Dark Interactions: new perspectives for theory and experiment
Online
To review and discuss the status and future of the searches for dark sector states, their implications for the mystery of Dark Matter, and new associated theoretical developments.
Topics:
- Theoretical Motivation for Dark Sectors
- Experimental Constraints from High Energy Colliders
- Constraints from non-Collider Experiments
- Cosmological Constraints
- Implications for Dark Matter
- Prospects for LHC and Future Intensity Frontier Experiments
Event ID: 44203
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Welcome AddressConvener: Haiyan Gao
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Session IConvener: Shufang Su (University of Arizona)
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Dark Matter as General Thermal Relics 30m
I will discuss dark matter candidates that are thermal relics of the early universe. In the first part of the talk, I will present a roadmap for exploring various theories including the WIMP, dark sectors and more, using the observed relic density as guidance. In the second part, I will focus on a class of thermal relics that decouple relativistically early on and require a dilution mechanism for obtaining the correct relic density. A novel cosmological observable for probing such warm dark matter candidates will be discussed.
Speaker: Yue Zhang (Carleton University) -
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Hunting for Dark Matter 30m
The content of the universe is well known from astrophysical observations, from which we conclude that about 27% of the universe consists of cold dark matter. Current theories of what a particle physics candidate for dark matter might behave like, provide several avenues for detection of this missing component of our universe. I will discuss the experimental efforts to detect dark matter candidates, with the current best limits on the properties of potential particle physics candidates for dark matter being set by detectors using high purity crystals, or liquid noble gas time projection chambers (TPCs). XENONnT is the latest in a series of such liquid xenon TPCs, which presented its first result on dark matter interactions this summer. I will briefly discuss limits set on axions, axion like particle and dark photons dark matter candidates as well as the future prospects for XENONnT with regards to WIMP dark matter.
Speaker: Jacques Pienaar (University of Chicago)
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Coffee Break 15m
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Session IIConvener: Maíra Dutra (Carleton University)
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Signatures and Detection Prospects for sub-GeV Dark Matter with Superfluid Helium 15m
We explore the possibility of using superfluid helium for direct detection of sub-GeV dark matter (DM). We discuss the relevant phenomenology resulting from the scattering of an incident dark matter particle on a Helium nucleus. Rather than directly exciting quasi-particles, DM in this mass range will interact with a single He atom, triggering an atomic cascade which eventually also includes emission and thermalization of quasi-particles. We present in detail the analytical framework needed for modeling these processes and determining the resulting flux of quasi-particles. We propose a novel method for detecting this flux with modern force-sensitive devices, such as nanoelectro-mechanical system (NEMS) oscillators and derive the sensitivity projections for a generic sub-GeV DM detection experiment using such sensors.
Speaker: Yining You (University of Florida) -
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Fast Moving Dark Matter Interacting with Electrons at Direct Detection Experiments 15m
Dark matter is one of the most interesting fundamental puzzles of our universe. While we have accumulated sufficient cosmological evidence supporting its existence, the character of the dark matter particle is still unknown. A myriad of models have been proposed, the majority of which introduce a single dark matter candidate for simplicity. Though they provide testable hypotheses at various experiments, little attempt has been made beyond single-candidate dark matter. In this talk, we go beyond single-candidate dark matter by focusing on two-component dark matter candidates. Surprisingly, their phenomenology is very different from that of single-candidate, providing a new avenue for dark matter experiments. In particular, we examine a novel thermal dark matter scenario where present-day annihilation of dark matter in the galactic center or in the Sun may produce subdominant but detectable boosted stable particles via neutral-current-like interactions. We scrutinize various scenarios where such dark matter of spin 0 and 1/2 interacts with electrons via an exchange of vector, scalar, axial-vector or pseudo-scalar mediators. Detailed detection prospects due to high or moderate Lorentz-boosted particles are studied at deep neutrino
experiments and traditional direct detection experiments. The atomic physics effects are studied in detail to account for low electron recoils expected at traditional direct detection experiments. Studying this type of fast moving dark matter at two different sets of experiments targeting different energy ranges allows to cover its parameter space and enhance the signal detection in the future.Speaker: Haider Alhazmi -
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Direct Detection of sub-GeV Hadrophilic Dark Matter 15m
In the first part of this talk, I will estimate the maximum direct detection cross section for sub-GeV dark matter scattering off nucleons. For dark matter masses in the range of 10 keV − 100 MeV, cross sections greater than $10^{−36} - 10^{−30} \text{cm}^2$ seem implausible. I'll introduce a dark matter candidate which realizes this maximum cross section: HighlY interactive ParticlE Relics (HYPERs). After HYPERs freeze-in, a dark sector phase transition decreases the mass of the mediator which connects HYPERs to the visible sector. This increases the HYPER’s direct detection cross section, but in such a way as to leave the HYPER’s abundance unaffected and avoid conflict with measurements of Big Bang Nucleosynthesis and the Cosmic Microwave Background. HYPERs present a benchmark for direct detection experiments in a parameter space with few known dark matter models.
