Invisibles 2021 Workshop

31 May 2021, 09:00 → 4 Jun 2021, 22:00 Europe/Madrid

Online

The Invisibles21 virtual Workshop will take place from May 31 to June 4, 2021, after the Invisibles21 School. This is the annual meeting of the Horizon 2020 Marie Curie ITN network HIDDeN, which continues the series of “Invisibles” events started in 2012 (Horizon 2020 Marie Curie ITN network Invisibles, Horizon 2020 Marie Curie ITN network Elusives and the Horizon 2020 RISE network InvisiblesPlus).

The focus of the workshop will be on "Neutrinos, Dark Matter, Axions and other Elusives".

• Invisible particles: neutrinos, axions, WIMPs;
• Invisibles at colliders: Beyond Standard Model searches;
• Invisibles in astrophysics and cosmology: dark matter searches, black holes, gravitational waves and the origin of Cosmic Rays.

Note: The workshop talks will be streamed and available afterwards through the HIDDeN YouTube channel: https://www.youtube.com/channel/UCmjgtR6aH7eph8u_WQkzRBg 

Talks are by invitation only, except for PhD students: they are welcome to apply during the registration process to participate in the PhD forum with a 5 min. plenary talk complemented with a poster on the same subject. Everyone is also welcome to request a poster contribution. Poster contributions may be accompanied by a video presentation of it of up to 10 mins. 

Important dates 

• April 12th, 2021: Deadline for student applications for "PhD Forum Talk + Poster Contribution". Applications for "Poster Contribution" only may also be accepted afterwards.

• May 3rd, 2021: Registration deadline.

The Invisibles21Workshop is organised in the context of the Horizon 2020 funded project HIDDeN. HIDDeN is a European ITN project (H2020-MSCA-ITN-2019//860881-HIDDeN) focused on revealing the (a)symmetries we have yet to discover, hence hidden (a)symmetries, and the particles on which they act, in particular the invisible sector, made of neutrinos, dark matter and other elusive particles. It has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 860881-HIDDeN”. 

Conference secretariat: Rebeca Bello, Chabely Prats, Mónica Vergel.

Email: invisibles21@uam.es. 

Phone: +34 912 999 892

 

          

Monday, 31 May

14:50 → 15:00 Welcome: Invisibles21 Workshop Welcome

15:30 → 16:00 "The future of collider physics: selected aspects"

Speaker: Beate Heinemann (DESY and University of Freiburg (Germany))

16:00 → 16:30 "Naturalness motivations for BSM physics"

Speaker: Anson Hook (University of Maryland)

AH_Invisibles.pdf

16:30 → 17:00 Coffee Chat

17:00 → 17:30 "Status of flavor physics"

Speaker: Yuval Grossman (Cornell)

invisibles–2021_Grossman.pdf

17:30 → 18:06 PhD Forum

17:30 Positivity bounds on Minimal Flavor Violation

Effective field theories are a very powerful mean to describe theories at energies well below a certain cutoff scale. However, not all points in the parameter space spanned by their coefficients allow for a UV completion that is both unitary and analytic, and various bounds have been derived in the literature. These bounds attain particular phenomenological relevance when applied to the Standard Model Effective Field Theory. The latter is a framework to which any BSM model containing modes heavier than the EW scale, where the Higgs phase transition happen, can be reduced at sufficiently low energies. I will discuss to what extent are these constraints in the Standard Model Effective Field Theory compatible with the Minimal Flavor Violation hypothesis. Since in this setting the coefficients of higher dimensional operators are expressed in terms of Yukawa matrices, I will show how this dependence reflects on the final parameter space the theory is allowed to span.

Speaker: Emanuele Gendy Abd El Sayed (DESY)

Invisibles_poster.pdf

17:36 Lepton Flavor Violation in b→sℓ1ℓ2 processes

Some New Physics scenarios that can explain the hints of Lepton Flavor Universality Violation (LFUV) observed in the B-meson decays also predict Lepton Flavor Violating (LFV) decay modes. We explore minimalistic scenarios involving leptoquark states at the $\mathcal{O}(\mathrm{TeV})$ scale which are consistent with low energy flavor physics observables. We show that the upper bound on LFV decay modes is already close to the experimental limit. Additionally the direct searches at LHC translate into a lower bound on $B\to K^{(*)}\mu\tau$ or $\Lambda_b\to\Lambda\mu\tau$ channels, a prediction that can be probed experimentally to test the validity of the proposed scenarios.

Speaker: Florentin Jaffredo (CNRS)

poster_v4.pdf

slides.pdf

17:42 Lepton universality tests with dineutrino modes

$SU(2)_L$-invariance links charged dilepton $\bar{q}\,q^\prime\,\bar{\ell}\,\ell$ and dineutrino $\bar{q}\,q^\prime\,\bar{\nu}\,\nu$ couplings.
This connection can be established using SMEFT and holds model-independently if only SM-like left-handed light neutrinos are present. This allows to perform complementary experimental tests of lepton universality and charged lepton flavour conservation with flavour-summed dineutrino observables.
It was recently shown in arXiv:2010.02225 that rare $|\Delta c|=|\Delta u|=1$ dineutrino transitions
constitute excellent null tests of the SM and signals of new physics can be just around the corner.

In this talk we present the phenomenological implications of this interplay between dineutrino and dilepton modes in different flavour systems, including charm and $B$-physics, and provide predictions
for i) universality and ii) for charged lepton flavour conservation that can be tested at $e^+ e^-$-machines including Belle II.

