Light Dark World 2025 (16-19 September 2025)

Tuesday, 16 September
- 13:45 → 14:15
  Registration
  - 13:45
    
    Registration 30m
- 14:15 → 14:25
  
  Welcome
- 14:25 → 16:05
  Forward Physics Experiments and Colliders
  - 14:25
    
    Overview of BSM searches at forward physics experiments 30m
    
    Speaker: Felix Kling
  - 14:55
    
    Dark Sector searches at Belle II 25m
    
    Speaker: Enrico Graziani
  - 15:20
    
    FIP/LLP searches at LHCb 25m
    
    Speaker: Andrii Usachov
  - 15:45
    
    Inelastic Dark Matter at ProtoDUNE 20m
    
    Liquid argon Time Projection Chambers (LArTPCs) have proven to be powerful instruments for detecting weakly interacting particles predicted by many beyond the Standard Model (BSM) scenarios. Thanks to their location at CERN, the ProtoDUNE detectors can intercept a sizeable flux of such particles, produced when the 400 GeV protons from the Super Proton Synchrotron (SPS) impinge on a fixed target. In this talk, I will focus on the inelastic dark matter (iDM) model and search for its dark photon mediator in ProtoDUNE. I will outline the projected sensitivity reach for its mixing parameter, $\varepsilon$, and its mass, $m_{A'}$.
    
    Speaker: Sara Bianco (DESY Hamburg)
- 16:05 → 16:35
  
  Coffee Break
- 16:35 → 17:45
  Rich dark sectors and Heavy Neutral Leptons
  - 16:35
    
    Overview: rich dark sectors and non-minimal HNL models 30m
    
    Speaker: Silvia Pascoli (Bolognia University)
  - 17:05
    
    Heavy Neutral Lepton searches at ICARUS-NuMI 20m
    
    Long-lived particles (LLPs) could serve as a portal to hidden sectors addressing different open problems of the Standard Model. Among these, the evidence for neutrino masses and mixings—observed in neutrino oscillation experiments—stands out as particularly promising. A simple extension to the SM involves the inclusion of heavy right-handed neutrinos, commonly known as heavy neutral leptons (HNLs). In minimal models, the HNL production and decay are governed by weak interactions, suppressed by their mixing with active neutrinos. This suppression leads to relatively long HNL lifetimes when their masses lie within the MeV–GeV range.
    The near-detector complexes of current and upcoming neutrino oscillation experiments provide an optimal environment for searching for visible HNL decays, given the high intensity of the beams and the volume of the detectors involved. We have conducted a comprehensive study on both the physics case and the technical feasibility of a dedicated HNL search utilizing the 120-GeV proton NuMI beam with an ICARUS-like detector. Our analysis indicates that the projected constraints on HNL mixing as a function of its mass will be highly competitive with existing experimental limits.
    
    Speaker: Dr. Josu Hernandez-Garcia (IFIC, CSIC-UV)
  - 17:25
    
    The cosmic origin of matter from exact proton stability 20m
    
    In this talk, we revisit a class of lepton-flavor non-universal gauge extensions of the Standard Model that provide a compelling framework for generating neutrino masses and mixing angles via a high-scale seesaw mechanism, while ensuring exact proton stability to all orders in the effective field theory. This setup naturally accommodates minimal thermal leptogenesis, offering a robust explanation for the observed matter-antimatter asymmetry. A feature of this construction is the prediction of a light pseudo-Nambu-Goldstone boson, the majoron, whose properties and couplings we examine in the context of dark matter, cosmology, and ongoing experimental searches.
    
    Speaker: Xavier Ponce Diaz (University of Basel)
- 17:45 → 18:00
  Lightning Talks
  - 17:45
    
    Invisible Higgs decay from dark matter freeze-in at stronger coupling 1m
    
    We study the Higgs boson decay into dark matter (DM) in the framework of freeze-in at stronger coupling. Even though the Higgs-DM coupling is significant, up to order one, DM does not thermalize due to the Boltzmann suppression of its production at low temperatures. We find that this mechanism leads to observable Higgs decay into invisible final states with the branching fraction of 10% and below, while producing the correct DM relic abundance. This applies to the DM masses down to the MeV scale, which requires a careful treatment of the hadronic production modes. For DM masses below the muon threshold, the Boltzmann suppression is not operative and the freeze-in nature of the production mechanism is instead guaranteed by the smallness of the electron Yukawa coupling. As a result, MeV DM with a significant coupling to the Higgs boson remains non-thermal as long as the reheating temperature does not exceed
    O
    O(100) MeV. Our findings indicate that there are good prospects for observing light non-thermal DM via invisible Higgs decay at the LHC and FCC.
    
