Clarifying origins and acceleration mechanisms of the most energetic particles in the universe has been the 100-year endeavor, being one of the most intriguing mysteries in an interdisciplinary research among astroparticle physics, high-energy physics and nuclear physics. Since ultra-high energy cosmic rays (UHECRs) are deflected less strongly by the Galactic and extra-galactic magnetic fields...
LHAASO keeps operating with high duty cycle and providing unique observations in gamma-ray sources and diffuse charged cosmic rays. Gamma-rays from the BOAT GRB, blazars, near-by AGNs and PeVatrons in our own galaxy are well detected. Physics associated with EBL, new physics searches, radiation mechanism of various sources are discussed. Particle acceleration in the galactic sources and...
We present new results in the search for WIMP dark matter-induced nuclear recoils using a 4.2 tonne year exposure of the LZ experiment, which operates on the 4850’ level of the Sanford Underground Research Facility.
There is an observed anisotropy in the arrival direction distribution of cosmic-rays in the TeV-PeV region with variations on the scale of one part in a thousand between different areas of the sky. Though the origin of this anisotropy is an open question a possible factor is cosmic-ray interactions with interstellar and heliospheric magnetic fields. These magnetic fields may change over time -...
Cosmic-ray antimatter, particularly low-energy antideuterons, constitute a sensitive probe of dark matter annihilating in our Galaxy. We study this smoking-gun signature and explore its complementary to indirect search via cosmic-ray antiprotons. We revisit the Monte Carlo simulation of antideuteron coalescence and cosmic-ray propagation, allowing us to assess uncertainties from both...
IceCube is actively working on a two-phased upgrade program. The IceCube 7-string Upgrade construction is underway: the detector instrumentation, from DOMs to cables and software, is being prepared for the 2025/26 South Pole field season when all of that is planned to come together to form a functioning detector 2700 m below the surface, in fewer than three months. It will provide...
Proto-neutron stars, formed in the center of Type-II supernovae, represent promising science targets for probing axions. The hypothetical particles are emitted via e.g. the Primakoff process and can modify the cooling rate of the proto-neutron stars and also convert to observable gamma rays while propagating through astrophysical magnetic field. Observations of Supernova 1987 (SN 1987A) from...
Indirect dark matter searches are novel ways of dark matter detection that differ from collider and direct dark matter searches. Information beyond standard model physics can potentially be obtained by focusing on the daughter particles generated from potential DM-DM interaction,
GAPS(General Antiparticle Spectrometer) is a balloon-borne indirect dark matter search experiment mainly...
Sensitivity to detecting sub-GeV dark matter in liquid xenon TPCs has been limited by instrumental backgrounds, namely delayed electron noise. For more than a decade, attempts to mitigate this background have proved inconclusive. In this talk, we will show new data that enlightens the mechanism of delayed electron noise, as well as pathways to its removal. With the assumption that this...
The IceCube Neutrino Observatory is a cubic kilometer neutrino telescope located at the South Pole instrumenting deep Antarctic ice. Uncovering the origin of high-energy astrophysical neutrinos is one of IceCube's major goals. We analyze a data sample of through-going track events produced by charged-current muon-neutrino interactions recorded between 2010 and 2023, focusing on the search for...
We present the measurements of cosmic H, He, Li and Be isotopes based on AMS data. We observed that over the entire rigidity range D exhibits nearly identical time variations with p, $^3$He, and $^4$He fluxes. Above 4.5 GV, the D/$^4$He flux ratio is time independent and its rigidity dependence is well described by a single power law $\propto$ R$^\Delta$ with $\Delta^4$D/$^4$He = $−0.108 \pm...
MicroBooNE is an 85-tonne active mass liquid argon time projection chamber (LArTPC) at Fermilab. The detector, with an excellent calorimetric, spatial and energy resolution, has collected beam data from two different beamlines between 2015 and 2020. Additionally, it has collected data when no neutrino beam was running. These characteristics make MicroBooNE a powerful detector not just to study...
Imaging Atmospheric Cherenkov Telescopes (IACTs) continue to be one of the best instruments to search for dark matter indirectly. One of the key criteria to an effective search is the selection of sources. In the past, these sources have been selected based on their high J-factors (e.g. the galactic center and dwarf spheroidal galaxies) but after many deep searches, IACTs have yet to find any...
Studying UHE $\gamma$-ray sources and their emission provide insights into the source of the most energetic ($\sim$ PeV) particles, which is key in identifying the origin of the galactic cosmic-ray spectrum. Recently, the Large High Altitude Air Shower Observatory (LHAASO) collaboration published the largest to-date catalog of UHE $\gamma$-ray sources. While most of the sources are either...
The current generation of Charged Cosmic Ray (CCR) experiments in operation in space (e.g. AMS-02, DAMPE, CALET) is providing novel information and is measuring unexpected features that are challenging the phenomenological community to revisit the paradigms behind the established theories of cosmic-ray origin, acceleration and propagation, and to formulate comprehensive models able to...
The Payload for Ultrahigh Energy Observations (PUEO) is a balloon-borne experiment that is designed to achieve world-leading sensitivity to ultrahigh energy (>1 EeV) astrophysical and cosmic neutrinos. Neutrino observations at this energy would provide valuable insights into both astrophysical sources and fundamental physics at extreme-energy scales. To do this, PUEO will leverage the Askaryan...
We study the prospect of simultaneous explanation of tiny neutrino masses, dark matter (DM), and the observed baryon asymmetry of the Universe in a $Z_3$-symmetric complex singlet scalar extended type-II seesaw model. The complex singlet scalar plays the role of DM. Analyzing the thermal history of the model, we identify the region of the parameter space that can generate a first-order...
"We report on a search for millicharged particles (mCPs) produced in cosmic ray proton atmospheric interactions using data collected during the first science run of the LUX-ZEPLIN experiment.
The mCPs produced by two processes---meson decay and proton bremsstrahlung---are considered in this study. This search is sensitive to mCPs with masses in the range between 90 MeV/c$^2$ -- 1100...
Dwarf Spheroidal (dSphs) galaxies are suspected dark matter dense sources within our galactic neighborhood. They are otherwise quiet locations that are low of other high energy gamma-ray sources which makes them ideal dark matter targets. HAWC's previous dark matter search toward dSph was performed with older reconstruction techniques and significantly less data. This iteration leverages...
TeV gamma rays from blazars interact with the extragalactic background light and produce ultrarelativistic, strongly forward-directed $e^+e^-$ pairs. The (in)stability of these pair beams is important for intergalactic magnetic field (IGMF) constraints, the distribution of secondary gamma rays, and the thermal evolution of the intergalactic medium (IGM). Pair beams drive a linear instability...