In the last part of the talk, I will consider an arguably simpler benchmark for direct detection: UV freeze-in dark matter at low reheating temperatures. I will present new work on simple UV completions of such a scenario and show how obtaining the correct relic abundance can predict detectable cross sections while evading collider and meson-decay bounds.
Speaker: Robert McGehee -
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Extending Dark Matter Search Down to Sub-GeV Mass Range 15m
Although the dark matter direct detection experiments have advanced a lot to set very stringent bound on the GeV~TeV scale WIMP particles, the sub-GeV window is still open and waiting for further exploration. In addition to inventing new experimental probes, it is of more interest to extend the physics potential of existing direct detection experiments. I will provide two examples of achieving this, the cosmirc ray boosted DM and the fermionic absorption DM. Both cases can overcome the experimental energy threshold to open the sub-GeV window. The first relies on near-relativistic DM flux accelerated by the high-energy cosmic rays while the second releases its mass into energy to make the target particles more energetic. Without making any modification to, direct detection experiments such as PandaX and Xenon1T can significantly extend their sensitive region down to the sub-GeV range.
Speaker: Shao-Feng Ge (TDLI-SJTU)
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Lunch Break 45m
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Session IIIConvener: Scott Snyder (Brookhaven National Laboratory (US))
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Overview on Ultraheavy Dark Matter 30m
"Ultraheavy" dark matter candidates with masses between roughly 10 TeV and the Planck scale present a wide and underexplored parameter space, with rich possibilities of models and cosmic histories. Both current detectors and novel search techniques -- direct and indirect -- are poised to hunt ultraheavy particle dark matter in the coming decade. I will present an overview of these with emphasis on tailored searches at next-generation liquid noble detectors and neutrino experiments.
Talk based on Snowmass white paper @ 2203.06508.Speaker: Nirmal Raj (TRIUMF) -
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Constraints on the nature of dark matter from quadruply-imaged quasars 15m
The abundance and density profiles of dark matter halos on sub-galactic scales, below $10^9 M_{\odot}$ solar masses, depend on the production mechanism, mass, and interactions of the dark matter particle(s). Galaxy-scale strong gravitational lenses provide the ideal observational platform with which to characterize the properties of low-mass halos because lensing depends only on gravity, and therefore circumvents the use of luminous matter as a tracer for unobservable dark matter. In particular, by forward modeling the relative brightness among images of quadruply-imaged quasars (quads), we can measure the halo mass function and the central densities of halos as a function of halo mass. I will discuss how we analyze lenses to extract this information, and present constraints on ultra-light and self-interacting dark matter from analyses of the existing sample of quads.
Speaker: Daniel Gilman -
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Identifying the fundamental nature of dark matter in the cosmic large-scale structure 15m
The fundamental nature of dark matter so far eludes direct detection experiments, but it has left its imprint in the large-scale structure (LSS) of the Universe. Extracting this information requires accurate modelling of structure formation and careful handling of astrophysical uncertainties. I will present new bounds using the LSS on two compelling dark matter scenarios that are otherwise beyond the reach of direct detection today. I will set the strongest limits to-date on the dark matter — proton cross section for dark matter particles lighter than a proton (mass < GeV) [1]. Ultra-light axion dark matter, particles with very low mass (< 10^-19 eV) and astrophysically-sized wavelengths (> kpc), is produced in high-energy models like string theory (“axiverse”). I will rule out axions that are proposed to resolve the so-called cold dark matter “small-scale crisis” (mass ~ 10^-22 eV) using the Lyman-alpha forest (a spectroscopic probe of the intergalactic medium) [2]. Further, I will demonstrate how a mixed axion dark matter model (as produced in the string axiverse) could resolve the S_8 cosmological parameter tension (mass ~ 10^-26 eV) using Planck, ACT and SPT cosmic microwave background and BOSS galaxy survey data [3,4]. The LSS model involves cosmic perturbation theory [3,4], a non-cold dark matter halo model [5] and, to capture the smallest scales, a machine learning model called an “emulator”, trained using hydrodynamical simulations and an active learning technique called Bayesian optimisation [6,7].