    Speaker: Vinícius Oliveira (Lund University)
  - 17:46
    
    New probes of supernovae axion-like particles in neutrino water Cherenkov detectors 1m
    
    In this talk I will present a new potential signature of supernovae axion-like particles (ALPs) in neutrino water Cherenkov detectors. If ALPs couple to protons, then they can be detected through ALP absorption on free protons, $a\ p→p\ γ$, where the resulting photon has approximately the energy of the ALP. This new signature is complementary to the usual one from oxygen de-excitation, and can be exploited in various ways.
    
    I will first argue that ALPs with MeV masses can be produced with semi-relativistic velocities in core-collapse galactic supernovae and that they can constitute a diffuse flux formed by the overlap of the ALP fluxes. Using Super-Kamiokande data, new constraints on the ALP-proton coupling can be derived in regions that cooling bounds cannot probe. For lighter ALPs, the conditions for a diffuse flux fail. Nevertheless, they can still be looked for on individual (future) neighbouring supernovae. I will show that this new signature, combined with the one expected from oxygen de-excitation, would allow us to disentangle ALP-neutron and ALP-proton couplings.
    
    Speaker: David Alonso-González (IFT (UAM-CSIC))
  - 17:47
    
    Constraining eV-scale axion-like particle dark matter: insights from the M87 Galaxy 1m
    
    Axion-like particles (ALPs) can account for the observed dark matter (DM) of the Universe and if their masses are at the eV scale, they can decay into
    infrared, optical and ultraviolet photons
    {with a decay lifetime larger than the age of the Universe}.
    We analyze multi-wavelength data obtained from the central region of Messier 87 (M87) galaxy
    by several telescopes, such as, Swift, Astrosat, Kanata, Spitzer and
    International Ultraviolet Explorer
    in the infrared to ultraviolet frequencies
    ($\sim 2\times10^{14} \, {\rm Hz} - 3\times10^{15}$ Hz),
    to constrain the narrow emission lines indicative of the eV scale ALP DM decay.
    We derive constraints on the ALP coupling to two photons ($g_{a\gamma\gamma}$) for ALP mass range $2 \, {\rm eV} < m_a < 20 \, {\rm eV}$,
    assuming ALPs form the DM in the M87 halo.
    We find that our bounds on ALP-two-photon coupling
    can become stronger than the existing ones by an order of magnitude in the ALP
    mass range $8 \, {\rm eV} < m_a < 20 \, {\rm eV}$.
    
    Speaker: Mr. Pratick Sarkar (Indian Association for the Cultivation of Science)
  - 17:48
    
    Ceilings from the Floor: Constraining light mediators with solar neutrino scattering 1m
    
    The recent observations of solar $\rm ^8B$ neutrinos via coherent elastic neutrino–nucleus scattering (CEνNS) by the PANDAX-4T and XENONnT collaborations mark the first detection of the so-called “neutrino fog” — an irreducible background for future direct dark matter searches. In this talk, I will show how these results enable powerful new probes of light mediators coupling to neutrinos and quarks. Using the new available datasets from PANDAX-4T and XENONnT, we derive leading constraints on sub-GeV scalar and vector mediators, including scenarios with flavor-universal or mass-proportional quark couplings.
    
    I will also discuss the impact of subdominant neutrino interaction channels — such as neutrino–electron scattering and the Migdal effect — and demonstrate that, while typically neglected, they can contribute non-negligibly in S2-only analyses. These results highlight the potential of next-generation liquid xenon detectors not only for dark matter discovery, but also as sensitive laboratories for light new physics in the neutrino sector.
    
    Speaker: Pablo Blanco (IFT UAM/CSIC)
  - 17:49
    
    Neutrinos from Dark Matter scatterings around blazars 1m
    
    Neutrinos from blazars can originate from inelastic scatterings between the protons within their jets and sub-GeV dark matter (DM) around them. I will show how this mechanism can potentially account for both the IceCube detections of neutrinos from the blazar TXS 0506+056, that are
    otherwise challenging for astrophysical models of its jet, and also saturate the measured diffuse astrophysical neutrino flux at high energies
    The same DM-proton interactions will also induce an upscattered DM flux, which could yield measurable nuclear recoil signals at neutrino detectors, such as Super-K, JUNO and DUNE. I will show that searches for such DM component leave room for a variety of DM models to explain observations of IceCube high-energy neutrinos, and will provide future tests of this hypothesis.
    
