News & Events

Astroparticle Physics HQP (Highly Qualified Personnel) were invited to attend the Professional Development Day, which began with a lively game of astroparticle physics-themed charades. After much laughter and some impressive performances, Rachel Pietersma, Acting Editorial Director at Canadian Science Publishing, gave a workshop on publishing with the Canadian Journal of Physics, especially for multi-authored, collaboration papers. The afternoon began with Zachary Kenny chairing a Post-Academic Careers Panel, featuring guests David Waller, Director General, CanmetENERGY-Ottawa, Natural Resources Canada, Colin Lewis, Senior Data Scientist, TELUS, and Alan DeKok, CEO Ink Bridge Networks and Founder of FreeRADIUS. The Alumni Entrepreneurship Pathways Panel followed with McDonald Institute Edward Thomas providing an overview of Lean Entrepreneurship, highlighting the difference between identifying a problem to solve, rather than developing a product as a starting point. Laura Suen, Founder and CEO of Fire and Steel, spoke about her experiences in finding work at TRIUMF, and starting a business making replica and costume weaponry. Alan DeKok returned for the entrepreneurship panel and shared his experience developing an open-source product with feature and support monetization. DeKok also encouraged the physics HQP on the value of research and method skills as highly transferable and relevant. After the panels, participants joined in a round-table networking session, providing an opportunity to ask questions and connect with the panellists. Dylan Rietz, an undergraduate biotechnology student and entrepreneur, joined as a special guest for the networking round tables and shared about his interest in supporting Indigenous and interdisciplinary innovators in the start-up process.

Tony Noble: Overview and Future Directions of the McDonald Institute and CFREF Programs

This presentation provided a comprehensive update on the Canadian Foundation for Innovation and Excellence in Research Funding (CFREF) programs managed by the McDonald Institute, focusing on astroparticle physics in Canada. The original CFREF (2016-2026), a $64 million, seven-year initiative extended due to COVID-19, aimed to build research capacity and support early R&D phases at Canadian universities, hiring 15 new faculty and greatly expanding the community from 34 to over 90 active researchers nationwide. The program supported diverse projects, including theory development, underground experiments (e.g., SuperCDMS, NEWS-G, PICO), and outreach activities, emphasizing cross-disciplinary internships and community building.

The new award ($45.5M over five years facilitated by the NSERC Major Resources Support (MRS) program) aims to enable Canadian scientists to lead major international projects by supporting engineering and technical R&D at universities, with plans to establish a distributed engineering “hub” and an Integrated Project Delivery Centre (IPDC). The new funding, administered via NSERC, comes with new eligibility and management challenges, including tighter restrictions on administrative costs and faculty position support.

Tony also discussed strategic priorities such as enhancing governance with stronger scientific prioritization, improving reporting and data collection, expanding education, outreach, and EDI programs, and ensuring sustainability through better long-term federal research frameworks. He emphasized the need for community-driven setting of flagship projects to concentrate efforts and improve impact. Four new partner institutes (University of Victoria, Simon Fraser, Sherbrooke, and CITA) have recently joined, broadening the institute’s reach.

Koby Dering: Engineering and Technical Support Infrastructure for Astroparticle Physics

Koby outlined the vision and early implementation plans for the Integrated Project Delivery Center (IPDC), a distributed network of engineering and technical support across Canada designed to underpin the next generation of large, complex astroparticle physics experiments. Highlighting the increasing scale, complexity, and safety demands of these projects (e.g., operations in extreme environments), the IPDC will provide expert mechanical, electrical, cryogenic engineering, and machining support.

A governance structure is being developed with two key committees: a scientific Resource Allocation Committee (RAC) prioritizing projects, and a Project Feasibility Committee assessing the technical and engineering feasibility of proposals. A management team, including a project officer, will coordinate requests, assign technical staff, and maintain communications.