Speaker: Keir Rogers -
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Dark Matter from a Conformal Dark Sector 15m
A compelling solution to the Dark Matter question is that DM particles are part of a “dark sector” with fields uncharged under the SM gauge group. On the other hand, conformal field theories are ubiquitous and appear as fixed points of gauge theories. CFTs are scale-invariant and UV complete. In this work, we consider dark sectors described by conformal field theories and couple to the SM via portal interactions. We make generic, model-independent predictions for the nature of dark matter, and show that light DM states are populated in the early universe via freeze-in in such models. The mass gap generated is directly proportional to the coupling to the SM.
Speaker: Gowri Kurup (University of Oxford)
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Coffee Break 15m
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Session IVConvener: Robert Szafron (Brookhaven National Laboratory)
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Mechanical quantum sensing for dark matter: heavy, light, and ultra-light 30mSpeaker: Daniel Carney (Berkeley National Lab)
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New Constraints on the Profiles and Masses of Dark Matter and Cosmic Neutrinos through Precision Astrometry and Quantum Sensors 15m
We derive purely gravitational constraints on dark matter and cosmic neutrino profiles in the solar system using asteroid (101955) Bennu. We focus on Bennu because of its extensive tracking data and high-fidelity trajectory modeling resulting from the OSIRIS-REx mission. We find that the local density of dark matter is bound by $\rho_{\rm DM} < 3.3\times 10^{-15}\;\rm kg/m^3 \simeq 6\times10^6\,\bar{\rho}_{\rm DM}$, in the vicinity of $\sim 1.1$ au (where $\bar{\rho}_{\rm DM}\simeq 0.3\;\rm GeV/cm^3$). We show that high-precision tracking data of solar system objects can constrain cosmic neutrino overdensities relative to the Standard Model prediction $\bar{n}_{\nu}$, at the level of $\eta\equiv n_\nu/\bar{n}_{\nu}< 1.7 \times 10^{11}(0.1 \;{\rm eV}/m_\nu)$ (Saturn), comparable to the existing bounds from KATRIN and other previous labora-tory experiments (with $m_\nu$ the neutrino mass). These local bounds have interesting implica-tions for existing and future direct-detection experiments. Our constraints apply to all dark matter candidates but are particularly meaningful for scenarios including solar halos, stellar basins, and axion miniclusters, which predict overdensities in the solar system. Furthermore, introducing a DM-SM long-range fifth force with a strength $\tilde{\alpha}_D$ times stronger than gravity, Bennu can set a constraint on $\rho_{\rm DM} < \bar{\rho}_{\rm DM}\left(6 \times 10^6/\tilde{\alpha}_D\right)$. These constraints can be improved in the future as the accuracy of tracking data improves, observational arcs increase, and more missions visit asteroids. I will con-clude with a proposal using space quantum sensors to probe ultralight dark matter close to the Sun.
This talk is mainly based on arXiv:2112.07674 (Nature Astronomy, 2022) and arXiv:2210.03749.Speaker: Yu-Dai Tsai (University of California, Irvine) -
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Stepped Dark Sectors and Cosmological Tensions 15m
Models of dark sectors with a mass threshold can have important cosmological signatures. If, in the era prior to recombination, a relativistic species becomes non-relativistic and is then depopulated in equilibrium, there can be measurable impacts on the CMB as the entropy is transferred to lighter relativistic particles. In particular, if this "step'" occurs near z = 20,000, the model can naturally accommodate larger values of $H_0$. If this stepped radiation is additionally coupled to dark matter, there can be a meaningful impact on the matter power spectrum as dark matter can be coupled via a species that becomes non-relativistic and depleted. This can naturally lead to suppressed power at scales inside the sound horizon before the step, while leaving conventional CDM signatures for power outside the sound horizon. We study these effects and show such models can naturally provide lower values of $S_8$ than scenarios without a step. This suggests these models may provide an interesting framework to address the $S_8$ tension, both in concert with the $H_0$ tension and without.
Speaker: Melissa Joseph
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Session IConvener: Diallo Boye (Brookhaven National Laboratory)
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Cosmic Probes of the Dark Sector 30m
In this talk, I will describe my efforts to understand the nature of the mysterious dark matter, using the assumption that dark matter is comprised of ultralight axions. From the optical to the X-ray and gamma-ray universe, astrophysics has a role to play in understanding the details of this major problem in particle physics. I will give some insight into how I am using a range of tools to get at the basic question of “what is the statistical mechanics of dark matter?” I will show that astrophysical phenomenology is dependent on the microphysical details of ultralight axion models, and I will present results from recent collaborations.
