Light Dark World 2026

28 Jul 2026, 08:01 → 31 Jul 2026, 23:59 America/Toronto

Carleton University, Ottawa, Canada

Light Dark World 2026 is the eleventh meeting of the annual Light Dark World International Forum, held at the Carleton University in Ottawa, Ontario, Canada.

Light Dark World 2026 will gather international specialists from both experimental and theoretical backgrounds to examine recent progress and create avenues for investigating new light particles that extend beyond the Standard Model. We will cover light gauge bosons, light scalars, light dark matter, axions, light sterile neutrinos, and dark energy fields. 

Confirmed Speakers
Haipeng An (Tsinghua University)
Asimina Arvanitaki (Perimeter Institute)
Josh Berger (Colorado State University)
Daniel Carney (LBNL)
Jodi Cooley (SNOLAB)
Paddy Fox (Fermilab)
Akshay Ghalsasi (Harvard University)
Saniya Heeba (Carleton University)
Alejandro Ibarra (TUM)
Gordan Krnjaic (Fermilab/University of Chicago)
Laura Miller (TRIUMF)
Gopolang Mohlabeng (Simon Fraser University)
Miha Nemevšek (Jozef Stefan Institute)
Zachary Picker (Queens University)
Alan Robinson (University of Montreal)
Katelin Schutz (McGill University)
Simon Viel (Carleton University)
Wei Wang (Sun Yat-sen University)
Matthew Wilson (University of Florida)
Yong Xu (McGill University)
...

Local Organising Committee:
Marcela Carena (Perimeter Institute & Chicago U.)
Seyda Ipek (Carleton)
David McKeen (TRIUMF & U Victoria)
David Morrissey (TRIUMF & U Victoria)
Yue Zhang (Carleton)

Steering Committee:
Brian Batell (Pittsburgh U.)
Pilar Coloma (IFT)
Felix Kahlhoefer (KIT)
Hye-Sung Lee (KAIST)
Laura Molina Bueno (IFIC)

Previous Meetings of the Light Dark World International Forum

• Light Dark World 2025, IFT UAM/CSIC, Madrid, Spain
• Light Dark World 2024, KAIST, Daejeon, Korea
• Light Dark World 2023, KIT, Karlsruhe, Germany
• Light Dark World 2022, KAIST, Daejeon, Korea (online)
• Light Dark World 2021, PITT PACC, Pittsburgh, USA (online)
• Light Dark World 2020, Sydney-CPPC, Australia (online)
• Light Dark World 2019, Erwin Schrödinger Institute, Vienna, Austria
• Light Dark World 2018, KAIST, Daejeon, Korea
• Light Dark World 2017, Pittsburgh, USA
• Light Dark World 2016, IBS Center for Theoretical Physics of the Universe, Daejeon, Korea

LDW2026 Poster

Tuesday 28 July

09:15 → 09:30 TBA: Welcome

09:30 → 10:00 TBA

Speaker: Gordan Krnjaic (Fermilab)

10:00 → 10:30 TBA

Speaker: Prof. Katelin Schutz

10:30 → 11:00 Coffee

11:00 → 11:30 TBA

Speaker: Patrick Fox

11:30 → 12:00 TBA

Speaker: Gopolang Mohlabeng (University of California, Irvine)

12:00 → 13:00 Lunch

13:00 → 15:00 Topical Highlights

13:00 Light Dark Matter Results From the LUX-ZEPLIN Experiment

The LUX-ZEPLIN (LZ) experiment employs a two-phase Xe time projection chamber designed to search for rare interactions between dark matter and ordinary matter, nearly a mile underground at the Sanford Underground Research Facility, South Dakota, USA. In this talk, I will present the latest results from LZ, focused on low-mass dark matter and solar neutrinos using a 5.7 tonne-year exposure and yielding the strictest constraints to date on spin-independent WIMP nucleus and spin-dependent WIMP–neutron scattering down to WIMP masses of 5 GeV/c^2, and competitive limits all the way down to 3 GeV/c^2. I will also discuss the sensitivity of LZ to known low-energy processes, including coherent elastic neutrino–nucleus scattering due to Boron-8 solar neutrinos, demonstrating both the breadth of physics now being probed by the experiment and the first greater than 3 sigma evidence for the neutrino fog of solar origin, which will ultimately limit spin-independent searches for WIMPs with masses below 10 GeV/c^2.

Speaker: Matthew Szydagis

13:15 New benchmarks for direct detection of freeze-in dark matter in vector portal models

In this talk, we discuss new freeze-in dark matter (DM) benchmarks for the next generation of direct detection experiments. We focus on the MeV-scale fermionic dark matter coupled to the Standard Model via a new vector mediator. First, we investigate the minimal kinetic mixing dark photon of a secluded $U(1)_{D}$. Then, we study the gauge bosons of the anomaly-free $U(1)_{L_{i}-L_{j}}$ with $i,j= e,\mu,\tau$ and $U(1)_{B-L}$, exploring the impact of low reheating scenarios on the DM production rates. In the ultralight dark photon scenario, DAMIC-M and PandaX-4T bounds can be avoided if the DM fermion constitutes less than 40\% of the total cold DM. In this regard, future direct detection experiments can be sensitive to a fraction below 1\% for masses below 1 MeV. For a massive dark photon, there are allowed regions of the parameter space with masses in the range 50 MeV $\lesssim m_{DM} \lesssim $ 500 MeV, within reach of direct detection experiments through nuclear recoils if freeze-in occurred at a low reheating temperatures. In the case of $U(1)_{L_{i}-L_{j}}$ and $U(1)_{B-L}$, freeze-in at low reheating temperatures can reproduce the observed relic abundance in large parts of the parameter space, up to gauge couplings of $g_{X}\sim10^{-2}$ for MeV DM. Direct detection experiments will be sensitive to considerable parts of this parameter space in nuclear recoils for 50 MeV $\lesssim m_{DM} \lesssim $ 500 MeV. In addition, we find beyond Standard Model (BSM) signals not only in the dark matter (DM) sector, but also in neutrino physics. Additionally, the enhanced signal from solar neutrino coherent scattering
is observable in these scenarios, which can serve as a further handle to identify the underlying particle physics model.

