a Universe expanding today at a (Hubble) rate which is significantly slower than what is measured locally via supernovae, if the ΛCDM model is assumed. Furthermore, the amplitude of matter fluctuations at late times measured by cosmic shear surveys is smaller than what is inferred from the same early Universe observations, assuming the ΛCDM model.
Barring unaccounted systematics, these may be the first hints of new components beyond the ΛCDM model.

In this talk, we present a new phenomenological Dark Sector (DS) model that addresses the tensions above. The scenario features a decaying dark energy fluid which raises the value of H_0 and an ultra-light axion, which suppresses the matter power spectrum. We present results of Monte Carlo Markov Chain searches of the parameter space of this DS model with several early and late Universe datasets. Furthermore, we discuss a possible particle physics realization of this model, with a dark confining gauge sector and its associated axion, highlighting its challenges.

Speaker: Fabrizio Rompineve (Tufts University)

DS.pdf

16:00 → 17:30 Light DM Detection 2

Convener: Alexis Plascencia (Case Western Reserve University)

16:00 Sources of Low-energy Events in Sub-GeV Dark Matter Detectors

We point out several unexplored low-energy backgrounds to sub-GeV dark matter searches, which arise from high-energy particles of cosmic or radioactive origin that interact with detector materials. In this talk, I will focus on Cherenkov radiation and luminescence from electron-hole pair recombination. I will show that these processes provide plausible explanations of the observed events at SENSEI and SuperCDMS HVeV. We also propose several important design strategies to mitigate such backgrounds, which could have a significant impact on the design of future dark matter experiments.

Speaker: Peizhi Du (Stony Brook University)

PPC 2021.pdf

16:15 An Attractive Scenario for Light Dark Matter Direct Detection

Direct detection of light dark matter (DM), below the GeV scale, through electron recoil can be efficient if DM has a velocity well above the virial value of v∼10^(−3). We point out that if there is a long range attractive force sourced by bulk ordinary matter, i.e.baryons or electrons, DM can be accelerated towards the Earth and reach velocities v∼0.1 near the Earth’s surface. In this “attractive scenario” all DM will be boosted to high velocities by the time it reaches direct detection apparatuses in laboratories. Furthermore, the attractive force leads to an enhanced DM number density at the Earth facilitating DM detection even more. We elucidate the implications of this scenario for electron recoil direct detection experiments and find parameters that could lead to potential signals, while being consistent with stellar cooling and other bounds.

Speaker: Julia Gehrlein

ppc_2021_gehrlein.pdf

16:30 Dark Matter Daily Modulation With Anisotropic Organic Crystals

Aromatic organic compounds, because of their small excitation energies $\sim \mathcal O$(few eV) and scintillating properties, are promising targets for detecting dark matter of mass $\sim \mathcal O$(few MeV). Additionally, their planar molecular structures lead to large anisotropies in the electronic wavefunctions, yielding a significant daily modulation in the event rate expected to be observed in crystals of these molecules. We characterize the daily modulation rate of dark matter interacting with an anisotropic scintillating organic crystal such as trans-stilbene, and show that daily modulation is an $\sim \mathcal O$(1) fraction of the total rate for small DM masses and comparable to, or larger than, the $\sim 10\%$ annual modulation fraction at large DM masses. As we discuss in detail, this modulation provides significant leverage for detecting or excluding dark matter scattering, even in the presence of a non-negligible background rate. Assuming a non-modulating background rate of 1/min/kg that scales with total exposure, we find that a 100${\rm kg \cdot yr}$ experiment is sensitive to the cross section corresponding to the correct relic density for dark matter masses between $1.3-14\;\rm{MeV}$ ($1.5-1000\;\rm{MeV}$) if dark matter interacts via a heavy (light) mediator. This modulation can be understood using an effective velocity scale $v^* = \Delta E/q^*$, where $\Delta E$ is the electronic transition energy and $q^*$ is a characteristic momentum scale of the electronic orbitals. We also characterize promising future directions for development of scintillating organic crystals as dark matter detectors.

Speaker: Dr Carlos Blanco (Princeton University & Stockholm University)

16:45 Halo uncertainties in electron recoil events at direct detection experiments

The dark matter direct detection rates are highly correlated with the phase space
distribution of dark matter particles in our galactic neighborhood. In this talk, we will discuss the impact of astrophysical uncertainties on electron recoil events at the direct detection experiments with Xenon and semiconductor detectors. We find that within the standard halo model there can be up to ∼ 50% deviation from the fiducial choice in the exclusion bounds from these observational uncertainties. For non-standard halo models, we report a similar deviation from the fiducial standard halo model when fitted with state-of-art N-body simulation while even larger deviations are obtained in case of the observational uncertainties.

Speaker: Tarak Nath Maity (Indian Institute of Science, Bangalore)

PPC21-Tarak.pdf

17:00 The PADME experiment

Traditionally, dark matter exploration at accelerators has been conducted in the domain of high-energy experiments with, up-to-now, no positive results. The search of dark-matter candidates requires innovative and open-minded approaches spanning a wide range of energies with high-sensitivity detectors. In this scenario, attractive opportunities are offered to low energy machines and flavour experiments. The Positron Annihilation into Dark Matter Experiment (PADME) ongoing at the Laboratori Nazionali di Frascati of INFN is searching a Dark Photon signal by studying the missing-mass spectrum of single photon final states resulting from positrons annihilation on the electrons of a fixed target. PADME is expected to reach a sensitivity of up to $10^{-8}$ in $\epsilon^2$ (kinetic mixing coefficient) for low-mass Dark Photons (< 23.7MeV). In 2020 PADME collected $\approx 5\times 10^{12}$ POT at 430 MeV. Here we present the performance of the detector and the preliminary results of the ongoing analyses. These concern SM final states: $\gamma \gamma$-events and positron Bremsstrahlung.

Speaker: Elizabeth Sarah Long (INFN - National Institute for Nuclear Physics)

ThePADMEExperiment.pdf

17:15 Status of the NEWS-G dark matter experiment

The NEWS-G collaboration aims to detect sub-GeV WIMPs using Spherical Proportional Counters (SPC). During the past 6 years, the collaboration developed a new 140 cm diameter detector. This detector - larger than the previous generation - is made from stringently selected materials for their radio-purity. The detector construction is discussed. This presentation will be followed by a review of the different methods for characterizations such as W-value, ionization yield measurement and calibration using UV laser, Ar-37, neutron, and gamma sources. The new detector performed a first measurement campaign at the Laboratoire Souterrain de Modane (LSM) in France in 2019 before being moved and installed at SNOLAB. A summary of the commissioning run at the LSM and current installation at SNOLAB will be presented.

Speaker: Alexis Brossard (Queen's University)

PPC_2021_Alexis_Brossard_NEWSG.pdf

16:00 → 17:30 Neutrinos 2

Convener: Anil Thapa

16:00 Majorana Dark Matter and Neutrino mass in a singlet-doublet extension of the Standard Model

A minimal extension of the Standard Model (SM) by a vector-like fermion doublet and three right handed (RH) singlet neutrinos is proposed in order to explain dark matter and tiny neutrino mass simultaneously. The DM arises as a mixture of the neutral component of the fermion doublet and one of the RH neutrinos, both assumed to be odd under an imposed $\mathcal{Z}_2$ symmetry. Being Majorana in nature, the DM escapes from $Z$-mediated direct search constraints to mark a significant difference from singlet-doublet Dirac DM. The other two $\mathcal{Z}_2$ even heavy RH neutrinos give rise masses and mixing of light neutrinos via Type-I Seesaw mechanism. The particle content automatically allows us to extend the model by an anomaly free gauged $U(1)_{B-L}$ symmetry, which brings an additional portal between DM and SM particles. Relic density and direct search allowed parameter space for both the cases are investigated through detailed numerical scan, while collider search strategies are also indicated.

Speaker: Mr Manoranjan Dutta (Indian Institute of Technology Hyderabad)

ppc_manoranjan.pdf

16:15 (Talk Cancelled) Rephasing invariant quartets in texture zero neutrino mass matrix and CP violation

In this article, I have re-investigated the CP invariants relevant at low energy, for all the seven viable ansatze of texture two zero neutrino mass matrix viz. \textbf{A1, A2, B1, B2, B3, B4 }and \textbf{C}, in the flavour basis. It is found that CP invariance for ansatze \textbf{A1, A2, B3, B4} suffices for model to be CP invariant, and in addition, the CP properties, which is defined through the imaginary part of the quartet of elements of neutrino mass matrix, for all the viable ansatz have common origin. The analytical relations of CP invariants in terms of physically measurable parameters have been presented, and subsequently shown that measurable CP phases are not separable. Assuming the neutrinos to be Dirac particle, some useful analytical expressions of Jarlskog rephasing parameter have been deduced in terms of Dirac CP phase for each viable ansatz. In the end, I have calculated the CP invariants for each viable ansatz in the light of neutrino oscillation data and studied the implications for the same.

Speaker: Madan Singh (M. N. S Government College Bhiwani Haryana India)

16:30 Massive sterile neutrinos in the Early Universe: from thermal decoupling to cosmological constraints

We consider heavy sterile neutrinos $\nu_s$ with mass in the range $10~\mathrm{MeV}≤m_s≤m_π∼135~\mathrm{MeV}$, which are thermally produced in the Early Universe, in collisional processes involving active neutrinos, and freezing out after the QCD phase transition. Notably, if these neutrinos decay after the active neutrino decoupling, they generate extra neutrino radiation and contribute to entropy production: they alter the value of the effective number of neutrino species $N_{\mathrm{eff}}$ and $^4\mathrm{He}$ production. We provide a detailed account of the numerical solution of the exact relevant Boltzmann equations. Finally, we also identify the parameter space allowed by current Planck satellite data and forecast the parameter space probed by future Stage-4 ground-based CMB observations, expected to match or surpass BBN sensitivity, improving the existing constraints on the sterile neutrino parameter space in both cases.