Speaker: Dr Chanda Prescod-Weinstein (University of New Hampshire) -
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Gravitational wave radiation as a probe of dark sectors 30m
The detection of gravitational wave radiation by LIGO in 2015 opened a new window onto the cosmos, and we are just now beginning to peer out into the unknown. Since this radiation can propagate unhindered through even an optically-thick medium, gravitational waves will prove to be a powerful probe of the early universe, which currently remains shrouded behind the photon’s surface of last scattering. This earliest epoch in our cosmic history is especially important to our understanding of the Universe, since it is the time at which the mysterious dark matter has its origin. In this talk, I will discuss cosmological first-order phase transitions as a source of both gravitational wave radiation as well as particle dark matter. I will describe how gravitational waves arise during such a phase transition, discuss the expected signal spectrum, and talk about some open questions in regard to the bubble wall dynamics. Next I will describe how dark matter may be produced during such a phase transition though the interactions of bubble walls and the ambient plasma.
Speaker: Andrew Long (Rice University) -
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Motivations for a Large Self-Interacting Dark Matter Cross Section from Milky Way Satellites 15m
Self-interacting dark matter is a compelling idea because it could solve the small-scale structure formation problems and it arises generically in new physics models with dark sectors. We explore the properties of Milky Way subhalos in self-interacting dark matter models for moderate cross sections of 1 to 5 cm$^2$/g using high-resolution zoom-in N-body simulations. We include the gravitational potential of a baryonic disk and bulge matched to the Milky Way, which is critical for getting accurate predictions. Using an analytic model to extend the simulation results, we are able to show that the most massive subhalos in models with cross sections between 1 and 5 cm$^2$/g are not dense enough to match the densest ultra-faint and classical dwarf spheroidal galaxies in the Milky Way. We also show that these subhalos have not entered the core collapse regime. This motivates exploring velocity-dependent cross sections with values larger than 5 cm$^2$/g at the velocities relevant for the satellites such that core collapse would occur in some of the ultra-faint and classical dwarf spheroidals
Speaker: Maya Silverman
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Coffee Break 15m
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Session IIConvener: Mary Bishai (Brookhaven National Laboratory (US))
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Long-Lived Particle Searches at the Large Hadron Collider 30m
For the last few decades, High Energy Physics has been a victim of its own early success. Despite numerous theoretical arguments why it cannot be the final explanation for the interactions of fundamental particles, the Standard Model of particle physics continues to withstand intense scrutiny of the most determined experimental physicists. One promising way to search for signs of new physics is at the Large Hadron Collider, probing energies comparable to those present very shortly after the Big Bang.
We often assume that new particles produced in particle collisions would decay immediately. But what if new particles had long lifetimes and traveled centimetres —even kilometres — before transforming into something we could detect? In this talk, I will discuss the challenges and strategies we use in searches for signs of long-lived new particle signatures at the LHC. I will highlight what we have achieved experimentally thus far and what we can expect in the future.Speaker: Matthias Danninger (Simon Fraser University (CA)) -
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Overview of New physics searches at the Forward Physics Facility 30m
High energy collisions at the High-Luminosity Large Hadron Collider (LHC) produce a large number of particles along the beam collision axis, outside of the acceptance of existing LHC experiments. The proposed Forward Physics Facility (FPF), to be located several hundred meters from the ATLAS interaction point and shielded by concrete and rock, will host a suite of experiments to probe Standard Model (SM) processes and search for physics beyond the Standard Model (BSM). In this talk, we will review the BSM physics case of the FPF which corresponds to a broad range of new physics models that can be probed through searches for new particle scattering, decay, and ionization signature.
Speaker: Sebastian Trojanowski (National Centre for Nuclear Research, Poland) -
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FASER at the LHC 20m
FASER, the ForwArd Search ExpeRiment, is an LHC experiment located 480 m downstream of the ATLAS interaction point, along the beam collision axis. FASER and its sub-detector FASERnu have two physics goals: (1) to detect and study TeV-energy neutrinos, the most energetic neutrinos ever detected from a human-made source, and (2) to search for new light and very weakly-interacting particles. FASER was designed, constructed, installed, and commissioned during 2019-2022 and has been taking physics data since the start of LHC Run 3 in July 2022. This talk will present the status of the experiment, including detector design and first detector performance results from Run 3 data.