Speaker: Rafa Lopez

13:30 Hydrogenated carbon structures as directional sub-GeV dark matter detectors

We propose hydrogenated carbon structures, such as graphene and carbon nanotubes, as targets with a remarkable sensitivity to dark matter-nucleon interactions, in the mass range between the 1 MeV and 100 MeV. The ejection of a proton following the interaction with a dark matter particle is a quasi-elastic process, with an extremely small energy threshold, and a clear experimental signature. The proposed detectors are simple, technologically ready, and inexpensive. Yet, they can be considerably more sensitive than current experiments. They also allow strong directionality, to be used towards efficient background rejection. We employ Density Functional Theory (DFT) to model the electron dynamics during the scattering events that result in proton emissions and to characterize the interactions of low-energy protons with carbon structures.

Speaker: Guglielmo Papiri (Cornell University)

13:45 Cavendish Searches for Millicharged Particles

A terrestrial population of millicharged particles can arise if they constitute a subcomponent of dark matter, or if sufficiently light millicharged particles are produced in cosmic-ray air showers. Through repeated scattering with ordinary matter, these particles thermalize to terrestrial temperatures in Earth’s environment. I will show that a simple electrified shell, such as a Van de Graaff generator, acts as an efficient accumulator of these room-temperature particles and can enhance their local density by up to twelve orders of magnitude. A millicharge detector placed inside the shell can therefore gain a dramatic boost in sensitivity. In particular, Cavendish tests of Coulomb’s law act naturally as both accumulators and detectors of this overdensity. Reinterpreting past Cavendish experiments already yields some of the strongest bounds on terrestrial millicharged-particle populations. I will also discuss a modified setup in which the Cavendish apparatus is surrounded by an additional charged shell, substantially improving the reach and potentially enabling detection of the minimum density generated by cosmic rays. With established electrostatic technology, such experiments can surpass the projected sensitivity of future accelerator searches for sub-GeV masses.

Speaker: Zachary Bogorad (Fermilab)

14:00 Axion Dark Matter Search with NV Centers: Hybrid-Spin Decoupling

I will discuss new ideas for direct detection of axion dark matter by employing quantum sensing techniques with nitrogen-vacancy (NV) centers in diamond. NV centers provide a well-motivated and mature quantum-sensing platform, consisting of fully controllable and measurable electron and nuclear spins. I will present our recent efforts to develop and validate quantum-sensing protocols, which we call hybrid-spin decoupling, that exploit the characteristic features of this system to realize co-magnetometry with broadband sensitivity to exotic spin interactions. Throughout the talk, I will emphasize that NV centers, as quantum-sensing devices, offer multiple avenues for quantum advantage, enabling searches over a wide mass range and improving sensitivity.

Speaker: So Chigusa (Massachusetts Institute of Technology)

14:15 Looking for Dark Matter with Two-Photon Superradiance

As large-volume experiments scale up, alternative quantum detection methods are being pursued, including searches that take advantage of quantum coherence. These experiments can have sensitivities scaling quadratically with the size of the experiment, as opposed to the linear scaling of large underground experiments. I discuss the theory behind one such experiment, CATCHY, which searches for dark photons via spontaneous two-photon superradiance of a large coherent volume of parahydrogen.

Speaker: Andrew Buchanan (Queen's University)

14:30 Charting the light dark matter landscape with matter-wave interferometers

Matter-wave interferometers (MWIs) provide a uniquely quantum route to dark matter (DM) detection: DM can be detected through phases and decoherence between spatially separated wavepackets, even when energy deposition is negligible and no recoil is resolvable. I will describe an open effective field theory for MWIs, formulated using the Schwinger-Keldysh formalism, that systematically computes these observables and clarifies the relation between them. A key outcome is a structural asymmetry between phase and decoherence: for elastic spin-independent DM scattering, decoherence can receive Bose enhancement or Pauli blocking factors, whereas the phase remains at most linear in the DM occupation number. Using these results, I will then turn to novel ideas for probing light DM with matter-wave interferometry, including trapped-ion platforms and correlated pairs of mesoscopic interferometers, which may open sensitivity to unexplored regions near the wave--particle boundary.

Speaker: Leonardo Badurina (California Institute of Technology)

14:45 Binary-boosted Dark Matter

Through gravitational interactions, binary systems can boost the energy of transiting dark matter (DM) particles. I will show how this effect is most efficient for double black hole binaries, which can eject DM with velocities substantially above its typical halo speed. The resulting boosted DM flux from a galactic population of these systems can extend the sensitivity of large-volume detectors, such as PandaX-4T or LZ, to sub-GeV masses in a nearly model-independent manner. Because this mechanism is also largely mass-independent, it can improve sensitivity to inelastic DM, even in the heavy-mass regime.

Speaker: Javier Acevedo (University of Victoria)

15:00 → 15:30 Coffee

15:30 → 17:30 Topical Highlights

15:30 Impact of Galactic Dark Matter Velocity Distribution on Single Phonon Scattering Rates

Direct-detection analyses typically assume the Standard Halo Model(SHM) with a Maxwell–Boltzmann distribution for the local galactic dark matter velocity, but deviations from this form and uncertainties in the velocity parameters must be quantified to reliably interpret experimental results. We carry out a systematic study of how these uncertainties propagate into single-phonon scattering rates, considering three benchmark halo models (SHM, Tsallis, and empirical) and four representative crystalline targets. Previous comparisons fixed the characteristic velocity across models, conflating shape differences with energy-scale differences. We instead introduce an rms-matching prescription that normalizes models to a common root-mean-square velocity. Under this prescription, the dominant source of uncertainty arises from the circular speed $v_\text{c}$, which controls the bulk of the distribution; differences in the velocity distribution function are subdominant compared to parameter variations within any single model. Uncertainties are largest at the lowest kinematically accessible dark matter masses and persist to higher masses for heavy mediators. For the daily modulation signal, parameter variations rescale the amplitude while leaving the phase robust across all halo model assumptions.

Speaker: Navaneetha Valsan (University of Utah)

15:45 Improved supernova bounds on CP-even scalars: cooling and decay constraints

Supernovae provide among the most powerful probes of weakly-coupled new particles in the MeV mass range, where laboratory experiments lose sensitivity. In this work, we constrain the mixing angle $\sin \theta$ of a Higgs mixed scalar to five orders of magnitude below the existing collider bounds ($\sin \theta \sim 10^{-9}$) using an improved supernovae cooling bound and with new decay-based constraints from the galactic 511 keV positron flux and energy deposition in low-energy Type II-P supernovae. We also extend our analysis to a hadrophilic scalar model, constraining Yukawa couplings down to $y_N \sim 10^{-10}$.

