Dark Interactions (DI) is a biennial workshop that brings together world leading physicists of different expertise (particle theorists, particle experimentalists, cosmologists, astrophysicists) to discuss recent progress and new directions in the search for dark matter and dark sectors. The DI 2024 workshop will be hosted at Simon Fraser University (SFU) in Vancouver, Canada. The workshop will run for three days (Oct 16–18, 2024) and will be composed of focused plenary talks covering topics such as: theoretical perspectives on dark sectors, current and future sensitivities from colliders and underground detectors, constraints from astrophysical and cosmological probes, and implications for neutrinos and dark energy.
The program will include both invited and contributed plenary talks. To apply to give a contributed talk, please submit a title and abstract through the "Call for Abstracts" link in the menu. Note: the program is now full and no new abstracts will be accepted.
DI 2024 is supported by the Canadian Institute for Theoretical Astrophysics (CITA), the Institute for Particle Physics (IPP), the McDonald Institute for Astroparticle Physics, the Perimeter Institute, Simon Fraser University (SFU), and TRIUMF.
The strongest constraints on sub-GeV feebly interacting particles are typically derived from beam dump facilities. Historically, these constraints rely on a conservative (under)estimate of the flux focussing only on production within the first interaction length. In this talk I will explain how to consistently include production from the subsequent electromagnetic cascade in the target. Sensitivity can be substantially enhanced at lower masses and weaker couplings (the ``lifetime frontier'') by including electromagnetic cascade production.
The Coherent CAPTAIN Mills (CCM) experiment uses a 10-ton liquid argon scintillation detector at Los Alamos National Laboratory to search for physics beyond the standard model. Such physics includes light dark matter (LDM), axion like particles (ALPs), and Dark Sector coupling to Meson Decay (DSCMD) produced by the LANSCE accelerator. The Lujan Center delivers a 100-kW, 800 MeV, 290 ns wide proton pulse onto a tungsten target at 20 Hz to generate a particle source. The fast pulse, in combination with the speed of the CCM scintillation detector, is crucial for isolating prompt speed of light particles generated by fast source processes such as stopped pions and electromagnetic showers to reduce neutron and steady state background. This talk will describe the CCM experiment and present published and preliminary results from completed runs, as well as the projected reach of our ongoing 3-year run.
PADME is a fixed-target, missing-mass experiment originally designed to search for dark photons using a beam of positrons with energy up to 500 MeV. The detector, located at the Laboratori Nazionali di Frascati, in Italy, has already collected initial physics data over the last few years. More recently, the experiment has been adapted to perform a direct search for on-shell X17 production. PADME will be able to provide independent confirmation of the anomalies observed in the ATOMKI spectroscopic measurements with Beryllium, Helium, and Carbon nuclei. The new experimental setup and the prospects for the observation of X17 production will be discussed, and new upgrades to the detector that will greatly expand the physics program of PADME will be introduced.
Paleo-detectors have been proposed to search for new physics through damage tracks formed by traversing recoiled nuclei in minerals deep underground, leveraging its high exposure time (~Gyr). Paleo-detection is expected to have a very low signal-to-background ratio, it is therefore particularly important to accurately model the expected signals. In previous studies, a one-to-one relationship between recoil energy and the length of the damage tracks was assumed. We used SRIM, a Monte Carlo simulation program that models the transports of ions in lattices, to characterise the track length distributions at various recoil energies. We found that a single track length could be resulted from a wide range of recoil energies. Consequentially, low energy recoils, which with the one-to-one assumption would otherwise result in tracks below currently achievable read-out resolution, in fact could now have measurable contributions to longer, detectable tracks. We used this improved calculation to model nuclear recoils by WIMPS and to search for new physics with light mediators through neutrino-nucleus scatterings.
An early dark energy (EDE) component during big bang nucleosynthesis (BBN) affects some observables like the deuterium abundance (D/H), helium fraction ($Y_p$), and the effective relativistic degrees of freedom ($N_{\rm eff}$). Thus, we propose a model of EDE present during the BBN epoch where the EDE remains constant until a critical time, after which it transitions into either coupled radiation, dark radiation, or kination. By comparing this model's outcomes with observed elemental abundances and $N_{\rm eff}$ from Cosmic Microwave Background (CMB) data, we constrain the EDE parameters and explore their relationship to BBN inputs like the baryon-to-photon ratio, neutron lifetime, and number of neutrino species. We also explore whether an EDE scenario can resolve the recent tension in primordial helium measurements from EMPRESS.