Speaker: Tobias Boeckh -
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Status of millIQan Run 3 Detector 15m
We will present the status of the of milliQan Run 3 Detector that has been installed in PX56 at CERN LHC P5. The Run 3 detector is expected to enhance the sensitivity to the search of milli-charged particles [1], comparing to that from the milliQan demonstrator which had been taking data during year 2018 of the LHC Run 2 [2].
[1] Phys. Rev. D 104, 032002
[2] Phys. Rev. D 102, 032002Speaker: Hualin Mei (Univ. of California Santa Barbara (US))
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Lunch Break 1h
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Session IIIConvener: Mauro Valli (YITP, Stony Brook)
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Bounds on Long-lived Dark Matter Mediators from Neutron Stars 15m
By measuring the flux of Dark Matter (DM) annihilations from a very long
distance, Indirect Detection (ID) can be used to investigate Dark Matter (DM) models with very weak couplings and long-lived mediators. And with a large population density and a strong gravitational bound, Neutron Stars (NS) are very effective to collect DM in Galactic Center (GC) to increase DM density, thus enhancing its measured flux. In this paper, using the calculation results of DM annihilation process into a long-lived mediator, we can provide some new limits for the DM-neutron cross-section. Our model of consideration is the Dark Photon model, with an additional U (1) group and a kinetic mixing term in the Lagrangian.
The Standard Model (SM) signal for ID is muon neutrino. With experimental results from IceCube and ANTARES, we provide some specific bounds for the Spin-Independent (SI) cross-section down to $10^{−46}$ cm$^{2}$ in the TeV-PeV range for this Dark Photon model.Speaker: Thông Nguyễn Trần Quang -
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Thermal Misalignment of Ultralight dark matter 15m
Abstract is attached as requested.
Speaker: Mudit Rai -
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Bounds on ultralight bosons from the Event Horizon Telescope observation of Sgr A$^*$ 15m
Recently, the Event Horizon Telescope (EHT) has observed the first image of the supermassive black hole
(Sgr A$^*$) at the center of our own Milky Way galaxy. EHT observations also give some information
about the spin of Sgr A$^*$. They found that the dimensionless spin parameters (a$^*$) 0.5 and 0.94
have passed all their tests. These observations can be used to study the Ultra light Bosonic (ULB) parti-
cles using Superradiance (SR), which is a process of a rotating BH losing its angular momentum and en-
ergy due to the existence of massive bosonic particles surrounding it. As a result of losing its angular
momentum, the BH is spun down. Assuming that the BH spin has not been depleted via SR, we derive
bounds on the masses of ULBs. If the scalar ULBs have self-interaction, self-interaction can prohibit the
growth of the ULB clouds around the BHs. We use this property to constrain the axion decay constant.
We constrain new regions in the parameter space of ultralight axion decay constant for a certain spin of Sgr A$^*$.Speaker: Priyank Parashari (Indian Institute of Science) -
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Faint light of old neutron stars from dark matter capture and detectability at the James Webb Space Telescope 15m
Neutron stars (NS) of age >109 yrs exhaust thermal and rotational energies and cool down to temperatures below O(100) K. Accretion of particle dark matter (DM) by such NS can heat them up through kinetic and annihilation processes. This increases the NS surface temperature to a maximum of ∼2550 K in the best case scenario. The maximum accretion rate depends on the DM ambient density and velocity dispersion, and on the NS equation of state and their velocity distributions. Upon scanning over these variables, we find that the effective surface temperature varies at most by ∼40%. Black body spectrum of such warm NS peak at near infrared wavelengths with magnitudes in the range potentially detectable by the James Webb Space Telescope (JWST). Using the JWST exposure time calculator, we demonstrate that NS with surface temperatures ≳2400 K, located at a distance of 10 pc can be detected through the F150W2 (F322W2) filters of the NIRCAM instrument at SNR ≳10 (5) within 24 hours of exposure time.
Speaker: Shiuli Chatterjee -
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A search for dark matter using sub-PeV $\gamma$-rays observed by Tibet AS$_{\gamma}$ 15m
Detection of high-energy diffuse gamma-rays is one of the most important aspects of modern astrophysics. Recently Tibet AS$_\gamma$ collaboration [1] has detected galactic sub-PeV diffuse gamma-rays, which also happens to be the highest energy diffuse gamma-rays detected to date. In this work [2], we show that these high-energy diffuse gamma rays can be an excellent probe for detecting PeV-scale decaying dark matter (DM). If heavy DM particles decay to various Standard Model (SM) states, they can ultimately hadronize or decay to final state high-energy photons which can then contribute to the diffuse gamma-rays detected. The recent detection agrees well with prior theoretical astrophysical models of diffuse gamma-ray production. Thus, considering various SM final states, different DM density profiles and various astrophysical background models we put bounds on the properties of decaying DM. We find that this gives us the strongest constraints on decaying DM for DM masses between a few PeV to a few tens of PeV. In future, an improved understanding of the astrophysical backgrounds and many such high energy gamma-ray detections can either discover or severely constrain heavy decaying DM.