Speaker: Anirudhan Alanthatta Madathil (University of Utah)

16:00 Cold and Fuzzy Dark Sector

In this talk, I will introduce the Fuzzy Dark Sector (FDS) scenario: a rich, interacting system and candidate for dark matter. This serves as a natural extension of the single-component, non-interacting Fuzzy Dark Matter (FDM) paradigm. Concretely, I will discuss an ultra-light Abelian-Higgs model, with interacting Higgs and dark photon degrees of freedom. In cosmology, the transfer function is characterized by a single scale dependent on the FDS parameters, allowing one to recover the LSS signature of single-field FDM. In contrast, galactic halos present a great diversity, unlike with the universality of single-field FDM, owing to the interaction between fields. This interaction introduces an instability that is not otherwise present for the case of four decoupled scalars. I will comment on the possible primordial production and portals to the Standard Model, and conclude with general lessons applicable to the many possible FDS realizations.

Speaker: Christian Capanelli (McGill University)

16:15 Cosmology-informed constraints on the fuzzy dark matter mass from dwarf-spheroidal stellar kinematics

Fuzzy dark matter (FDM) predicts a solitonic core within halos, in contrast to the cuspy inner profiles expected in the standard cold dark matter (CDM) model.
We investigate differences in the inner structure of dark matter halos through the stellar kinematics of dwarf spheroidal galaxies, which place constraints on the FDM particle mass.
We analyze the parameter space using a statistical framework with cosmology-informed priors derived from the Semi-Analytical SubHalo Inference ModelIng (SASHIMI), which restricts the outer NFW-like halo parameters to cosmologically motivated regions.
Guided by recent FDM simulations, we further assume a smooth connection between the inner soliton and outer NFW-like profiles, enabling an efficient constraint on the FDM mass. As shown in the previous study, Segue 1 provides the most stringent constraint $m_{FDM}\gtrsim10^{-21}\ \mathrm{eV}$ even when the cosmological priors are taken into account.

Speaker: Shunichi Horigome (Tohoku University)

16:30 Circumstellar Medium of Supernovae as New Probes for Feebly-interacting Particles

We propose a novel strategy to probe feebly-interacting particles (FIPs) by exploiting the dense, confined circumstellar medium (CSM) surrounding core-collapse supernovae (CCSNe). FIPs produced in the proto-neutron star can deposit substantial visible energy into the CSM via decay prior to the shock breakout from the progenitor star. This energy injection heats and ionizes the CSM, establishing a FIP-induced photosphere that generates distinctive precursor blackbody emission. Using early-time observations of SN 2023ixf, we translate the non-detection of excessive precursor luminosity into stringent new constraints on MeV-scale dark photons as an exemplary model. Our results significantly extend existing CCSN bounds and exclude previously unexplored regions of parameter space. We further demonstrate that the FIP-induced dust sublimation offers robust diagnostics for future Galactic SNe, opening a new avenue to explore the dark sector.

Speaker: Chui-Fan Kong

16:45 Axion and dark photon emission modified by magnetic dispersion: A case study of magnetic white dwarfs

Some of the strongest constraints on axions and dark photons (DPs) come from their emission in astrophysical plasmas. However, many of these studies assume isotropic plasma conditions, which are rarely realized in realistic environments due to the ubiquitous presence of magnetic fields. In magnetized plasmas, the standard transverse and longitudinal photon polarization modes become mixed, leading to new propagation eigenmodes. In this talk, I will present a general formalism to determine these modified normal modes and their couplings to axions and DPs in anisotropic magnetized media. Using magnetic white dwarfs (MWDs) as a case study, I will demonstrate how magnetic dispersion modifies the resonance structure and leads to strongly directional emission, extending or reshaping the regions where resonant production can occur inside the star.

Speaker: Nirmalya Brahma (McGill University)

17:00 X-rays from Inelastic Freeze-in

Inelastic dark matter (iDM) consists of two almost mass-degenerate Majorana states with a small mass splitting and has been widely studied for its unique phenomenology. We consider iDM with a light dark photon/lepton-specific scalar mediator which feebly couples to the Standard Model particles. iDM is produced by freeze-in: the couplings are too small to put iDM in chemical equilibrium but can still gradually generate it to the observed abundance. Since the mediator is lighter than iDM, the coupling for DM abundance directly relates to the decay rate of the heavier state. The mass-splitting smaller than two electron masses and feeble couplings make the heavier state cosmologically long-lived. The suppressed decay of the heavier state emits three/two photons, which can be detected by an X-ray telescope. We conduct the Bayesian analysis of the 16-year data from the spectrometer onboard the INTEGRAL telescope using python-based platform 3ML; we then set the limits for the coupling of 100-MeV scale dark photon/lepton-specific scalar mediator and GeV-scale iDM. The resulting constraints are complementary to those from the existing collider and beam dump experiments.

Speaker: Riku Mizuta (TRIUMF / University of British Columbia)

17:15 New bounds on light scalars from the tip of the red-giant branch

Light, weakly coupled new particles are produced efficiently in the hot and dense interior of stars. The resulting effects on stellar evolution can have distinct observable impacts on stellar populations, leading to some of the strongest bounds on new light particles. We revisit stellar bounds on electrophilic scalars arising from the tip of the red-giant branch (TRGB) of globular clusters, and set new bounds stronger by more than an order of magnitude in the coupling squared. We improve upon previous constraints, which relied on a rescaling of neutrino emission rates, by self-consistently simulating the effects of stellar energy loss using the MESA stellar evolution code, accounting for relevant backreaction processes. We also account for all the in-medium production channels of light scalars more accurately, including both resonant and continuous emission. We find that scalar emission leads to a significantly brighter TRGB, and set bounds by comparing our predictions to bolometric luminosity observations of 14 globular clusters from the Gaia database.