I present a novel mechanism for creating primordial black holes and MACHOs via a self interacting dark matter. A heavy dissipative dark sector can come to dominate the universe, creating an early matter dominated era prior to Big Bang Nucleosynthesis (BBN). At this time the dark matter can form halos which persist after the phase transition back to radiation domination, and slowly collapse at late times. This leads to the late time formation of MACHOs and subsolar mass primordial black holes.
Semi-visible jets (SVJs) arise in strongly interacting dark sector, resulting in jets geometrically enclosing dark hadrons and overlapping with missing transverse momentum direction. The first experimental results from ATLAS and CMS are public, and we will start with a quick debriefing. There are proposals to look at more specialised SVJ signatures, we will focus on SVJ with heavy flavours, which allows us to look at different jet reconstruction techniques for these signatures. We will also cover different ways to simulate these signals, and if current LHC searches and measurements in similar final states constrain the available SVJ phase space.
QFT shows that fundamental constants are not fixed but vary with energy scales. This opens the possibility that in the early universe, gauge couplings may differ from those predicted by the Standard Model, potentially leading to observable non-standard phases. The low-energy spectrum of generic models that aim to archive this usually has a light singlet that couples through higher-dimensional operators to gauge bosons originating from a Dark Sector. In this work, we explore these scenarios in detail and show that in renormalizable QFT UV descriptions, drastic changes in the gauge coupling cannot occur at low energies, and given the nontrivial dynamics of the singlet field, the changes are entirely described by a dynamical RG equation with changing thresholds.
Telescope observations of background radiation in the Milky Way point to an anomalous excess in ultraviolet, radio, and x-ray signals. The unconventional Axion Quark Nugget (AQN) dark matter model may provide an interpretation for this as-yet-unexplained excess. The model proposes that dark matter is dominated by macroscopic composite objects of nuclear density, in the form of matter and antimatter nuggets. Baryonic matter from ionized gas in the Warm Hot Intergallactic Medium (WHIM) surrounding the Milky Way may collide with antimatter AQNs and annihilate, resulting in an emission of a broad spectrum of electromagnetic radiation similar in form to Bremsstrahlung. The resulting spectrum was estimated to match the excesses in radio, UV, and x-ray signals in the galaxy. The aim of this project is to compare the AQN annihilation radio emissions with the observed radio haze from WMAP. This is done by computing the signal from AQN annihilations within a cosmological hydrodynamic simulation of a Milky Way-like galaxy, and using a Markov chain Monte Carlo method to produce constraints on the AQN mass range and the dark matter density distribution. Understanding the source(s) of this excess radiation in our galaxy may bring us a step closer to revealing the nature of dark matter.
Dark compact objects can arise naturally in a variety of dark sectors. Clouds of dark matter between a source star and an observer could effectively act as a "lampshade" and dim starlight if the dark sector couples to the Standard Model photon. These dimming effects can be searched for in microlensing surveys, which measure the brightness of stars as a function of time. By considering the EROS-2 and OGLE surveys, we demonstrate how dimming effect searches could be complementary probes for extended structures of dark matter, and can be used to place constraints on dark sectors.
Primordial black hole (PBH) dark matter (DM) can be probed by "picolensing". Widely spatially separated gamma-ray detectors near Earth would observe parallax of an intervening PBH lens with respect to a cosmologically distant gamma-ray burst (GRB). This parallax can be of order the Einstein angle of the lens, resulting in differential magnification of the source as viewed from the two detectors. Simultaneous brightness measurements of the same GRB made by two detectors is sensitive to this effect. Two recent studies in the literature have shown this approach could be a promising way to search for PBH dark matter in part of the the "asteroid mass gap", roughly $10^{-15} < M_{\mathrm{PBH}}/ M_{\odot} < 10^{-10}$. In this talk, I will discuss some ongoing work to explore the robustness of this signal to various uncertainties not previously carefully accounted for: e.g., uncertainties in the transverse extent of the GRB emission region, its intensity profile, detector background rates, sensitivity of the projection to outlier GRB events, etc. I'll show that, while the large GRB source size uncertainties do degrade previous projections somewhat, it is still possible to probe most of the PBH DM asteroid mass gap with a 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 gap, potentially as high as $M_{\mathrm{PBH}} \sim 10^{-6} M_{\odot}$.
A QCD axion with a decay constant below $ 10 ^{ 11} ~{\rm GeV} $ is a strongly-motivated extension to the Standard Model, though its relic abundance from the misalignment mechanism or decay of cosmic defects is insufficient to explain the origin of dark matter. Nevertheless, such an axion may still play an important role in setting the dark matter density if it mediates a force between the SM and the dark sector. In this work, we explore QCD axion-mediated freeze-out and freeze-in scenarios, finding that the axion can play a critical role for setting the dark matter density. Assuming the axion solves the strong CP problem makes this framework highly predictive, and we comment on experimental targets.