Koby discussed the process for soliciting engineering requests from researchers and categorizing work by scale and complexity, with smaller tasks delegated locally and larger projects requiring committee review. The team will support activities from design through installation and operations with ongoing oversight. He emphasized the importance of coordination with existing Major Resources Support (MRS) programs in Canada and expressed intent to share resources and expertise collaboratively to meet broad community needs. Some challenges include managing provincial regulatory compliance, balancing resource allocation among centers, and embedding skilled engineers within experiments versus shared technical teams.

Nik Arora: Education and Outreach at the McDonald Institute

Nik Arora, the new Education and Outreach Officer, shared his vision and recent activities to enhance public understanding and community engagement with astroparticle physics in Canada. He distinguished education—training the next generation of scientists—from outreach, which aims to excite the public and demonstrate the societal value of research funded by taxpayers. Nik highlighted established partnerships with Perimeter, SNOLAB, TRIUMF, and local organizations to run programs such as “Astronomy on Tap” events, International Masterclasses for high school students (including live Antarctic IceCube connections), and large public Science Rendezvous events attracting thousands.

He emphasized expanding Outreach beyond Kingston to reach partner institutes across Canada, including upcoming events at Simon Fraser University and New Brunswick, and proposed sharing educational resources and exhibits nationally. Teacher engagement efforts include hosting a provincial physics teachers conference and developing a teacher-in-residence program to create accessible classroom materials. Nik welcomed community input and collaboration, expressing plans to develop digital science communication platforms incorporating podcasts, articles, and multimedia content to highlight cutting-edge research and the people behind it.

Edward Thomas: External Partnerships and Alumni Networking

Edward provided a strategic review of the Institute’s partnerships portfolio, emphasizing turning isolated nodes into a richly connected network that extends opportunities for trainees and researchers into entrepreneurship and supply chains. He contextualized this within shifting global economic and scientific leadership, noting moves toward increased European collaboration.

Key recent successes include a formal partnership with the Polish AstroCent collaboration, funded by EU Horizon Europe and strengthening ties with Australian theory groups and Japanese institutions. The Institute has bolstered its Visiting Scientist Awards and Research Partnership Workshops to facilitate international collaboration, technology demonstration, and workforce sustainability.

The alumni network received special attention, leveraging an extensive, global cohort of highly skilled researchers who have transitioned into industry roles such as cybersecurity, green tech, data science, and specialized manufacturing. The goal is to build strong mentorship and networking opportunities so that graduate students have multiple professional contacts by their second year.

Despite complexities from evolving global funding rules and geopolitical risks, maintaining and expanding these partnerships and career development frameworks remains a major focus for sustaining Canadian leadership in astroparticle physics.

Highly Qualified Personnel Advisory Committee (HQPAC) Initiatives (Zachary Kenny, Brian Krar, Jeremy Savoie, Hussain Rasiwala, and Rob Collister)

This segment presented updates from the HQPAC, representing graduate students, postdocs, and early-career researchers. The committee facilitates community leadership and coordinates initiatives to support HQP career development and community engagement.

Current projects include a monthly seminar series offering presentation opportunities to HQP nationwide, developing a centralized newsletter and resource page, and organizing social/networking events such as HQP Day. A mental health survey is planned to better understand community wellness challenges.

A new pilot HQP Excellence Awards program (HEXAs) was introduced to recognize outstanding achievements in research, leadership, and science communication across career stages, including undergraduate students.

The committee also reviewed progress on last year’s recommendations to improve connectivity, professional development programs (including re-establishing postdoc training), and financial support through pooled funding. New recommendations focus on broader meeting topics, improving networking, especially for job seekers, and launching an astroparticle PhD thesis award with an associated presentation opportunity.

Efforts to better welcome and integrate new and existing HQP into the McDonald community were emphasized through upcoming welcome packages and increased communication.

Koby Dering: Retrospective and Current Activities of McDonald Institute Engineering Team

This retrospective presentation highlighted nearly a decade of engineering achievements supporting astroparticle physics projects. Case studies included the delicate design and manufacture of an inner quartz vessel for PICO-500, demanding extreme precision under unconventional material and thermal constraints.