Speaker: Rigo Bause (TU Dortmund)

invisibles_2021_poster_Rigo_Bause.pdf

invisibles_2021_talk_Rigo_Bause.pdf

17:48 More light on Higgs flavor at the LHC: Higgs couplings to light quarks through h+γ production

Higgs production in association with a photon at hadron colliders is a rare process, not yet observed at the LHC. We show that this process is sensitive to significant deviations of Higgs couplings to first and second generation SM quarks (particularly the up-type) from their SM values, and use a multivariate neural network analysis to derive the prospects of the High Luminosity LHC to probe deviations in the up and charm Higgs Yukawa couplings through $h + \gamma$ production.

Speaker: Jose Manuel Cano (IFT UAM-CSIC)

JMCano_Invisibles21_poster.pdf

JMCano_Invisibles21_slides.pdf

17:54 Fermion mass hierarchies from vector-like families with an extended 2HDM and a possible explanation for the electron and muon anomalous magnetic moments

We study an extended 2 Higgs doublet model (2HDM) in which the Standard Model (SM) Yukawa interactions are forbidden due to a global $U(1)^\prime$ symmetry, but may arise via mixing with vector-like families. In this model, the hierarchical structure of Yukawa couplings of quarks and leptons in the SM arises from the heavy masses of the fourth and fifth vector-like families. Within this model, we consider various non-standard contributions to the electron and muon anomalous magnetic moments. We first consider the $W$ exchange at one-loop level, consistent with the $\mu \rightarrow e \gamma$ constraint, and show that it yields a negligible contribution to both electron and muon anomalous magnetic moments. We then consider Higgs scalar exchange, together with vector-like leptons, at one-loop level and show that it is possible to have non-standard contributions to the electron and muon anomalous magnetic moments within the $1\sigma$ constraint of certain experiments. We present some benchmark points for both the muon and the electron anomalies, together with some numerical scans around these points, which indicate the mass regions of the Higgs scalars of the 2HDM in this scenario.

Speaker: Huchan Lee (The university of Southampton)

Poster_HuchanLee_Invisibles21.pdf

Presentation_HuchanLee_Invisible21.pdf

18:00 Charting the Fifth Force Landscape

In recent years particle physics research has undergone somewhat of a phase transition, looking increasingly towards hidden sectors and the feebly interacting frontier. In this talk I will introduce a new approach to parameterising dark sector forces, underpinned by the Källén-Lehman representation, in which the effects of any general scalar fifth force are captured by a single positive-definite spectral function. Using this language, I will demonstrate how the effects of loop-level forces can be simply obtained, without needing to explicitly perform loop calculations. I will also show how experimental observables can be expressed in completely general terms, facilitating the straightforward extraction of limits to any specific model. Finally, I will discuss how this framework opens the possibility to speculatively probe violations of unitarity, causality or locality within hidden sectors

Speaker: Hannah Banks (University of Cambridge)

Charting the Fifth Force Landscape.pdf

poster.pdf

18:06 → 18:36 "Lepton Flavour in Colliders: status and prospects"

Speaker: Shikma Bressler (Weizmann Institute of Science (IL))

2021_05_21_Invisibles21.pdf

Tuesday, 1 June

15:00 → 15:30 "Neutrino mass-mixing parameters, circa 2021"

Speaker: Eligio Lisi (INFN, Bari, Italy)

Lisi_Invisibles_2021.pdf

15:30 → 16:00 PhD Forum

15:30 An on-shell perspective on neutrino oscillations and non-standard interactions

We apply on-shell amplitude techniques to the study of neutrino oscillations in vacuum, focussing on processes involving W bosons. We start by determining the 3-point amplitude involving one neutrino, one charged lepton and one W boson, highlighting all the allowed kinematic structures. The result we obtain contains terms generated at all orders in an expansion in the cutoff scale of the theory, and we explicitly determine the lower dimensional operators behind the generation of the different structures. We then use this amplitude to construct the 4-point amplitude in which neutrinos are exchanged in the s-channel, giving rise to oscillations. We also study in detail how flavor enters in the amplitudes, and how the PMNS matrix emerges from the on-shell perspective.

Speaker: Gabriel Massoni Salla (Sao Paulo University)

GMS_onshell_perspective.pdf

GMS_onshell_perspective_poster.pdf

15:36 Enhanced violation of Leggett-Garg Inequality in three flavour neutrino oscillations via non-standard interactions

Neutrino oscillations occur due to non-zero masses and mixings and most importantly
they are believed to maintain quantum coherence even over astrophysical length scales. In the present study, we explore the quantumness of three flavour neutrino oscillations by studying the extent of violation of Leggett-Garg inequalities (LGI) if non-standard interactions are taken into account. We report an enhancement in violation of LGI with respect to the standard scenario for appropriate choice of NSI parameters.

Speaker: Sheeba Shafaq (School of Physical Sciences, Jawaharlal Nehru University)

SheebaShafaq_Invisibles21_poster.pdf

SheebaShafaq_Invisibles21_talk.pdf

15:42 Constraining the tau-neutrino transition magnetic moment at DUNE

Current limits for the tau-neutrino transition magnetic moment to a sterile neutrino are far weaker than its electron and muon counterparts. In this poster/talk I discuss on-going work to investigate possible constraints on the transition magnetic moment between the tau neutrino and an O(MeV) sterile neutrino at DUNE: the proposed neutrino-beam experiment at FermiLab. I compare this with existing limits and limits at proposed neutrino experiments such as SHiP.

