Detecting low-mass dark matter with liquid argon

• Shawn Westerdale (University of California, Riverside)

Room: Faculty Club Dual-phase liquid argon time projection chambers (LArTPCs) have demonstrated the capability of achieving sub-keV thresholds in the electron-counting S2-only channel, making them powerful tools for light dark matter searches and other low-energy applications. However, efforts to study the lowest accessible energies in these detectors are complicated by spurious electron (SE) signals that dominate the lowest energies. In this presentation, we will discuss observations of SEs in the DarkSide-50 LArTPC, along with potential interpretations that can inform R&D needs and the design of future detectors. We will also discuss the prospect of doping LAr to enhance its ionization yield, along with R&D needs to deploy such technology in a future detector, and the potential sensitivity of the DarkSide-LowMass experiment, currently being planned.

Performance of the SuperCDMS High Voltage Tower at CUTE

• Yan Liu (TRIUMF)

Room: Faculty Club SuperCDMS SNOLAB aims to conduct a wide-band dark matter search by cooling down the Germanium and Silicon crystals to cryogenic temperatures. The good performance of these detectors is crucial in achieving the experiment's science goals. One of the SuperCDMS towers, consisting of six High Voltage detectors, was deployed in CUTE (Cryogenic Underground TEst facilities) and tested over a period of five months to evaluate its properties. This marks the first time the SuperCDMS SNOLAB detectors are operated in a deep underground, low background environment. In this talk, I will present the results from the tower testing and discuss their implications for the upcoming SuperCDMS SNOLAB experiment.

The Scintillating Bubble Chamber (SBC)

• Kenneth Clark (Queen's University)

Room: Faculty Club The Scintillating Bubble Chamber (SBC) collaboration is combining the liquid argon scintillation and bubble chamber technologies to measure sub-keV nuclear recoils. SBC detectors benefit from the excellent electron-recoil insensitivity inherent in bubble chambers with the addition of energy reconstruction provided from the scintillation signal. Noble liquids can be superheated to a greater extent than Freons used in past bubble chambers for dark matter searches while remaining blind to electron recoils backgrounds allowing for a targeted energy threshold of 100 eV. The collaboration is building two functionally-identical detectors. The first, soon-to-be moving underground in the MINOS tunnel at Fermilab, will be used for engineering and calibration studies and has further potential in measurement of the coherent elastic neutrino-nucleus scattering on argon. A low-background version for the dark matter search will be operated underground at SNOLAB. I will discuss the motivation for sub-keV nuclear recoil studies, the current status of the SBC experimental program, and the low-mass dark matter potential.

Multiphonon excitations in direct detection: beyond the spherical cow

• Tongyan Lin (UC San Diego)

Room: Faculty Club

Scintillating Methods to Detect Dark Matter from Nano to Astro Scales

• Carlos Blanco (Princeton U/Stockholm U)

Room: Faculty Club While the attention of the dark matter community is shifting towards dark matter candidates beyond the WIMP paradigm, the majority of the dark matter parameter space outside of the weak scale remains experimentally inaccessible. Molecular systems have recently emerged as exceptionally capable and scalable targets to detect sub-GeV dark matter through both nuclear and electronic recoils. Here, I will present the theoretical basis of molecules as detector targets, as well as the road map towards their experimental deployment. I will then discuss the development of machine learning techniques to find optimal detector material candidates. Finally, I will conclude with a discussion of how these material-centric theoretical frameworks are applied to astrophysical objects to yield powerful new indirect probes of dark matter.

Looking for starlight underground

• Gonzalo Alonso Alvarez (U Toronto)

Room: Faculty Club The dark sector may feature long-range and inelastic interactions that can lead to the formation of dark matter substructure and dark stellar objects. A general prediction of these scenarios is that dark matter may be shinning in the dark photons that mediate this force. I will describe under which conditions low-threshold dark matter experiments are sensitive to this dark starlight, and discuss the role of the sun as a foreground in these searches. Finally, I will present a new experimental setup that has the potential to improve the current reach and test new scenarios.