    Speaker: Jacopo Nava (U. Bologna)
  - 17:50
    
    Heavy neutral lepton searches in cosmic ray beam dump experiments 1m
    
    We demonstrate the possibility of testing Heavy Neutral Leptons (HNLs) using "cosmic ray beam-dumps'' : setups where high-energy incident cosmic rays impinge on the Earth's atmosphere and then on the Earth's surface. We focus on HNL production from atmospherically produced parent meson decays, and examine them as a possible explanation of the appearing Cherenkov showers observed by the SHALON Cherenkov telescope and the ultra-high energy events detected by the ANITA neutrino experiment. Further, we propose two new experimental setups with improved sensitivities, namely a Cherenkov telescope pointing at a sub-horizontal angle and shielded by the mountain cliff at Mt. Thor, and SPYGLASS: a geostationary satellite that observes part of the Sahara desert. Our results show that that the Mt. Thor experiment can probe currently untested HNL parameter space below the kaon mass; while SPYGLASS can significantly increase the HNL parameter space coverage in the mass range from 10 MeV up to 2 GeV and test neutrino mixing $|U_{\alpha4}|^2$ down to $10^{-11}$ for masses around 300 MeV.
    
    Speaker: Baibhab Pattnaik (Instituto de Física Corpuscular (Universidad de Valencia-CSIC))
  - 17:52
    
    A Monte Carlo approach for simulating photon-ALP interconversion at gamma-ray energies in astrophysical environments 1m
    
    Axion-like particles (ALPs), theoretical extension of the QCD axion, are some of the numerous candidates for constituting dark matter. Several theoretical and experimental efforts aim to probe and constrain their properties, namely mass and potential coupling to standard model particles. Among these, assuming coupling with photons, the low-mass ALPs range, viz. m_{ALP} < 10^{-6} eV, could be explored through gamma-ray observations. In fact, gamma rays propagating in spaces permeated by cosmic magnetic fields could oscillate into ALPs, and viceversa. This effect could alter the gamma-ray fluxes emitted by different classes of sources before, actually, reaching our observatories. Furthermore, gamma rays could interact with soft background photons along their path, initiating electromagnetic cascades. A new implementation to account for ALP-gamma ray coupling within the CRPropa Monte Carlo simulation framework is presented. Its potential in predicting hints of ALPs in gamma-ray fluxes lies in the detailed modeling of astrophysical environments and the processes in play. Hence, the propagation of gamma rays over disparate astrophysical environments, in particular the extragalactic and the galactic ones, is consistently treated in the scenario of ALP-photon oscillation. In this talk, we present preliminary results using the new tool, paving the way for a discussion on the impact of this refined simulations for current and future investigations on ALPs through GeV-TeV gamma rays.
    
    Speaker: Gaetano Di Marco (IFT UAM/CSIC)
  - 17:53
    
    A Search for Dark Sectors Using Lasers 1m
    
    The dark photon is a new gauge boson that naturally arises in many beyond the Standard Model theoretical models, featuring
    interactions that resemble quantum electrodynamics. Due to this feature, it is often considered the portal between dark and visible
    sectors. For this reason, it has become the target of many experimental searches worldwide. In this work, we propose a search for dark
    photons based on the Inverse Compton scattering, $\gamma e^- \rightarrow A^\prime e^-$, to be conducted at the Brazilian
    Synchrotron Light Laboratory (LNLS). In this setup, photons from a laser source would impinge on the accelerated electron beam
    present at the LNLS, producing a dark photon in the final state. Taking advantage of the photon counting technique, we derive the
    projected sensitivity of this proposed dark sector detector by considering the energy of the incident photon about 1 eV and an electron
    beam of 3 GeV. We show that this experimental setup could pave the way to the first Latin-American Dark Sector detector capable of
    covering an unexplored region of parameter space and confirming results from previous searches via astrophysical sources, thus
    constituting a promising probe for dark sectors in the future.
    
    Speaker: Silvia Lucia Correa Angel (Federal University of Rio Grande do Norte -UFRN, International Institute of Physics - IIP)
  - 17:54
    
    New benchmarks for direct detection of freeze-in dark matter 1m
    
    In this work, we apply recent direct detection constraints on electron recoils to freeze-in Dark Matter (DM) models. Due to recent results obtained by direct detection experiments, especially DAMIC-M, the dark photon scenario is severely constrained. However, there are different scenarios in which these bounds can be avoided. In freeze-in models, the scaling of the DM relic abundance allows the dark photon to be a subdominant component. DAMIC-M results rules out up to 50 %, with future experiments aiming to constraint up to 0.001 %. Next, we show that in scenarios where the main DM production channels are not electron-positron or plasmon decay, such as Lμ − Lτ , the main contributions comes from ν, that are now charged to the Z′. Thus, such models avoid the current direct detection constraints on electron recoils.
    As a result, we provide new targets for upcoming direct detection experiments looking for electron recoils such as DAMIC, SuperCDMS or Oscura.
    