The energy density of ultra-high-energy cosmic rays is at the same level as that of high-energy neutrinos measured at IceCube, suggesting a plausible common origin scenario. Here, we report a combined fit utilizing data from the Pierre Auger and the IceCube Neutrino Observatories to test this hypothesis. We incorporate flux and mass composition, including 𝑋max distributions, for energy bins...
In this talk, we discuss the cosmological effects of a tower of neutrino states (equivalently a tower of warm dark matter ) on cosmic microwave background (CMB) and large-scale structure. For concreteness, we considered the $N$-Naturalness model which is a proposed mechanism to solve the electroweak Hierarchy problem. The model predicts a tower of neutrino states, which act as warm dark...
The measurement of the energy spectrum of ultra-high-energy cosmic rays (UHECRs) is an essential step towards understanding their acceleration, propagation and intergalactic origin.
With the Pierre Auger Observatory, it is possible to probe UHECRs with energies up to $10^{20}\,$eV and beyond.
Located in Argentina it comprises more than 1600 water Cherenkov detectors spread over an area of...
Active galactic nuclei (AGN) power relativistic outflows that remain collimated over kiloparsec scales. These outflows, known as jets, accelerate cosmic rays (CRs) to high energies, exceeding the PeV regime, and potentially contribute significantly to the observed CR spectrum on Earth. As CRs interact with their surrounding medium, they produce multiwavelength (MW) emission spanning over ten...
In this presentation, I will investigate the influence of the reheating temperature of the visible sector on the freeze-in dark matter (DM) benchmark model for direct detection experiments, where DM production is mediated by an ultralight dark photon. I will consider a new regime for this benchmark where the initial temperature of the thermal Standard Model (SM) bath to be below the DM mass....
The detection of 1.5-15 TeV neutrino signals from the nearby Seyfert galaxy NGC 1068 by the IceCube Collaboration provides evidence of nonthermal processes at the heart of a supermassive black hole. In this talk, I discuss the possible production mechanisms, taking into account the constraints from neutrino and electromagnetic observations (Fermi-LAT, MAGIC, NuSTAR, etc.). We utilize the...
Ultra-high-energy cosmic rays (UHECRs) are the most energetic messengers in the Universe, with energies reaching up to 10$^{20}$ eV. More than half a century after their discovery, the origins of UHECRs remain an open question. Investigating anisotropies in their arrival directions is crucial to unraveling this mystery. The Pierre Auger Observatory, located in Mendoza, Argentina, is the...
Recent observations from optical surveys have discovered the presence of a multitude of ultra-faint compact stellar systems (UFCSs) orbiting the Milky Way (MW) that have the potential to be the most compact and faintest galaxies observed so far. If they were confirmed to be dark matter (DM) dominated, these objects would be ideal for indirect searches of DM annihilation, due to their proximity...
The Probe of Extreme Multi-Messenger Astrophysics Balloon with Radio (PBR) is a proposed mission that will fly on a NASA Super pressure Balloon in 2027 from Wanaka, New Zealand. The PBR optical design consists of a 1.1 m aperture Schmidt telescope with a primary mirror of roughly 2m by 2m and a radius of curvature of 1.6m. The hybrid focal surface is made of a fluorescent camera (FC) and a...
DAMIC-M aims to directly detect DArk MAtter in CCDs in the Laboratoire Souterrain de Modane. By employing fully depleted Charge-Coupled-Devices (CCDs) and a floating gate ("skipper") amplifier, the detector can resolve eV-Scale interactions in the silicon bulk. This unprecedented resolution enables DAMIC-M detector to probe new area of parameter space for Hidden Sector Dark Matter. The DAMIC-M...
The High Energy cosmic-Radiation Detection (HERD) facility is a gamma-ray and cosmic-ray telescope planned for installation aboard China's Space Station around 2027. Operating for at least 10 years, HERD aims to precise measure the spectra and composition of charged cosmic rays up to the "knee" region (~few PeVs), monitor the high-energy gamma-ray sky above 100 MeV, and advance the indirect...
MeV gamma-ray astronomy will be soon revolutionized by the advent of new telescopes such as COSI, GECCO, and AMEGO-X. In this talk, I will discuss how these telescopes would probe the nature of dark matter (DM) within and beyond the WIMP paradigm. Light DM particles, with masses in the keV-GeV range, would generate gamma rays in the bandpasses of COSI, GECCO, and AMEGO-X through their decay...
We started a new air shower observation experiment, ALPACA, to observe cosmic gamma rays and cosmic rays of several TeV or more from the southern sky of the galaxy. The ALPACA’s location is at an altitude of 4,740 m on the hillside in Chacaltaya, Bolivia, The ALPACA consists of a ground-based air shower detector array of 401 scintillation detectors and a large-area water Cherenkov-type...
High-energy neutrinos propagating over cosmological distances are the ideal messenger particle for astrophysical phenomena, but the neutrino landscape above 10 PeV is currently completely uncharted.
At these extreme energies and the frugal flux expected, the dominant experimental strategy is to detect radiofrequency emissions from particle cascades produced by neutrinos interacting in the...
The Pierre Auger Observatory is the largest detector for measuring ultra-high-energy cosmic rays. Located in Argentina and spanning over 3000 square kilometers, the Observatory samples the particle content of Extensive Air Showers using an array of Water-Cherenkov Detectors (WCDs). The shower longitudinal profile is measured with Fluorescence Detectors. In this contribution, the...
The two most favored explanations of the Fermi Galactic Center gamma-ray
excess (GCE) are millisecond pulsars and self annihilation of the smooth dark matter halo
of the galaxy. In order to distinguish between these possibilities, we would like to optimally
use all information in the available data, including photon direction and energy information.
To date, analyses of the GCE have...
The Radar Echo Telescope for Cosmic Rays (RET-CR), a pathfinder experiment for a future ultra-high-energy neutrino detector, is a recently deployed experiment designed to detect the ionization trail from a cosmic-ray-induced particle cascade penetrating a high-altitude ice sheet. In high-elevation ice sheets, a high-energy cosmic ray (E $>$ 10 PeV) at shallow zenith angle deposits more than 10...
Over the past five years, almost all experiments operating novel sensors with thresholds lower than keV energies have observed large excess rates over expected radioactive backgrounds. These excess rates have been studied in detail over this time, in part through the EXCESS Workshop series. While many of these excess rates share common features, they are not yet fully understood. Moreover, a...
The Askaryan Radio Array (ARA) is an in-ice ultrahigh energy (UHE) neutrino experiment at the South Pole. ARA aims to detect the radio emissions from neutrino-induced particle showers using in-ice clusters of antennas buried ~200 m deep on a roughly cubical lattice with side length of ~10 m. ARA has five such independent stations which have collectively accumulated ~30 station-years of...