Speaker: Natnael Debru (McGill University)

Wednesday 29 July

09:00 → 09:30 TBA

Speaker: Akshay Ghalsasi (University of Pittsburgh)

09:30 → 10:00 TBA

Speaker: Asimina Arvanitaki

10:00 → 10:30 Dark matter drag on Saturn's Rings

If dark matter is sufficiently light, it can coherently scatter with macroscopic objects, greatly enhancing its scattering cross-section. This allows the wind of dark matter through our Solar System to apply sizeable forces on objects. It turns out that the ideal size of object for which the coherent effect is maximized but the acceleration is still large is in the 1-10 cm range. This motivates us to look for observational effects in the dense planetary ring systems in which these particles sizes dominate. We find that the dark matter creates a drag force on Saturn's rings which can be larger than the equivalent effect from Solar radiation, and which would affect smaller particles more than larger ones. It may have been possible to use this to constrain the dark matter---however, as it turns out, there actually is a yet-unexplained mass segregation which has been observed in Saturn's main rings.

Speaker: Zachary Picker (Queen's University, Kingston)

10:30 → 11:00 Coffee

11:00 → 11:30 TBA

Speaker: Prof. Miha Nemevsek (Jožef Stefan Institute and University of Ljubljana)

11:30 → 12:00 The SuperCDMS SNOLAB experiment: overview and status of commissioning and the first science run

SuperCDMS SNOLAB is a cryogenic experiment projected to achieve world-leading sensitivity for dark matter particles below 10 GeV/$c^{2}$ using semiconductor crystal detectors. The experiment employs two detector types: iZIP detectors, which utilize both phonon and charge channels to provide excellent nuclear recoil/electron recoil discrimination, and HV detectors, which utilize the NTL effect to amplify the measurable phonon signal in proportion to an applied external electric field to achieve lower detection thresholds. Commissioning of the full 24 detector payload, comprising both silicon and germanium iZIP and HV detectors, began in early 2026. This talk presents preliminary results from the characterization and commissioning of the full detector payload, along with a first look at early SuperCDMS SNOLAB data. As the experiment begins its first science run, this talk will also discuss the experimental outlook and ongoing R\&D efforts aimed at developing the next generation of low-background detectors for sub-GeV dark matter detection.

Speaker: Matthew Wilson (University of Toronto)

12:00 → 13:00 Lunch

13:00 → 15:00 Topical Highlights

13:00 Probing Neutrino Compositeness with Invisible and Displaced Signals

We explore the possibility that neutrinos couple to an interacting sterile sector, providing a novel portal that generalizes the heavy neutral lepton portal to a composite setting. For a low confinement scale, high-energy neutrino beams can disintegrate into collimated sprays of hidden states, referred to as dark jets. This dynamics gives rise to two characteristic signatures in high energy neutrino beams. First, long-lived dark resonances can enhance the neutral-current to charged-current ratio. Second, shorter-lived dark states produced in neutrino neutral currents can produce single or multiple displaced vertices and even emerging jets, depending on the kinematics. These signals probe regions of parameter space beyond existing constraints from meson and electroweak decays, as well as from searches at beam dump experiments. Finally, we outline an experimental program spanning both the intensity and energy frontiers. Near-term neutrino facilities (DUNE, FPF) and running flavor experiments (LHCb, Belle II) can probe neutrino compositeness through neutrino disintegration into dark jets and displaced B-meson decays. Future colliders, particularly the Future Circular Collider (FCC-ee), will ultimately provide the strongest sensitivity to the compositeness scale via displaced Z decays.

Speaker: Marco Costa

13:15 Can the LHC be sensitive to the Light Dark World?

We propose a novel method to probe visibly decaying dark photons at the LHC with masses of 10 MeV to 10 GeV, providing complementarity with short baseline beam dump experiments. Dark photons can be produced at the LHC through neutral meson decays, bremsstrahlung off baryons, or directly produced in association with a jet. We consider visible decays to electron or muon pairs as the signal channel and describe methods to control backgrounds. We present the projected sensitivities considering various background estimations and signal threshold requirements.

Speaker: Dr Deepak Sathyan

13:30 eta/eta' mesons as laboratories for new light physics

Rare and symmetry-constrained decays of η, η′ mesons offer a flavor-conserving window into BSM physics that is complementary to other searches. Potential signatures include new light particles such as hidden photons or photon-like bosons, light Higgs bosons, or axion-like particles that mimic rare SM decays. In this talk, I will present theoretical models and motivations, as well as experimental prospects, for BSM searches at current and future η, η′ factories (and beyond).

Speaker: Sean Tulin (York University)

13:45 Long-lived vectors from electromagnetic cascades at SHiP

We simulate dark-vector, V, production from electromagnetic cascades at the recently approved SHiP experiment. The cascades (initiated by photons from π0 →γγ) can lead to 3-4 orders of magnitude increase of the event rate relative to using primary production alone. We provide new
SHiP sensitivity projections for dark photons and electrophilic gauge bosons, which are significantly improved compared to previous literature. The main gain in sensitivity occurs for long-lived dark
vectors with masses below∼50−300 MeV. The dominant production mode in this parameter space is low-energy annihilation e+e−→V(γ). This motivates a detailed study of backgrounds and efficiencies in the SHiP experiment for sub-GeV signals.

Speaker: Tao Zhou (Texas A&M University)

14:00 Opening the GeV Window at the LHC

In this talk, I present a recently proposed search strategy for GeV-scale particles that couple predominantly to light quarks at the LHC. Such models have often been assumed to be experimentally indistinguishable from QCD jets. We demonstrate that this is not the case. These particles can be perturbatively produced at the LHC and promptly decay into only a few hadrons, giving rise to jets with anomalously low charged-track multiplicity and mass. I will also discuss possible improvements that can be made for HL-LHC.

Speaker: Carlos Henrique de Lima (TRIUMF)

14:15 Global analysis of ALP-mediated multiboson production at the LHC

A SM extension with a light Axion-like Particle (ALP) in a large mass range can be parametrised in terms of a linear ALP-EFT, which couples the ALP to SM particles through momentum-dependent dimension-5 operators.
These interactions can lead to distinctive signatures in various processes at collider experiments such as the LHC.
Couplings of ALPs to SM fermions, in particular to top quark, can be probed by reinterpreting SM LHC measurements and assuming the ALP collider stable.
In this talk, I will focus on multiboson production, where the ALP appears as an off-shell mediator rather than a narrow resonance and assume that the ALP couples only to the gauge sector of the SM.
I then present the first global analysis of ALP-mediated multiboson processes, combining measurements of diphoton, ZZ, W+W−, dijet, and vector-boson–fusion final states.
Using Run-2 LHC measurements, bounds can be cast on the Wilson coefficients (cG, cW , cB) that parametrise gluonic and electroweak ALP interactions.