    Speaker: Rafael Lopez Noe (IFT UAM-CSIC)
  - 17:55
    
    Dark Matter in an Evanescent Three-Brane Randall-Sundrum Scenario 1m
    
    Apart from its gravitational interactions, dark matter (DM) has remained so
    far elusive in laboratory searches. One possible explanation is that the relevant interactions
    to explain its relic abundance are mainly gravitational. In this work we consider an extra-
    dimensional Randall-Sundrum scenario with a TeV-PeV IR brane, where the Standard
    Model is located, and a GeV-TeV deep IR (DIR) one, where the DM lies. When the
    curvatures of the bulk to the left and right of the IR brane are very similar, the tension
    of the IR brane is significantly smaller than that of the other two branes, and therefore
    we term it “evanescent”. In this setup, the relic abundance of DM arises from the freeze-
    out mechanism, thanks to DM annihilations into radions and gravitons. Focusing on a
    scalar singlet DM candidate, we compute and apply current and future constraints from
    direct, indirect and collider-based searches. Our findings demonstrate the viability of this
    scenario and highlight its potential testability in upcoming experiments. We also discuss
    the possibility of inferring the number of branes if the radion and several Kaluza-Klein
    graviton resonances are detected at a future collider.
    
    Speaker: Alejandro Muñoz Ovalle (IFIC (CSIC/UV))
- 18:00 → 19:30
  
  Cocktail + Poster Session
Wednesday, 17 September
- 09:30 → 10:40
  Fixed Target Exps (I)
  - 09:30
    
    Overview of FIP searches at fixed-target experiments 30m
    
    Speaker: Maksym Ovchynnikov
  - 10:00
    
    Long-lived particles at Spallation Neutron Sources 20m
    
    Spallation neutron sources can provide an intense source of new, light particles from the decay at rest of pions, muons, and kaons.
    Considering a variety of spallation sources around the world, we study the sensitivity of existing neutrino detectors to the decay of these new particles.
    At J-PARC, we show that the fast, magnetized, gaseous argon chambers of the ND280 detector could place leading limits on light particles decaying to $e^+e^-$ and that the liquid-scintillator detectors of the J-PARC Sterile Neutrino Search at the JSNS (JSNS$^2$) experiment can exploit double- and triple-coincidence signals from $\mu^+\mu^-$ and $\pi^+\pi^-$ to place new limits on heavy neutral leptons.
    At Oak Ridge, we show that the suite of detectors at the COHERENT experiment, despite their smaller size, would also have world-leading sensitivity to axion-like-particles and muonphilic light scalars.
    We also discuss new opportunities for Coherent Captain Mills at Los Alamos and compare our results to on-going searches at the Short-Baseline Neutrino Program at Fermilab.
    Spallation sources have the potential to explore more than an order of magnitude beyond current constraints in some new physics models, encouraging further study on data acquisition and background rejection by experimental collaborations.
    
    Speaker: Salvador Urrea González (IJCLab)
  - 10:20
    
    Single pion production from interactions with dark matter 20m
    
    We present a comprehensive theoretical framework describing single pion resonant production through inelastic dark fermion–nucleon interactions mediated by resonances in the GeV-scale regime. Building upon the Rein–Sehgal approach, we derive differential cross sections for processes in which an incoming dark fermion scatters off a nucleon, exciting a resonance that subsequently decays into a nucleon and a pion. Our formulation accommodates various mediator types—namely, dark photons with vector and axial couplings, as well as scalar and pseudoscalar mediators—thereby extending the conventional approach that Rein, Sehgal and Berger performed for neutrino interactions. Transition amplitudes for the nucleon-to-resonance conversion are computed using the relativistic harmonic-oscillator quark model from Feynman, Kislinger and Ravndal, while a Breit–Wigner prescription is employed to incorporate finite resonance widths. This framework offers a useful tool for interpreting experimental data in dark sector and dark matter searches and represents a contribution to elucidate the possible role of resonances in GeV-scale phenomenology.
    