References:
[1] Tibet ASgamma collaboration, M. Amenomori et al., First Detection of sub-PeV Diffuse Gamma Rays from the Galactic Disk: Evidence for Ubiquitous Galactic Cosmic Rays beyond PeV Energies, Phys. Rev. Lett. 126 (2021) 141101, [2104.05181].
[2] T. N. Maity, A. K. Saha, A. Dubey and R. Laha, Search for dark matter using sub-PeV γ-rays observed by Tibet ASγ, Phys. Rev. D 105 (2022) L041301, [2105.05680].Speaker: Akash Kumar Saha
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Session IConvener: Hooman Davoudiasl
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Recent Advances in Machine Learning for High Energy Physics 30m
Abstract: I will give a high-level overview of recent advances om machine learning for high energy physics, including developments in neural network architectures (e.g., graphs, transformers, and equivariant networks), generative modeling, anomaly detection, and fast inference.
Speaker: Javier Mauricio Duarte (Univ. of California San Diego (US)) -
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CURTAINs for your sliding window 15m
CURTAINs is a fully data driven technique for creating background templates for use in searches for new physics processes. We employ invertible neural networks to learn the transformation to map any data point from its value of the resonant variable (e.g., invariant mass) to another chosen value. This conditional transformation allows us to create a template in the signal window, by mapping the data from the sidebands into the signal region. We demonstrate the effectiveness of this method by applying it to Anomaly Detection in a collider physics experiment and use it to enhance the sensitivity to new physics in a bump hunt. Using the LHCO dataset, we demonstrate that CURTAINs is competitive with other leading approaches, which aim to improve the sensitivity of bump hunts and can be trained on a much smaller range of the invariant mass. The method is applicable to any search for a resonant signal, including those resulting from dark interactions.
Speaker: Debajyoti Sengupta (Universite de Geneve (CH)) -
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Search for invisible Higgs bosons with interpretation for dark matter at the LHC using the ATLAS detector 15m
In this work, the invisible Higgs sector was investigated, where Higgs bosons are produced via the vector boson fusion (VBF) process and subsequently decay into invisible particles. The hypothesis under consideration is that the Higgs boson might decay into a pair of weakly interacting massive particles (WIMPs), which are candidates for dark matter. The observed number of events are found to be in agreement with the background expectation from Standard Model (SM). Assuming a 125 GeV Higgs boson with SM production cross section, the observed and expected upper limits on the branching fraction of its decay into invisible particles are found to be 15% at 95% confidence level.
Combination of searches for an invisibly decaying Higgs boson produced via the main Higgs production modes at the LHC using 2011–2018 data is conducted and discussed.Speaker: Mohamed Zaazoua (Universite Mohammed V (MA)) -
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Search for new spin-1 boson using ATLAS detector data 15m
This paper presents the search for a new spin-1 boson in a four-lepton final state through the channel $H\rightarrow Z_dZ_d\rightarrow 4l$ where $Z_d$ is the new spin-1 boson, and $4\ell$ could be 4e 4$\mu$ or 2e2$\mu$. This analysis' mass range of the $Z_d$ probed lies between 15 - 60 GeV. We conducted this search using $pp$ collision data from the ATLAS detector corresponding to an integrated luminosity of 139 fb$^{-1}$ and a centre of mass energy of $\sqrt(s) = $~13 TeV. We observed no significant deviation from the Standard Model in this analysis. We observed improvements from the previous iteration of the analysis' limits set on the Higgs branching ratio and the fiducial cross-section. We also set limits on the mixing parameter related to the Beyond Standard Model framework used in this analysis.