The Pierre Auger Observatory is an experiment dedicated to the detection of ultra-high-energy cosmic rays (UHECRs), which have energies higher than the limits reached at the most powerful particle accelerators. Such high-energetic particles can be indirectly detected by measuring extensive air showers using several detection techniques. At the Pierre Auger Observatory, a hybrid technique...
Astrophysical cosmic-ray accelerators capable of reaching ultra-high energies (UHEs) may produce very-high energy (VHE) neutrinos due to interactions of the cosmic rays within their sources or their surrounding environments. Suborbital and space-based optical Cherenkov detectors search for upward-moving extensive air showers generated by decaying tau-leptons produced by the interactions of >~...
The searches for the signals associated with the interaction of dark matter particles with target material of liquified noble gases have now entered a region of parameter space where nuclear and electronic recoils lead to no more than a few keV of deposited energy. Under those conditions, uncertainties on the response of the medium to the low-energy recoiling particles become crucial to...
Core-collapse supernovae (CCSNe) are one of the most energetic particle generators due to their extremely high densities and temperatures. If sterile neutrinos exist, these may also be produced in the supernova core through their mixing with active neutrinos. These heavy sterile neutrinos can escape the stellar envelope and then decay into photons and neutrinos, which can be detected at...
The distribution of the number of muons over an ensemble of proton-induced showers at ultra-high energies is shaped by the energy spectrum of secondary neutral pions in cosmic ray-air interactions.
This work finds that the steepness of the muon number distribution in muon-poor showers, quantified by the parameter $\Lambda_\mu$, decreases with the depth of the shower maximum, $X_{\max}$, with...
The IceCube Neutrino Observatory is a neutrino detector at the South Pole, which uses the Cherenkov radiation emitted by charged secondaries from neutrino-nucleon interactions in the ice to reconstruct neutrino events. Events where this interaction vertex is contained inside the detector volume are termed “starting events”. At energies ranging from 1 TeV to 100 TeV, starting event samples are...
Identification of high-energy neutrino point sources by IceCube is exciting for particle phenomenology, as propagation of neutrinos over large distances allows us to test properties that are otherwise hard to access. However, many beyond-Standard Model effects would show up as distortions of the energy spectrum, making it difficult to distinguish new physics from uncertainties in the source...
The TESSERACT collaboration will search for dark matter particles below the proton mass through interactions with two types of novel, ultra-sensitive detectors, These detectors, SPICE and HeRALD, aim to provide leading sensitivities to low mass dark matter candidates. The HeRALD experiment will use superfluid He-4 as a target material, which is an ideal kinematic match for dark matter nuclear...
We present a new study on the prediction of the cosmic positron flux from catalogued pulsars. The flux is computed on parameters derived from massive simulations performed within several theoretical frameworks. The flux from the Galactic pulsars is then summed to a state-of-the-art prediction on the secondary positron contribution, and compared to AMS-02 data. A synthesis of our analysis...
I will talk about gravitational waves from thick cosmic strings expected in a supersymmetric U(1)_{B-L} extension of the MSSM. The talk would be based on the two paper, JCAP 11 (2023) 016 and JCAP 01 (2024) 015.
The hypothesis of Cold Dark Matter (CDM) has been spectacularly confirmed on the largest scales of the Universe and must now be stress-tested on sub-galactic scales. Many well-motivated and generic alternatives to CDM can leave spectacular signatures on precisely these scales, affecting the evolution of galaxies as well as their population statistics. Excitingly, over the course of the next...
The Cherenkov Telescope Array Observatory (CTAO) is the upcoming next-generation ground-based gamma-ray observatory. The CTAO will achieve superior sensitivity, angular, and spectral resolution over a broader energy range (tens of GeV to hundreds of TeV) compared to currently operating imaging air Cherenkov telescopes (IACTs). Full-sky coverage will be achieved with two IACT arrays in the...
Tornadoes are severe weather phenomena characterized by a violently rotating column of air connecting the ground to a parent storm. Within the United States, hundreds of tornadoes occur every year. Despite this, the dynamics of tornado formation and propagation are not particularly well understood, in part due to the challenge of instrumentation. Many existing instruments are in-situ...
The first stars are expected to form through molecular-hydrogen (H$_2$) cooling, a channel that is especially sensitive to the thermal and ionization state of gas, and can thus act as a probe of exotic energy injection from decaying or annihilating dark matter (DM). I will discuss using a toy halo model to study the impact of DM-sourced energy injection on the H$_2$ content of the first...
The IceCube Neutrino Observatory is sensitive to the full sky, with nearly 100% up time. It is therefore well suited to search for neutrinos accompanying transient sources, including the sources of gravitational waves. Various models predict that neutrinos could be produced by compact object mergers including at least one neutron star or even by binary black hole mergers. For every...
Primordial black holes (PBH), while still constituting a viable dark matter component, are expected to evaporate through Hawking radiation.
Assuming the semi-classical approximation holds up to near the Planck scale, PBHs are expected to evaporate by the present time, emitting a significant flux of particles in their final moments, if produced in the early Universe with an initial mass of...
Fifth force and equivalence principle tests search for new physics by precisely measuring forces between macroscopic objects and their properties under free fall. These experiments test the interactions between macroscopic collections of atoms and molecules, and any new interactions effectively take place between these low energy degrees of freedom.
In contrast, the early Universe plasma...
We analyse a model that connects the neutrino sector and the dark sector of the universe via a mediator $\Phi$, stabilised by a discrete $Z_4$ symmetry that breaks to a remnant $Z_2$ upon $\Phi$ acquiring a non-zerovacuum expectation value ($v_\phi$). The model accounts for the observed baryon asymmetry of the universe via additional contributions to the canonical Type-I leptogenesis. The...
The heating of an old neutron star (NS) due to dark matter annihilation and kinetic heating provides a compelling avenue for dark matter detection. This process can significantly elevate the temperature of the NS, potentially making it observable as a black body with telescopes like the E-ELT or TMT, particularly for those NSs in close proximity. Given that the majority of NSs have been...
Observation of high-energy neutrinos from the direction of nearby active galaxy, NGC 1068, was a major step in identifying for the origin of high-energy neutrinos. This observation revealed that high-energy neutrinos originated at the heart of active galaxies which are opaque to gamma-ray emission. The realization that is reinforced by the excess of neutrinos in the direction of NGC 4151,...
Dark matter can be captured in stars and annihilate, providing the star with a new energy source in addition to nuclear fusion. This significantly changes stellar evolution at the Galactic Center, where the dark matter density is extremely high. As dark matter burning replaces nuclear fusion partially or completely, stars become longer-lived, as they use up hydrogen more conservatively, or...