Speaker: Fabian Esser

14:30 TeV-scale Unification of Light Dark Matter and Neutrino Mass

We demonstrate that TeV-scale heavy neutral leptons (HNLs) responsible for inverse-seesaw neutrino mass generation can simultaneously fix the cosmological abundance and decay properties of dark matter (DM). The spontaneous breaking of lepton number gives rise to a pseudo-Nambu-Goldstone boson that serves as a light DM candidate, whose mass originates from a small explicit symmetry-breaking term. The same HNLs that generate neutrino masses produce the DM via freeze-in and mediate its decay into neutrinos, leading to a tight correlation among neutrino masses, DM relic abundance, and DM lifetime. For collider-accessible TeV-scale HNLs, the observed relic density and lifetime constraints point to sub-GeV DM, yielding observable neutrino signals at JUNO and next-generation detectors such as Hyper-Kamiokande and DUNE. This framework establishes a predictive and experimentally testable link between neutrino mass generation and DM.

Speaker: Dr Shu-Yu Ho (Academia Sinica)

14:45 Constraining Neutrinophilic Scalars from Electroweak Precision

Strong self-interaction among the active neutrinos mediated by a neutrinophilic scalar is a well-motivated target of particle physics and cosmological probes. In this talk, I will present precision electroweak constraints on models for neutrino self-interaction, pointing out the importance of neutrino charged-current coupling correction and its impact on the Fermi constant measurements. This effect was overlooked previously and allows us to derive the leading constraint on the neutrinophilic couplings for the mediator mass above a few hundred MeV. Further, I will talk about a UV completion including a TeV-scale $SU(2)_L$ triplet scalar and show that the simplified model constraints continue to hold for a wide range of parameter space. These results serve as a useful road map for future explorations of the self-interacting neutrino paradigm.

Speaker: Drona Vatsyayan (Carleton University)

15:00 → 15:30 Coffee

15:30 → 17:30 Topical Highlights

15:30 Superradiant interactions in the non-perturbative regime

A large ensemble of two-level systems where each is prepared in an equal superposition of ground and excited states is the quantum analogue of a classical oscillating dipole. Scattering of weakly interacting cosmic relics off such a dipole is dramatically enhanced due to collective effects analogous to Dicke superradiance, where the de-excitation and excitation rates of the ensemble scale as the square of the number of particles in the system, $N^2$. We coined the term ``superradiant interactions’’ to describe these effects. Because of this collective enhancement, the cross-section of these scattering processes can quickly become non-perturbative, as $N$ is increased. In this talk, I will explain this new regime, exhibited by a variety of particles both within and beyond the Standard Model. I will describe how one goes beyond the Born approximation to scattering and into the eikonal regime, and how observables on quantum detectors, such as energy transfer and decoherence, appear and scale in this regime. If time permits, I will show the new parameter space that can be probed using these effects, utilizing the recently proposed SIREN (Superradiant Interactions for Relic detection with Entangled Nuclear spins) quantum protocol.

Speaker: Marios Galanis (Stanford University)

15:45 Baryogenesis catalyzed by leptonic sphalerons: Rise of the Lepto-Axion

We construct a ``theory of many things'' based on gauging the approximate $SU(3)_H$ lepton flavor symmetry of the Standard Model. The lepton sector parallels the quark sector as its own Higgsed QCD with $N_c = 3, N_f = 2$. From the quark sector, the DFSZ axion solves strong CP and gives rise to QCD axion DM. Meanwhile the parallel lepto-axion can bias the early-universe $\text{SU}(3)_H$ sphaleron transition to generate chiral lepton asymmetries, which are reprocessed into a baryon asymmetry via electroweak sphalerons. We analyze contributions to the mass of the lepto-axion from UV instantons of $\text{SU}(3)_H$, as well as a dynamical contribution from the presence of lepton-flavor monopoles.

Speaker: Maximilian Volker Berbig

16:00 Light Dark Matter from QCD-like dynamics

QCD-like theories provide a compelling dark matter candidate in the form of dark pions—light particles emerging as Nambu–Goldstone bosons from the spontaneous breaking of chiral symmetry. The dynamics of dark pions can induce sizeable dark matter self-interactions, potentially alleviating some tensions between simulations of collisionless cold dark matter and observations of dwarf galaxies and other small-scale structures. The introduction of a portal connecting the dark sector to the Standard Model offers additional phenomenological insight. In this talk, I will discuss dark pion self-interactions in halos and examine the implications of explicit portal scenarios, focusing in particular on those involving axion-like particles and sterile neutrinos.

Speaker: Giacomo Landini (LNF-INFN)

16:15 DM genesis in the reheating era

The post-inflationary reheating era plays a pivotal role in shaping the thermal history of the Universe,
yet its dynamics remain poorly understood. In this talk, I will examine how various reheating scenarios impact dark matter (DM) production, encompassing both thermal and non-thermal origins.
Using general parametrizations for the Hubble expansion rate and the evolution of the Standard
Model temperature, I will present a unified framework to study DM genesis, including freeze-out
mechanisms (WIMPs, SIMPs, ELDERs, Cannibals), ultra-relativistic freeze-out (UFO) and freeze-in
processes (both infrared and ultraviolet regimes). These dynamics can significantly alter the viable
DM parameter space, enabling much heavier thermal DM candidates and extending the reach for
light feebly interacting particles. I will highlight the interplay between theoretical predictions and
experimental constraints, emphasizing how future searches could uncover distinctive imprints of
DM production during reheating.

Speaker: Kuldeep Deka (New York University Abu Dhabi)

16:30 On ground states of self-gravitating scalar fields

Axion-like particles have become a popular dark matter candidate in the past decade, in part due to their fascinating wave-like dynamics. This small-scale behavior is due to characteristic observable cores in ULDM called solitons, which also correspond to the ground state of the equations governing the particles’ dynamics. Thus, one promising avenue for studying ULDM dynamics is by treating individual halos as gravitating hydrogen atoms and calculating the full spectrum of their eigenstates, which are then linked to the qualitative behaviours of the halo. In this talk, I will outline a way forward for predicting distinct phases of ground states of two axion species models, in line with expectations from cold atoms research. The ultimate aim of this research direction is to create a link between UV axiverse predictions to testable astrophysical predictions.