Speaker: Leonardo Mastrototaro (INFN - National Institute for Nuclear Physics)

Massive sterile neutrinos in the early universe_from thermal decoupling to cosmological constraints .pdf

16:45 Testing the stability of heavy dark matter with up-coming radio neutrino telescopes

In the next decade, ultra-high-energy neutrinos in the EeV energy range will be potentially detected by next-generation neutrino telescopes. Although their primary goals are to observe cosmogenic neutrinos and to gain insight into extreme astrophysical environments, they have the great potential of indirectly probing the nature of dark matter. In this talk, we study the projected sensitivity of up-coming radio neutrino telescopes, such as RNO-G, GRAND and IceCube-gen2 radio array, to decaying dark matter scenarios. We investigate different dark matter decaying channels and masses, from $10^{7}$ to $10^{15}$ GeV. By assuming the observation of cosmogenic or newborn pulsar neutrinos, we forecast conservative constraints on the lifetime of heavy dark matter particles. We find that these limits are competitive with and highly complementary to previous multi-messenger analyses.

Speaker: Rasmi Enrique Hajjar Muñoz

PPC2021_HDDM_RHajjar.pdf

17:00 Dark Matter in the Type Ib Seesaw Model

We study the connection between the two indications of physics beyond the Standard Model (SM): the masses and mixing of neutrinos and the existence of dark matter (DM). To have a more testable connection, we consider a minimal type Ib seesaw model instead of the traditional type I seesaw model. In the minimal type Ib seesaw model, the effective neutrino mass operator involves two different Higgs doublets and two right-handed neutrinos which form a single heavy Dirac pair. To account for DM, we consider neutrino portal couplings to a dark fermion and a dark scalar. We explore the parameter space of the extended model consistent with both oscillation data and DM relic abundance. Within this framework, we show how DM can be directly related to laboratory experiments when the heavy Diracneutrino mass is around 1~100 GeV.

Speaker: Bowen Fu (University of Southampton)

DM_NP.pdf

17:15 (Talk Cancelled) Constraining Sommerfeld-Enhancement via Inflationary Perturbations: Dark Matter and Neutrino Interactions

In ΛCDM cosmology, Dark Matter (DM) and neutrinos are assumed to be non-
interacting. However, several BSM scenarios require DM-neutrino interaction, leading to

DM-neutrino scattering and annihilation of DM into neutrinos. We investigate this scenario
by analysing the PLANCK-2018 and BOSS-BAO 2014 dataset and constrain strength of such
interactions. We also discuss a particle DM model which gives rise to such viable processes,
we then map the constraints to the parameter space of the model.

Speaker: Anish Ghoshal (L)

Thursday, 20 May

08:30 → 10:30 Plenary: Dark Matter

Convener: John Stupak (University of Oklahoma (US))

08:30 Accelerator-based Searches for Dark Matter: An Overview

Speaker: Andrew James Whitbeck (Texas Tech University (US))

PPC_accelerator_based_DM_whitbeck.pdf

09:00 Astrophysical probes to new physics beyond the Standard Model - EHT and GW experiments

Speaker: Yue Zhao (University of Utah)

09:30 Light Mediators

Speaker: Bhaskar Dutta (Texas A&M University)

PPC_dutta.pdf

10:00 Some Recent Progress on Searches for Sub-GeV Dark Matter

Speaker: Rouven Essig

10:30 → 11:00 Break

11:00 → 12:30 Plenary: Axions

Convener: stefania gori (UC Santa Cruz)

11:00 New Developments in Axion Physics

Speaker: JiJi Fan (Brown University)

PPC_Fan_2021.pdf

11:30 BSM physics with magnetars and neutron star mergers

The dense nuclear matter present in neutron star cores as well as the remnant of a neutron star merger may serve as an ideal environment for the production of axions or other BSM particles. In this presentation I will review two topics: the possible signals of axions in the photon spectrum of magnetars and the role of BSM particles in neutron star mergers. Axions may be produced in the interior of a magnetar and then escape the magnetar, turning into photons in the magnetosphere with some efficiency as a consequence of the Primakoff effect. I will review results which use this axion-induced photon spectrum to constrain the coupling of the axion to nucleons and photons. In the second part of the talk, I will discuss calculations of the axion mean free path in hot, dense nuclear matter that show that axions are not trapped in mergers, and instead cool down the system as they are emitted. On the other hand, other BSM particles could still be trapped in mergers, and would perhaps contribute to evening out temperature gradients in the interior of the merger.

Speaker: Steven Harris (Washington University in St. Louis)

PPC_2021_presentation_harris.pdf

12:00 New Ideas in Lab-based Axion Searches

Speaker: Doojin Kim (University of Florida)

12:30 → 14:00 Lunch

14:00 → 15:30 Axions 1

Convener: Steven Harris (Washington University in St. Louis)

14:00 New Roles of the (QCD) Axion in Dark Matter, Baryogenesis, and Gravitational Waves

We propose a paradigm where the unexplored cosmological evolution, a rotation in the field space, of the QCD axion or an axion-like particle gives rise to the dark matter abundance, the observed baryon asymmetry of the Universe, and/or gravitational waves. The rotation is initiated by explicit Peccei-Quinn symmetry breaking effective in the early Universe. The abundance of axion dark matter is determined by the rotational speed via the mechanism we call kinetic misalignment. With the aid of the Standard Model sphaleron processes (and optionally the neutrino Majorana mass term), the Peccei-Quinn charge associated with the rotation is transferred to the baryon asymmetry. We name these baryogenesis mechanisms by axiogenesis (and lepta-axiogenesis). The paradigm with dark matter and baryogenesis predicts 1) an axion coupling stronger than predicted by the conventional evolution and 2) an electroweak phase transition temperature higher than in the Standard Model (or instead the presence of the neutrino Majorana mass). If the axion couples to a dark photon, this new axion dynamics can also generate gravitational wave signals across the entire range of observable gravitational wave frequencies.

Speaker: Dr Raymond Co (University of Michigan)

Axion_Co_PPC2021.pdf

14:15 Magnetars and Axion-like Particles

Magnetars, with their extreme magnetic fields, are ideal laboratories to constrain axion-like particles. Historically, axions are beyond-the-Standard-Model particles introduced to explain the strong CP problem of QCD. Axion-like particles are generalizations of axions that are ubiquitous in top-down approaches to high-energy physics like string theory. If they exist, they are however difficult to constrain due to their light mass and weak coupling.

Since axion-like particles mix with Standard Model photons in the presence of magnetic fields, they can be investigated through axion-to-photon conversion in the magnetosphere, leading to modifications to the observed photon spectra of magnetars. In this talk, we will discuss the conversion probability of axion-like particles created in the core of magnetars to oscillate into photons as they travel through the magnetosphere. For an arbitrary initial state at the magnetar's surface, we will focus on the effects of the conversion, computing the resulting intensities and polarizations of the photon signal originating from axion-like particles. By comparing with observed luminosities for several magnetars, we will put bounds on the axion-like particle parameter space.

Speaker: Jean-Francois Fortin (Laval University)

ALP.pdf

14:30 Using Radio Observations of Neutron Stars to Probe QCD Axion Dark Matter

Axions represent one of the most promising dark matter candidates to date. Although experimental searches have recently made huge progress, much of the axion parameter space remains unexplored. In this talk, I will show that radio observations of neutron stars (NSs) can be used to search for axion dark matter. I will then explore how dense substructures, called axion miniclusters, can lead to bright radio transients in the Galactic center through their interactions with NSs.

Speaker: Thomas Edwards (Stockholm University)

PPC2021_May.pdf

14:45 ENHANCED Supernova AXION EMISSIVITY BY PIONIC PROCESSES

Axions might be copiously emitted during a supernova explosion, leading to an additional energy-loss channel that would shorten the duration of the neutrino burst. In this context, I will revise the axion bounds from
SN 1987A neutrino observation.

I will present recent results on axions from supernovae including(a) a state-of-the-art calculation of the axion emission via nucleon-nucleon bremsstrahlung;(b) an investigation of the axion emission via pionic Compton processes

Speaker: Alessandro Mirizzi

SN_axion_PPC.pdf

15:00 Supernova bounds on axion-like particles coupled with nucleons and electrons

We investigate the potential of core-collapse supernovae (SNe) to constrain axion-like particles (ALPs) coupled to nucleons and electrons. ALPs coupled to nucleons can be efficiently produced in the SN core via nucleon-nucleon bremsstrahlung and, for a wide range of parameters, leave the SN producing a large ALP flux. For ALP masses exceeding 1 MeV, these ALPs would decay into electron-positron pairs, generating a positron flux. For Galactic SNe the annihilation of the created positrons with the galactic electron background would contribute to the 511 keV annihilation line. Using the observation of this line by the spectrometer SPI (SPectrometer on INTEGRAL), we obtain stringent constraints for the electron-ALP coupling, excluding the range $10^{-18} < g_{ae} < 10^{-11}$ for $g_{ap}\sim 10^{-9}$. Furthermore, ALP decays and subsequent electron-positron annihilations in the extra-galactic medium would yield a contribution to the cosmic X-ray background. Using this allows to set constraints down to the level $g_{ae} \sim 10^{-21}$.

Speaker: Pierluca Carenza (INFN Bari)

Pres_PPC.pdf

15:15 Axion-like Particles from Hypernovae

It was recently pointed out that very energetic subclasses of supernovae (SNe), like hypernovae and superluminous SNe, might host ultra-strong magnetic fields in their core.
Such fields may catalyze the production of feebly interacting particles substantially, changing the predicted emission rates.
Here we consider the case of axion-like particles (ALPs) and show that the predicted large scale magnetic fields in the core contribute significantly to the ALP production, via a coherent conversion of thermal photons.
Using recent state-of-the art SN simulations including magnetohydrodynamics, we find that if the ALPs have masses $m_a \sim {\mathcal O}(10)\, \rm MeV$, their emissivity via magnetic conversions is over two order of magnitude
larger than previously estimated. Moreover, the
radiative decays of these
massive ALPs
would lead to
peculiar delays in the arrival times of the daughter
photons. Therefore, high-statistics gamma-ray satellites can potentially discover MeV ALPs in an unprobed region of the parameter space and shed light on the magnetohydrodinamical nature of the SN explosion.