Other engineering feats involved custom heavy shielding crates, complex pressure vessels at SNOLAB, and the design and operational support of the massive PICO-500 pressure vessel assembled underground in sections. The team also contributed mechanical and process engineering expertise to helium liquefaction plant installation at Queen’s, dark side anode deflection control system, and pressure system registration and regulatory compliance.

The talk emphasized the collaborative nature of their work, supporting projects from conceptual design through construction, installation, operations, and troubleshooting. The Institute now operates a machining shop offering services to the community at costs covering materials and consumables but no labor fee yet.

The team is growing with new staff and students, taking on leadership roles in projects, quality management, and professional engineering development, including training junior engineers toward certification. Future plans include expanding expertise in cryogenics and better publicizing engineering accomplishments.

Jodi Cooley: SNOLAB Future Planning

The presentation provided an update on SNOLAB’s 15-year strategic plan, focusing on facility expansion, science priorities, and community engagement. SNOLAB, located 2 km underground in a nickel mine near Sudbury, is a leading international lab primarily focused on dark matter and neutrino physics, hosting over 1,200 users from 165 institutions worldwide. The plan centers on three pillars—excellent science, cutting-edge research, and skilled people—supported by core values like safety and diversity. It highlights growing efforts in quantum technologies and underground biology alongside core particle astrophysics. New initiatives include emeritus and affiliate programs, a summer lectureship series, and an outreach program for grades 4–8 to engage young students in underground science.

Facilities are nearing capacity, prompting detailed proposals for surface and underground expansions under three funding scenarios: maintaining current operations, fully supporting Canadian research, and boosting global competitiveness. Planned upgrades include larger surface buildings with better changing facilities, new labs, enhanced utilities, and excavation of new underground “ladder labs” and a large cavern for next-generation experiments such as Theia and advanced dark matter detectors. Staffing increases are proposed, especially in research positions and postdocs, enabled by new funding frameworks. The strategic plan emphasizes flexibility to adapt to evolving scientific priorities and funding. Final submission to Canadian funding agencies is due in mid-September 2025, with excavation slated to begin around 2030.

Overall, SNOLAB aims to maintain its leadership in underground physics while expanding educational outreach and supporting a broad science portfolio within a sustainable, community-driven vision.

Nigel Smith: TRIUMF Future Planning

Nigel Smith, Director of TRIUMF, outlined the laboratory’s strategic direction and funding landscape as Canada’s national particle accelerator center. TRIUMF, located at UBC, operates a 500 MV cyclotron supporting diverse research in nuclear astrophysics, particle physics, and medical isotope production, guided by a 20-year vision developed in 2022. TRIUMF’s funding follows rigid five-year federal operational tranches, supplemented by capital funding from agencies like CFI. The recent 2024 federal budget provided CAD 400 million—less than the requested 450 million—supporting major projects including the Ariel accelerator upgrade and the Institute for Advanced Medical Isotopes (IAMI). To complete these, TRIUMF plans a year-long accelerator shutdown in 2026, prioritizing essential infrastructure and beamline refurbishments.

The laboratory emphasizes strategic, long-term planning: updating its 20-year vision every five years, coordinating project prioritization internally, and preparing for uncertain post-2030 funding amid evolving Major Research Facility (MRF) frameworks. TRIUMF also focuses on strengthening Canada’s international research connections, notably with CERN and the Astroparticle Physics European Consortium. Smith stressed the importance of tailored government advocacy, framing TRIUMF as a vital national asset underpinning innovation, resilience, and the training of highly qualified personnel. Despite funding and operational challenges, TRIUMF aims to secure sustainable support to maintain its world-class science and infrastructure over the coming decades.