Speaker: Xola Mapekula (University of Johannesburg (ZA))
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Coffee Break 15m
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Session IIConvener: Yu-Dai Tsai (University of California, Irvine)
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Pulsar Timing Arrays: The Next Window to Open on the Gravitational-Wave Universe 30m
Galaxy mergers are a standard aspect of galaxy formation and evolution, and most (likely all) large galaxies contain supermassive black holes. As part of the merging process, the supermassive black holes should in-spiral together and eventually merge, generating a background of gravitational radiation in the nanohertz to microhertz regime. An array of precisely timed pulsars spread across the sky can form a galactic-scale gravitational wave detector in the nanohertz band. I describe the current efforts to develop and extend the pulsar timing array concept, together with recent limits which have emerged from international efforts to constrain astrophysical phenomena at the heart of supermassive black hole mergers.
Speaker: Chiara Mingarelli (University of Connecticut) -
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Opening up window of post-inflationary QCD axion 15m
The QCD axion cosmology depends crucially on whether the QCD axion is present during inflation or not. We point out that contrary to the standard criterion, the Peccei-Quinn (PQ) symmetry could remain unbroken during inflation, even when the axion decay constant, $f_a$, is (much) above the inflationary Hubble scale, $H_I$. This is achieved through the heavy-lifting of the PQ scalar field due to its leading non-renormalizable interaction with the inflaton, encoded in a high-dimensional operator which respects the approximate shift symmetry of the inflaton. The mechanism opens up a new window for the post-inflationary QCD axion and significantly enlarges the parameter space, in which the QCD axion dark matter with $f_a > H_I$ could be compatible with high-scale inflation and free from constraints on axion isocurvature perturbations. There also exist non-derivative couplings, which still keep the inflaton shift symmetry breaking under control, to achieve the heavy-lifting of the PQ field during inflation.
Additionally, by introducing an early matter domination era, more parameter space of high $f_a$ could yield the observed DM abundance.Speaker: LINGFENG LI (Brown U.) -
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Massive Neutrinos, Light Relics, and Ultra-Light Axions in the Halo Bias 15m
Cosmological data provide a powerful tool in the search for physics beyond the Standard Model (SM). Light but massive relics (LiMRs) which decoupled from the SM while relativistic contribute to the radiation energy budget, and are commonly searched through variations in the effective number $N_{\rm eff}$ of neutrino species. In addition to this effect, LiMRs with masses on the eV scale (meV-10 eV) be-come non-relativistic before today, and thus behave as matter instead of radiation. This leaves an imprint in the clustering of the large-scale structure of the universe, as light relics have important streaming motions, mirroring the case of massive neutrinos. Likewise, ultra-light axions with masses approximately greater than the Hubble scale transition equation of state before today, including dur-ing matter domination. Further, ultra-light axion fields possesses macroscopic de Broglie wave-lengths of astrophysical scales. These two properties of ultra-light axions have important conse-quences for structure formation. In this work, we model the effects massive neutrinos, LiMRs, and ul-tra-light axions in the scale dependent halo bias. We forecast how well current and upcoming cosmo-logical surveys can probe massive neutrinos and LiMRs - considering minimal extensions to the SM by both fermionic and bosonic relic degrees of freedom. By combining current and upcoming cosmic-microwave-background and large-scale-structure surveys, we forecast the significance at which each LiMR, with different masses and temperatures, can be detected. We also explore how the mass and relic abundance of a single, ultra-light axion species imprints on the scale dependent bias. Accurate models of the scale dependent bias will be critical tools for efforts to use galaxy data in exploring dark sector physics.
Speaker: Nicholas DePorzio
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Lunch Break 45m
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Session IIIConvener: Robert McGehee
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15:35
Searching for New Physics with Neutrino Experiments 30m
In this talk, we discuss the unique potential of neutrino experiments to probe a wide range of low-energy new physics models. We review some of the main ways dark sectors have already been studied at neutrino experiments and how we can further probe new physics with next-generation experiments. As a case study, we consider the example of HNLs endowed with hidden sector interactions and how such models can already be constrained by MicroBooNE’s recent search for single photons from NC $\Delta(1232)$ radiative decays.
Speaker: Asli Abdullahi -
16:05
Probing Neutrino Portal Dark Matter: From Colliders to Supernovae 15m
New beyond-the-Standard Model mediators that couple predominantly to neutrinos are not yet probed by existing experimental searches. Such a neutrinophilic mediator is well motivated for addressing the origin of several neutrino-portal dark matter candidates, including thermal freeze-out and sterile-neutrino dark matter scenarios. In this talk, we explore the sensitivity to this scenario from two different approaches. In the first part of the talk we will explore the potential of the Forward Physics Facility (FPF) using the so-called “mono-neutrino signature”: neutrino charged-current scattering events associated with large missing transverse momentum, and excessive apparent tau-neutrino events. We will show that with this smoking-gun signature, the FPF has excellent sensitivity to probe this model in new regions of parameter space. the In the second part of the talk we focus on astrophysical constraints on sterile neutrino DM, namely from core-collapse supernovae. Production and emission of DM can result in excessive energy loss of the supernova, leading to additional cooling. We will show that supernova cooling can constrain new regions of parameter space that complements terrestrial and cosmological probes. The results of this work present a nice complementarity among the collider and astrophysical frontiers.