Speaker: GIUSEPPE LUCENTE (University of Bari)

Lucente_PPC2021.pdf

14:00 → 15:30 BSM with Compact Objects 1

Convener: Aniket Joglekar (UC Riverside)

14:00 (Talk Cancelled) Axion Stars: Towards the Planck Scale

Axion stars are gravitationally-bound, ground-state configurations composed of very large numbers of axion particles. Their macroscopic properties are determined, in large part, by two fundamental energy scales: $m \ll$ eV, the mass of the axion; and $f \gg$ GeV, the decay constant or symmetry-breaking scale. In this talk, I will show how the properties of axion stars derived in previous literature, including the mass-radius relation and stability conditions, cannot be extrapolated to large values of $f \sim M_P \sim 10^{19}$ GeV (the Planck scale). In particular, I will show that as $f$ approaches $M_P$, the usual separation of axion star configurations onto a stable dilute branch and an unstable dense branch breaks down, and that contrary to previous assumptions, states on the dilute branch can decay with very short lifetime when $f > 10^{17}$ GeV. Finally, I will discuss possible detection of axions with large decay constants, which is made difficult (but not impossible!) by the suppression of Standard Model couplings by $1/f$.

Speaker: Dr Joshua Eby (Weizmann Institute of Science)

14:15 Two-Scalar Bose-Einstein Condensates: From Stars to Galaxies

We study the properties of Bose-Einstein Condensate (BEC) systems consisting of two scalars, focusing on both the case where the BEC is stellar scale as well as the case when it is galactic scale. After studying the stability of such systems and making contact with existing single scalar limits, we undertake a numerical study of the two interacting scalars using Einstein-Klein-Gordon (EKG) equations, including both non-gravitational self-interactions and interactions between the species. We show that the presence of extra scalars and possible interactions between them can leave unique imprints on the BEC system mass profile, especially when the system transitions from being dominated by one scalar to being dominated by the other. At stellar scales (nonlinear regime,) we observe that a repulsive interaction between the two scalars of the type $+ \phi_{1}^2 \phi_{2}^2$ can stabilize the BEC system and support it up to high compactness, a phenomenon only known to exist in the +$\phi^4$ system. We provide simple analytic understanding of this behavior and point out that it can lead to interesting gravitational wave signals at LIGO-Virgo. At galactic scales, on the other hand, we show that two-scalar BECs can address the scaling problem that arises when one uses ultralight dark matter mass profiles to fit observed galactic core mass profiles. In the end, we construct a particle model of two ultralight scalars with the repulsive $\phi^2_{1} \phi^2_{2}$ interaction using collective symmetry breaking. We develop a fast numerical code that utilizes the relaxation method to solve the EKG system, which can be easily generalized to multiple scalars.

Speaker: Dan Vagie

PPC2021.pdf

14:30 Gravitational Microlensing by Dark Matter Subhalos and Boson Stars

Multiple microlensing surveys have been conducted to place limits on primordial black holes in nearby dark matter halos. We show that these existing limits on PBHs can be recast to constrain dark matter lenses that are more spatially extended than PBHs. As two representative cases, we consider NFW subhalos and boson stars, which are predicted in many models such as axion miniclusters and axion stars. For the Subaru-HSC survey, we find visible deviations from PBHs limits when the lens size exceeds 0.1 solar radii, and the survey can probe NFW subhalos up to O(100) solar radii and boson stars up to O(1000) solar radii.

Speaker: Zihui Wang (NYU)

PPC.pdf

14:45 Will axions be discovered as oscillons?

Real scalar fields with attractive self-interaction may form self-bound states, called oscillons. These dense objects are ubiquitous in leading theories of dark matter and inflation; of particular interest are long-lived oscillons which survive past 14 Gyr, offering dramatic astrophysical signatures into the present day. In this talk, I will review some of the most striking observables coming from oscillons at late times, and address what kinds of models support this phenomenology.

Speaker: David Cyncynates

Oklahoma2021.key

15:00 Adiabatic contraction of haloes with Bose-Einstein-condensed dark matter

In recent years, Bose-Einstein-condensed dark matter, also called scalar-field dark matter (SFDM), has become a popular alternative to CDM, due to its potential resolution of the small-scale problems faced by CDM. We focus on SFDM with a strong, repulsive self-interaction; the Thomas-Fermi regime of SFDM ("SFDM-TF") which provides a length scale $\sim R_\text{TF}$ below which formation of structure is suppressed. We consider galactic halos in this model and investigate the evolutionary change of their density profiles and rotation curves through the process of adiabatic contraction (AC), as a result of the presence of baryons within these halos. In doing so, we first provide a thorough analysis of the underlying Quantum-Hamilton-Jacobi framework appropriate for SFDM, and the notion of orbits, in order to verify the validity of the assumptions usually required for AC. Then, we calculate the impact of AC onto SFDM-TF halos with various core radii, $R_\text{TF} \sim 0.1 - 1$ kpc, and find that the model exhibits notable differences to the predictions of CDM, or SFDM without self-interaction.

Speaker: Kevin Pils (University of Vienna)

PPC_ACinSFDM.pdf

15:15 Exoplanets as Sub-GeV Dark Matter Detectors

We present exoplanets as new targets to discover dark matter (DM). Throughout the Milky Way, DM can scatter, become captured, deposit annihilation energy, and increase the heat flow within exoplanets. We estimate upcoming infrared telescope sensitivity to this scenario, finding actionable discovery or exclusion searches. We find that DM with masses below the GeV scale can be probed with exoplanets, with DM-proton and DM-electron scattering cross sections down to about 10-37  cm^2, stronger than existing limits by up to six orders of magnitude. Supporting evidence of a DM origin can be identified through DM-induced exoplanet heating correlated with galactic position, and hence DM density. This provides new motivation to measure the temperature of the billions of brown dwarfs, rogue planets, and gas giants peppered throughout our Galaxy.

Speaker: Juri Smirnov (Ohio State University, CCAPP)

Exoplanets as Sub-GeV DM Detectors.pdf

14:00 → 15:30 Collider BSM

Convener: Samuel Homiller (Harvard)

14:00 Signatures of toponium formation in LHC run 2 data

Measurements in top-antitop events at the LHC unraveled some anomalies. We examine the possibility that those reflect some mismodeling in Standard Model top pair-production. While subdominant, so-far neglected toponium contributions yield the additional production of dileptonic systems of small invariant mass and small azimuthal angle separation, which could explain the anomalies. We propose a method to discover toponium in present and future data. This paves the way to further experimental and phenomenological studies, as understanding toponium effects is essential for precision measurements of one of the most important parameters of the Standard Model, the top mass.

Speaker: Ya-Juan Zheng

toponium.pdf

14:15 Flavor anomalies from asymptotic safety

We use the framework of asymptotically safe quantum gravity to derive predictions
for scalar leptoquark solutions to the b → s flavor anomalies. The presence
of an interactive UV fixed point in the system of gauge and Yukawa couplings imposes a set of boundary conditions at the Planck scale, which allows one to determine low-energy values of the leptoquark Yukawa matrix elements. As a consequence, the allowed leptoquark mass range can be significantly narrowed down. We find that a consistent asymptotic safety-driven solution to the b → s anomalies predicts a leptoquark with the mass of 4 - 7 TeV, entirely within the reach of a future hadron-hadron collider.

Speaker: Dr Kamila Kowalska (National Centre for Nuclear Research)

2021.05.20_PPC.pdf

14:30 $R_{D^{(*)}}$, $R_{K^{(*)}}$ and muon $g-2$ anomalies in RPV supersymmetry and the discovery prospect at LHC

In R-parity violating supersymmetric scenario, assuming the third-generation superpartners to be the lightest (calling the scenario RPV3), we show that there are some benchmark scenarios in which RD and / or RK and / or muon g-2 anomalies can be addressed and also can be detected at LHC 14 TeV or future 27 TeV hadron collider. We consider t tau tau or t mu mu for different cases as our final states to be detected at colliders because there is no simple Standard Model (SM) process can have this kind of final state and the background cross-section is thus very small.

Speaker: Fang Xu

PPC2021-FangXu.pdf

14:45 Resonant Leptogenesis and Collider Signals from Discrete Flavor and CP Symmetries

In this talk, I’ll discuss about the production of baryon asymmetry through resonant leptogenesis and phenomological signatures of type-I seesaw scenario with a flavour and a CP symmetry that strongly constrain lepton mixing angles, and both low- and high-energy CP phases. I’ll specially focus on the effect of these symmetries on the collider signals in minimal $U(1)_{B-L}$ model and effective neutrino mass ($m_{\beta\beta}$) in neutrinoless double beta decay ($0\nu\beta\beta$), while also requiring production of the experimentally observed baryon asymmetry ($\eta_B$).

Speaker: Garv Chauhan (Washington University in St. Louis)

PPC_May_21__Leptogenesis_and_Collider.pdf

15:00 Exploring Multilepton Signatures From Dark Matter at the LHC

Limitations on the most general mono-X Dark Matter signature at colliders motivate searches beyond this, such as multilepton plus missing energy signatures. In this talk I present our latest limits on the inert 2-Higgs Doublet model (I2HDM) and Minimal Fermion Dark Matter model (MFDM) for 8/13 TeV pp collisions at the LHC, producing 2-3 leptons plus missing energy final states, using CheckMATE. I will show how 3 lepton final states play an important role, with a leading role in the MFDM case via cascading Higgs decays. We also provide limits and efficiencies for re-interpretation of any scalar of fermion DM model by the community.

Speaker: Arran Charles Freegard (Queen Mary University of London (GB))

Exploring Multilepton Signatures From Dark Matter at the LHC PPC 2021 20_05_21.pdf

15:15 Search for lepton flavor violation at the EIC

The Electron-Ion Collider (EIC) will collide electrons with protons at high energy with unprecedented luminosity. The EIC is being optimized to map out the structure of the proton and nuclei. Its capability also presents another opportunity to search for physics beyond the Standard Model. In this talk, I will discuss the potential sensitivity of the EIC to charged-lepton-flavor violating electron-tau transition within the framework of the Standard Model Effective Field Theory.

Speaker: Kaori Fuyuto (Los Alamos National Laboratory)

PPC2021KaoriFuyuto.pdf

14:00 → 15:30 Higgs/EW Physics 1

Convener: Dr Rahool Barman (Department of Physics, Oklahoma State University, Stillwater, Oklahoma, 74078, USA)

14:00 Off-shell Higgs Couplings in H*→ZZ→ℓℓνν

We explore the new physics reach for the off-shell Higgs boson measurement in the ${pp \to H^* \rightarrow Z(\ell^{+}\ell^{-})Z(\nu\bar{\nu})}$ channel at the high-luminosity LHC. The new physics sensitivity is parametrized in terms of the Higgs boson width, effective field theory framework, and a non-local Higgs-top coupling form factor. Adopting Machine-learning techniques, we demonstrate that the combination of a large signal rate and a precise phenomenological probe for the process energy scale, due to the transverse $ZZ$ mass, leads to significant sensitivities beyond the existing results in the literature for the new physics scenarios considered.