Speaker: Albert Zhou (KIT)

zhou_poster.pdf

zhou_pres.pdf

15:48 GeV scale neutrinos: meson interactions and DUNE sensitivity

The simplest extension of the SM to account for the observed neutrino masses and mixings is the addition of at least two singlet fermions (or right-handed neutrinos). If their masses lie at or below the GeV scale, such new fermions would be produced in meson decays. Similarly, provided they are sufficiently heavy, their decay channels may involve mesons in the final state. Although the couplings between mesons and heavy neutrinos have been computed previously, significant discrepancies can be found in the literature. The aim of this paper is to clarify such discrepancies and provide consistent expressions for all relevant effective operators involving mesons with masses up to 2 GeV. Moreover, the effective Lagrangians obtained for both the Dirac and Majorana scenarios are made publicly available as FeynRules models so that fully differential event distributions can be easily simulated. As an application of our setup, we numerically compute the expected sensitivity of the DUNE near detector to these heavy neutral leptons.

Speaker: Manuel González-López (Universidad Autónoma de Madrid)

ManuelGonzalezLopez_Invisibles21_Poster.pdf

ManuelGonzalezLopez_Invisibles21_Talk.pdf

15:54 Flavoured leptogenesis and type-II seesaw mechanism with two Higgs triplet scalars

Type-II seesaw mechanism has been widely studied already as the link between neutrino mass generation beyond Standard Model (SM) and leptogenesis. In this study, the SM is minimally extended by two triplet Higgs scalars (with hypercharge $Y=2$), with one triplet having complex vacuum expectation value (vev) to impose generality. The triplet vevs are bounded by the $\rho$-parameter constraint as, $\omega_{1}$, $\omega_{2}\ll v$, where $v$ is the vev of the SM Higgs doublet. The neutrino mass gets generated by two massive triplet Higgs, without any right-handed neutrino in this model. On the other hand, purely flavoured leptogenesis is achieved when the triplet Higgs scalar of mass $M_{T}\sim10^{9}$ GeV, undergoes out-of-equilibrium bi-lepton decay, specially through lepton loop. The lepton asymmetries further get converted into baryon asymmetry via nonperturbative sphaleron process. This study shows the efficiency of phenomenologically promising type-II seesaw mechanism with two triplet scalars, in order to estimate the baryon asymmetry through fully flavoured leptogenesis. Here, baryon asymmetry of the order $\sim 10^{-10}$ is achieved through the stated model, which falls within the experimentally obtained range. The dependence of the baryon asymmetry on the branching ratios of triplet scalar is also studied here. To further increase the predictability of the mechanism, two-zero texture- $B_{2}$ is introduced in the neutrino mass matrix. The neutrino mass matrix elements are bounded by the latest neutrino oscillation parameter data and the sum of neutrino mass is taken to be $\Sigma_{i} m_{i}<0.16$ eV. The efficacy of two-zero texture $B_{2}$ in two Higgs triplet scenario is mentioned.

Speaker: Sreerupa Chongdar (National Institute of Technology Rourkela, India)

schongdarposter.pdf

schongdarppt.pdf

16:00 → 16:30 "Physics with Forward LHC Neutrino Detectors"

Speaker: Felix Kling (SLAC)

FPF@Invisibles-06_21.pdf

16:30 → 17:00 Coffee Chat

17:00 → 17:30 “Coherent elastic neutrino-nucleus scattering: status and prospects”

Speaker: Francesca Dordei (Universita e INFN, Cagliari (IT))

cevns_invisible.pdf

17:30 → 18:00 PhD Forum

17:30 NUCLEUS outer veto prototype for the CEʋNS detection at nuclear reactors

The detection of Coherent Elastic Neutrino-Nucleus Scattering (CEʋNS) represents an experimental challenge because of its unique signature: a nuclear recoil with low energy in range of 10 to 100 eV on average.
This process, largely unexplored until today, could probe physics beyond the Standard Model such as non-standard neutrino interactions and electromagnetic form factors.

NUCLEUS is a nuclear reactor neutrino experiment conceived for CEʋNS detection using a new type of ultra-low energy threshold (below 20 eV) cryogenic calorimeters based on the CRESST technology.

Thanks to the greatly enhanced CEʋNS cross-section (10 to 1000 times greater than the standard neutrino detection channels), NUCLEUS is aiming for its first phase to develop a miniaturized detector of only 10 g target mass.

The detector will be installed at the Very Near Site (VNS), a shallow depth experimental hall located in between of the 2 nuclear reactors of the Chooz B power plant in France, with reactor baselines of 72 m and 102 m.
At this location with shallow-overburden, a highly efficient background suppression system will be fundamental.

It will include an active cryogenic outer veto designed to work in anti-coincidence with the target detector in order to identify and reject gammas due to the environmental radioactivity and neutron interactions, events that can mimic the CEʋNS signal.
In this "talk+poster" I will present the preliminary promising results obtained with our cryogenic outer veto prototype.