Carsten Krauss: IPP Future Planning

Carsten Krauss discussed the early stages of preparing the Institute of Particle Physics (IPP) brief for Canada’s upcoming Long Range Plan (LRP) covering 2027–2033. The plan must address concerns from funding agencies by providing tangible priorities and realistic resource assessments, including human capital, to better align the community’s science goals with funding realities. The IPP has received 26 submissions from experiments and collaborations, covering key areas like double beta decay, dark matter searches, and high-energy neutrinos. Krauss emphasized the need to consider critical mass and sustainability, as many dark matter projects appear too numerous for current community capacity. The planning process will weigh how to best prioritize projects given limited personnel and funding.

An important theme was the need to tailor the plan not only for scientific excellence but also to resonate with government decision makers by clearly demonstrating societal benefits and impacts. Computing resources, including challenges with national infrastructure like the Digital Research Alliance of Canada (DRAC), must also be addressed as a key enabling technology. Two more town halls are planned to gather community input before finalizing the brief. Krauss underlined that the process remains iterative and community-driven, aiming to produce a coherent, funder-friendly strategy that supports Canada’s leadership in particle and astroparticle physics.

Edward Thomas: McDonald Institute White Paper

Edward Thomas outlined a new community-driven strategic planning process for the McDonald Institute aimed at guiding future priorities in fundamental physics. The initiative will develop a white paper that integrates scientific goals with practical factors like timelines, costs, infrastructure, and risks—including political and technological disruptions. Key research areas such as dark matter, double beta decay, neutrino physics, and enabling technologies will be addressed through working groups engaging the community.

The planning emphasizes tracing impact backward from desired outcomes to identify necessary activities, balancing scientific ambition with benefits to Canada, including training and technology development. The process prioritizes transparency and flexibility, recognizing that long-range plans must adapt to changing circumstances, with iterative updates and open communication. This white paper will inform not only the Institute’s strategic plan but also broader national exercises like the IPP and Long Range Plan, supporting both detailed community input and clear messaging to stakeholders. Working groups will finalize in the coming weeks, with community consultations and a draft expected by early October, aiming to map out resources and strategies over 5–15+ year horizons.

PANEL: Science, Diplomacy, and International Collaborations

The panel discussion on science diplomacy, moderated by Edward Thomas, brought together experts from academia, diplomacy, and government to explore the evolving role and challenges of science diplomacy in international research, especially within Canada. Science diplomacy is framed as a crucial tool for fostering international collaboration on large-scale scientific projects, such as astroparticle physics experiments. It has regained importance after a period of diminished focus during the “unipolar moment” (1991–2008) and is now increasingly relevant amid geopolitical shifts and global challenges.

Panellists:

Darren Grant (Simon Fraser University, Astroparticle Physicist): Emphasized that nearly all major scientific projects today depend on international partnerships, so scientists must care about and engage in science diplomacy. However, scientists are mostly not yet active players in diplomatic or strategic negotiations—they need to develop these skills urgently.

Jean-François Doulet (French Embassy in Canada): Highlighted the complexity of modern science diplomacy due to geopolitical fragmentation and competition. He introduced a framework with four “regimes of action”: an Idealistic regime: science as a common good with global cooperation. Crisis regime: driven by urgent multilateral issues like climate or space. Like-minded regime: cooperation among aligned countries/clubs, e.g., G7, Francophone nations. Sovereign regime: prioritizing national interests above others (e.g., U.S. and China). These regimes coexist and vary by nation and context. This complexity challenges the traditional ideal of science diplomacy but reflects the current geopolitical reality.

Marc-André Hawkes (Global Affairs Canada): Affirmed the necessity of government engagement in science diplomacy to address global challenges, with agencies already working on policies and agreements to foster collaboration. He stressed the importance of managing risks like foreign interference, research security, and export controls. Canada currently lacks a unified overarching science diplomacy strategy but operates through targeted policies and partnerships. He encouraged scientists to understand national interests, legal obligations, and institutional resources, advocating for scientists to acquire diplomacy-related skills.