Speaker: Han Qin (University of Pittsburgh)

OffShell_Higgs_PPC2021.pdf

14:15 Directly Probing the Higgs-top Coupling at High Scales

The top-quark Yukawa coupling $y_t$ is the strongest interaction of the Higgs boson in the Standard Model (SM) with $y_t \sim 1$. Due to its magnitude, it plays a central role in Higgs phenomenology in the SM and would be most sensitive to physics beyond the Standard Model. The top Yukawa can be directly measured at the LHC via top pair production in association with a Higgs boson  $t\bar{t}h$. We study new physics effects for the Higgs-top coupling at high scales, using jet substructure techniques. We present the high-luminosity LHC sensitivity to new physics parametrized in the EFT framework and through a general Higgs-top form factor.

Speaker: Roshan Mammen Abraham (Oklahoma State University)

higss_top_coupling_PPC2021.pdf

14:30 Electroweak Restoration at the LHC and Beyond

The LHC is exploring electroweak (EW) physics at the scale EW symmetry is broken. As the LHC and new high energy colliders push our understanding of the Standard Model to ever-higher energies, it will be possible to probe not only the breaking of but also the restoration of EW symmetry. We propose to observe EW restoration in double EW boson production via the convergence of the Goldstone boson equivalence theorem. We measure this convergence through the ratio of differential cross sections for VH production. We present a method to extract this ratio from collider data. With a full signal and background analysis, we demonstrate that the 14 TeV HL-LHC can confirm that this ratio converges to one to 40% precision while at the 27 TeV HE-LHC the precision will be 6%. We also investigate statistical tests to quantify the convergence at high energies. Our analysis provides a roadmap for how to stress test the Goldstone boson equivalence theorem and our understanding of spontaneously broken symmetries, in addition to confirming the restoration of EW symmetry.

Speaker: Samuel Lane (University of Kansas)

ParallelTalk-Samuel-Lane.pdf

14:45 The partonic picture at high-energy lepton colliders

After the triumph of discovering the Higgs boson at the CERN Large Hadron Collider, people are getting increasingly interested in studying the Higgs properties in detail and searching for the physics beyond the Standard Model (SM). A multi-TeV lepton collider provides a clean experimental environment for both the Higgs precision measurements and the discovery of new particles. In high-energy leptonic collisions, the collinear splittings of the leptons and electroweak (EW) gauge bosons are the dominant phenomena, which could be well described by the parton picture. In the parton picture, all the SM particles should be treated as partons that radiated off the beam particles, and the electroweak parton distribution functions (EW PDFs) should be adopted as a proper description for partonic collisions of the initial states. In our work, both the EW and the QCD sectors are included in the Dokshitzer-Gribov-Lipatov-Altarelli-Parisi (DGLAP) formalism to perturbatively resum the potential large logarithms emerging from the initial-state radiation (ISR). I will show the results of QCD jet production as well as some other typical SM processes at a possible high-energy electron-positron collider and a possible high-energy muon collider obtained using the PDFs.

Speaker: Yang Ma (University of Pittsburgh)

PPC2021.pdf

15:00 Multi-TeV Signals of Baryogenesis in Higgs Troika Model

A modest extension of the Standard Model by two additional Higgs doublets - the Higgs Troika Model - can provide a well-motivated scenario for successful baryogenesis if neutrinos are Dirac fermions. Adapting the ``Spontaneous Flavor Violation'' framework, we consider a version of the Troika model where light quarks have significant couplings to the new multi-TeV Higgs states. Resonant production of new scalars leading to di-jet or top-pair signals are typical predictions of this setup. The initial and final state quarks relevant to the collider phenomenology also play a key role in baryogenesis, potentially providing direct access to the relevant early Universe physics in high energy experiments. Viable baryogenesis generally prefers some hierarchy of masses between the observed and the postulated Higgs states. We show that there is a complementarity between direct searches at a future 100 TeV $pp$ collider and indirect searches at flavor experiments, with both sensitive to different regions of parameter space relevant for baryogenesis. In particular, measurements of $D-\bar{D}$ mixing at LHCb probe much of the interesting parameter space. Direct and indirect searches can uncover the new Higgs states up to masses of $\mathcal{O}(10)$ TeV, thereby providing an impressive reach to investigate this model.

Speaker: Dr Matthew Sullivan (Brookhaven National Laboratory)

HiggsTroika.pdf

15:15 Charged Lepton Flavor Violation in General Two-Higgs Doublet Model

The rates of charged lepton flavor violating (cLFV) processes in the Standard Model (SM) are highly suppressed$-$practically zero$-$due to tiny neutrino masses. Therefore, the observation of cLFV phenomena would be an indisputable sign of physics beyond the SM. In this talk, we will discuss cLFV processes in the framework of the general two-Higgs doublet model (g2HDM) without $Z_2$ symmetry. The g2HDM naturally contains flavor violating Higgs couplings, which can induce cLFV transitions. We will cover $\tau$ decays: $\tau\to\mu\gamma$, $\tau\to 3\mu$ , muon decays: $\mu\to e\gamma$, $\mu\to 3 e$, and $\mu\to e$ conversion in nuclei, and reassess the possibility of their potential discovery at the upcoming array of experiments. In particular, we will emphasize the importance of two-loop contributions driven by the extra flavor conserving top Yukawa coupling, $\rho_{tt}$ , which is naturally ${\cal O}(\lambda_t)\sim 1$, and show that these contributions can enhance the cLFV rates to the vicinity of experimental sensitivity.

Speaker: Dr Girish Kumar (National Taiwan University)

cLFV_PPC.pdf

14:00 → 15:30 Strings/Formal 1

Convener: Rashmish Mishra (Harvard University)

14:00 A Tale of Two U(1)s: Kinetic Mixing from Lattice WGC States

We point out that the states required by the Lattice Weak Gravity Conjecture, along with certain genericity conditions, imply the existence of non-vanishing kinetic mixing between massless Abelian gauge groups in the low-energy effective theory. We carry out a phenomenological estimate using a string-inspired probability distribution for the masses of superextremal states and compare the results to expectations from string theory and field theory, estimating the magnitude of kinetic mixing in each case. In the string case, we compute the kinetic mixing in an ensemble of 1858 MSSM-like heterotic orbifolds. From the field theory perspective, we consider compactifications of a $5D$ gauge theory. Finally, we discuss potential loopholes that can evade the bounds set by our estimates.

Speaker: Aditya Parikh (Harvard University)

KineticMixing_PPC_AdityaParikh.pdf

14:15 Constraints on SM from AdS conjectures

We discuss how the AdS distance conjecture applied to the dimensional reduction of the SM in a circle leads to constraints on the mass of the lightest neutrino and to ruling out pure Majorana masses. We also consider an extension of the SM including a quintessence field and show how the generalization of the dS conjecture to AdS vacua leads to similar results. Both constraints can also shed light on the hierarchy problem. Finally, a light fermion swampland conjecture is presented, extending the rationale behind the quantum gravity requirement of light fermions to more general EFTs in D dimensions.

Speaker: Eduardo Gonzalo

ppc2021.pdf

14:30 Cosmological predictions from infinite classical action

The destructive interference of the neighboring field configurations with infinite classical action in the gravitational path integral approach serves as a dynamical mechanism resolving the black hole singularity problem. It also provides an isotropic and homogeneous early universe without the need for inflation.

The path integral approach yields a powerful framework in the quantum theory. It emphasizes Lorentz covariance and allows for the description of non-perturbative phenomena. In the path integral, one sums over all possible configurations of a field(s) $\Phi$ weighted by $e^{iS[\Phi]}$, where $S[\Phi]$ is the classical action of the theory. 
In the Minkowski path integral, the classical action approaching infinity causes fast oscillations in the exponential weight and hence the destructive interference of the neighboring field configurations. Such configurations do not contribute to the physical quantities. Furthermore, in Wick rotated path integral is weighted by $e^{-S[\Phi]}$, and the field(s) configurations on which the action is infinite do not contribute at all. This provides theoretical motivation for the Finite Action Principle, saying that an action of the universe should be finite. This principle has a significant impact on the nature of quantum gravity and the cosmological evolution, once the higher-curvature terms are included. In the framework of Horava-Lifshitz gravity, field configurations with finite classical action describe a universe with a homogeneous and isotropic beginning, without black hole singularities and ghost particles.

Speaker: Jan Chojnacki (University of Warsaw)

Finite_action_presentation (6).pdf

14:45 de Sitter vacua in String Theory with fluxes and antibranes

The swampland de Sitter conjecture reflects the great difficulty in finding de Sitter metastable vacua in the String Theory landscape. Arguably the most debated proposals for such vacua are the seminal work by KKLT and the Large Volume scenario, which both work with fluxes, warped throats and an anti-D3-brane uplift from an AdS vacuum into a near Minkowski positive vacuum. In this talk I will summarise the recent works on the warped throat, its interplay with the brane uplift and the tadpole cancelation problem, and present a new dS solution in a previously unexplored region of parameter space. I will discuss whether this and earlier solutions lie in the String Theory landscape or provide further hints of a swampland conspiracy.

Speaker: Bruno Bento (University of Liverpool)

de Sitter vacua in string theory with fluxes.pdf

15:00 Entanglement Entropy at Critical Points in the Multiverse

Recently the entanglement entropy between universes has been calculated, an entropy which somehow describes the quantumness of a homogeneous multiverse. The third quantization formalism of canonical quantum gravity is used here. I will show improvements of the results in a more general scenario, studying what happens at critical points of the evolution of a classical universe. We infer the relation of that entanglement entropy with the Hubble parameter of single universes.