Speaker: Beatrice Mauri (CEA/IRFU/DPhP)

Invisibles21_poster_MAURI.pdf

Invisibles21_talk_MAURI.pdf

17:36 Search for neutrinoless double beta decay of 128-Te with the CUORE experiment

The CUORE experiment is a ton-scale array of TeO$_2$ cryogenic bolometers located at the underground Gran Sasso National Laboratories, in Italy. The CUORE detector consists of 988 crystals operated as source and detector at a base temperature of $\sim$10 mK. The primary goal of CUORE is the search for neutrinoless double beta (0$\nu\beta\beta$) decay of $^{130}$Te, but thanks to its large target mass and ultra-low background it is suitable for the study of other rare processes as well, one of these being the 0$\nu\beta\beta$ decay of another tellurium isotope: the $^{128}$Te. The $^{128}$Te is an attractive candidate for the search of this process, due to its high natural isotopic abundance of 31.75%. The transition energy at Q$_{\beta\beta}=(866.6\pm0.9)$ keV lies in a highly populated region of the energy spectrum, dominated by the contribution of the $2\nu\beta\beta$ decay of $^{130}$Te and the natural $\gamma$ background due to environmental radioactivity. With its ton-scale mass, CUORE is able to achieve a factor >10 higher sensitivity to the 0$\nu\beta\beta$ decay of this isotope with respect to past direct experiments.

Speakers: Valentina Dompè (GSSI / INFN-LNGS / La Sapienza Università di Roma), Valentina Dompè

poster_Invisibles21_VDompè.pdf

slides_Invisibles21_VDompè.pdf

17:42 Novel Active Noise Cancellation Algorithms for CUORE

The Cryogenic Underground Observatory for Rare Events (CUORE) experiment is an ongoing search for neutrinoless double beta decay located at the Gran Sasso National Laboratory (LNGS) in Italy. Recent work has found that the CUORE calorimeters are sensitive to acoustic and seismic events originating from outside the detector at LNGS. To measure the effect of these mechanical disturbances on the calorimeter signals, microphones and accelerometers were installed around the CUORE cryostat. Existing adaptive algorithms which use auxiliary devices (e.g. accelerometers) to remove microphonic noise from high-purity germanium detectors may be changed to remove excess noise from low-temperature calorimeters. Here I will present how said changes can be implemented for noise removal from calorimeters instrumented with neutron transmutation doped (NTD) germanium detectors or transition edge sensors (TES) and demonstrate how this new adaptive algorithm improves the energy resolution of these devices.

Speaker: Kenny Vetter (University of California, Berkeley)

Poster_Invisibles21_Vetter.pdf

Slides_Invisibles21_Vetter.pdf

17:48 Neutrinoless Double Beta Decay with R-Parity Violating SUSY and Light Neutralinos

The exotic contributions of sfermions, neutralinos, and gluinos to neutrinoless double beta decay (0νββ) in the presence of R-parity violating (RPV) couplings have been known for some time. In this talk and poster, we update the sensitivity of 0νββ to the lightest mostly-bino neutralino over the neutralino mass range 0.1 MeV - 10 TeV, constraining the RPV coupling in a way that is compatible with collider searches for SUSY partners. A neutralino lighter than the average momentum transfer of 0νββ has not been constrained in this way before. We compare to other experimental constraints on the RPV coupling and neutralino mass.

Speakers: Patrick Bolton (University College London), Patrick Bolton

poster-pb-corrected.pdf

poster-pb.pdf

talk_pb.pdf

17:54 Relaxing Cosmological Neutrino Mass Bounds with Unstable Neutrinos

At present, cosmological observations set the most stringent bound on the neutrino mass scale. Within the standard cosmological model ($\Lambda$CDM), the Planck collaboration reports $\sum m_\nu < 0.12\,\text{eV}$ at 95 % CL. This bound, taken at face value, excludes many neutrino mass models. However, unstable neutrinos, with lifetimes shorter than the age of the universe $\tau_\nu \leq t_U$, represent a particle physics avenue to relax this constraint.
Motivated by this fact, we present a taxonomy of neutrino decay modes, categorizing them in terms of particle content and final decay products. Taking into account the relevant phenomenological bounds, our analysis shows that 2-body decaying neutrinos into BSM particles are a promising option to relax cosmological neutrino mass bounds.
We then build a simple extension of the type I seesaw scenario by adding one sterile state $\nu_4$ and
a Goldstone boson $\phi$, in which $\nu_i \to \nu_4 \, \phi$ decays can loosen the neutrino mass bounds up to $\sum m_\nu \sim 1\,\text{eV}$, without spoiling the light neutrino mass generation mechanism. Remarkably, this is possible for a large range of the right-handed neutrino masses, from the electroweak up to the GUT scale. We successfully implement this idea in the context of minimal neutrino mass models based on a $U(1)_{\mu-\tau}$ flavor symmetry, which are otherwise in tension with the current bound on $\sum m_\nu$.

Speaker: Stefan Sandner (IFIC)

Invisbiles21_Presentation.pdf

Invisibles21_Poster.pdf

18:00 → 18:30 "Charting New Directions in the BSM Landscape with Neutrino Experiments"

Speaker: Ian Shoemaker (Virginia Tech)

18:30 → 19:30 Social Activity: "Colours and Flavours”

Wednesday, 2 June

15:00 → 15:30 "Indirect searches for dark matter"