The panel underscored that science diplomacy is a vital, complex, and evolving field essential for advancing large-scale international scientific endeavours like astroparticle physics. Scientists must become more aware of geopolitical contexts and develop strategic skills to navigate diplomacy effectively. Governments, including Canada’s, are increasingly integrating science diplomacy into their foreign policy frameworks, though formal overarching policies remain limited. As global scientific cooperation faces new challenges from competition and fragmentation, science diplomacy requires a nuanced approach balancing idealism with realism, risk management, and national interests.

PANEL: Neutrinoless Double Beta Decay

The panel focused on the future directions of neutrinoless double beta decay (0νββ) research, emphasizing various experimental approaches, challenges, and strategies to advance sensitivity and maintain momentum in the global and Canadian communities.

Panellists:

Mark Chen (SNO+ Project) uses ^{130}Te loaded into a liquid scintillator detector. Benefits from tellurium’s high natural abundance and cost-effectiveness, aiming for scalable detectors capable of probing normal neutrino mass ordering. Interested in exploring improved detector media for better resolution.

David Sinclair (Carleton University / Snow Lab) Advocates advanced technology development in liquid xenon detectors, focusing on improved background rejection using electron track imaging and pixelated sensors. Emphasizes modular detector designs and international collaboration for isotope procurement and funding.

Thomas Brunner (nEXO Project / McGill University) supports near-term construction of a next-generation liquid xenon TPC targeting a sensitivity of about 10^{28} years half-life. Encourages balancing R&D with building a large-scale experiment and flexible incorporation of improvements. Highlights Canada’s strong role in global 0νββ efforts.

The panel recognized neutrinoless double beta decay as a key physics goal facing substantial technical and financial challenges. Discussions centered on isotope availability, detector performance, and the importance of community coordination. A shared consensus emerged on the need for global partnerships, flexible experimental designs, and a clear strategic roadmap that combines ongoing R&D with timely deployment of competitive experiments.

IceCube Neutrino Observatory

Darren Grant presented an overview of the IceCube Neutrino Observatory, situated at the South Pole, focusing on its mission to solve the century-old mystery of the origin of ultra-high-energy cosmic rays via neutrino astronomy. IceCube detects neutrinos by capturing Cherenkov radiation produced when neutrinos interact with the Antarctic ice, using a cubic-kilometer array of photomultiplier tubes deployed over 86 strings. Different neutrino flavors create distinct event signatures—muon neutrinos leave long tracks offering precise directional info; electron neutrinos produce localized cascades with superior energy resolution; tau neutrinos yield unique “double bang” events. Recent results include precise measurements of the astrophysical neutrino flux revealing a broken power-law spectrum around 30 TeV, hinting at a transition between galactic and extragalactic sources, and the first detection of tau neutrinos. IceCube has yet to detect neutrinos at the extreme PeV-EeV scale consistent with models involving cosmic ray interactions with cosmic microwave background photons, leading to a tension with KM3NeT observations. IceCube is embarking on an upgrade deploying tighter instrumentation in its core to improve sensitivity to lower energy neutrinos and oscillation parameters, as well as plans for a future 10-cubic-kilometer-scale detector to enhance high-energy neutrino astrophysics.

P-ONE Neutrino Detector

Carsten Krauss gave an update on the P-ONE (Pacific Ocean Neutrino Experiment), a next-generation neutrino telescope planned in the deep, clear waters of the Cascadia Basin off the coast of Canada. P-ONE aims to build on IceCube’s successes by employing improved detector geometry and newer, more sophisticated photo-detection technology to optimize particle identification, angular resolution, and flavour reconstruction, especially for tau neutrinos. The site benefits from existing Ocean Networks Canada infrastructure, simplifying deployment and power provision, although the area’s recent designation as a marine protected zone adds some complexities. Initial exploratory instrumentation (“straw” phase) has validated optical properties of the local water, showing attenuation lengths favourable for detector operation and manageable levels of bioluminescence. The project is currently assembling full-scale detector strings with 20 modules each, featuring enhanced calibration capabilities and novel muon trackers to accelerate track reconstruction. Deployment is planned soon, with the ultimate goal of constructing a multi-cubic-kilometre detector to complement global neutrino observatories and enhance multi-messenger astrophysics.