Speaker: Samuel Barroso Bellido (University of Szczecin)

PPC2021 - Entanglement Entropy - Samuel Barroso.pdf

15:15 Landscape Higgs and sparticle mass predictions from a logarithmic soft term distribution

Recent work on calculating string theory landscape statistical predictions for the Higgs and sparticle mass spectrum from an assumed power-law soft term distribution yields an expectation for m(h)~ 125 GeV with sparticles (save light higgsinos) somewhat beyond reach of high-luminosity LHC. A recent examination of statistics of SUSY breaking in IIB string models with stabilized moduli suggests a power-law for models based on KKLT stabilization and uplifting while models based on large-volume scenario (LVS) instead yield an expected logarithmic soft term distribution. We evaluate statistical distributions for Higgs and sparticle masses from the landscape with a log soft term distribution and find the Higgs mass still peaks around ~125 GeV with sparticles beyond LHC reach, albeit with somewhat softer distributions than those arising from a power-law.

Speaker: Shadman Salam (UNIVERSITY OF OKLAHOMA)

Conference_talk_2021.pdf

14:00 → 15:30 WIMP Models/Detection 1

Convener: Felix Kling (SLAC)

14:00 Where is a Miracle-less WIMP Ruled out?

We examine a real electroweak triplet scalar field as dark matter, abandoning the requirement that its relic abundance is determined through freeze out in a standard cosmological history (a situation which we refer to as `miracle-less WIMP'). We extract the bounds on such a particle from collider searches, searches for direct scattering with terrestrial targets, and searches for the indirect products of annihilation. Each type of search provides complementary information, and each is most effective in a different region of parameter space. LHC searches tend to be highly dependent on the mass of the SU(2) charged partner state, and are effective for very large or very tiny mass splitting between it and the neutral dark matter component. Direct searches are very effective at bounding the Higgs portal coupling, but ineffective once it falls below $\lambda_{\text{eff}} \sim 10^{-3}$. Indirect searches suffer from large astrophysical uncertainties due to the backgrounds and $J$-factors, but do provide key information for $\sim 100$ GeV to TeV masses. We determine the parameter space for this example of miracle-less WIMP dark matter that can be robustly excluded, and which parts of it remain viable.

Speaker: Jason Arakawa

14:15 Constraints on CP-Violating Higgs Portal Majorana Dark Matter

We discuss the viability of higgs portal majorana dark matter in light of current constraints, considering parameter ranges motivated by the thermal relic abundance and the potential GCE annihilation signal. Typically in these models, the mass of the dark matter is tuned so that annihilation occurs through the higgs resonance, in order to get a large enough annihilation signal while avoiding direct detection constraints. By considering a CP violating coupling, we explore an alternative possibility. Here, this hierarchy between annihilation and scattering strengths is achieved by tuning the phase of the dark matter higgs coupling, since the imaginary part of the coupling controls annihilation while the real part controls scattering. By analyzing both the dark matter EFT and several UV completions, we show that there is viable parameter space in the minimal singlet-doublet case, despite strong EDM constraints on the CP violating phase.

Speaker: Katherine Fraser (Harvard University)

PPC_Talk_CPV_Higgs_May_2021.pdf

14:30 Phenomenology of Dark matter in two higgs doublet model with complex scalar singlet

Extensions of the two higgs doublet models with a singlet scalar can easily accommodate all current experimental constraints and are highly motivated candidates for Beyond Standard Model Physics. It can successfully provide a dark matter candidate, explain baryogenesis and provide gravitational wave signals. In this work, we focus on the dark matter phenomenology of the two higgs doublet model extended with a complex scalar singlet which serves as the dark matter candidate. We study the variations of the dark matter observables, i.e relic density and direct detection cross-section, with respect to the model parameters. We obtain a few benchmark points in the light and heavy dark matter mass region. We are also currently studying possible signatures of this model at current and future colliders and the possibility to distinguish this model from other new physics scenarios.

Speaker: Juhi Dutta (University of Hamburg)

JuhiDutta_PPC.pdf

14:45 Scalar Multiplet Dark Matter in a Fast Expanding Universe: resurrection of the desert region

We examine the impact of a faster expanding Universe on the phenomenology of scalar dark matter (DM) associated with SU(2)L multiplets. Earlier works with radiation dominated Universe have reported the presence of desert region for both inert SU(2)L doublet and triplet DM candidates where the DM is under abundant. We find that the existence of a faster expanding component before BBN can revive a major part of the desert parameter space consistent with relic density requirements and other direct and indirect search bounds. We also review the possible collider search prospects of the newly obtained parameter space and show that such region can be probed at the future colliders with improved sensitivity via a stable charged track.

Speaker: Dr Abhijit Kumar Saha (Indian Association for the Cultivation of Science)

PPC 2021.pdf

15:00 Twin Higgs Portal Dark Matter

Many minimal models of dark matter (DM) or canonical solutions to the hierarchy problem are either excluded or severely constrained by LHC and direct detection null results. In particular, Higgs Portal Dark Matter (HPDM) features a singlet scalar minimally coupled to the Higgs, and because the same coupling mediates both thermal freeze out and direct detection the measured dark matter relic abundance leads to definite predictions for direct detection experiments that are now almost entirely excluded. The Twin Higgs solves the little hierarchy problem without coloured top partners by introducing a twin sector related to the Standard Model by a discrete symmetry. In this talk we generalize HPDM to arbitrary Twin Higgs models and introduce Twin Higgs Portal Dark Matter (THPDM), which features a scalar dark matter candidate with an $SU(4)$-invariant quartic coupling to the Twin Higgs scalar sector. Loop corrections motivate the DM mass to be near the Twin Higgs scale, which means DM annihilation proceeds through the unsuppressed Twin Higgs portal coupling while direct detection is suppressed by the pNGB nature of the 125 GeV Higgs. For a standard cosmological history, this mismatch results in a predicted direct detection signal for THPDM that is orders of magnitude below the HPDM prediction with very little dependence on the precise details of the twin sector. Many Twin Higgs models additionally feature asymmetric reheating mechanisms in order to suppress unobserved twin radiation contributions to $\Delta N_{\text{eff}}$. These mechanisms dilute the DM relic abundance, further reducing the expected direct detection signatures to near or below the neutrino floor.

Speaker: Shayne Gryba (University of Toronto)

PPC2021_Shayne_Gryba.pdf

15:15 Constraints on dark matter-nucleon effective couplings in the presence of kinematically distinct halo substructures using the DEAP-3600 detector

DEAP-3600 is a WIMP dark matter direct-detection experiment located deep underground at the SNOLAB facility (Sudbury, Canada) which uses liquid argon as the target material. During the first year of search, zero candidate events were observed, resulting in limits on the isoscalar, spin-independent WIMP-nucleon cross-section above 3.9 x 10-45 cm2 (1.5x10-44 cm2) for 100 GeV/c2 (1 TeV/c2) WIMP masses. This new study reinterprets these results by using a Non-Relativistic Effective Field Theory (NREFT) framework to consider other dark matter-nucleon interactions expressed in terms of effective contact operators (O1,O3,O5,O8 and O11) as well as specific interactions (millicharge, magnetic dipole, electric dipole, and anapole) and isospin-violating scenarios (isovector, xenonphobic) where we achieved world-leading limits for some model parameters. The research further examined how DEAP-3600’s constraints are modified due to the presence of potential substructures in the local dark matter halo, motivated by the observations of stellar distributions from the Gaia satellite and other astronomical surveys.

Speaker: Ariel Zuñiga Reyes (Universidad Nacional Autónoma de México (UNAM))

PPC2021_20May_Ariel.pdf

15:30 → 16:00 Break

16:00 → 17:30 Axions 2

Convener: Raymond Co (University of Michigan)

16:00 The Cosmic Axion Background

Existing searches for cosmic axions relics have relied heavily on the axion being non-relativistic and making up dark matter. However, light axions can be copiously produced in the early Universe and remain relativistic today, thereby constituting a Cosmic axion Background (CaB). In this talk I will discuss the production and detection of a CaB. Prototypical examples of axion sources are thermal production, dark-matter decay, parametric resonance, and topological defect decay. Each of these has a characteristic frequency spectrum that can be searched for in axion direct detection experiments. I will focus on the axion-photon coupling and study the sensitivity of current and future versions of ADMX, HAYSTAC, DMRadio, and ABRACADABRA to a CaB, finding that the data collected in search of dark matter can be repurposed to detect axion energy densities below limits set by measurements of the energy budget of the Universe. In this way, direct detection of relativistic relics offers a powerful new opportunity to learn about the early Universe and, potentially, discover the axion.

Speaker: Dr Jeff Dror (Lawrence Berkeley National Laboratory)

16:15 Constraints on Axions from Cosmic Distance Measurements

Axion couplings to photons could induce photon-axion conversion in the presence of magnetic fields in the Universe. The conversion could impact various cosmic distance measurements such as luminosity distances to type Ia supernovae and angular distances to galaxy clusters in different ways. We consider different combinations of the most updated distance measurements to constrain the axion-photon coupling. Ignoring the conversion in intracluster medium (ICM), we find the upper bounds on axion-photon couplings to be around 510^-12 (nG/B) GeV^-1 for axion mass below 510^-13 eV, where B is the strength of the magnetic field in the intergalactic medium (IGM). When including the conversion in ICM, the upper bound gets stronger and could reach 510^-13 GeV^-1 for ma<510^-12 eV. While this stronger bound moderately depends on the ICM modeling, it is independent of the IGM parameters. All the bounds are determined by the shape of Hubble rate as a function of redshift reconstructable from various distance measurements, and insensitive to today's Hubble rate, of which there is a tension between early and late cosmological measurements.

Speaker: Dr Chen Sun (Tel Aviv University)

16:30 Cosmic Axion Background: the QCD axion as a hot relic

QCD Axions can be produced in various ways in the Early Universe by scatterings and decays from Standard Model particles, forming thus a Cosmic Axion Background that contributes to the abundance of relativistic relics (N_eff). We review in various setups how this is already constrained by present experiments and how it could be observed by future CMB experiments, in particular focusing on the coupling to quarks and leptons, the bounds on the DFSZ model, and also the connection with the Xenon1T excess.

Speaker: Alessio Notari

TalkPPC2021.pdf

16:45 Cosmic Birefringence Triggered by Dark Matter Domination

Cosmic birefringence is predicted if an axion-like particle (ALP) moves after the recombination. We show that this naturally happens if the ALP is coupled to the dark matter density because it then acquires a large effective mass after the matter-radiation equality. We give a simple model to realize this scenario, where dark matter is made of hidden monopoles, which give the ALP such a large effective mass through the Witten effect. The mechanism works if the ALP decay constant is of order the GUT-scale without a fine-tuning of the initial misalignment angle.