    Speaker: Jaime Hoefken Zink (Narodowe Centrum Badań Jądrowych (NCBJ))
- 10:40 → 11:10
  
  Coffee Break
- 11:10 → 12:40
  Fixed Target Exps (II)
  - 11:10
    
    Overview of the X17 anomaly (20'+ 5') 25m
    
    Speaker: Luc Darmé
  - 11:35
    
    PADME results on X17 searches (15'+5') 20m
    
    The PADME experiment at the Frascati National Laboratory of INFN has performed a
    search for the hypothetical X17 particle, by observing the product of the collisions
    of the positron beam from the DAΦNE LINAC on a diamond fixed target.
    The beam energy has been varied in the range
    265–300 MeV, corresponding to values of √s between 16.4 and 17.5 MeV,
    completely covering the the CoM region identified by the
    ATOMKI collaboration as significant for observing the postulated X17 particle.
    The result of the analysis shows an about 2-sigma excess corresponding to the mass indicated by
    the ATOMKI experiment. A new data taking campaign, with an improved detector is
    planned to start in the summer of 2025, with the aim of pushing forward the
    sensitivity of the search.
    
    Speaker: Mario Antonelli (INFN)
  - 11:55
    
    Latest results from NA64 (20'+5') 25m
    
    Speaker: Paolo Crivelli
  - 12:20
    
    Exploring the Light Dark World with NA64 (15'+5') 20m
    
    In the last years, the efforts towards finding subGeV new physics have increased. This Light Dark World is vast and unknown, however, we know that the components of different theories must live in that world. From the experimental side, there is also a great effort to disentangle and understand what could hide the Light Dark World. NA64 is a fixed target experiment at CERN SPS that search for the inhabitants of the Light Dark World using high energy electron, positron and muon beams. In this talk, we will focus on how NA64 is able to shed some light in several corners of this dark sector with the latest results on muon beam data. First of all, we will use the recent muon data to constraint for the first time the SMEFT operators that involve muon flavour. Following with EFT, we contrast the $\nu$SMEFT operators that relates muon flavour with heavy neutral leptons. And finally, we will see how muon data can tell us more about subGeV inelastic dark matter.
    
    Speaker: Víctor Martín Lozano (IFIC/UV)
- 12:40 → 14:30
  
  Lunch
- 14:30 → 16:00
  Cosmology
  - 14:30
    
    Overview of recent results from cosmological observations and implications for particle physics 30m
    
    Speaker: Eleonora Di Valentino
  - 15:00
    
    Detecting Ultralight Dark Matter with Matter Effect 20m
    
    Ultralight particles, with a mass below the electronvolt scale, exhibit wave-like behavior and have arisen as a compelling dark matter candidate. A particularly intriguing subclass is scalar dark matter, which induces variations in fundamental physical constants. However, detecting such particles becomes highly challenging in the mass range above $10^{-6}\,\text{eV}$, as traditional experiments face severe limitations in response time. In contrast, the matter effect becomes significant in a vast and unexplored parameter space. These effects include (i) a force arising from scattering between ordinary matter and the dark matter wind and (ii) a fifth force between ordinary matter induced by the dark matter background. Using the repulsive quadratic scalar-photon interaction as a case study, we develop a unified framework based on quantum mechanical scattering theory to systematically investigate these phenomena across both perturbative and non-perturbative regimes. Our approach not only reproduces prior results obtained through other methodologies but also covers novel regimes with nontrivial features, such as decoherence effects, screening effects, and their combinations. In particular, we highlight one finding related to both scattering and background-induced forces: the descreening effect observed in the non-perturbative region with large incident momentum, which alleviates the decoherence suppression. Furthermore, we discuss current and proposed experiments, including inverse-square-law tests, equivalence principle tests, and deep-space acceleration measurements. Notably, we go beyond the spherical approximation and revisit the MICROSCOPE constraint on the background-induced force in the large-momentum regime, where the decoherence and screening effects interplay. The ultraviolet models realizing the quadratic scalar-photon interaction are also discussed.
    
    Speaker: Dr. Xucheng Gan (DESY)
  - 15:20
    
    New approach for study of dynamics of neutrinos in the primordial era 20m
    
    Cosmological observations, such as Big Bang Nucleosynthesis (BBN) and the Cosmic Microwave Background (CMB), provide vital insights into the early Universe, allowing us to trace its evolution to times as short as $t \sim 0.01$ s and to test extensions of the Standard Model. Accurately modeling the non-trivial dynamics of neutrinos typically requires solving a system of Boltzmann equations numerically, a method that comes with inherent limitations, particularly in terms of computational efficiency. In this talk, a novel approach based on the Direct Simulation Monte Carlo (DSMC) method is presented, which offers significant advantages over traditional techniques, particularly in scenarios involving high-energy neutrino injections.
    