HELIX Cosmic Ray Experiment

Connor McGrath presented HELIX (High Energy Light Isotope eXperiment), a balloon-borne magnetic spectrometer designed to study cosmic ray propagation by precisely measuring isotope ratios, particularly beryllium-9 to beryllium-10. The isotope ratio serves as a “clock” to estimate cosmic ray propagation times, offering insights into galactic cosmic ray transport mechanisms beyond traditional boron-to-carbon ratio studies. HELIX’s instrument suite includes time-of-flight scintillator paddles, a superconducting magnet with a gas drift chamber for rigidity measurements, and a ring imaging Cherenkov detector for velocity determination. The first successful 6-day flight launched from Sweden, traversed the Atlantic, and landed in northern Canada, capturing over 120 million cosmic ray events. Data are under analysis, with promising preliminary results for elemental separation and velocity measurements. Future plans focus on longer duration flights, improved spatial resolution, and expanded energy reach up to ~10 GeV/nucleon to refine isotopic measurements, ultimately enhancing the understanding of cosmic ray sources and propagation in the local galaxy.

Global Argon Dark Matter Program (DEAP, DarkSide, and ARGO)

Mark Boulay provided a comprehensive review of the global argon-based dark matter search program. He summarized the status and upgrades of the DEAP-3600 detector, focusing on challenges with alpha particle backgrounds and the implementation of innovative wavelength-shifting coatings to improve pulse-shape discrimination. Mark discussed the formation of the large Global Argon Dark Matter Collaboration aiming to build the DarkSide-20k detector and eventually the multi-hundred-ton ARGO detector at SNOLAB, designed for background-free searches at unprecedented sensitivity levels. He also outlined R&D activities, technical innovations in photo-detectors, and the physics potential to explore solar neutrinos, neutrino coherent scattering, and possibly neutrinoless double beta decay with isotope doping.

NEWS-G Low Mass Dark Matter Search

Guillaume Giroux presented on the NEWS-G experiment, which utilizes spherical proportional counters filled with light gases such as neon and helium to search for low mass dark matter particles. He explained the design advantages of the spherical geometry, including low capacitance and electronic noise, enabling very low-energy threshold detection down to tens of eV. Guillaume reviewed recent runs with large diameter pure copper spheres, background reduction techniques including electroplating and surface etching, and novel sensor development to improve event discrimination. He highlighted the challenges of single-electron background events, ongoing R&D efforts to mitigate them, and prospects for scaling up detector size and future deployments.

Low Mass Dark Matter Searches with Argon

Michela Lai discussed plans and challenges for sub-GeV-scale dark matter searches using dual-phase argon time projection chambers with a focus on S2-only (ionization) signal analysis. She described efforts to optimize low-background detectors, particularly by doping liquid argon with xenon to shift scintillation light to a more detectable wavelength and improve timing properties, potentially eliminating the need for wavelength shifters. The talk covered implications for pulse shape discrimination, improvements in light collection, and synergies with other experiments like DUNE and nEXO. Michela also addressed challenges in xenon doping at cryogenic temperatures, radon removal techniques, and ongoing R&D aimed at lowering energy thresholds and enhancing sensitivity to light dark matter candidates.

THEORY PRESENTATIONS:

Constraints on Heavy Neutrinos from Big Bang Nucleosynthesis (BBN)

Yu-Ming Chen presented a detailed study on how observations from the early universe, specifically Big Bang nucleosynthesis (BBN), can be used to constrain properties of hypothetical heavy neutrinos (sterile neutrinos or heavy neutral leptons). BBN occurred roughly 1 second to 10 minutes after the Big Bang, during which light elements such as deuterium and helium formed. These primordial abundances are measured with high precision and are sensitive to new physics beyond the Standard Model, including the presence and characteristics of heavy neutrinos.