Status and prospects of the SuperCDMS Dark Matter experiment

• Stefan Zatschler (U Toronto)

Room: Faculty Club The SuperCDMS collaboration is currently constructing its next generation of a direct DM search experiment at the SNOLAB underground facility in Sudbury, Canada. SuperCDMS will employ two types of state-of-the-art cryogenic Ge and Si detectors capable of detecting sub-keV energy depositions. The unique mix of target substrates and detector technologies allows for a simultaneous study of intrinsic and external backgrounds as well as exploring the DM mass range below 10 GeV with world-leading sensitivity. In order to extend the sensitivity to lower DM masses, a precise understanding of the detector response down to the semiconductor band gap energy is required. This effort is driven by a comprehensive prototype testing program and the development of a sophisticated Detector Monte-Carlo to guide the data analysis and model building. This talk will present an overview of our detector technology and recent milestones towards science operation with SuperCDMS at SNOLAB.

Resonant or asymmetric: The status of sub-GeV dark matter

• Felix Kahlhoefer (Kalsruhe Institute of Technology)

Room: Faculty Club

Proposal for a new quantum tech based dark matter experiment: QuaDMOS

• Adrian Bevan (Queen Mary University)

Room: Faculty Club

Search for ultralight dark matter using superfluid helium mechanical resonator

• Brigitte Vachon (McGill University)
• Brigitte Vachon (McGill University)

Room: Faculty Club

Some recent results on searching for sub-GeV dark matter

• Rouven Essig (Stony Brook University)

Room: Faculty Club

H-Parity: Why Vector-like Confining Dark Sectors Are Non-Scintillating

• Pouya Asadi (U Oregon)

Room: Faculty Club I show that vector-like confining dark sectors are endowed with a hitherto overlooked parity akin to SM’s G-parity. This parity forbids all the leading interactions of such confining dark sectors with SM, effectively suppressing their scattering rate in direct detection experiments. This suggests a vast part of the parameter space of this class of models that was presumed ruled out is still viable and constitutes a well-motivated target for collider searches.

Capture of atomic dark matter in the earth

• Keegan Humphrey (U Toronto)

Room: Faculty Club Atomic Dark Matter (aDM) is a well motivated class of models which has potential to be discovered at ground based Direct Detection experiments. The class of models we consider contains a massless dark photon and two Dirac fermions with different masses and opposite dark charge (dark protons and dark electrons), which will generally interact with the Standard Model through a kinetic mixing portal with our photon. The dark fermions have the potential to be captured in the Earth. Due to the mass difference, evaporation efficiencies are lower for dark protons than dark electrons, leading to a net dark charge in the Earth. This has the potential to alter the incoming flux of aDM in complex ways, due to interactions between the ambient dark plasma and the dark charged earth. This modifies event rates in ground based direct detection experiments compared to the standard DM expectation. In this talk I will describe our ongoing effort to calculate aDMs interaction with and subsequent capture in the Earth through the dark photon portal. We identify regions of the aDM parameter space where there may be significant accumulation of aDM in the Earth.

Accelerator Searches for Sub-GeV DM

• Cameron Bravo (SLAC)

Room: Faculty Club A new generation of dark matter experiments focusing on sub-GeV Dark Sectors capable of explaining the observed relic abundance have attracted increasing interest over the last decade. One of the most general models with a sub-GeV mediator is a Dark Sector which introduces a new U(1) gauge symmetry, with a corresponding boson called a "dark photon", "heavy photon", or A' (read A prime). The Heavy Photon Search (HPS) is one of the first experiments dedicated to the search for dark photons, specifically in the case that they decay to standard model charged leptons. HPS has successfully completed two physics runs in 2019 and 2021. I will present an estimate of the sensitivity of this data for dark photons and discuss other models the data could also be sensitive to. Meanwhile, a recently proposed project called the Light Dark Matter eXperiment (LDMX) will be sensitive to the production of sub-GeV dark matter particles, such as those with interactions mediated by dark photons. The LDMX detector concept, its rejection of key backgrounds, and sensitivity to new physics will be presented.