Dark matter has been a key area of research in physics for over ninety years. The dark photon is a proposed model of dark matter that extends the Standard Model to add a new force mediator to interact with the dark sector. The focus of this paper was to investigate the plausibility of using modern computational techniques, most prominently genetic algorithms, to simulate and detect production...
The Gamma-Ray and AntiMatter Survey (GRAMS) is a next-generation experiment using a Liquid Argon Time Projection Chamber (LArTPC) detector to detect gamma rays and antiparticles. Gamma-ray surveys are important for understanding multi-messenger and time-domain astronomy, enabling exploration of the universe's most potent events, such as supernovae and neutron star mergers etc. Despite the...
The IceCube Neutrino Observatory has reported evidence of TeV-scale neutrinos emitted from NGC 1068, a nearby Seyfert II galaxy. The evidence suggests that active galactic nuclei could be potential sources of high-energy astrophysical neutrinos. The absence of the expected accompanying flux of TeV gamma-rays indicates that they could have been efficiently obscured at their production site,...
Dark kinetic heating of neutron stars has been previously studied as a promising dark matter detection avenue. Kinetic heating occurs when dark matter is sped up to relativistic speeds in the gravitational well of high-escape velocity objects, and deposits kinetic energy after becoming captured by the object, thereby increasing its temperature. We show that dark kinetic heating can be...
The recent DESI 2024 Baryon Acoustic Oscillations (BAO) measurements combined with the CMB data from the Planck 18 PR3 dataset and the Planck PR4+ACT DR6 lensing data, with a prior on the sum of the neutrino masses $\sum m_\nu>0$, leads to a strong constraint, $\sum m_\nu<0.072$ eV, which would exclude the inverted neutrino hierarchy and put some tension on even the standard hierarchy. We...
The DArk Matter Particle Explorer (DAMPE) is a satellite-borne experiment, in operation since 2015, aimed at studying high-energy cosmic rays and gammas. Protons are the most abundant element in cosmic rays. Given their smaller interaction cross-sections with the interstellar medium (compared to heavier nuclei), they can travel larger distances, thereby becoming important probes to cosmic-ray...
The search for neutrinoless double beta (0$\nu\beta\beta$) decay is ongoing and aims to determine whether the neutrino is Majorana in nature. Discovery of such a process would immediately imply lepton number violation and represent new physics beyond the standard model. This search has been ongoing for a few decades with multiple experimental strategies and choices of isotope. CUPID (CUORE...
Capture and annihilation of WIMP-like dark matter in red giant stars can lead to faster-than-expected ignition of the helium core, and thus a lower tip of the red giant branch (TRGB) luminosity. We use Gaia data to place constraints on the dark matter-nucleon cross section using TRGB of 22 globular clusters with measured TRGB luminosities, and place projections on the sensitivity resulting...
In this talk, we discuss loosely bound composite states of dark matter, where the binding energy per constituent particle is much lower than the constituent’s bare mass. In particular, we investigate the direct detection signatures of nuclear and molecular dark matter, in which constituents are separated by scales much larger than the inverse constituent mass. We find that these composites can...
The IceCube Neutrino Observatory is a neutrino detector located at the South Pole, comprising a cubic-kilometer volume within the Antarctic ice. IceCube has recently observed a diffuse flux of neutrinos from the Galactic Plane. However, no individual point source of astrophysical neutrinos from the Milky Way have been detected yet. Hadronic gamma rays produced through the decay of neutral...
Most stars are M dwarfs, many of which possess kilogauss magnetic fields. For the subset of those with fields arranged into strongly dipolar magnetospheres, the simplest application of the Hillas criterion suggests that these magnetospheres could trap protons with energies up to 20 PeV, and a more cautious estimate puts the limit at tens of TeV. This presentation explores the prospects for...
The microphysical properties of Dark Matter (DM), such as its mass and coupling strength, are typically assumed to retain their vacuum values for any given model when considering DM behaviour at a range of scales. However, DM interactions in different astrophysical and cosmological environments are impacted by the properties of the background which in turn can substantially affect both DM...
Cloud and bubble chambers have historically been used for particle detection, capitalizing on supersaturation and superheating, respectively. Now we will present new results from a prototype snowball chamber, in which an incoming particle triggers crystallization of a purified, supercooled liquid. We demonstrate, for the first time, simulation agreement with our first results from 5 years ago:...
We investigate the scenario in which primordial black holes (PBHs) with masses MPBH ≲ 109g undergo Hawking evaporation, around the Big-Bang nucleosynthesis (BBN) epoch. The evaporation process modifies the Universe’s expansion rate and the baryon-to-photon ratio, leading to an
alteration of the primordial abundance of light nuclei. We present upper bounds for the PBH relative abundance at...
Recently, the IceCube Neutrino Observatory has reported a deviation from a single power law in the extragalactic diffuse neutrino flux. This deviation is primarily driven by the hardening of the low-energy flux below 30 TeV. However, the behavior of the spectrum at higher energies remains uncertain; it is unclear whether it continues, cuts off, or exhibits other features. Partially-contained...
Cosmic ray measurements have reached a remarkable level of precision in recent years. The nature of cosmic ray sources, however, remains elusive. Our limited knowledge about the source properties and positions poses a challenge for predictions of cosmic ray fluxes in our Galaxy. Thus, it is a common model assumption that cosmic rays are injected by a smooth and steady source continuum....
Hawking radiation sets stringent constraints on Primordial Black Holes (PBHs) as a dark matter candidate in the $M \sim 10^{16} \ \mathrm{g}$ regime based on the evaporation products such as photons, electrons, and positrons. This motivates the need for rigorous modeling of the Hawking emission spectrum. Using semi-classical arguments, Page [Phys. Rev. D 16, 2402 (1977)] showed that the...
Cosmic ray (CR) upscattering of dark matter is one of the most straightforward mechanisms to accelerate ambient dark matter, making it detectable at high threshold, large volume experiments. In this work, we revisit CR upscattered dark matter signals at the IceCube detector, considering both proton and electron scattering, in the former case including both quasielastic and deep inelastic...
The cores of active galactic nuclei (AGN) are potential accelerators of 10-100 TeV cosmic rays, which in turn can produce high-energy neutrinos. This hypothesis has been supported by compelling evidence of a TeV neutrino signal from the nearby active galaxy NGC 1068. However, the specific site and mechanism of cosmic ray acceleration remain open questions. One promising candidate is magnetized...
The PICO collaboration uses bubble chambers to search for dark matter. The degree of superheat is chosen so that the detectors are insensitive to electron recoils; only nuclear recoils above several keV produce bubbles. C3F8 is used as the target fluid; the fluorination is ideally suited for investigating spin-dependent WIMP-proton interactions. The PICO-40L detector, currently being...