Speaker: Luna Zagorac (McGill University)

16:45 SQWARE-ing the Circle: A new strategy to close the meV axion gap

Since the mass scale of QCD axion dark matter is not known, a diverse array of experimental techniques are required to ensure complete coverage over the space of theories. Currently coverage is lacking at meV masses, corresponding to the so-called terahertz gap. In this talk I will describe the Semiconductor-Quantum-Well Axion Radiometer Experiment (SQWARE) — a new experimental platform for direct detection of axion dark matter in the meV mass range — based on resonantly enhanced axion-photon conversion through the inverse Primakoff effect in engineered quantum semiconductor heterostructures. I will describe the operating principles of the proposed experiment, present the projected sensitivity to axion dark matter, and discuss ongoing work in laboratories at the Rice Center for Quantum Materials.

Speaker: Andrew Long (Rice University)

17:00 Axion string birefringence from AMR simulations

Axion-like particles (ALPs) can form a network of cosmic strings that persists after recombination and induces birefringence in the cosmic microwave background (CMB), rotating the plane of polarization of propagating photons. In this work, we analyze a high-resolution simulation of an axion string network generated using adaptive mesh refinement (AMR) techniques. By performing ray tracing through the three-dimensional field configuration, we compute the cumulative rotation angle experienced by CMB photons along their line of sight from the last scattering surface to the present epoch. Our results show how the spatial distribution and evolution of the string network imprint characteristic spatial variations in the birefringence angle, and assess their detectability with current and next-generation CMB polarization experiments.

Speaker: Moira venegas villa

17:15 WIMP Meets ALP: Coherent Freeze-Out of Dark Matter

We consider the cosmological history of a weakly interacting massive particle (WIMP) coupled to a light axion-like particle (ALP) via a quadratic coupling. Although the coupling is too feeble to thermalize the ALP, coherent forward scattering between the two sectors induces temperature-dependent mass shifts that substantially modify both WIMP freeze-out and ALP misalignment dynamics, giving rise to a novel coherent freeze-out mechanism. At high temperatures, the WIMP thermal bath spontaneously breaks the symmetry of the ALP potential, displacing the field to a new vacuum. The resulting back-reaction reduces the WIMP effective mass and delays its freeze-out. Depending on the strength of the coupling, symmetry restoration occurs via either a first-order phase transition (FOPT) or a crossover. In the FOPT regime, dark matter consists solely of WIMPs, whose delayed freeze-out permits annihilation cross sections up to two (five) orders of magnitude above the standard value for s-wave (p-wave) annihilation, while still yielding the correct relic density. In the crossover regime, both WIMP and ALP can contribute to dark matter. Remarkably, we find an "ALP miracle": a Planck-suppressed quadratic coupling yields an ALP abundance comparable to the observed dark matter density, largely independent of its initial displacement and mass.

Speaker: Maxim Perelstein (Cornell University)

Thursday 30 July

09:00 → 09:30 TBA

Speaker: Alan Robinson (Université de Montréal)

09:30 → 10:00 Probing Inflationary Reheating with Dark Matter

The thermal history of the Universe before Big Bang Nucleosynthesis (BBN) remains one of the least constrained epochs in cosmology, owing to the absence of direct observational probes. Reheating, which bridges the end of inflation and the onset of the radiation-dominated era, plays a central role in shaping the thermal history before BBN, yet its dynamics remain poorly understood. Since dark matter (DM) production depends sensitively on the thermal history prior to BBN, it can serve as a probe of reheating and, more broadly, of the pre-BBN Universe. Using representative examples such as sterile neutrinos, axions and ALPs, I will show how DM production and possible observational signatures can extract information about reheating dynamics and key parameters. DM is therefore not only a major cosmic component, but also a record of the cosmological history that shaped its production.

Speaker: Yong Xu (McGill University)

10:00 → 10:30 Mirror Stars

Speaker: David Richard Curtin (University of Toronto)

10:30 → 11:00 Coffee

11:00 → 11:30 Exploring hidden sectors with the DarkLight experiment

The nature of dark matter remains one of the largest open questions in particle physics. Despite numerous theories and experimental searches, both small-scale and large-scale, it has so far remained unobserved at the particle level. The DarkLight experiment located at TRIUMF in Vancouver, Canada aims to leverage the ARIEL electron linear accelerator to search for a new dark sector force carrier in the 10-20 MeV range. Such a force carrier would undergo kinetic mixing with Standard Model photons, and could provide possible explanations for experimental anomalies like the X17. The DarkLight experiment was installed in 2025, and completed its first commissioning runs in early 2026. This talk will primarily focus on highlighting the results of this commissioning as well as future plans.

Speaker: Laura Miller (TRIUMF)

11:30 → 12:00 TBA

Speaker: Daniel Carney (Berkeley National Lab)

12:00 → 13:00 Lunch

13:00 → 13:30 Topical Highlights

13:00 Sub-GeV Dark Matter Detection with Dark Rates in Liquid Scintillators

It was recently shown that standard sub-GeV dark matter candidates can be effectively probed by large neutrino observatories via annual modulation of the total photomultiplier hit rate. That work focused on the production of light by the excitation of scintillator molecules and considered the JUNO detector, surpassing limits from dedicated dark-matter detectors and reaching theoretical targets. Here, we significantly generalize that work, now also taking into account ionization channels and extending the analysis to other liquid-scintillator detectors, including SNO+, Daya Bay, Borexino, and KamLAND. Last, we present a call to action: with multiple detectors achieving competitive sensitivity, there is an opportunity to validate this new technique across experiments and to refine it using each detector’s strengths.

Speaker: Lillian Santos-Olmsted

13:15 New Strategies for sub-GeV Direct Detection

Anisotropic direct detection experiments can discover dark matter even in the presence of irreducible Standard Model backgrounds, by using daily modulation to isolate the dark matter signal. Our new ab initio molecular physics package, SCarFFF, makes it possible to sift through millions of molecules to find the ones best suited for dark matter detection. What properties should we be looking for? In this talk, I show how an ensemble of different materials could provide the foundation for an unambiguous discovery of dark matter, and I explain why the ideal detector should include both parity-breaking and parity-symmetric materials.