Speaker: Tracy Slatyer

Invisibles21_Slatyer_IndirectDetection.pdf

15:30 → 16:00 PhD Forum

15:30 Phenomenological consequences of an interacting multicomponent dark sector

We consider a dark sector with multiple dark fermions interacting under a dark U(1) gauge interaction, mediated by a massless dark photon, with no kinetic mixing. Apart from this self interaction, a portal interaction, mediated by scalar messengers, exists between dark fermions and SM fermions. The species which contribute to the total matter relic density of the Universe, are the stable dark fermions. To complement the existing limits on such a dark sector framework coming from precision physics, astrophysics, and collider physics, we assess the viability of this setup using cosmological observables and current direct detection limits. In studying the early Universe history under this scenario, we track both the number densities of the dark fermions, and the temperatures of the dark and visible sector reservoirs, by numerically solving a system of Boltzmann equations which account for number-changing processes and entropy exchanges between the reservoirs. We determine the couplings and masses in the dark sector framework which are consistent with the known matter relic density and CMB constraint on extra radiation components. Meanwhile, potential signals from direct detection searches are assumed to be mainly driven by dipole and charge radius interactions, between the dominant dark matter component and nuclei, mediated by long-range SM and dark photon mediators. We find that limits on these DM-nuclei effective interaction operators from null results on direct detection, are competitive with projected limits from the magnetic dipole moment of leptons and cooling of stellar systems.

Speaker: Jan Tristram Acuña (SISSA)

acuna_invisibles21_5min.pdf

AFU_poster_Invisibles21_acuna.png

15:36 Searches for Dark Photons at Belle II

Belle II is a B-Factory experiment designed to produce precision measurements of CP violation in the weak sector as well as search for Beyond the Standard Model particle physics. The $e^{+}e^{-}$ collisions are created by the SuperKEKB accelerator which has achieved a world record of instantaneous luminosity of $2.4 \times 10^{34} {\text{cm}^{-2}}{\text{s}^{-1}}$. One of the highest priorities for the early data of the experiment is the search for dark photons that decay to dark matter. A dark photon is a mediator within the dark sector which mixes with the Standard Model (SM) photon. The experimental signature is a single energetic photon observed in the detector. A dark photon would produce an excess of events in the single photon recoil mass. A particularly challenging case is when the visible photon carries the full beam energy, which corresponds to a low-mass dark photon. There is a significant background from the SM process $e^{+}e^{-}\rightarrow \gamma\gamma$, where one of the photons is missed due to detector imperfections. This has motivated us to study the structure of the sub-detectors and compare the data and Monte Carlo response. By understanding the photon detection sensitivity of the sub-detectors, we will estimate the background for dark photon studies. This talk will discuss the ''single photon search'' and the approach to quantifying this background.

Speaker: Miho Wakai (University of British Columbia)

MihoWakai_Invisibles2021.pdf

MihoWakai_Invisibles_poster.pdf

15:42 Semi-visible dark photons as a solution to (g−2)μ

In light of the recent measurement of the anomalous muon magnetic moment which confirms a tension with the standard model, we revisit the light vector boson explanation of this discrepancy and show that there is still available parameter space in the context of models with co-annihilating dark matter or dark heavy neutral fermions. Reinterpreting the bounds from B factories with a semi-visible dark photon, we show that they may be an excellent place to look for hints of this new physics.

Speaker: Asli Abdullahi (University of Durham)

semivisDP_Invisibles21_AA.pdf

semivisDP_poster_AA.pdf

15:48 Dark Photon Searches at the PADME Experiment

Massive photon-like particles are predicted in many extensions of the Standard Model as possible portals to a hidden sector where Dark Matter is secluded [1]. They are vector bosons mediating the interaction between ordinary and dark matter and can be produced in different processes through a feeble mixing to the photon. The PADME experiment [2], conducted at Laboratori Nazionali di Frascati of INFN, searches for a signal of a Dark Photon $A’$ in the reaction $e^+e^−\rightarrow\gamma A’$ in a positron-on-target experiment. For this purpose, the missing mass spectrum of annihilation final states with a single photon is analysed. Collecting approximately 1013 POT, a sensitivity on the interaction strength down to 0.001 is achievable in the mass region M($A’$) <23.7 MeV.
In addition, the PADME approach allows searches for any new particle produced in $e^+e^−$ collisions through a virtual off-shell photon, such as long lived Axion-Like-Particles (ALPs), proto-phobic X bosons, Dark Higgs, etc. In the talk, the scientific program of the experiment and its current status will be illustrated.

References
[1] B. Holdom, Phys. Lett B 166, 196 (1986).
[2] V. Kozuharov and M. Raggi, Adv. High Energy Phys. 2014, 959802 (2014).

Speaker: Elizabeth Long (Sapienza Univerisity of Rome, INFN - National Institute for Nuclear Physics)

PADMEPoster.pdf

SearchingForDarkPhotonAtPADME.pdf

15:54 Dark Matter in light flavored U(1)' gauge models

In this talk I will discuss the possibility of obtaining a viable Dark Matter candidate in the context of a gauged, anomaly-free, flavor dependent U(1)' symmetry. I will discuss the relic density constraints, as well as the direct detection and neutrino physics input to the model. Possible detection at future experiments, such as SuperCDMS SNOLAB, is also considered.

Speaker: León Manuel García de la Vega (Universidad Nacional Autonoma de Mexico)

invisiblesPhDForum.pdf

poster_invisibles21.pdf

16:00 → 16:30 "New Techniques for Direct Detection of Light Dark Matter"

Speaker: Yonit Hochberg (Hebrew University)

YH_Invisibles21.pdf

16:30 → 17:00 Coffee Chat

17:00 → 17:30 "Dark matter bound states"

Speaker: Kalliopi Petraki (Sorbonne Université)

Petraki_Invisibles21_DarkMatterBoundStates.pdf

17:30 → 18:00 PhD Forum

17:30 Accidental Dark Matter models

In this talk I will give an overview of my research work on Accidental Dark Matter models. I briefly discuss some general aspects of Dark Matter model building and I show examples of specific models I have studied.