Speaker: Masaki Yamada (Tohoku University)

MYamada.pdf

17:00 Axi-Higgs Cosmology

If the electroweak Higgs vacuum expectation value $v$ in early universe is $\sim 1 \%$ higher than its present value $v_0=246$ GeV, the $^7$Li puzzle in BBN and the CMB/$\Lambda$CDM tension with late-universe measurements on Hubble parameter are mitigated. We propose a model of an axion coupled to the Higgs field, named ``axi-Higgs'', with its mass $m_a \sim 10^{-30} - 10^{-29}\,{\rm eV}$ and decay constant $f_a \sim 10^{17} - 10^{18}\,{\rm GeV}$, to achieve this goal. The axion initial value $a_{\rm ini}$ yields an initial $\Delta v_{\rm ini}/v_0 \sim 0.01$ throughout the BBN-recombination epoch and a percent level contribution to the total matter density today. Because of its very large de Broglie wavelength, this axion matter density $\omega_a$ suppresses the matter power spectrum, alleviating the CMB/$\Lambda$CDM $S_8/\sigma_8$ tension with the weak-lensing data. It also explains the recently reported isotropic cosmic birefringence by its coupling with photons. Adding the axion ($m \sim 10^{-22}\,$eV) in the fuzzy dark matter model to the axi-Higgs model allows bigger $\Delta v_{\rm rec}$ and $\omega_a$ to address the Hubble and $S_8/\sigma_8$ tensions simultaneously. The model predicts that $\Delta v$ may be detected by the spectral measurements of quasars, while its oscillation may be observed in the atomic clock measurements.

Speaker: LINGFENG LI (HKUST)

Axi_Higgs_Short.pdf

17:15 The QCD Axion and Unification

The QCD axion is one of the most appealing candidates for the dark matter in the Universe. In this talk, I will discuss the possibility to predict the axion mass in the context of renormalizable grand unified theories where the Peccei-Quinn scale is determined by the unification scale. In the minimal theory with the KSVZ mechanism the axion mass is predicted to be in the range m = (3 - 13) neV. In addition, the minimal theory with the DFSZ mechanism predicts the axion mass to be m = (2 - 16) neV. I will also discuss the axion phenomenology and argue that the ABRACADABRA and CASPEr-Electric experiments will be able to fully probe these predictions.

Speaker: Alexis Plascencia (Case Western Reserve University)

Alexis_Plascencia_PPC2021.pdf

16:00 → 17:30 BSM with Compact Objects 2

Convener: Nirmal Raj (TRIUMF)

16:00 Dark Heating of Neutron Stars : Electron Edition

Dark matter can deposit energy in neutron stars and heat them to temperatures that could be detectable by upcoming infrared telescopes like James Webb Space Telescope (JWST). These observations have a potential to complement and outperform terrestrial direct detection in a large range of dark matter masses. Electrons are also present in neutron stars in significant proportion. Capture due to electrons can aid with the capture of leptophilc dark matter. Ultrarelativistic nature of these electrons make the calculation challenging. In this talk, I will discuss the fomulation of this capture calculation and its interesting consequences for understanding the nature of dark matter.

Speaker: Aniket Joglekar (UC Riverside)

PPC_Aniket_2.pdf

16:15 Mirror Neutron Stars

The paradigm of neutral naturalness suggests the existence of highly non-minimal hidden sectors. In particular, the Mirror Twin Higgs model postulates that some of dark matter is in the form of mirror matter, featuring mirror quarks, leptons and gauge bosons whose masses are a few times heavier than their Standard Model counterparts. I will discuss the possibility that mirror matter could have coalesced into Mirror Neutron Stars, invisible cousins of ordinary neutron stars. I will show how the properties of Mirror Neutron Stars can be determined using repurposed Lattice QCD data, and discuss the gravitational wave signatures of Mirror Neutron Star mergers. Given the impressive reach of current and future gravitational wave detectors, gravitational wave astronomy may offer a novel and powerful means of detecting (or constraining) non-minimal dark sectors.

Speaker: Jack Setford (University of Toronto)

16:30 Low Mass Black Holes from Dark Core Collapse

Unusual masses of the black holes being discovered by gravitational wave experiments pose fundamental questions about the origin of these black holes. Black holes with masses smaller than the Chandrasekhar limit $\approx1.4\,M_\odot$ are essentially impossible to produce through stellar evolution. We propose a new channel for production of low mass black holes: stellar objects catastrophically accrete non-annihilating dark matter, and the small dark core subsequently collapses, eating up the host star and transmuting it into a black hole. The wide range of allowed dark matter masses allows a smaller effective Chandrasekhar limit, and thus smaller mass black holes. We point out several avenues to test our proposal, focusing on the redshift dependence of the merger rate. We show that redshift dependence of the merger rate can be used as a probe of the transmuted origin of low mass black holes.

Speaker: Dr Ranjan Laha (Indian Institute of science (IN))

PPC_2021.pdf

16:45 Black Holes from Atomic Dark Matter

Dissipative dark matter models, a relatively new solution to the dark matter problem, have been suggested to form black holes with a novel mass spectrum in an analogous way to Population III star formation. We present here our efforts to verify this analytic prediction using an "atomic" dark matter model, with microphysics that we have extended into the molecular regime, and utilized, as part of an expansion to the KROME astrochemical software package, in a simple halo collapse scenario. Our results demonstrate the necessity of including molecular chemistry in this model for dark black hole formation, as well as the need for further semi-analytic and eventually full numerical simulations to compare with constraints coming from gravitational wave observatories.

Speaker: Michael Ryan (Penn State University)

2021 PPC Talk.pdf

17:00 Using PySiUltraLight to Model Scalar Dark Matter with Self-Interactions

We introduce PySiUltraLight, a modification of the PyUltraLight code -- which models the dynamical evolution of ultralight axion-like scalar dark matter fields -- now with self-interaction terms. Using a particle mass of $10^{-22} \mathrm{eV}/\mathrm{c}^2$, we show that PySiUltraLight to produces collapsing solitons, spatially oscillating solitons, and exploding solitons which prior analytic work shows will occur with attractive self-interactions. Using our code, we test the maximum mass criteria described in arXiv:1604.05904 for a soliton to collapse when attractive self-interactions are included. We calculate the oscillation frequency as a function of soliton mass and equilibrium radius in the presence of attractive self-interactions. We show that when the soliton mass is below the critical mass ($M_c = \frac{\sqrt{3}}{2}M_{\mathrm{max}}$) described in arXiv:1604.05904 and the initial radius is within a specific range, solitons are unstable and explode. We also analyze both binary soliton collisions and a soliton rotating around a central mass with attractive and repulsive self-interactions. We find that when attractive self-interactions are included, the density profiles get distorted after a binary collision. We also find that a soliton is less susceptible to tidal stripping when attractive self-interactions are included. We find that the opposite is true for repulsive self-interactions in that solitons would be more easily tidally stripped.

Speaker: Noah Glennon (University of New Hampshire)

PPC Presentation (2).key

17:15 Gravitational Decoherence with Applications to Dark Matter Phenomenology

Nontrivial quantum arrangements of matter, such as Schrodinger cat-like states, are sensitive to decoherence from their environment. However, matter that interacts only gravitationally is weakly coupled to its environment, and thus may exhibit slower rates of decoherence. Since dark matter (DM) may only interact via gravity, we explore the decoherence rate of a dark-matter-Schrodinger-cat-state (DMSCS). In the nonrelativistic approximation of gravity, we find that a superposition of distinct DM density profiles can undergo decoherence from the scattering of nearby standard model (SM) particles on observable timescales. In addition, when considering light bosonic DM like an axion, one can conceive of a superposition of the phase of oscillation of the scalar (axion) field, requiring a truly relativistic formalism of gravitational scattering. We derive such a formalism and find that for typical DM populations in the Milky Way, a DMSCS of the axion phase can maintain quantum coherence for exponentially long times, while exotic configurations including DM near a black hole and dense boson stars can experience rapid decoherence. This can have potential observable consequences for direct detection experiments that are sensitive to the axion’s phase, such as haloscopes which rely on resonant cavities to detect axions. This talk will be based on the work in Refs. 2005.12287, 2012.12903, and 2103.15892.

Speaker: Itamar Allali

PPC2021_Decoherence.pdf

16:00 → 17:30 DM: Lab-based Searches

Convener: Christopher Verhaaren (University of California, Irvine)

16:00 Probing new physics at the LUXE experiment

The proposed LUXE experiment at the DESY aims to probe QED at the nonperturbative regime in collisions between high-intensity laser pulses and high-energy electron or photon beams. This setup also provides a unique opportunity to search for physics beyond the standard model. In this talk we show that by leveraging the large photon flux generated at LUXE, one can probe axion-like-particles (ALPs) up to a mass of 350 MeV and with photon coupling of 3x10^{-6} GeV^{-1}. This reach is comparable to FASER2 and NA62. In addition, we will discuss other probes of new physics such as the ALP-electron coupling.

Speaker: Yotam Soreq (Technion- Israel Institute of Technology (IL))

2021_05_PPC21.pdf

16:15 Forward Physics Facility

A rich physics program remains unexplored in the far-forward region at the LHC. The Forward Physics Facility (FPF) is a proposal to enlarge an existing cavern in the far-forward region of ATLAS to house a suite of experiments with groundbreaking new capabilities for neutrinos, long-lived particle searches, milli-charged particle searches, QCD, dark matter, dark sectors, and cosmic rays. The FPF will be located 500 m from the ATLAS interaction point. It is shielded from the ATLAS interaction point by 100 m of concrete and rock, creating an extremely low-background environment, ideal for many standard model studies and new physics searches. In this talk, we describe the FPF’s location and general features, its physics potential in the HL-LHC era, and topics for further study.

Speaker: Felix Kling (SLAC)

FPF@PPC-05_21.pdf

16:30 Detecting Dark Matter with Far-Forward Emulsion and Liquid Argon Detectors at the LHC

New light particles may be produced in large numbers in the far-forward region at the LHC and then decay to dark matter, which can be detected through its scattering in far-forward experiments. In the talk, we will discuss the discovery potential of such far-forward searches for light dark matter scattering off electrons or nuclei in an emulsion or liquid argon detector placed on the beam collision axis during HL-LHC. For illustration, we will focus on a popular example of invisibly-decaying dark photons, which decay to dark matter through 𝐴′→𝜒𝜒, while further prospects for probing BSM interactions of neutrinos will also be presented. These results motivate the construction of far-forward emulsion and liquid argon (FLArE) detectors, as well as a suitable location to accommodate them, such as the proposed Forward Physics Facility.