    Speaker: Vsevolod Syvolap (Instituto de Física Teórica)
  - 15:40
    
    Phasing-in dark matter 20m
    
    Despite being an elegant mechanism to explain Dark Matter (DM) production, freeze-in introduces challenges: If DM interacts via non-renormalizable operators, the predictions are highly sensitive to initial conditions, such as the reheating temperature of the universe. These issues are particularly relevant in models in which the universe deviates from radiation domination and the entropy of the Standard Model (SM) thermal bath is not conserved.
    In this talk, I will present a general freeze-in scenario in which a scalar field dominates the energy density of the universe before undergoing a first-order phase transition and then slowly decaying to visible particles. The decays lead to a second phase of reheating of the radiation bath and to additional contributions to DM freeze-in. I will explore the conditions under which these late contributions dominate over the initial DM abundance produced at primordial reheating. In this scenario, referred to as phase-in, the final abundance of DM is primarily determined by the details of the phase transition and subsequent reheating, and insensitive to the details of inflationary reheating.
    Additionally, I will revisit the commonly made assumption that the universe becomes early matter dominated after such a phase transition, discuss scenarios in which this may break down and highlight its relevance to the phase-in mechanism.
    
    Speaker: Henda Mansour (Karlsruhe Institute of Technology)
- 16:00 → 16:30
  
  Coffee Break
- 16:30 → 17:50
  Astrophysics (I)
  - 16:30
    
    Overview of astrophysical constraints on light dark sectors 30m
    
    Speaker: Seokhoon Yun
  - 17:00
    
    Core-collapse supernova explosions hindered by eV-mass sterile neutrinos 25m
    
    Light sterile neutrinos, $\nu_s$, are often introduced to explain an anomalous deficit in the electron antineutrino flux from nuclear reactors. If they exist, sterile neutrinos would also be produced in collapsing massive stars through the active-sterile neutrino oscillation. In order to investigate the impacts of sterile neutrinos on supernova dynamics, we perform two-dimensional neutrino-radiation hydrodynamic simulations of stellar core-collapse coupled with the active-sterile oscillation through the Mikheyev–Smirnov–Wolfenstein effect. As the initial condition of our simulations, we adopt a blue supergiant model that is tuned to reproduce observational features of the SN 1987A progenitor to compare our models with observations of the event. It is found that the active-sterile oscillation reduces the $\nu_{e}$ and $\bar{\nu}_e$ fluxes and decreases the explosion energy. We also find that, if the mixing angle $\theta$ and the mass difference $\delta m_\mathrm{s}^2$ between $\nu_e$ and $\nu_s$ are large enough, the star fails to explode. This suggests that these mixing parameters relevant to sterile neutrinos could be constrained by supernova explodability, though other uncertainties in supernova theory need to be addressed to refine them. In addition, we predict neutrino signals from a nearby supernova event and find that the neutrino event number can significantly decrease because the $\nu_e$ and $\bar{\nu}_e$ fluxes are reduced. In particular, DUNE observations of $\nu_e$ will be useful to search for a signature of sterile neutrinos with a tiny mixing angle because a smaller mixing angle leads to a larger effect on the $\nu_e$ flux.
    
    Speaker: Kanji Mori (National Astronomical Observatory of Japan)
  - 17:25
    
    The CMZ anomalous Ionization rate explained by MeV DM 25m
    
    Recent observations of a variety of ionization tracers have revealed an unexpectedly high ionization rate in the Central Molecular Zone (CMZ), that cannot be explained by ionization of cosmic rays. The current observations point to a source of particles that is very concentrated around the Galactic Center and should emit low energy ionizing particles (to avoid propagating too far away from the CMZ). In this talk, I'll show that the anomalous ionization rate observed in the CMZ can be attributed to MeV dark matter annihilation for galactic dark matter profiles with slopes γ > 1 and that the low annihilation cross-sections required avoid (by a few orders of magnitude) the current cosmological constraints and imply no detectable inverse Compton, bremsstrahlung or synchrotron emissions in radio, X and gamma rays.
    Moreover, I'll discuss the possible common origin of this anomaly with the puzzling 511 keV line emission in the Galactic Center
    
    Speaker: Pedro De la Torre Luque (Universidad Autónoma de Madrid & Institute of theoretical physics (IFT-UAM))
Thursday, 18 September
- 09:30 → 10:40
  Dark Matter (I)
  - 09:30
    