Speaker: Giacomo Landini (INFN - National Institute for Nuclear Physics)

Giacomo Landini Poster Invisibles 2021.pdf

Giacomo Landini Talk Invisibles 2021.pdf

17:36 Constraints on CP-Violating Higgs Portal Majorana Dark Matter

In this talk I 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 types of 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, I explore an alternative possibility where this hierarchy between annihilation and scattering strengths can be 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, I will show 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)

Fraser_Invisibles2021_talk_to_accompany_poster.mp4

Fraser_invisibles_poster.pdf

Invisibles_talk_CPV_Higgs.pdf

17:42 A model independent probe for elusive dark sectors at future experiments

The existence of a SM-neutral and light dark sector coupled to the visible sector via irrelevant portal interactions was considered in $2012.08537$. Such scenarios tend to be common in dark matter models arising as various extensions of the Standard Model.
The authors of $2012.08537$ use the conformal behaviour of this dark sector at energies $\Lambda_{IR} << E << \Lambda_{UV}$ to study their phenomenology in a model independent way, where $\Lambda_{UV}$ is the scale at which the heavy mediator exchange generates the portal operators and $\Lambda_{IR}$ is the infrared scale.
Our work extends the work of $2012.08537$ as we derive bounds from various classes of future facilities aimed at detecting long lived particles (transverse detectors like MATHUSLA, CODEX-b etc. as well as fixed target experiments like SHiP etc.) to complement the bounds obtained in $2012.08537$ by showing an improved reach on small $\Lambda_{IR}$.
We hope this study would encourage that future experimental analyses be performed for generic dark sectors without a focus on a particular benchmark model.

Speaker: Sonali Verma (Scuola Normale Superiore Pisa)

invisibles21_poster_SVerma.mp4

invisibles21_poster_SVerma.pdf

invisibles21_slides_SVerma.pdf

17:48 Invisible traces of conformal symmetry breaking

In our work we study the cosmological phase transition (PT) in a conformal extension of the Standard Model (SM). The model considered is called SU(2)cSM, it extends the SM gauge group by an additional hidden SU(2)$_X$ gauge group, and a scalar doublet (whilist singlet under SM gauge group). The tree-level potential has no mass terms, all the masses are generated via the Coleman-Weinberg mechanism. The new gauge boson $X$ can be considered as a dark matter candidate, also the model may be extended in order to include a mechanism of baryogenesis as well. Due to the large supercooling a strong gravitational waves (GWs) signal can be generated during the PT.
We carefully investigate the PT, taking into account recent developments in order to improve existing results and provide meaningful information for the forthcoming LISA searches.
We study the RG improved potential, distinguish between percolation and nucleation temperature of the bubbles, discuss the hydrodynamics, i.e possible runaway, and present resulting GW spectra. We briefly comment on the dark matter phenomenology.

Speaker: Maciej Kierkla (University of Warsaw)

maciej_kierkla_slides.pdf

mk_poster.png

17:54 Mergers as a Probe of Particle Dark Matter

Unusual masses of black holes being discovered by gravitational wave experiments pose fundamental questions about the origin of these black holes. More interestingly, black holes with masses smaller than the Chandrasekhar limit ($\sim$ 1.4 $M_{\odot}$) are essentially impossible to produce through any standard stellar evolution. Primordial black holes, with fine-tuned parameters and with no well-established formation mechanisms, are the most discussed explanation of these objects. In this talk, I will discuss a simple production channel of these low mass black holes. Particle dark matter with no antiparticle counterpart, owing to their interaction with stellar nuclei, can catastrophically accumulate inside compact stars and eventually transmute them to sub-Chandrasekhar mass black holes, ordinarily forbidden by the Chandrasekhar limit. I will point out several avenues to test the origin of these low mass black holes, concentrating on the cosmic evolution of the binary merger rate. I will show that binary merger rates especially at high redshift are distinctively different for primordial and transmuted black holes, and measurement of these merger rates by the imminent gravitational wave detectors can conclusively test the origin of low mass black holes.

Speaker: Anupam Ray (Tata Institute of Fundamental Research, India)

Anupam_Invisibles_poster.pdf

Anupam_Invisibles_talk.pdf

18:00 → 18:30 "Primordial black hole dark matter"

Speaker: Guillermo Ballesteros (IFT UAM-CSIC)

PBH Invisibles_Ballesteros.pdf

Thursday, 3 June

15:00 → 15:30 "Novel signatures of dark matter bound formation"

Speaker: Maxim Pospelov

Invisibles2021_ M. Pospelov.pdf

15:30 → 16:00 PhD Forum

15:30 One-loop corrections to ALPs effective couplings

I present the one-loop contributions to ALP-SM couplings stemming from effective ALP operators, including all finite corrections. The complete leading-order (dimension five) effective linear Lagrangian is considered. These corrections can become a useful tool to test ALP-SM interactions which are hard to measure via their loop impact on other observables that are more experimentally constrained. As an example, ALP-WW interaction is hardly observed at tree level, but competitive constraints are obtained via its contribution to ALP-γγ interaction at one-loop order. These results are of particular impact on non-resonant LHC and accelerator searches of ALP coupling to γγ, ZZ, Zγ, WW and fermions.