Speaker: Sebastian Trojanowski

DMscat_STrojanowski.pdf

16:45 Paleo-Detectors - Digging for Dark Matter and Neutrinos

Paleo-Detectors are natural minerals which record damage tracks from nuclear recoils over geological timescales. Minerals commonly found on Earth are as old as a billion years, and modern microscopy techniques may allow to reconstruct damage tracks with nanometer scale spatial resolution. Thus, paleo-detectors would constitute a technique to achieve keV recoil energy threshold with exposures comparable to a kiloton-scale conventional "real-time" detector. In this talk, I will discuss the potential of paleo-detectors for the direct detection of dark matter as well as for detecting low-energy neutrinos as are e.g. emitted by core collapse supernovae or our Sun. Furthermore, the age of the minerals provides the ability to look back across Gyr-timescales, giving paleo detectors the unique ability to probe changes in the cosmic ray rate or the galactic supernova rate over such timescales as well as dark matter substructure Earth might have encountered during its past few trips around our Galaxy.

Speaker: Sebastian Baum (Stanford University)

Baum_PPC.pdf

17:00 Searching for light dark matter at Fermilab's proton-fixed target experiment: DarkQuest

Accelerator-based searches for dark matter provide a unique opportunity to expand the search for particle dark matter to the sub-GeV mass regime. In this region, there are exciting opportunities to search for dark sector signatures, mediators and the dark matter itself, that are unconstrained. DarkQuest is a proton fixed-target experiment that would use a high-intensity beam of 120 GeV protons to produce dark sector mediators. These mediators will interact feebly with the SM and decay into visible states with displaced lepton, photon and hadron decay signals. DarkQuest will exploit the short baseline and compact spectrometer of the current beam dump experiment at Fermilab, SpinQuest, to search for these decays. Because it builds on existing accelerator and detector infrastructure, it offers a powerful yet low-cost experimental initiative that can be realized on a short timescale. In this talk we will discuss the current detector design, proposed upgrades and recent studies on the signal topology and the detector acceptance.

Speaker: Yongbin Feng (Fermi National Accelerator Lab. (US))

DQ_PPC_0520_v1.pdf

17:15 Higgsino Dark Matter in Electron Electric Dipole Moments

Higgsinos are a particularly compelling form of dark matter, and are on the verge of detection by multiple current experimental avenues. They can arise in models with decoupled scalars that enjoy the benefits of depending on very few parameters while still explaining gauge coupling unification, dark matter, and most of the hierarchy between the Planck and electroweak scales, and they remain undetected to past experiments. My talk will cover the reach for current and upcoming electron electric dipole moment experiments to observe higgsino dark matter models.

Speaker: Benjamin Sheff

Sheff_PPC.pdf

16:00 → 17:30 Higgs/EW Physics 2

Convener: Matthew Sullivan (University of Kansas)

16:00 Higgs Flavor and Multi-Higgs Production

While precision measurements of the Higgs at the LHC continue to confirm its Standard Model-like nature, many of its properties, in particular its couplings to light quarks and to itself, remain essentially unconstrained. Di-Higgs production is well known to be a direct probe of the self coupling, but as I will argue, it is also a powerful probe of Higgs flavor. In models where enhanced Yukawas arise from new scalars with large couplings to light quarks, gigantic di-Higgs — and even tri-Higgs — production rates can be obtained, which can be used to constrain or discover these theories. In this talk, I’ll motivate such theories and describe how they avoid constraints from flavor while enhancing the Higgs Yukawa couplings to light quarks by orders of magnitude. I will then demonstrate that Multi-Higgs production is the most stringent constraint on the Higgs Yukawas in this context, setting limits on the down Yukawa at roughly 30 times its Standard Model value. I will also show that the currently unexplored triple Higgs production topology could be a potential discovery channel for a variety of extended Higgs sectors at the LHC — including not only models where extra Higgses couple to light quarks, but also popular theories where they couple predominantly to the the top quark.

Speaker: Samuel Homiller (Harvard)

210520_hh_flavor_homiller.pdf

16:15 Electroweak Phase Transition with an SU(2) Dark Sector

We consider a non-Abelian dark SU(2) model where the dark sector couples to the Standard Model (SM) through a Higgs portal. We investigate two different scenarios of the dark sector scalars with Z2 symmetry, with Higgs portal interactions that can introduce mixing between the SM Higgs boson and the SM singlet scalars in the dark sector. We utilize the existing collider results of the Higgs signal rate, direct heavy Higgs searches, and electroweak precision observables to constrain the model parameters. The SU(2) partially breaks into U(1) gauge group by the scalar sector. The resulting two stable massive dark gauge bosons and pseudo- Goldstone bosons can be viable cold dark matter candidates, while the massless gauge boson from the unbroken U(1) subgroup is a dark radiation and can introduce long-range attractive dark matter (DM) self-interaction, which can alleviate the small-scale structure issues. We study in detail the pattern of strong first-order phase transition and gravitational wave (GW) production triggered by the dark sector symmetry breaking, and further evaluate the signal-to-noise ratio for several proposed space interferometer missions. We conclude that the rich physics in the dark sector may be observable with the current and future measurements at colliders, DM experiments, and GW interferometers.

Speaker: Hongkai Liu (PITT)

Hongkai_PPC.pdf

16:30 Di-Higgs resonance searches in weak boson fusion

We examine the weak boson fusion (WBF) production of exotic heavy Higgs states with subsequent decay into 125 GeV Higgs bosons. We include contributions from the gluon fusion production channel and study the interplay of both production modes to improve the discovery potential at the LHC. We observe that in scenarios with isospin singlet mixing in the Higgs sector, resonant di-Higgs production in the WBF mode becomes a phenomenologically relevant channel at small mixing angles, and the inclusion of weak boson sideline can lead to a sizeable improvement in the discovery potential.

Speaker: Dr Rahool Barman (Department of Physics, Oklahoma State University, Stillwater, Oklahoma, 74078, USA)

WBF-diHiggs_PPC-2021.pdf

16:45 Higgs to Charm Quarks in Vector Boson Fusion plus a Photon

Probing the charm Yukawa coupling is very important to confirm Higgs-fermion interactions and search for deviations from the Standard Model (SM), yet extremely challenging due to enormous QCD background. In this study, we examine the sensitivity of probing Higgs-charm coupling at Large Hadron Collider (LHC) via vector boson fusion with a photon radiation. This additional photon provides an extra handle in triggering and helps suppress gluon-rich background. With a proposed trigger strategy and utilizing multivariate analysis, we find a projected sensitivity of about 5 times the SM charm Yukawa coupling at 95% C.L. at High Luminosity LHC (HL-LHC). Our result is comparable and complementary to existing projections at HL-LHC.

Speaker: Sze Ching Iris Leung (University of Pittsburgh)

Hcc_PPC2021.pdf

17:00 Collider and GW complementarity in the 2HDM

We study electroweak phase transition and resultant GWs of a CP conserving 2HDM with a softly broken $Z_2$ symmetry. We analysed the parameter space of both type I and type II 2hdm without relying on any decoupling limit. We observe $M_{H^\pm} \approx M_H$ or $M_{H^\pm} \approx M_A$ favours SFOEWPT in 2HDM. In addition to di-Higgs production, scalar to fermion decay channel is also important to probe phase transition behaviour in 2HDM. We also comment about the shape of potential leading to SFOEWPT in 2hdm.

Speaker: AJAY Kaladharan (Oklahoma State University)

R2HDM_GW (1).pdf

17:15 Searching for Heavy Higgses decaying into SM and Supersymmetric final states

We search specifically for the heavy resonant scalars (H/A) decaying via $H\to hh$, $H\to t\bar{t}$ and $(b\bar{b})H\to \tau\tau$ final states, at the HL-LHC. After performing multivariate analysis using the BDT algorithm in various final states, we set upper limits on the production cross-section of a heavy scalar times its branching ratio into final state products for different heavy scalar masses values. Finally, we translate these limits and put strong constraints on the $m_A-tan\beta$ parameter space in the context of Minimal Supersymmetric Standard Model (MSSM). We further explore the supersymmetric (susy) final states coming from MSSM Higgs decaying via neutralinos and charginos, collectively called electroweakinos. They give rise to mono-(h/Z) + missing energy final states. We consider backgrounds coming from Standard Model (SM) and susy processes. The susy backgrounds have not been considered in this kind of analysis earlier, which comes from direct electroweakino production via SM mediators. The case of wino-like long-lived chargino decaying from MSSM Higgs is also discussed. They improve the sensitivity in disappearing charged track searches at the LHC because of the boost received from heavy Higgs bosons.

Speaker: Mr Amit Adhikary (Centre for High Energy Physics, Indian Institute of Science, Bangalore 560012, India)

PPC2021_AmitAdhikary.pdf

16:00 → 17:30 Strings/Formal 2

Convener: Jason Kumar

16:00 Superheavy Dark Matter from String Theory

I argue that generic features of string compactifications, namely a high scale of supersymmetry breaking and one or more epochs of modulus domination, can accommodate superheavy neutralino dark matter with a mass around 10^10−10^11 GeV. Interestingly, this mass range may also explain the recent detection of ultra-high-energy neutrinos by IceCube and ANITA via dark matter decay.

Speaker: Rouzbeh Allahverdi (University of New Mexico)

PPC21.pdf

16:15 The Price of Curiosity: Information Recovery in de Sitter Space

Recent works have revealed that the fine-grained entropy of a non-gravitating subsystem, when entangled with a gravitating region, can receive contributions from so-called quantum extremal islands. Applied to black holes, this reproduces the unitary Page curve for Hawking radiation. In this talk, I will show how these results can be applied to the thermal radiation measured by a static observer in de Sitter space. Focusing on JT gravity, I will emphasize the necessity of going beyond the thermal equilibrium of the Bunch-Davies state. We will see that a quantum extremal island can contribute to the fine-grained entropy, suggesting unitarity of the radiation, but this comes at a price: when the island appears a singularity forms that a static observer will eventually hit.

