Benjamin Broerman
Queen's University

 

Abstract

Understanding the properties of dark matter is one of the most important goals of modern physics. Noble liquids, like argon, can be used as a target to search for dark matter over a wide range of masses from the GeV-scale through the TeV-scale. As a member of the Scintillating Bubble Chamber (SBC) collaboration, I am involved in developing liquid-noble bubble chambers sensitive to the sub-keV nuclear recoils expected from dark matter-nucleus scattering of GeV-scale dark matter. These detectors combine the excellent electron-recoil insensitivity inherent in bubble chambers with the ability to reconstruct energy based on the scintillation signal for further background suppression. The targeted nuclear recoil threshold of 100 eV is made possible by the high level of superheat attainable in noble liquids while remaining electron-recoil insensitive. In order to verify this reduced threshold, the SBC collaboration is building two functionally-identical 10 kg liquid argon detectors. The first, SBC-LAr10, to be operated at Fermilab, will be used for engineering and calibration studies. The second detector, SBC-SNOLAB, for a low-background dark matter search will be operated underground at SNOLAB. An overview of scintillating liquid-noble bubble chambers, the physics potential of SBC-SNOLAB, and new ideas for detector materials will be presented along with the physics reach of a proposed future, large volume dark matter search with liquid argon to cover masses through the TeV-scale.

 

Timbits, coffee, tea will be served in STI A before the colloquium.

 

 

Kim Berghaus
Caltech

 

Abstract

Dark matter comprises 85% of the matter density of our Universe, yet all of its known evidence lies in its gravitational imprint. One of the most important scientific goals of the next decade in fundamental physics is to reveal the nature of dark matter by measuring its non-gravitational interactions in the laboratory. To accomplish this goal, the experimental landscape must delve deep and search wide. Ensuring success requires overcoming emerging challenges in low threshold dark matter detection, such as quantifying how dark matter signals and backgrounds manifest in detectors. My research bridges the critical intersection of theoretical prediction and experimental verification of signals and backgrounds. As an example, I will discuss my work on quantifying the Migdal effect, a rare atomic ionization process that occurs when a neutron or dark matter scatters off a nucleus, in semiconductors, with relevance for experiments such as SENSEI and DAMIC. I will also discuss the role of phonon backgrounds from gamma-rays for sub-GeV dark matter experiments such as EDELWEISS and SuperCDMS. Lastly, I will show that phonons efficiently couple to paramagnetic qubits, opening up potential new pathways for single phonon detection. 

 

Timbits, coffee, tea will be served in STI A before the colloquium.

 

 

Michela Lai
University of California Riverside

 

Abstract

Since the 1930s, many astrophysical and cosmological observations have motivated the search for dark matter particles, building a wide variety of experiments specifically designed to perform their very first direct detection. Liquid argon is one of the most sensitive targets for GeV-scale candidates, such as Weakly Interacting Massive Particles (WIMPs), as demonstrated so far by the DEAP-3600 experiment and DarkSide-50 experiment, featuring respectively a 3.3 tonne single-phase and a 50 kg double-phase Time Projection Chamber design. In the meantime, unique R&D has led to the design of the first experiment within the Global Argon Dark Matter collaboration, DarkSide-20k, currently under construction at LNGS. Its 50-tonne ultra-pure argon target, together with the extraordinarily low background level, will allow for investigating for the very first time in argon dark matter-nucleon cross-section as low as 7.4 x 10^{-48} cm^2 for a WIMP mass of 1 TeV/c^2 in a 200 t yr run.

DarkSide-20k, and after it, ARGO, will give the ultimate answer to whether WIMPs exist and whether we can detect them. But there is more to investigate with noble liquids. Argon detectors are indeed not only the favorite for ultra-heavy dark mark candidates but are also at the very center of a multi-messenger physics program, including the detection of neutrinos released by core-collapse supernovae, by neutron star binary mergers as well as by the accretion disk on black holes. While extending the physics program of argon detectors, we will also investigate how we can push their sensitivity to sub-GeV dark matter candidates by just adding a few part-per-millions of xenon or other photosensitive dopants. If scaled to a tonne-scale experiment, this innovative technology will pave the way for searching unexplored dark matter candidates while opening a new window into our Universe.

 

Timbits, coffee, tea will be served in STI AUD before the colloquium.

 

 

 

Prof. Stefanie Czischek
University of Ottawa

 

Abstract

Large language models, like transformers, have recently demonstrated immense powers in text and image generation. This success is driven by the ability to capture long-range correlations between elements in a sequence. The same feature makes the transformer a powerful wavefunction ansatz that addresses the challenge of describing correlations in simulations of qubit systems. In this talk I consider two-dimensional Rydberg atom arrays to demonstrate that transformers reach higher accuracies than conventional recurrent neural networks for variational ground state searches. I further introduce large, patched transformer models, which consider a sequence of large atom patches, and show that this architecture significantly accelerates the simulations.

 

Timbits, coffee, tea will be served in STI A before the colloquium.

 

 

 

Dr. Ilsa Cooke (UBC),
Harrison-MacRae Lecture

 

Abstract

Dr. Ilsa Cooke will present "The unusual chemistry of interstellar molecules" to the Queen’s University community with funding from the Harrison-MacRae Lectureship in the Department of Chemistry.