The detection of high-energy astrophysical neutrinos by IceCube has opened a new window on our Universe. While IceCube has measured the flux of these neutrinos at energies up to several PeV, much remains to be discovered regarding their origin and nature. Currently, the discovery of point sources of neutrinos is hindered by atmospheric neutrino backgrounds; likewise, astrophysical neutrino...
Cold interstellar gas clouds are a powerful way of probing Beyond Standard Model (BSM) interactions, such as those of dark matter, through their calorimetric impact. The immense size and extremely long lifetime of these clouds makes them uniquely sensitive to a variety of BSM interactions, from those ultra-light dark matter acting like a classical background field to ultra-heavy composites...
Primordial Black Holes (PBHs) could play a relevant role in several physical phenomena. They are particularly attractive as a candidate for dark matter, seeds of supermassive black holes, sources of gravitational waves, etc. In addition, the observation of an evaporating black hole would pro- vide definitive information on the elementary particles present in nature, including new degrees of...
The Payload for Ultrahigh Energy Observations (PUEO) experiment is an Antarctic balloon-borne detector targeting astrophysical neutrinos with energies exceeding 100 PeV. PUEO aims to observe neutrinos via the detection of coherent radio emission sourced from in-ice neutrino interactions. The dominant channel for these interactions is the charged current interaction, which produces both a...
The COSINE-100 experiment aims to investigate the dark matter-induced annual modulation signal previously observed by the DAMA/LIBRA experiment. Commencing its physics operations in September 2016, the experiment concluded its initial phase in March 2023 at the Yangyang underground laboratory in Korea, employing 106 kg of low-background NaI(Tl) detectors. To further enhance light collection...
The paradigm of the Standard Model of particle physics has only been extended, in the recent past, by the addition of neutrino masses and oscillations. Today, we can use neutrinos to verify our most fundamental theories, such as Lorentz invariance, which, if broken, introduces a preferred reference frame in the Universe. For neutrinos, the resulting phenomenology can predict flavour...
Dwarf Spheroidal galaxies (dSphs) are suspected dark matter dense astrophysical objects within our galactic neighborhood. They are otherwise low of other high energy neutrino sources which makes them ideal dark matter targets. The previous IceCube dark matter search toward dSphs was performed with an incomplete detector with fewer strings and significantly less data. This iteration will...
The Scintillating Bubble Chamber (SBC) Collaboration aims to use the liquid-noble bubble chamber technology as a low-threshold detector for dark matter particles of 1-10 GeV/c2. The detector combines the remarkable electron recoil (ER) discrimination of the bubble chamber with the event-by-event energy resolution provided by liquid argon (LAr) scintillation, with the crucial added...
Various cosmological scenarios give rise to primordial black holes in the early universe. If these black holes were light enough ($\lesssim 10^8$ g), they would have disappeared before BBN due to Hawking evaporation. Thus, their abundance is only weakly constrained by observations. Even if the abundance was small, the universe could have gone through an era of black-hole domination before they...
Interpreting observations of extreme astrophysical phenomena requires a detailed understanding of the microphysical processes responsible for cosmic ray acceleration. In the standard picture, supernova remnants and other astrophysical shocks accelerate these particles via diffusive shock acceleration (DSA), an efficient mechanism that produces power-law distributions in momentum. However, both...
In previous work [1] we have shown that within the natural warm inflationary paradigm (WNI) observational constraints on the primordial power spectrum from the cosmic microwave background (CMB) can be satisfied without going beyond the Planck scale of the effective field theory. Moreover, WNI can inevitably provide perfect conditions for the production of primordial black holes (PBHs) in the...
A powerful beacon for penetrating the Neutrino Fog obscuring direct detection of heavy dark matter would be direction-sensitive detection of the recoil atoms. Negative-ion drift is being pursued for this purpose by a number of collaborations, but it is hard to see how this could achieve sensitive mass competitive with noble liquid TPCs. Direction sensitivity based on columnar recombination...
The nearly-pure thermal Higgsino remains one of our best-motivated and least-tested theories of dark matter. The shortest path to discovering such a candidate is likely via observations of TeV-scale gamma rays at the Galactic Center. In this talk I discuss the prospects of current and near future observatories for finding or ruling out Higgsino DM, and how underlying systematics and analysis...
In this talk, I’ll discuss the status and prospects of direct searches for >1 GeV dark matter, which includes TeV-scale astrophysical particles!
Decades of astrophysical observations point to the existence of a feebly interacting particle comprising 85% of the matter content of the universe. A promising candidate is the QCD axion, a natural product of the Peccei-Quinn mechanism that solves the strong CP problem. This talk will focus on the use of resonant haloscopes to search for axion dark matter, notably, the Axion Dark Matter...
I will discuss direct detection prospects for meV-GeV scale dark matter, including the SuperCDMS SNOLAB dark matter program, R&D towards meV-scale thresholds for scattering events, and new concepts in axion detection.
Ultra-high energy neutrinos (>100 PeV) are expected to be unique messengers to the distant universe. This is because the other classic UHE messengers--photons and cosmic rays--are attenuated for sources further away than ~100 MPc. Additionally, as neutral and weakly interacting particles, neutrinos travel in straight lines, and so they point at their sources. However, the flux of UHE neutrinos...
Over a decade after the discovery of diffuse astrophysical neutrinos, the first evidence of individual neutrino sources has emerged. These sources exhibit several distinct characteristics: 1) they are powerful and abundant; 2) they are likely opaque to the gamma rays that accompany neutrino production; and 3) extragalactic neutrino emitters are significantly more powerful than Galactic ones....
The circular velocity curve, one of the first pieces of evidence for dark matter (DM), is a direct probe of the Galaxy’s potential, which allows studies of the nature of DM. Recent large surveys have provided valuable information for determining the Milky Way circular velocity curve.
In this talk, I will describe our recently derived circular velocity curve of the Milky Way out to ~30 kpc,...
Compact objects such as neutron stars possess some of the strongest electric and magnetic fields in the observed universe. Non-thermal electromagnetic emission from neutron stars is sourced in regions with accelerating electric fields, $\vec{E} \cdot {\vec{B}} \ne 0$. These regions are also very efficient axion factories. Once produced, axions may (1) convert to photons, giving rise to...
Cosmic rays interact in the Earth's atmosphere to produce extensive air-showers (EASs). The EASs have Cherenkov and fluorescence emission associated to them that can be detected by ground-based, sub-orbital and satellite-based neutrino telescopes.
Ground-based and sub-orbital telescopes are also subject to the atmospheric flux of muons which arrive at the detectors as a potential background....