Speakers: Bonilla Jesús (UAM/ IFT ), Jesus Bonilla

Jesus-Bonilla_PhDforum_One-loop corrections to ALPs effective couplings.pdf

Jesus-Bonilla_Poster_One-loop corrections to ALPs effective couplings.pdf

15:36 Revisiting K→πa decay

The theoretical calculation for pseudo--scalars hadronic decays $P \to M a$, with the Axion-Like-Particle escaping
the detection, is reviewed. While one-loop penguin contributions are usually considered, tree-level processes have
most often been overlooked in literature. Following the Brodsky/Lepage approach the tree-level contribution to the
ALP pseudo--scalar decay is estimated. Assuming generic ALP couplings to SM fermions, the latest NA62 results for
the $K^+ \to \pi^+ a$ decay and the present and future KOTO results for the $K^0 \to \pi^0 a$ decay are used to
study the tree-level vs one-loop interplay and provide updated bounds on the ALP--fermion Lagrangian sector.

Speaker: Alfredo Walter Mario Guerrera (University of Padua)

Guerrera_Poster_Final.pdf

Guerrera_Poster.pdf

Guerrera-Presentation.pdf

New_Guerrera_Poster.pdf

15:42 Searching for pseudo-Nambu-Goldstone boson dark matter production in association with top quarks

Pseudo-Nambu-Goldstone bosons (pNGBs) are attractive dark matter (DM) candidates since they are coupled to the Standard Model (SM) predominantly through derivative interactions. Thereby, they naturally evade the strong existing limits inferred from DM direct detection experiments. Working in an effective field theory that includes both derivative and non-derivative DM-SM operators, we perform a detailed phenomenological study of the Large Hadron Collider reach for pNGB DM production in association with top quarks. Drawing on motivated benchmark scenarios as examples, we compare our results to other collider limits as well as the constraints imposed by DM (in)direct detection experiments and the relic abundance. Furthermore, we explore implications on the viable parameter space of pNGB DM. In particular, we demonstrate that the sensitivity of DM direct detection experiments can be achieved via loop-induced interactions. The search strategies we discuss can serve as a starting point for dedicated experimental analyses by the ATLAS and CMS collaborations.

Speaker: Stefan Schulte (Max Planck Institute for Physics (Munich))

Schulte_Poster_Invisibles.pdf

Schulte_Slides_Invisibles.pdf

15:48 Novel signatures of pseudo-Goldstone dark matter

In my talk and poster, I will motivate dark matter from composite Higgs models. In this framework, the dark matter candidate is a pseudo-Nambu Goldstone boson (pNGB) of a spontaneously broken symmetry, that lies naturally at the electroweak scale. In non-minimal scenarios, other pNGBs arise which can be lighter than the dark matter candidate and therefore affect its phenomenology significantly (a possibility which has been often disregarded in the literature). I will motivate this scenario in concrete composite Higgs models and discuss the emerging signatures at direct and indirect detection experiments. I will finally present the complementarity between these and future collider probes.

Speakers: Maria Ramos, Maria Ramos (LIP)

MRamos_poster.mp4

MRamos_poster.pdf

MRamos_talk.pdf

15:54 Primordial gravitational waves revealed by a spinning axion

A fast-spinning axion can dominate the Universe at early times and generates the so-called kination era. The presence of kination imprints a smoking-gun spectral enhancement in the primordial gravitational-wave (GW) background. Current and future-planned GW observatories could constrain particle theories that generate the kination phase. Surprisingly, the viable parameter space allows for a kination era at the TeV scale and generates a peaked spectrum of GW from either cosmic strings or primordial inflation, which lies inside ET and CE windows.

Speaker: Peera Simakachorn (Universität Hamburg and DESY)

invisibles21_simakachorn_poster.pdf

invisibles21_simakachorn_talk.pdf

16:00 → 16:30 "Looking for Imprints of Microphysics on Large Scale Structure"

Speaker: Chanda Prescod-Weinstein (University of New Hampshire)

16:30 → 17:00 Coffee Chat

17:00 → 17:30 "An even lighter QCD axion"

Speaker: Pablo Quilez Lasanta (DESY)

An even lighter QCD axion - Invisibles 21.pdf

17:30 → 18:00 "Superconducting axion string and Cosmic axion background"

Speaker: Hitoshi Murayama (CERN - DG/CS)

18:00 → 19:00 OUTREACH TALK: "Einstein, agujeros negros y ondas gravitacionales."

Convener: Gabriela Gonzalez

Friday, 4 June

15:00 → 15:30 "Solar Neutrinos: Is There a Future?"

Speaker: John Beacom (Ohio State University)

Beacom-Invisibles21.pdf

15:30 → 16:00 PhD Forum

15:30 Easing the sigma8-tension with nu-DM interactions

The $\sigma_8$-tension of Planck data with weak lensing and redshift surveys is one of the main problems with the $\Lambda$CDM model of cosmology. We show that the tension can be alleviated by introducing an interaction between dark matter and neutrinos. We model the interaction using a linear Boltzmann treatment, introducing a novel implementation that for the first time uses the full massive neutrino hierarchy. We also provide upper limits on the interaction cross-section between neutrinos and dark matter.

Speaker: Markus Rasmussen Mosbech (The University of Sydney)

Invisibles21_Poster_final.pdf

Invisibles21_Presentation.pdf

15:36 Supernova constraints on dark flavor sectors

I will present recent application of the SN 1987A cooling bound to set a constraint on dark flavored sectors. This is possible thanks to the fact that the protoneutron stars are hot and dense environments where hyperons can be efficiently produced. Therefore a decay of the form Λ→nX0, where X^0 is a new bosonic dark particle, will be severely constrained. I will explain the ingredients required and the application to flavored (massless) dark photons, axions and ALPs.