Interstellar space is not empty, it contains a huge variety of molecules including some that have been found in space and never on Earth! In this talk, I will discuss how astrochemists find these molecules in space and what clues they can give us about other stars and planets. In addition, I will discuss how interstellar space provides an opportunity to study strange and exotic reactions that can defy chemical intuition.

About the Speaker

Dr. Ilsa Cooke is an Assistant Professor in the Department of Chemistry at the University of British Columbia. She leads the UBC Astrochem Lab, which studies how complex organic molecules form in the interstellar medium. Dr. Cooke is also a co-Principal Investigator with the GOTHAM collaboration and uses radio telescopes to probe aromatic molecules and their precursors in star-forming regions of space. Dr. Cooke was a lead researcher for the recent discovery the largest molecule ever detected by radioastronomy (and the third-largest in space!) published this fall in Science. She has won many awards for her research, most recently the Laboratory Astrophysics Division of the American Astronomical Society 2024 Early Career Award.

 

 

 

Leo Kim
PhD student, Queen's University

 

Abstract

In dissipative models of dark matter, radiative processes in the dark sector can give rise to dark structure formation -- leading to the formation of dark compact objects and (dark) black holes. The macroscopic properties of these compact objects are directly connected to the microphysics of the underlying particle physics model. Additionally, if the formation of these objects occur in an early matter-dominated Universe, this can be a new way to make primordial black holes. The resulting distribution of these compact objects and their related observable phenomena can be used to constrain and differentiate between models of dark matter.

 

Timbits, coffee, tea will be served in STI A before the colloquium.

 

 

 

Braulio Antonio
PhD student, Queen's University

 

Abstract

Coherent control of electron dynamics has proven to be a reliable way of generating attosecond pulses from gaseous media;  however, there are experimental advantages to using solid state media in coherent control experiments. In this work I will show a mechanism to achieve coherent control of optically injected current in gated single layer graphene, using a two-colored optical field at 808 and 404 nm.

 

Timbits, coffee, tea will be served in STI A before the colloquium.

 

 

 

Marie Vidal
Stanford University

 

Abstract

I am fascinated by studying neutrinos because despite being the most abundant particle in the universe, our knowledge about them is limited. Key elements about the neutrinos, like their mass and place in the Standard Model are still unknown today. The observation of neutrino oscillations, which is possible only if neutrinos have mass, was the first hint of physics beyond the Standard Model. One proposed mechanism to explain the neutrinos’ small mass compared to other fermions, is that neutrinos could be Majorana particles, meaning that the neutrino is its own antiparticle. The question of whether the neutrino is a Majorana particle could explain the origin of the asymmetry between matter and antimatter we observe today. The nEXO experiment will search for neutrinoless double beta (0νββ) decay using a 5-tonne liquid xenon (LXe) time projection chamber (TPC), enriched to 90 % in 136Xe, with a projected half-life sensitivity > 1028 years after 10 years of data. With a general overview of the nEXO experiment, I will present the R&D efforts lead by the nEXO collaboration to maintain our sensitivity goal. I am also interested in coherent elastic neutrino-nucleus scattering, or CEνNS, because of the science we can learn from it. Coherent elastic neutrino-nucleus scattering provides a new observable that is a neutral current to detect neutrinos. This neutral current interaction is flavor blind, so we can detect all neutrino flavors, even the neutrinos that oscillated to another flavor! It can be used as a tool to study remaining discrepancies in reactors (5 MeV) and Gallium anomalies, and probe for the existence of a fourth sterile neutrino. NEWS-G (New Experiments With Spheres-Gas) is a rare event search experiment using Spherical Proportional Counters (SPCs). Primarily designed for the direct detection of dark matter, this technology also has appealing features for CEνNS studies. A study to assess the feasibility of observing CEνNS at a nuclear reactor will be presented. Both direct dark matter detection and CEνNS consist of nuclear recoils from elastic scatters. The calibration to nuclear recoils is primordial for both searches. I will present the experimental method and analysis framework that were used to extract the first calibration to neon nuclear recoils in neon gas.

 

Timbits, coffee, tea will be served in STI A before the colloquium.

 

 

 

Ana Botti
University of Chicago

 

Abstract

In recent years, advancements in theoretical frameworks motivated searches for light-dark matter particles in the meV-GeV mass region by showing the compatibility of these models with cosmological observations. New emerging technologies, such as skipper-CCDs, facilitated the development of small- and medium-sized experiments tailored for exploring these theoretical models. Skipper-CCDs are pixeled silicon detectors with a deep sub-electron resolution that allows the detection of eV energy transfers, such as that expected from light-dark matter interacting with electrons in a silicon target. SENSEI is the first experiment to use skipper-CCD for this purpose and to produce world-leading results using this technology. In this talk, I present an overview of the SENSEI experiment and the current status after successfully commissioning the second science run at SNOLAB. I will also discuss the prospects in rare-events searches with skipper-CCDs: from SENSEI’s 100 g detector to OSCURA’s 10 kg array and more.

 

Timbits, coffee, tea will be served in STI A before the colloquium.