The Fermi Large Area Telescope, with its exceptional sensitivity, has played a crucial role in the indirect search for Weakly Interacting Massive Particles (WIMPs) as dark matter (DM) candidates using gamma rays. However, the domain of dark matter with masses exceeding TeV energies remains less explored. In the case of such heavy dark matter, secondary gamma rays can be produced when...
Using the 3D simulation option of the GALPROP framework we modelled Galactic cosmic-ray (CR) diffusion utilising a distribution of CR sources stochastically placed in position and time within the Galaxy. This source distribution more accurately represents the formation rates and finite lifetimes compared to the steady-state CR injection models that are typically assumed.
We investigate the...
Ultra-light axions with weak couplings to photons are motivated extensions of the Standard Model. We perform one of the most sensitive searches to-date for the existence of these particles with the NuSTAR telescope by searching for axion production in stars in the M82 starburst galaxy and the M87 central galaxy of the Virgo cluster. This involves a sum over the full stellar populations in...
While direct and indirect detection experiments have yet to find dark matter interacting with standard model particles, cosmological probes provide a complementary approach for exploring the physics of dark matter. Phenomenological dark matter-baryon scattering models can probe several particle physics scenarios with cosmological data. These models have two parameters vulnerable to prior...
Planned to fly the Austral summer of 2025, the Payload for Ultrahigh Energy Observations (PUEO) is a balloon experiment built to search for Askaryan emission from showers from > EeV neutrinos and air showers from ultra-high energy cosmic rays (UHECRs). The instrument is designed to maximize sensitivity to these signals while rejecting backgrounds. The payload includes two instruments: the Main...
Adding an electroweak triplet fermion, or wino, to the Standard Model gives one of the simplest particle explanations of dark matter. In addition to this bottom-up, economical motivation, such a state automatically arises in supersymmetric extensions of particle physics. For masses near 2.8 TeV, its relic density from thermal freezeout would provide a complete resolution of the dark matter...
We study multiple corrections to the ALP-photon conversion process in neutron stars, especially the isolated ones. The result may inspire further studies.
Dark matter may exist today in the form of ultraheavy composite bound states. Collisions between such dark matter bound states may release intense bursts of radiation that include gamma rays among the final products appearing as gamma ray transients. Given their $\textit{a priori}$ unknown durations and occurrence rates, such bursts may have been missed not necessarily because of their low...
The Radio Neutrino Observatory in Greenland (RNO-G) is situated at Summit Station and is intended to detect Askaryan emission from ultra-high energy neutrinos above 10 PeV. The detector is proposed to have 35 stations of which 7 have been installed so far. Each station consists of 3 strings carrying dipole antennas embedded down to 100 meters in ice. These antennas capture the horizontal and...
High-energy neutrino and γ-ray emission are expected from the Galactic plane, generated by interactions between cosmic rays and the interstellar medium or radiation fields. Recent observations from LHAASO have detected diffuse γ-rays from the Galactic plane and an ultrahigh-energy γ-ray bubble (Cygnus Bubble) in the Cygnus region up to PeV energies, suggesting the possibility of neutrino...
The talk will provide an updated overview of the search for particle dark matter signals by means of cross-correlations between multiwavelength observations, with special focus on the gamma-ray band, and large scale structure tracers like galaxy and galaxy cluster distributions and cosmic voids.
The events detected by the IceCube Neutrino Observatory have two main topologies: cascades and tracks. Cascades are particle showers, and historically, due to their short extension (on the order of meters) relative to the spacing between optical modules, the main focus for cascade events has been on measuring the total light yield as a proxy for energy, rather than their spatial features....
Active Galactic Nuclei (AGNs) and Gamma-ray Bursts (GRBs) are characterised by highly relativistic outflows. In the first part of the talk, I will discuss how the production of axion-like particles (ALPs) close to the central engine can, on the one hand, either power or disrupt the outflow, and on the other hand, can lead to various observational signatures involving either changes in the...
Observations by the HAWC and HESS telescopes have found extended TeV emission consistent with a handful of young and middle-aged pulsars. In this talk, I will show that these detections have significant implications for our understanding of both pulsar emission and TeV astrophysics. Most importantly, the high-luminosity and spatial extension of TeV halos indicate that cosmic-ray diffusion on...
The Fermi Large Area Telescope (LAT) has set stringent constraints on dark matter (DM) properties. We propose a comprehensive search for DM annihilation signals in highly concentrated DM regions, known as DM spikes, around intermediate-mass black holes (IMBHs). First, we investigate excess emission in dwarf active galactic nuclei (AGNs), likely hosting central IMBHs, due to classical...
A supermassive black hole (SMBH) at the core of an active galactic nucleus (AGN) provides room for the elusive ultra-light scalar particles (ULSP) to be produced through a phenomenon called $\textit{superradiance}$. This phenomenon produces a cloud of scalar particles around the black hole by draining its spin angular momentum. In this work, we present a study of the superradiant instability...
Cosmic neutrinos are hadronic processes messengers and at high energies provide a clear window into their astrophysical sources. Starting around a PeV, Tau neutrino interactions within the Earth can provide a substantial flux of Earth-emergent tau-leptons which then decay to form upward-moving extensive air showers (EAS). This effectively uses the Earth as a neutrino target and the...
The age of WIMP-like dark matter direct detection is drawing to a close due to their non-detection at exquisitely sensitive liquid-noble detectors. However, models where the dark matter is lighter than the mass of a proton remain largely inaccessible to experimental probes. Recently, molecular targets have emerged as particularly well-suited detector materials to look for this sub-GeV dark...
Understanding intermediate-mass black holes (IMBHs) can provide crucial insights into active galactic nuclei (AGN) feedback, black hole-galaxy co-evolution, and the origins of supermassive black holes. One promising method to study IMBHs is by searching for their high-energy emission in nearby dwarf galaxies. Using 13 years of Fermi LAT observations, we conducted a stacking analysis to detect...
Some fraction of the diffuse photon background is supposed to be linked to high-energy neutrinos by astrophysical mechanisms of production and electromagnetic cascades. This article presents a simulation study of axion-like particles (ALPs) implications for that component, exploiting transport equations. Alternations of that spectrum due to ALP-photon conversion in the intergalactic magnetic...
The Askaryan Radio Array (ARA) is an ultrahigh energy (UHE) neutrino experiment at the South Pole that aims to detect radio emissions from neutrino-induced particle showers using in-ice antennas buried up to 200m in depth. The depth-dependent refractive index profile in ice affects calibration efforts and neutrino sensitivity predictions of ARA as well as other UHE neutrino experiments at...
Black hole binaries are observed from radio to gamma rays. While it is believed that the radio and X-ray emission comes from relativistic jets and accretion flows, respectively, the origin of the gamma-ray emission is still under debate. When a black hole binary is in the hard state, it likely has a magnetically arrested disk (MAD), where the magnetic flux threading the black hole is in a...