Chen reviewed the role of heavy neutrinos in astrophysics, emphasizing that they have no electromagnetic, strong, or standard weak interactions and can be produced via oscillations from active neutrinos. The talk highlighted the interplay between the mass and mixing angle of heavy neutrinos, showing how too large a mixing or abundance can disrupt BBN predictions by altering the expansion rate or causing photodissociation of light nuclei. The analysis presented multiple decay and interaction channels through which heavy neutrinos impact nuclear abundances, quantifying constraints and showing that BBN limits complement terrestrial experiments. Chen concluded by outlining the parameter space regions constrained by different effects and discussed the implications for neutrino mass generation mechanisms like the seesaw model.

Expanding Dark Matter Searches via Hadronic Loop Effects

Melissa Diamond discussed innovative theoretical work on expanding the reach of dark matter detection by considering loop-level hadronic interactions. Current dark matter searches often assume direct interactions between dark matter and a single Standard Model particle (e.g., electrons or nuclei). However, due to the complexity of the Standard Model, interactions with one particle can induce effective couplings to others through quantum loops, especially involving hadrons.

Diamond explained how these loop-induced interactions allow experiments designed to detect one type of interaction (like dark matter-electron scattering) to also set constraints on others (e.g., dark matter-nucleon scattering). The work focused on vector mediators and low-mass dark matter (1 to 100 MeV), utilizing effective field theory and chiral QCD in the non-perturbative regime. She showed that electron recoil experiments can constrain nuclear scattering cross sections, providing complementary sensitivity to conventional searches. The talk also touched on other mediator types (scalars, pseudoscalars), photon interactions via loops, and the connection to cosmological bounds. Diamond emphasized the broad applicability of loop considerations in designing future dark matter searches, which could probe parameter spaces previously inaccessible.

Ab Initio Nuclear Theory and Neutrinoless Double Beta Decay

Alex Todd (Master’s student) and Taiki Schickele (undergraduate) of the TRIUMF Theory Group presented state-of-the-art ab initio nuclear theory methods applied to calculations of nuclear matrix elements critical for interpreting neutrinoless double beta decay (0νββ) experiments. The 0νββ process, sensitive to whether neutrinos are Majorana particles and to the absolute neutrino mass scale, requires accurate nuclear matrix elements to extract fundamental physics from measured decay rates.

The speakers described the progress in extending ab initio techniques to increasingly heavy isotopes relevant for experiments, highlighting computational advances in methods like the in-medium similarity renormalization group (IMSRG). They compared phenomenological approaches, which suffer from large matrix element spread and model dependence, with the more predictive and systematically improvable ab initio calculations grounded in realistic nuclear forces from chiral effective field theory.

They presented results showing reduced theoretical uncertainties and improved consistency in matrix elements, which lead to more reliable interpretations of 0νββ limits and sensitivities. The talk also included prospects for future improvements such as including three-body operators and subleading decay mechanisms. Finally, they addressed how ab initio calculations can probe exotic mechanisms beyond light neutrino exchange, such as heavy neutrino contributions, underscoring the method’s importance for future experimental efforts.

The MATHUSLA Experiment: Searching for Long-Lived Particles at the LHC

Caleb Miller introduced the MATHUSLA (MAssive Timing Hodoscope for Ultra-Stable neutraL pArticles) experiment, a proposed surface-level, modular detector designed to search for neutral long-lived particles (LLPs) at the Large Hadron Collider (LHC). LLPs arise naturally in theories beyond the Standard Model and could provide insight into dark matter and other open physics questions. Due to their long lifetimes (decaying tens of meters away from the collision), LLPs often evade detection in main LHC detectors. MATHUSLA aims to cover less-explored transverse parameter space, complementing approved forward experiments like SHiP and FASER.