Direct detection of the millicharged background

• Saniya Heeba (McGill/Carleton U)

Room: Faculty Club

Detecting µeV photons and meV phonons via inelastic charge tunneling across Josephson junctions

• Max Hofheinz (U Sherbrooke)

Room: Faculty Club Superconducting quantum devices usually operate Josephson junctions in the superconducting state as nonlinear inductors to form anharmonic oscillators. In this talk I will show that Josephson junctions can also yield useful quantum measurement devices when operated in the voltage state. In this configuration, called Josephson photonics, Cooper pairs tunnel inelastically through a junction biased at a voltage V below the gap, by transferring their energy 2eV into one or more photons in the harmonic modes of the circuit in which the junction is embedded. In Josephson photonics, the junction, therefore, acts as a nonlinear drive and has very low inductance. This allows Josephson photonics devices to operate more easily at high frequencies which we expect to be only limited by the superconducting gap, corresponding to 100 GHz (400 µeV) for Aluminium and 900 GHz (3.7 meV) for Nb, the two most commonly used materials in superconducting circuits. I will discuss two Josephson-photonics devices we are developing, a quantum-limited amplifier and a single photon detector which could help enable QCD axion search experiments in mass ranges that are currently difficult to access. I will also briefly discuss some preliminary ideas on how tunneling of quasiparticles across voltage-bias Josephson junctions could be used to measure energy deposited in a substrate in the form of phonons with meV resolution. In this regime inelastic Cooper-pair tunneling constitutes a background signal which must be carefully avoided.

Cryogenic Platforms at Fermilab: Recent Results and Outlook

• Dylan Temples (Fermilab)

Room: Faculty Club The Cosmic Quantum group at Fermilab operates three cryogenic facilities dedicated to the development and calibration of superconducting low-threshold detectors and qubits. One of which (LOUD) is located at the surface, while the other two (NEXUS and QUIET) are located 100 m underground enabling low-background device characterization and rare event searches. Recently, we have demonstrated world-leading resolution in the quasiparticle channel for kinetic inductance phonon-mediated detectors as well as the lowest rate of spatially- and temporally- correlated errors (“charge jumps”) in superconducting qubit chips. We have additionally made significant progress in expanding the suite of tools for simulating signal production and readout of these devices. In this talk, I will review these recent results, discuss some nascent projects focused on enhancing sensitivity of these detectors to sub-GeV dark matter, and highlight activities in these facilities over the next year.

TESSERACT: light dark matter search with transition edge sensors and multiple targets

• Xinran Li (LBL)

Room: Faculty Club The TESSERACT collaboration searches for light dark matter particles (MeV to GeV) through interactions with various target materials and the transition edge sensor (TES) readout. The project includes HeRALD and SPICE experiments with superfluid helium and polar crystal targets, respectively. Recently, we have achieved several R&D milestones. We built crystal detectors with eV to sub-eV energy resolutions. These detectors have sensitivity to O(10) MeV dark matters. We identified the stress-induced low-energy events as a main background source in our detectors. We also detected quantum evaporation signals from a stably operated superfluid helium detector. Finally, I'll discuss our plans for a full-scale underground package.

Direct Detection of HYPER Dark Matter

• Gilly Elor (U Texas Austin)

Room: Faculty Club Faced with null results in the direct search of WIMP dark matter, there is growing motivation to explore dark matter candidates too light to be directly detected at current experiments. Indeed, there exists a vast array of proposals for direct detection experiments sensitive to sub-GeV dark matter coupled to nucleons. But can dark matter with a consistent cosmological history populate the regions of parameter space these proposals would be sensitive to? Furthermore, is there a maximum cross section for sub-GeV dark matter scattering off nucleons in light of present day constraints? In this talk, I will first estimate this maximum cross section. I will then introduce a novel dark matter candidate which realizes this cross section: HighlY interactive ParticlE Relics (HYPERs). The HYPER relic abundance is set by UV freeze-in, after which 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. HYPERs present a benchmark for direct detection experiments that probe light dark matter.