Speaker: Douglas Tuckler -
16:20
Opportunities for Axion Searches at Beam Dumps and Stopped-Pion Facilities 15m
Pseudo-Nambu-Goldstone Bosons (pNGBs) are a byproduct of many theories that address long-standing puzzles of the Standard Model (SM). Axions and axion-like particles (ALPs) which have spawned from solutions to the strong-CP problem can also make good dark matter candidates and arise ubiquitously in string theory, and in other theories with spontaneously broken symmetries. ALPs in the MeV mass range are of particular interest, as it still remains a blind spot in the parameter space between bounds from astrophysical constraints and existing beam dump probes. This presents an exciting opportunity to test MeV-scale ALPs with couplings to electrons and photons at stopped-pion sources where electromagnetic cascades in the beam targets permit many production modes for ALPs. I will illustrate a few search strategies that stopped-pion facilities like CCM have already begun to implement to probe this region of parameter space, and connect this with MiniBooNE’s sensitivity and the implications for a future search at DUNE.
Speaker: Adrian Thompson
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15:35
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16:35
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16:50
Coffee Break 15m
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16:50
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17:50
Session IVConvener: Matheus Hostert (Perimeter Institute)
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16:50
Do dark matter and neutrinos talk to each other? 30m
In this presentation, I will review the current status of searches for connections between dark matter and neutrinos. Neutrinos can be a gateway to the dark sector as, e.g., they allow for the tree-level decay or annihilation of dark matter into neutrinos. I will describe the constraints on dark matter annihilation, decay, and scattering to neutrinos. Finally, I will provide an outlook for upcoming measurements.
Speaker: Carlos A. Argüelles-Delgado (Harvard University) -
17:20
Neutrinos from the Sun as a discovery tool for dark matter - electron scattering 15m
We will discuss a novel strategy to search for dark matter (DM)-electron scattering. DM interacting with electrons may get captured inside the Sun. These captured DM may annihilate to produce different Standard Models (SM) particles. Neutrinos produced from these SM states can be observed in IceCube and DeepCore. Although there is no excess of neutrinos from the Solar direction, we find that the current results of IceCube and DeepCore set the strongest constraint on DM-electron scattering cross section in the DM mass range above ~10 GeV. This implies that future observations of the Sun by neutrino telescopes have the potential to unravel DM-electron interactions.
Speaker: Tarak Nath Maity (Indian Institute of Science) -
17:35
Non-standard neutrino interactions in light mediator models at reactor experiments 15m
Compared to other neutrino sources, the huge anti-neutrino fluxes at nuclear reactor based experiments empower us to derive stronger bounds on non-standard interactions of neutrinos with electrons mediated by light scalar/vector mediators. At neutrino energy around $200$~keV reactor anti-neutrino flux is at least an order of magnitude larger compared to the solar flux. The atomic and crystal form factors of the detector materials related to the details of the atomic structure becomes relevant at this energy scale as the momentum transfers would be small. Non-standard neutrino-electron interaction mediated by light scalar/vector mediator arises naturally in many low-scale models. We also propose one such new model with a light scalar mediator. Here, we investigate the parameter space of such low-scale models in reactor based neutrino experiments with low threshold Ge and Si detectors, and find the prospect of probing/ruling out the relevant parameter space by finding the projected sensitivity at $90 \%$ confidence level by performing a $\chi^2$-analysis. We find that a detector capable of discriminating between electron recoil and nuclear recoil signal down to a very low threshold such as $5$~eV placed in reactor based experiment would be able to probe a larger region in parameter space compared to the previously explored region. A Ge (Si) detector with $10$~kg-yr exposure and 1 MW reactor anti-neutrino flux would be able to probe the scalar and vector mediators with masses below 1 keV for coupling products $\sqrt{g_\nu g_e}$ $\sim$ $1 \times 10^{-6}~(9.5 \times 10^{-7}) ~{\rm and}~ 1\times 10^{-7} ~(8\times 10^{-8})$, respectively.
Speaker: Ankur Verma
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16:50
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12:20
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13:35