The current design features a 40m × 40m decay volume instrumented with tracking scintillator layers for identifying displaced vertices, allowing reconstruction of LLP decay products. Timing techniques provide spatial resolution of order centimeters. Backgrounds from cosmic rays were studied in simulation, with veto layers and directional cuts giving promising background rejection. The modular detector design can grow over time and integrates trigger strategies to send signals to nearby LHC detectors. The presentation highlighted ongoing R&D prototypes, engineering challenges, and physics reach, showing MATHUSLA’s potential to map new LLP parameter space during the LHC’s high luminosity phase beginning ~2030.

PICO Dark Matter Bubble Chamber Experiments

Jeremy Savoie reviewed the current status and recent developments of the PICO collaboration’s bubble chamber detectors searching for dark matter via nuclear recoils. Bubble chambers operate by superheating a fluid (typically fluorocarbons) under carefully controlled temperature and pressure, where energy depositions from particle interactions cause phase transitions visible as bubbles. PICO’s detectors leverage acoustic and optical techniques to discriminate nuclear recoils (potential dark matter signals) from backgrounds such as alpha particles and electron recoils.

PICO 40L, their existing detector, uses an “upside-down” configuration to eliminate buffer fluids causing spurious bubbles and employs acoustic parameters to resolve alpha decays for background characterization. PICO 500L, under construction and significantly larger, will incorporate improved shielding, temperature control, and instrumentation including advanced piezo sensors and cameras. It aims to reach sensitivity probing the neutrino floor for spin-dependent WIMP interactions. The talk outlined experimental techniques, handling of background sources like radon, technical challenges such as assembly of large fused silica jars, and projected timelines for commissioning. PICO’s modular fluid target design allows it to explore a broad parameter space in dark matter direct detection.

The SuperCDMS Experiment for Low-Mass Dark Matter Detection

Professor Miriam Diamond from the University of Toronto presented the SuperCDMS experiment, a direct dark matter detection experiment focusing on low-mass WIMP-like candidates (sub-GeV to ~10 GeV scale). Located at SNOLAB, SuperCDMS uses ultra-pure silicon and germanium detectors equipped with transition edge sensors (TES) to detect phonons and ionization signals from dark matter interactions. Key features include phonon amplification through a high-voltage bias in some detectors (HV detectors) to reach lower energy thresholds, and discrimination between nuclear and electron recoils based on ionization-to-phonon ratios in other detectors (iZIP detectors). The experiment is currently in the installation and integration phase and benefits from SNOLAB’s low-background environment and underground facilities like CUTE for detector testing. Preliminary results on background modeling and detector responses were shared, including studies on the “low energy excess” widely observed in similar experiments. Miriam also described future R&D efforts on scaling detectors, utilizing new materials, and improving sensitivity to even lighter dark matter candidates, encouraging student involvement. The talk conveyed both the technical complexity and the promising sensitivity reach of SuperCDMS in exploring dark matter parameter space down to the neutrino floor.

The Search for Lower Threshold Bubble Chambers: The Spherical Bubble Chamber (SBC)

Ken Clark discussed the development of a new type of bubble chamber, the Spherical Bubble Chamber (SBC), motivated by limitations of the PICO style fluorocarbon detectors, particularly the rise in electron recoil backgrounds as the energy threshold is lowered below a few keV. SBC aims to achieve ultra-low energy thresholds (~100 eV) by using a noble element target (argon doped with xenon) contained in a fused silica vessel cooled to about 100 K. The key innovation is leveraging the different energy loss mechanisms in noble gases, where electron recoils primarily cause ionization and scintillation rather than heat that triggers bubble nucleation, significantly reducing background at low thresholds. Ken also highlighted challenges in maintaining thermal stability and controlling acoustic discrimination in this new medium.

Preliminary tests with a small xenon bubble chamber demonstrate insensitivity to gammas down to 500 eV thresholds, promising for probing low-mass dark matter not accessible by other detectors. The talk emphasized the physics motivation for lowering thresholds to extend dark matter sensitivity to sub-GeV masses and outlined plans and lessons learned during Fermilab and SNOLAB deployments of prototype detectors. The SBC represents a promising next-generation technology advancing the bubble chamber method.