Electromagnetic fields surrounding pulsars may source coherent ultralight axion signals at the known rotational frequencies of the neutron stars, which can be detected by laboratory experiments (e.g., pulsarscopes). As a promising case study, we model axion emission from the well-studied Crab pulsar, which would yield a prominent signal at $f \approx 29.6$ Hz regardless of whether the axion...
The decay of asymmetric dark matter (ADM) can lead to distinct neutrino signatures characterized by an asymmetry between neutrinos and antineutrinos. In the high-energy regime, the Glashow resonant interaction $\bar{\nu}_{e} + e^{-} \rightarrow W^{-}$ yields an increase in sensitivity to the neutrino flux, and stands out as the only way of discerning the antineutrino component in the diffuse...
Gravitational-wave (GW) signals offer unique probes into the early universe dynamics, particularly those from topological defects. We investigate a scenario involving a two-step phase transition resulting in a network of domain walls bound by cosmic strings. By introducing a period of inflation between the two phase transitions, we show that the stochastic GW signal can be greatly enhanced....
We highlight the existence of a residual symmetry in the IR phase of a broad class of confining dark sectors that suppresses their signals at direct detection experiments. Our conclusions apply to all vectorlike confining dark sectors, regardless of the number of flavors and color, confinement scale, and dark matter mass. Our results highlights the irreplaceable role of a continuing collider...
Charged leptons produced by high-energy and ultrahigh-energy neutrinos have a substantial probability of emitting prompt internal bremsstrahlung $\nu_\ell + N \rightarrow \ell + X + \gamma$. This can have important consequences for neutrino detection. We discuss observable consequences at high- and ultrahigh-energy neutrino telescopes and LHC's Forward Physics Facility. Logarithmic...
We consider pre BBN energy injection via PBH evaporation or Moduli decay into universe and it's possible detection via Gravitational waves via phase transitions in hidden sectors. The energy injection leads to three correlated peaks gravitational wave signatures instead of the usual one peak. The resultant GW amplitude is also stronger than the usual scenario, and hence can be probed via...
The quantum chromodynamics (QCD) axion, which may explain the absence of a neutron electric dipole moment, arises as the pseudo-Goldstone mode of a spontaneously broken abelian Peccei-Quinn (PQ) symmetry. If the scale of PQ symmetry breaking occurs below the inflationary reheat temperature, then there is a unique axion mass that gives the observed dark matter (DM) abundance. Computing this...
Telescopes such as ANTARES and IceCube can detect ultra high-energy neutrinos from the atmosphere and outer space. The information carried by these neutrinos sheds light on new interactions of matter, not yet explained by the standard model of particle physics. Recently, strong constraints on these non-standard interactions were achieved by ANTARES and Icecube through events with energies up...
Previous studies have shown the effect of the Large Magellanic Cloud (LMC) on the local speed distribution of the dark matter particles. Since it dominates the high speed tail of the distribution and the gravitational interaction also boosts the solar neighbourhood dark matter particles to higher velocities, such an effect has an impact on direct detection searches. In this talk, I will...
Ultra-light axions with masses $10^{-33} < m_\phi/{\rm eV} < 10^{-22}$ , even as a small fraction of the observed dark matter abundance, may yet produce a visible impact on the cosmology due to their macroscopic quantum scale. Next generation galaxy survey data are poised to challenge this possibility, but in order to do so, all aspects of structure formation in this quasi-linear regime must...
Supermassive binary black holes (SMBHBs) are by-products of our theories of galaxy formation, crucial gravitational wave (GW) sources that will be observed with future observatories such as LISA. In this talk, we will give an overview of the subject, focusing on the expected SMBHB electromagnetic counterparts. We will present new calculations of the EM emission that take into account the...
The QCD axion and axion-like particles, as leading dark matter candidates, can also have interesting implications for dark matter substructures if the Peccei-Quinn symmetry is broken after inflation. In such a scenario, axion perturbations on small scales will lead to the formation of axion miniclusters at matter-radiation equality, and subsequently the formation of axion stars. Such compact...
To enable the detection of gravitational waves, the state of the interferometer must be known as precisely as possible. We describe a wavefront sensor in form of a camera, measuring the phase and intensity of all facilitated sidebands simultaneous for the 1550 nm interferometer of the Einstein Telescope. As novel feature, a fiber array of 8 x 8 is used with each fiber read-out by an individual...
The string theory axions can naturally form stable string-domain wall network. The later collapse of the domain walls produce more than one type of axion mass eigenstates apart from gravitational waves.
The Askaryan Radio Array (ARA) is an experiment with the goal of detecting ultra-high energy (>10 PeV) neutrinos at the South Pole for the first time. ARA uses arrays of antennas designed to detect radio-frequency radiation emitted from relativistic particle showers produced by neutrinos interacting within the ice. South Pole ice behaves as a biaxially birefringent medium at radio frequencies,...
The nearest radio galaxy, Centaurus A, known for its large-scale jet, has been monitored by multiwavelength observations. Analysis of the Fermi-LAT and H.E.S.S. observation data in 2019 showed up an unnatural hardening in very high energy gamma-ray spectrum [1], and its origin is still a matter of controversy. Imaging analysis also reveals that gamma-rays are distributed over the entire jet,...
The Askaryan Radio Array (ARA) is an in-ice ultra high energy (UHE, >10 PeV) neutrino experiment at the South Pole that aims to detect UHE-neutrino induced radio emission in ice. ARA consists of five independent stations each consisting of a cubical lattice of in-ice antenna clusters with side length ~10m buried ~200 m below the ice surface. The fifth station of ARA (A5) is special as this...
The SABRE experiment aims to detect an annual rate modulation from dark matter interactions in ultra-high purity NaI(Tl) crystals in order to provide a model independent test of the signal observed by DAMA/LIBRA. It is made up of two separate detectors that rely on joint crystal R&D activity; SABRE South located at the Stawell Underground Physics Laboratory (SUPL), in regional Victoria,...
The LIGO-Virgo-KAGRA Collaboration has observed ~100 gravitational-wave sources to date, including mergers between black holes, neutron stars, and mixed neutron star—black holes. These neutron stars and black holes connect many astrophysical puzzles, including the lives and deaths of stars, cosmic chemical enrichment, and the expansion history of the Universe. I will discuss some astrophysical...
Last year, multiple pulsar timing array collaborations across the globe announced the first evidence of a stochastic background of nHz-frequency gravitational waves. A population of inspiraling supermassive black hole binaries can generate a stochastic background, but there may also be contributions from exotic cosmological sources that formed around the time of the Big Bang. In this talk, I...