Speaker: Lars Aalsma

PPC 2021.05.20.pdf

16:30 The Standard Model Quiver from Singular de Sitter String Compactifications

With the advent of the string landscape, the realisation of the Standard Model in general string theory compactifications to 4D has become a primary focus. This talk concerns novel constructions of the Standard Model in global set-ups of type IIB Calabi-Yau compactifications. We argue that the Standard Model quiver can be embedded into Calabi-Yau threefolds through orientifolded D3 branes at del Pezzo singularities dPn with n ≥ 5. To illustrate our approach, we explicitly construct three distinct local dP5 models via a combination of Higgsing and orientifolding. This procedure reduces the original dP5 quiver model to the Left-Right symmetric model with three families of quarks and leptons and a Higgs sector to further break the symmetries to the Standard Model gauge group. Subsequently, we discuss an explicit embedding of the local model in a global Calabi-Yau compactification. We show that moduli can be stabilised in 4-dimensional de Sitter vacua with uplifting provided by T-branes.

Speaker: Andreas Schachner (Cambridge University)

16:45 Swampland conjectures and single field inflation in modified cosmological scenarios

Swampland Conjectures have attracted quite some interest in the Cosmological Community. They have been shown to have wide ranging implications , like Constraints on Inflationary Models, Primordial Black Holes, Dark Energy to name a few. Particularly, their implications on Single Field Inflationary Models in General Relativity Based Cosmology has gathered huge attention. Swampland Conjectures in their usual form have been shown to be incompatible with these kind of Single Field Models, or have been shown to induce severe Fine Tuning in these Inflationary Models for them to be consistent with the Conjectures. In this work, we show that a Large Class of Single Field Inflationary Models can in fact bypass the problems faced by Inflationary Paradigms in GR Based Cosmology. We use the Exact Solution Approach to Inflation for the same purpose and show how String Theoretic Motivations of the Swampland Conjectures can be in perfect symphony with various Single Field Inflationary Models in Modified Cosmological Scenarios.

Speaker: Oem Trivedi (Ahmedabad University)

17:00 Lorentz Invariance from Locality of Massless Spin 2

It is known that local, Lorentz invariant, unitary theories involving particles with spin 1 demand
that the matter sector they couple to are organized by internal physical symmetries and the as-
sociated charge conservation, while spin 3/2 demands supersymmetry. However, the introduction
of a spin 2 graviton does not obviously demand new symmetries of the matter sector (although it
does demand a universal coupling). In recent work we relaxed the assumption of Lorentz boost symmetry, while maintaining a basic notion of locality that there is no instantaneous signaling at a distance. In order to avoid potential problems with longitudinal modes of the graviton, we chose to project them out, leaving only two degrees of freedom. This nevertheless leaves a large classes of theories that a priori may violate Lorentz boost invariance. By requiring the tree-level
exchange action be local, consistency demands that the Lorentz boost symmetry must be satisfied by the graviton and the matter sector, which in turn recovers general relativity uniquely at this
order of analysis. In this sense, the Lorentz boost symmetry can be seen to be an underlying physical symmetry that is demanded of the graviton and matter sectors, analogous to internal symmetries of theories involving spin 1, a fact which is usually taken for granted.

Speaker: Jacob Litterer (Tufts University)

JLittererSpin2.pdf

16:00 → 17:30 WIMP Models/Detection 2

Convener: Michael Fedderke (Stanford University)

16:00 The Galactic potential and dark matter density from angular stellar accelerations

We present an approach to measure the Milky Way (MW) potential using the angular accelerations of stars in aggregate as measured by astrometric surveys like Gaia. Accelerations directly probe the gradient of the MW potential, as opposed to indirect methods using e.g. stellar velocities. We show that end-of-mission Gaia stellar acceleration data may be used to measure the potential of the MW disk at approximately 3σ significance and, if recent measurements of the solar acceleration are included, the local dark matter density at ∼2σ significance. Since the significance of detection scales steeply as t^(5/2) for observing time t, future surveys that include angular accelerations in the astrometric solutions may be combined with Gaia to precisely measure the local dark matter density and shape of the density profile.

Speaker: Dr Malte Buschmann (Princeton University)

16:15 Cosmic-ray antiprotons in the AMS-02 era: A sensitive probe of dark matter

Cosmic-ray antiprotons are a remarkable diagnostic tool for the study of astroparticle physics’ processes in our Galaxy. While the bulk of measured antiprotons is consistent with a secondary origin, the precise data of the AMS-02 experiment provides us with encouraging prospects to search for a subdominant primary component, e.g. from dark matter. In this presentation, we discuss limits on heavy dark matter as well as a tentative signal from annihilation of dark matter with a mass 􏰀of around 100 GeV. We emphasize the special role of systematic errors that can affect the signal. In particular, correlated errors in the AMS-02 data that originate from uncertainties in the cross sections for cosmic-ray absorption in the detector have a large impact on data interpretation.

Speaker: Dr Jan Heisig (Université catholique de Louvain (UCL))

Heisig_PPC_May2021.pdf

16:30 Hints for decaying dark matter from S8 measurements

Recent weak lensing surveys have revealed that the direct measurement of the parameter combination S8 = σ8 (Ωm/0.3)^0.5-- measuring the amplitude of matter fluctuations on 8 Mpc/h scales -- is ∼3σ discrepant with the value reconstructed from cosmic microwave background (CMB) data assuming the ΛCDM model. In this talk, I discuss that it is possible to resolve the tension if dark matter (DM) decays with a lifetime of Gamma^{-1} ∼ 55 Gyrs into one massless and one massive product, and transfers a fraction ε ∼ 0.7 % of its rest mass energy to the massless component. The velocity-kick received by the massive daughter leads to a suppression of gravitational clustering below its free-streaming length, thereby reducing the σ8 value as compared to that inferred from the standard ΛCDM model, in a similar fashion to massive neutrino and standard warm DM. Contrarily to the latter scenarios, the time-dependence of the power suppression and the free-streaming scale allows the 2-body decaying DM scenario to accommodate CMB, baryon acoustic oscillation, growth factor and uncalibrated supernova Ia data. Based on arXiv:2008.09615

Speaker: Guillermo Franco Abellán (Laboratoire Univers et Particules de Montpellier (LUPM))

Presentation_GFA_PPC.pdf

16:45 Nonthermal hot DM from early matter dominated epoch and S_8 anomaly.

abstract : Decay of the inflaton or moduli which dominated the energy density of the universe at early times leads to a matter to radiation transition epoch. We consider nonthermal sterile dark matter (DM) particles produced as decay product during such transitions. The particles have a characteristic energy distribution—that associated with decays taking place in a matter dominated universe evolving to radiation domination. We primarily focus on the case when the particles are hot dark matter, and study their effects on the cosmic microwave background (CMB) and large scale structure (LSS), explicitly taking into account their nonthermal momentum distribution.

we explore the possibility that the 'S_8 -tension' is due to a non-thermal hot dark matter (HDM) fractional contribution to the universe energy density leading to a power suppression at small-scales in the matter power spectrum. Taking the specific example of a sterile particle produced from the decay of the inflaton during a matter dominated era, we find that from Planck only the tension can be reduced below $2\sigma$.

Speaker: Mr Ravi kumar sharma Sharma (indian institute of strophysics bangalore)

17:00 Constraints on Dark Matter Microphysics from Dwarf Galaxies

As luminous tracers of small dark matter halos, ultra-faint dwarf galaxies offer a unique window into dark matter physics. In this talk, I will describe how our census of these faint systems places stringent constraints on microphysical dark matter properties including its warmth, Standard Model couplings, and de Broglie wavelength. I will also describe recent work that combines dark matter constraints from dwarf galaxies and strong gravitational lensing, and new simulations that highlight the effects of self-interacting dark matter in Milky Way-like systems.

Speaker: Ethan Nadler (Stanford University)

PPC 2021.pdf

17:15 Viscous Self-Interacting Dark Matter and Accelerated Expansion of the Universe

Self-Interacting Dark Matter (SIDM) is a lucrative candidate to address the small-scale issues faced by the collisionless cold dark matter. We propose that the collisional nature of the SIDM particles on the small scales can lead to dissipative effects. We estimate the shear and bulk viscosity of SIDM using the kinetic theory in relaxation time approximation. We investigate the effect of SIDM dissipation on cosmic evolution and find that $ \sigma/m $ constraints on SIDM from astrophysical data provide sufficient viscosity to account for the observed cosmic acceleration. Furthermore, we also found that the energy dissipation from the viscous SIDM fluid was small at a large redshift but became important at the recent epochs of cosmic evolution (when the Universe is dominant by the non-linear structure). Consequently, the viscous SIDM fluid can also explain the low redshift cosmological observations without any need for the extra dark energy component. The entire analysis is independent of any specific particle physics motivated model for SIDM.

Speaker: Mr Arvind Kumar Mishra (Physical Research Laboratory, Ahmedabad, India)

Arvind@PPC(2021).pdf

Friday, 21 May

08:30 → 10:30 Plenary: Precision/Flavor

Convener: Gordon Kane (University of Michigan)

08:30 Rare Processes and Precision Measurements

Speaker: Alexey Petrov (Wayne State University)

Petrov_PPC2021.pdf

09:00 Searches for Exotic Physics with ATLAS and CMS

Speaker: Gabriel Facini (University of Warwick (GB))

20210521_ATLASCMSSearchFocusLLP.pdf

09:30 Physics at LHCb

Speaker: Sheldon Stone (Syracuse University (US))

OKla-2021-LHCb.pdf

10:00 New physics and precision at the energy frontier

Speaker: Laura Reina (Florida State University (US))

ppc21.pdf

10:30 → 11:00 Break

11:00 → 12:30 Plenary

Convener: Dorival Gonçalves (Oklahoma State University)

11:00 Challenges in Flavor Physics

Speaker: Dean Robinson (Lawrence Berkeley National Laboratory (LBL))

ppc_flavor19.pdf

11:30 HIggs at the HL-LHC

Speaker: Tao Han (University of Pittsburgh)

2021-PPC.pdf

12:00 The Visible Sector

Speaker: Gordon Kane (University of Michigan)

OKLAHOMA.pdf

OKLAHOMA.pptx

12:30 → 12:40 PPC 2022

Convener: Bhupal Dev (Washington University in St. Louis)