Speaker: Benjamin Lillard (Pennsylvania State University)

13:30 → 14:00 TBA

Speaker: Thomas Brunner (McGill University)

14:00 → 14:30 TBA

Speaker: Prof. Wei Wang (Sun Yat-sen University)

14:30 → 15:00 Direct detection searches for dark matter with liquid argon

Liquid argon is an excellent target material in direct detection experiments searching for physics beyond the Standard Model. It is an abundant noble element, is transparent to its own scintillation light, and features exquisite performance in pulse-shape discrimination, enabling ultra-low-background searches. This talk will discuss results from DEAP-3600 and DarkSide-50 in the search for new particles, including light dark matter and solar axions. The sensitivity of next-generation detectors will also be explored: DarkSide-20k, a time projection chamber under construction at LNGS with essential Canadian contributions; ARGO, a 300-tonne fiducial mass detector being designed for deployment at SNOLAB; and AURORA, a proposed tonne-scale time projection chamber optimized as a low-threshold electron-counting measurement using only the ionization channel to have sensitivity to GeV-scale dark matter.

Speaker: Prof. Simon Viel (Carleton University)

15:00 → 15:30 Coffee

15:30 → 17:30 Topical Highlights

15:30 Finite temperature and density effects and BSM phenomenology

In-medium properties of particles differ significantly from vacuum ones, due to finite temperature and density effects. For example, the photon in a plasma acquires an effective mass and can thus decay into neutrinos, a process forbidden in vacuum. Finite temperature and density effects are also crucial for accurate Beyond the Standard Model (BSM) phenomenology. Indeed, processes involving BSM particle are often studied inside a medium, for example in stars or in the primordial plasma. However, many calculations still rely on the vacuum particle physics treatment, which can miss important effects like new decay channels and resonances.

In this talk, I will present a comprehensive procedure to take into account in-medium effects for BSM physics phenomenology. I will focus on qualitatively new in-medium effects, such as resonances and interference diagrams with the medium particles. I will also present concrete applications of these effects in models of scalar BSM particles.

Speaker: Hugo Schérer (McGill University)

15:45 Probing Hadronic Dark Matter Annihilation with Big Bang Nucleosynthesis

The first elements in the Universe were synthesized within a few minutes after the Big Bang, in the epoch known as Big Bang Nucleosynthesis (BBN). Precise measurements from astrophysical observations, the cosmic microwave background (CMB), and nuclear reaction rates render BBN an essentially parameter-free theory, making it a powerful test of new physics. In this talk, I will show how BBN can be used to probe residual annihilations of sub-GeV thermal relic dark matter (DM). I will focus on candidates with velocity-suppressed annihilation channels and show that DM annihilation to pions and kaons beyond freeze-out, and their subsequent interaction with protons and neutrons prior to the deuterium bottleneck provide a sensitivity to annihilation that surpasses that of the CMB and indirect detection in the galaxy.

Speaker: Afif Omar

16:00 The Sound of the Universe: A Resonant Gravitational Instability Driven by Baryon-Dark Matter Relative Drift

The classical Jeans instability states that baryonic perturbations grow only above the Jeans scale, while cold dark matter is unstable on all scales. In this talk, I will show that the relative drift between baryons and dark matter after decoupling fundamentally alters this picture.
When the projected DM drift is subsonic, a new resonant gravitational instability – the Shalaby‑Broderick instability – drives exponentially growing sound waves in the baryons, with growth rates exceeding the intrinsic DM growth rate. In baryon‑dominated environments, the instability also opens a stable window between the Jeans scale and the resonant scale.
I will demonstrate that the associated timescales range from years to tens of millions of years across diverse astrophysical systems – planets, stars, molecular clouds, galaxies, and galaxy clusters – typically much shorter than their ages. On cosmological scales, the instability enhances baryon density perturbations for appropriately oriented modes while suppressing those aligned with the DM stream, leaving a distinct anisotropic imprint on the 21 cm signal and the distribution of early galaxies.
Crucially, this resonant mechanism provides a fundamentally new way to detect dark matter directly – not through particle‑particle collisions, but through the gravitational resonance between baryonic sound waves and Doppler‑shifted DM modes. This opens observational windows via seismic vibrations (Earth, Moon, ice sheets), galactic spiral structure, and pulsar timing arrays – turning the relative motion of dark matter from a nuisance into a powerful diagnostic tool.

Speaker: Dr Mohamad Shalaby (University of Waterloo)

16:15 Gravothermal collapse beyond minimal models of self-interacting dark matter

Light mediators in the dark sector can give rise to dark matter self-interactions. Looking beyond minimal models of self-interacting dark matter that typically only have elastic interactions, there is growing interest in dissipative dark sectors, which can significantly modify the evolution of dark matter halos through inelastic processes. We consider an inelastic dark matter model made up by a fermion and a light U(1) gauge boson, and assume that the fermion splits into two states due to a Majorana mass term. We obtain cross sections for the relevant dark sector interactions by solving the two-state Schrödinger equation, which we then use to simulate the gravothermal collapse of dark matter halos. Finally, we demonstrate how one can place constraints on the allowed parameter space of the underlying dark matter model by comparing with constraints on the self-interaction cross section from galactic observations.

Speaker: Leo Kim

16:30 Dark Matter–Induced UV Radiation and the Formation of Supermassive Black Hole Seeds

The recent discoveries of the high-redshift quasars at $z\sim6-10.1$ present a challenge to conventional supermassive black hole (SMBH) formation scenarios: their central SMBH is too large to have grown from early stellar remnants, even under efficient super-Eddington accretion. An alternative approach is the direct collapse of primordial, dust and metal-free gas clouds into black hole seeds as early as $z\sim20$. To prevent fragmentation from highly efficient molecular hydrogen cooling and allow such a collapse, a strong flux of UV photons is required to photodissociate molecular hydrogen, suppressing star formation. We investigate the decay or annihilation of dark matter with masses below a few hundred eV to produce sufficient UV radiation, both from the cosmological background and within early dark matter halos. Using thermal simulations of a one-zone primordial gas cloud model with the Grackle chemistry and cooling library, we map the resulting gas behavior across a range of dark matter lifetimes, cross sections, and masses. From this, we determine regions of parameter space where direct collapse into an SMBH is possible and determine the corresponding minimum halo mass required.