    Direct detection of light dark matter 30m
    
    Speaker: Kimberly Palladino
  - 10:00
    
    Sub-GeV Thermal Relics Enabled by a Light Higgs Portal 20m
    
    In this talk, I will discuss minimal realizations of light thermal dark matter (DM) candidates. These scenarios typically require a light mediator to ensure sufficient DM annihilation rates. We demonstrate that such mediators can arise from additional Higgs doublet(s). Within this framework, we focus on two specific scenarios: (1) Forbidden DM, where DM predominantly annihilates into SM charged leptons through kinematically forbidden channels, and (2) Neutrinophilic DM, where neutrinos serve as the primary annihilation products. In both cases, all BSM states lie at or below electroweak scale, making these models testable at upcoming colliders, beam-dump experiments, future sub-GeV gamma-ray telescopes, and next-generation neutrino detectors.
    
    Speaker: Vishnu Padmanabhan Kovilakam (Institute of Theoretical Physics, University of Münster)
  - 10:20
    
    From ANAIS-112 to ANAIS+: eight years of dark matter search at the Canfranc Underground Laboratory 20m
    
    The ANAIS-112 experiment has completed nearly eight years of continuous data taking, aiming to test the annual modulation signal reported by the DAMA/LIBRA collaboration, using the same NaI(Tl) target and detection technique. Located at the Canfranc Underground Laboratory, ANAIS-112 has accumulated over 800 kg·yr of exposure, achieving excellent long-term stability and background control. In this talk, I will present the six-year results from ANAIS-112, which lead the international, model-independent effort to test the DAMA/LIBRA signal, and are compatible with the absence of modulation and incompatible with DAMA/LIBRA for a sensitivity above 4σ, with the potential to reach 5σ level by the end of 2025. Systematics affecting the comparison will also be reviewed, particularly those related to the response of detectors to nuclear recoils.
    
    Beyond ANAIS-112, the ANAIS+ project proposes a significant technological upgrade: the replacement of conventional PMTs with SiPMs operated at low temperatures. This innovation is expected to reduce radioactive backgrounds, lower the energy threshold, and improve light collection efficiency -thereby increasing the experiment’s sensitivity to low-mass dark matter. Furthermore, it will allow for a more robust and systematics-independent comparison with DAMA/LIBRA, while opening new opportunities for searches of spin-dependent interactions and coherent elastic neutrino-nucleus scattering.
    
    Speaker: Iván Coarasa Casas (CAPA - Universidad de Zaragoza)
- 10:40 → 11:10
  
  Coffee Break
- 11:10 → 12:30
  Dark Matter (II)
  - 11:10
    
    Light DM detection in neutrino experiments 30m
    
    Speaker: Jong-Chul Park
  - 11:40
    
    New results of DAMIC-M 25m
    
    Speaker: Olivier Deligny
  - 12:05
    
    Inelastic DM constraints and viable scenarios 25m
    
    Speaker: Renata Zukanovich Funchal
- 12:30 → 14:30
  
  Lunch
- 14:30 → 15:40
  Very light and ultra-light DM
  - 14:30
    
    New approaches in light DM detection 30m
    
    Speaker: Christina Gao
  - 15:00
    
    The Dawn of Nuclear Supremacy: First Bounds on Ultralight Dark Matter from the Thorium Isomer Transition 20m
    
    The recent laser excitation of the low-lying Th-229 isomer transition is starting a revolution in ultralight dark matter searches. The enhanced sensitivity of this transition to the large class of dark matter models dominantly coupling to quarks and gluons will ultimately allow us to probe coupling strengths eight orders of magnitude smaller than the current bounds from optical atomic clocks, which are mainly sensitive to dark matter couplings to electrons and photons. We argue that, with increasing precision, observations of the Th-229 excitation spectrum will soon give world-leading constraints. Using data from the pioneering laser excitation of Th-229 by Tiedau et al. [Phys. Rev. Lett. 132, 182501 (2024)], we present a first dark matter search in the excitation spectrum. While the exclusion limits of our detailed study of the lineshape are still below the sensitivity of currently operating clock experiments, we project the measurement of Zhang et al. [Phys. Rev. Lett. 133, 013201 (2024)] to surpass it.
    