Speaker: Jorge Terol Calvo (Inst. Astrophys. of Canary Islands (ES))

Invisibles_poster.pdf

Invisibles_Talk.pdf

15:42 Cuspy to cored galaxy profiles from late-time dark matter oscillations

The reason why dwarf spheroidal and other galaxies appear to have a lower central density than predicted from N-body simulations based on LCDM cosmology is still an open question.
Apart from the possibility that baryonic physics could play a leading role in shaping the inner density profile of galaxies, the most popular new-physics explanation is to assume heat transfer caused by dark matter (DM) self-interactions.
Here, we present a novel mechanism of solving the core-cusp problem through reactivation of DM annihilation in galaxies at late times. This can happen in asymmetric DM models when there is a very small DM-number violating mass term that causes oscillations between DM and its antiparticle.
Using analytical methods as well as N-body galactic simulations, we show that this mechanism can convert cuspy DM profiles into cored ones for light fermionic DM with mass in the range (0.1 − 1) GeV and a lighter mediator into which the DM can annihilate.
We identify regions of parameter space where annihilation of DM particles is more efficient than elastic scattering at reducing the inner density of the DM profile. Dark matter annihilation is therefore a qualitatively distinct alternative to the mechanism of elastic self-interacting dark matter for addressing the cusp-core problem.

Speaker: Matteo Puel (McGill University)

Poster_Invisibles21_MPuel.pdf

Talk_Invisibles21_MPuel.pdf

15:48 Abundance of LIGO/Virgo Black Holes from Quasar Microlensing

Could Dark Matter (DM) be made of Primordial Massive Black Holes (PMBHs) with such mass as detected by LIGO? The amplitude and frequency of gravitational microlensing can be used to detect PBHs. However, they can be mixed with the normal stellar population that can also contribute to microlensing. To separate the contributions from both populations, we perform numerical simulations to study the possible degeneracy of a bimodal distribution of masses with a single-mass function plus a smooth component. This degeneracy is supported by analytical calculations in the low mass surface density case but needs to be studied with numerical simulations in the general case. From this analysis and the experimental microlensing results by Mediavilla et al. (2017), we discuss the possible existence of a PBHs population mixed with the stellar component.

Speakers: Ana Esteban Gutiérrez, Ana Esteban Gutiérrez

Invisibles21-oral_presentation.pdf

Invisibles21-poster_presentation.mp4

Invisibles21_workshop_poster.pdf

self_presentation_invisibles21.mp4

15:54 A negative cosmological constant in the dark sector?

Following theoretical (high-energy physics) considerations, we explore the possibility that our Universe contains a negative cosmological constant, dubbed $\lambda$, on top of an additional component $X$ accounting for the late-time accelerated stage of expansion. In this talk, I will present some of the cosmological implications of introducing $\lambda$. In particular, we will assess the viability of such models when considering Baryon Acoustic Oscillations, SNeIa and CMB (geometrical) measurements. We estimate the Bayesian evidence in various cosmological scenarios through a nested sampling of the parameter space, and compare it to base-$\Lambda$CDM for model selection. We will briefly comment on their capability to address the current Hubble tension when a high-$H_0$ is taken into account.

Speaker: Rodrigo Calderon (University of Montpellier)

NegativeCC (Interactive) Poster

Negative_CC_invisibles21.pdf

16:00 → 16:30 "Baryogenesis and Particle Oscillations"

Speaker: Seyda Ipek (University of Washington)

ipek_invisibles.pdf

16:30 → 17:00 Poster Award

17:00 → 17:30 "Gravitational waves from the early Universe: challenges and opportunities"

Speaker: Djuna Croon (University of Sussex)

Invisibles2021.pdf

17:30 → 18:00 "Our Galactic Center: A Unique Laboratory for the Physics & Astrophysics of Black Holes"

The proximity of our Galaxy's center presents a unique opportunity to study a galactic nucleus with orders of magnitude higher spatial resolution than can be brought to bear on any other galaxy. After more than a decade of diffraction-limited imaging on large ground-based telescopes, the case for a supermassive black hole at the Galactic center has gone from a possibility to a certainty, thanks to measurements of individual stellar orbits. The rapidity with which these stars move on small-scale orbits indicates a source of tremendous gravity and provides the best evidence that supermassive black holes, which confront and challenge our knowledge of fundamental physics, do exist in the Universe. This work was made possible through the use of speckle imaging techniques, which corrects for the blurring effects of the earth's atmosphere in post-processing and allowed the first diffraction-limited images to be produced with these large ground-based telescopes.

Further progress in high-angular resolution imaging techniques on large, ground- based telescopes has resulted in the more sophisticated technology of adaptive optics, which corrects for these effects in real time. This has increased the power of imaging by an order of magnitude and permitted spectroscopic study at high resolution on these telescopes for the first time. With adaptive optics, high resolution studies of the Galactic center have shown that what happens near a supermassive back hole is quite different than what theoretical models have predicted, which changes many of our notions on how galaxies form and evolve over time. By continuing to push on the cutting-edge of high-resolution technology, we have been able to capture the orbital motions of stars with sufficient precision to test Einstein’s General theory of Relativity in a regime that has never been probed before.

Speaker: Andrea Ghez (University of California)