Speaker: Han Wu (Queen's University, McDonald Institute)

16:45 Primordial Black Holes from Domain Wall Nucleation during Inflation: an Update

We revisit the mechanism for production of primordial black holes (PBHs) via collapse of domain walls nucleated during inflation. We highlight the importance of the intrinsic domain wall asymmetry that precludes formation of light black holes — an effect overlooked in the previous studies. As a result, the mass spectrum of PBHs produced by this mechanism gets cut at the low PBH mass end, making it compatible with the existing constraints. A spectrum peaked in the asteroid mass window can account for all of dark matter and possesses a model-independent power-law tail extending towards higher masses. It will be probed by the upcoming Roman microlensing survey.

Speaker: Dr Sergey Sibiryakov (McMaster U. & Perimeter Inst.)

17:00 Analytic Approximations for Fermionic Preheating

Light non-thermal fermions can be produced non-perturbatively in the early universe during coherent oscillations of a scalar field. We explore fermion production in $\lambda\phi^{4}$ inflation through this mechanism and analyze the momentum spectrum of the fermions produced, which depends on a coupling parameter $q$. For $q \gtrsim 0.01$, the main contribution to the total number density comes from an approximately half-filled Fermi sphere as a result of non-adiabaticity. For $q\lesssim 0.01$, we find that the major contributions instead come from resonance peaks at higher momentum values. We find a simple relation to predict the momentum values corresponding to resonance peaks for any $q$. We also obtain analytic power-law approximations for the total number density of fermions and find that it is proportional to $q^{1/2}$ for $q\lesssim 0.01$ and proportional to $q^{3/4}$ for $q\gtrsim 10$. If the light fermions produced by this mechanism make up the entirety of dark matter, we estimate lower bounds on their mass.

Speaker: Fazlul Yasin (Carleton University Ottawa)

17:15 Picolensing as a probe of massive compact dark objects

Compact supermassive dark-matter (DM) states act as gravitational lenses. Widely spatially separated space-based gamma-ray detectors would observe geometrical parallax of such an intervening lens with respect to cosmologically distant gamma-ray bursts (GRB). This parallax can be of order the Einstein angle of the lens, resulting in a significant differential magnification of the source as viewed from the two detectors. Simultaneous brightness measurements of the same GRB made by two detectors can therefore detect or exclude such DM states. Recent studies have shown that this "picolensing" signal could be a promising way to search in particular for primordial black hole (PBH) dark matter in part of the "asteroid mass window", roughly $10^{-15} < M_{\text{PBH}}/ M_{\odot} < 10^{-10}$. In this talk, I will discuss my work to explore the robustness of this signal to various uncertainties not previously carefully accounted for: most importantly, to uncertainties in the transverse extent of the observed GRB emission region. I'll show that, while large GRB source-size uncertainties do degrade previous projections somewhat, it is still possible to probe most of the PBH DM asteroid mass window with a future mission that employs two Swift/BAT-class detectors separated by a distance on the order of an AU. Depending on the total number of GRBs that such a mission ultimately observes, it may even be possible to robustly probe new subcomponent DM parameter space at PBH masses above the window, potentially as high as $2 \times 10^{-8} M_{\odot}$. Time permitting, I will also discuss recent work to extend this observable to the detection of spatially extended dark lenses, such as QCD axion miniclusters.

Speaker: Dr Michael Fedderke (Perimeter Institute for Theoretical Physics)

Friday 31 July

09:00 → 09:30 Topical Highlights

09:00 NGC 1068 constraints on neutrino-dark matter scattering

The IceCube observations of neutrinos from two active galactic nuclei allow one to constrain the interactions of neutrinos with dark matter. The presence of a dark matter spike around the central supermassive black hole leads to limits on the scattering cross section that can exclude new regions of parameter space, depending upon the spike density profile and the energy-dependence of the cross section. The utility of the model-independent constraints is illustrated for dark photon mediators that couple to B-L.

Speaker: James Cline (McGill University, (CA))

09:15 Future gamma-ray searches for light dark matter

Detecting gamma-ray signals that could be due to dark matter (DM) particles would give us invaluable information about the nature of DM. In particular, gamma-ray lines could provide a way to measure the DM mass scale. The excellent energy resolution of the upcoming MeV gamma-ray telescope COSI will allow us to probe underexplored regions of the DM parameter space while being sensitive to distinctive spectral features of potential DM signals. In this talk, I will discuss the case of a fermionic sub-GeV DM charged under a new U(1) gauge symmetry. Both the DM and the new gauge boson Z' acquire mass from a new singlet scalar. The masses of the new particles in this class of vector-scalar portal models are naturally at the MeV scale, which enables detectable gamma-ray lines in the bandpasses of COSI and proposed missions such as AMEGO-X. We estimate the sensitivity of COSI and AMEGO-X to sub-GeV DM in this context, considering a B-L and a purely axially coupled Z' as benchmark examples. We find regions of the parameter space where COSI will provide leading constraints, beyond the strong CMB limits. On the other hand, AMEGO-X would probe most of the viable parameter space leading to continuum gamma rays.

Speaker: Maíra Dutra (NASA Goddard)

09:30 → 10:00 TBA

Speaker: Joshua Berger (Colorado State University)

10:00 → 10:30 TBA

Speaker: Alejandro Ibarra (Technical University of Munich)

10:30 → 11:00 Coffee

11:00 → 11:30 TBA

Speaker: Dr Saniya Heeba (McGill University)

11:30 → 12:00 Advancing Science Underground: Capabilities and Research at SNOLAB

Located deep underground in Canada, SNOLAB is a world-leading facility for astroparticle physics and rare-event science, and a global hub for discovery at the frontiers of knowledge. Its exceptional depth and ultra-clean environment provide an unparalleled setting for next-generation experiments searching for some of the universe’s most elusive phenomena. This talk will explore SNOLAB’s unique capabilities, its role in the international research ecosystem, and highlight the scientific advances and innovations emerging from its program.

Speaker: Jodi Cooley (SNOLAB)

12:00 → 13:00 Lunch