    Speaker: Dr. Eric Madge (IFT-UAM/CSIC)
  - 15:20
    
    Scattering meets absorption in dark matter detection 20m
    
    We explore the interplay between dark matter scattering and solar dark photon absorption in two dark matter models with light dark photon mediators. Sub-keV dark photons, abundantly produced in the solar core, provide complementary detection channels to scattering of dark matter from the halo. Incorporating astrophysical and cosmological constraints—including dark matter self-interactions and solar cooling —we identify the viable parameter space for both Dirac and atomic dark matter. For Dirac dark matter, simultaneous detection of scattering and dark photon absorption is possible at direct detection experiments in the near future. In the atomic dark matter case, an interesting interplay of signals from dark atoms, their ionized constituents, and solar dark photons could be observed. To disentangle these signals, the measurement of energy recoil spectra is essential. Combining the detected signals could help to distinguish between different dark matter models.
    
    Speaker: Anh Vu Phan (Radboud University; Nikhef)
- 15:40 → 16:00
  
  Group Photo 20m
- 16:00 → 16:30
  
  Coffee Break
- 16:30 → 17:50
  Millicharged particles / Kaon Experiments
  - 16:30
    
    Millicharged particles 30m
    
    Speaker: Yu-Dai Tsai
  - 17:00
    
    FIP/LLP searches at NA62 25m
    
    Speaker: Jan Jerhot
  - 17:25
    
    Searches for Dark Sectors at the Kaon experiments (NA62, KOTO) 25m
    
    Speaker: Evgueni Goudzovski
- 20:00 → 22:00
  
  Dinner
Friday, 19 September
- 09:30 → 10:40
  Light scalars and axion-like particles
  - 09:30
    
    Phenomenology of axion and axion-like particles 30m
    
    Speaker: Javier Redondo
  - 10:00
    
    Axion dark matter from heavy quarks 20m
    
    Axions and axion-like particles (ALPs) remain compelling dark matter (DM) candidates, provided that the associated Peccei-Quinn (PQ) symmetry breaking scale is sufficiently large to ensure cosmological stability. In this talk, I will explore a novel framework in which ALPs possess flavor-violating (FV) couplings to Standard Model (SM) quarks, allowing them to be produced via freeze-in in the early universe. I will demonstrate that rare meson decays, such as $K \rightarrow \pi a \quad \text{and} \quad B \rightarrow K a,$ allow us to probe decay constants as high as $f_a \sim 10^{10{-}12}~\mathrm{GeV}.$ Remarkably, this parameter space is typically thought to be inaccessible to terrestrial experiments. The structure of FV couplings opens up opportunities to test otherwise elusive ALP scenarios, while remaining consistent with astrophysical and cosmological constraints. I will highlight key differences between the lepton and quark FV scenarios, particularly in their sensitivity to decay versus scattering production channels, the degree of suppression required to evade X-ray constraints, and the relevance of next-to-leading order (NLO) corrections. Altogether, this framework connects the flavor and dark matter frontiers, offering a new avenue to search for light dark matter candidates through precision flavor experiments and future X-ray telescopes.
    
    Speaker: Mohammad Aghaie Moghadam Ozbak (University of Pisa and INFN Pisa)
  - 10:20
    
    Constraints on ultralight scalars from compact stars 20m
    
    Ultralight scalar fields that interact with Standard Model particles through electromagnetic and electrophilic couplings can be efficiently sourced by compact stars, leading to the emergence of long-range forces within binary systems. In certain regimes, these scalars may also be emitted from the stars, giving rise to distinctive observational signatures. In this talk, I will present constraints on such scalar fields derived from a variety of astrophysical observables, including pulsar spin-down rates, orbital period decay in binaries, gravitational redshift measurements, and key timing data from objects such as the Crab pulsar, PSR J0737–3039, SGR 1806–20, and GRB 080905A. I will further examine how interactions with the cosmic neutrino background can attenuate these effects, potentially relaxing the resulting bounds. Finally, I will highlight how future radio surveys and precision astrophysical measurements could significantly tighten current limits, enhancing our sensitivity to new light degrees of freedom.
    
    Speaker: Dr. Tanmay Kumar Poddar
- 10:40 → 11:10
  
  Coffee Break
- 11:10 → 12:30
  Astrophysics (II)
  - 11:10
    
    Searches for axions and DM using indirect detection 30m
    
    Invited talk (overview)
    
    Speaker: Dr. Elena Pinetti (Flatiron Institute)
  - 11:40
    
    DM in celestial bodies 25m
    
    Speaker: Sandra Robles
  - 12:05
    
    Neutrino Self-Interactions: Solar and Astrophysical Constraints 20m
    
    Speaker: Saeid Foroughi-Abari
- 12:30 → 12:40
  
  Closing

Light Dark World 2025

IFT UAM/CSIC