Primordial black holes, which could have potentially formed after inflation, can have significant implications for the early Universe's history. Such a population of black holes, which may have differing mass and spin, can undergo evaporation due to Hawking radiation at different points in time. In this talk, I will review the potential impact of this evaporation on various cosmological...
This talk will review the status of the Galactic Center Excess (GCE). Discovered fifteen years ago in Fermi data, the GCE appears almost exactly as WIMP dark matter annihilations were predicted to emerge in gamma rays. Despite this and the fact that the excess is seen at high significance, its exact nature remains unclear. I will discuss the status of various aspects of the excess that could...
Slow-roll inflation is a successful paradigm. However, even small couplings of the inflaton to other light fields can dramatically alter the dynamics and predictions of inflation. As an example, the inflaton can generically have an axion-like coupling to gauge bosons. Even relatively small couplings will automatically induce a thermal bath during inflation. The thermal friction from this bath...
The use of machine learning techniques has significantly increased the physics discovery potential of neutrino telescopes. In the upcoming years, we are expecting upgrades of currently existing detectors and new telescopes with novel experimental hardware, yielding more statistics as well as more complicated data signals. This calls for an upgrade on the software side needed to handle this...
We explore baryon number violating interactions (BNV) using a simple model involving a charged iso-singlet, color-triplet scalar and a Majorana fermion with interactions in the quark sector. This model has been useful for explaining baryogenesis and the DM-baryon coincidence puzzle. We revisit this model, with chiral perturbation theory as a guide, at the level of baryons and mesons in the...
The Compton-Getting effect — an apparent dipolar anisotropy of cosmic rays generated by Earth's orbital motion around the Sun — serves as a known calibration source for cosmic-ray anisotropy studies. The amplitude of the Compton-Getting dipole depends on both the orbital speed and the mean spectral index of the cosmic-ray flux. It therefore provides an indirect method for studying the energy...
The accelerator complex at Fermilab is currently undergoing improvements which will increase the available beam power to the complex and is known as Proton Improvement Plan-II (PIP-II). The PIP-II Linac is slated for operation near the end of this decade and will be the main proton driver for Fermilab experiments moving forward and provide the beam to LBNF/DUNE. However, the DUNE physics...
Primordial magnetic fields (PMFs) can enhance baryon perturbations on scales on small scales. However, a magnetically driven baryon fluid becomes turbulent near recombination, thereby damping out baryon perturbations below the magnetic jeans scale. In this talk, I show that the initial growth in baryon perturbations gravitationally induces growth in the dark matter perturbations, which are...
Abstract: In this work, we present preliminary results from our analysis of cosmic-ray showers collected by the IceTop surface array, with a focus on studying cosmic ray anisotropy. By leveraging enhanced statistical power and improved Monte Carlo event simulations, we investigate cosmic ray anisotropy across four energy ranges, from approximately 100 TeV to 10 PeV. This analysis enables us...
Milky Way satellite galaxies include some of the oldest, faintest, and most dark matter dominated stellar systems known. By performing a rigorous census of Milky Way satellite galaxies, we are able to extend previous analyses to present novel constraints on a mixed dark matter scenario that contains both cold and warm dark matter components (CWDM). We use the semi-analytical model SASHIMI to...
We study the kinetic heating of neutron stars due to their coherent scatterings with relic neutrinos via the neutral-current interactions. A neutron star gravitationally attracts relic neutrinos as it travels through the universe, gaining energy from heavy relic neutrinos by scatterings. The heating effect turns out to be possibly detectable by current and future optical/infrared telescopes....
Abstract: IceAct is an array of compact imaging air Cherenkov telescopes acting as a sub-detector of the IceCube Neutrino Observatory. The telescopes are optimized to operate in the harsh environmental conditions of the geographic South Pole. Since 2019, the first two IceAct telescopes have been operating in a stereoscopic configuration in the center of IceCube’s surface detector, IceTop,...
Axion-like particles (ALPs) are good candidates for mediators to the dark sector. We explore scenarios in which an ALP mediates interactions between dark matter and electroweak gauge bosons. These models yield testable electromagnetic signals in astrophysical, cosmological, and terrestrial probes. We find promising prospects for both indirect detection and accelerator tests, with interesting...
The production of high-energy neutrinos, accompanied by a flux of high-energy gamma rays, is attributed to hadronic interactions within cosmic accelerators. Besides TXS 0506+056, no other gamma-ray sources have been identified as neutrino emitters. Instead, sources opaque to gamma rays are emerging as the most likely source of IceCube neutrinos. Active Galactic Nuclei (AGN) with obscured...
Models of a dark radiation sector with a mass threshold have been shown to ease the two currently outstanding cosmological tensions. In particular, addition of radiation in the early universe can naturally raise $H_0$ by widening the sound horizon at recombination. An additional coupling between the radiation and dark matter at early times induces dark matter scattering at small scales, which...
The polar ice sheets can serve as detection media for neutrinos with energies above 10 PeV. This detection can be achieved by observing Askaryan radiation or measuring in-ice radar echoes from the ionization trail left in the wake of the particle cascade. Ice-based radio neutrino detectors deploy antennas within or near the first 100-150 m of compacted snow, known as the firn layer, where the...
Semi-analytic modeling furnishes an efficient avenue for characterizing dark matter halos associated with satellites of Milky Way-like systems, as it easily accounts for uncertainties arising from halo-to-halo variance, the orbital disruption of satellites, baryonic feedback, and the stellar-to-halo mass (SMHM) relation. We use the SatGen semi-analytic satellite generator – which incorporates...
Dark substructures and compact objects composed entirely of dark matter can hold crucial information regarding the particle nature of dark matter as well as the astrophysical and cosmological processes involved in their formation. We show that if the dark sector couples to the Standard Model photon, then clumps of dark matter between a source star and an observer on Earth could effectively act...
Recent observations of black holes in two nearby low-mass X-ray binaries have indicated the possible presence of dark matter density spikes. While the evidence is compelling, one issue with this interpretation is that light black holes formed from stellar collapse are not expected to form dark matter spikes, and so it is unclear how the stellar-mass black holes in these binaries could have...
The angular correlation of pulsar residuals observed by NANOGrav and other pulsar timing array (PTA) collaborations show evidence in support of the Hellings-Downs correlation expected from stochastic gravitational wave background (SGWB).
In this talk, I will give a non-gravitational wave explanation of the observed pulsar timing correlations as caused by an ultra-light gauge boson dark...
Cosmic rays were discovered over a century ago, but the sources of the highest energy components remain unknown. Next-generation neutrino telescopes with significantly improved sensitivity are needed to identify the sources of the diffuse astrophysical neutrinos detected by IceCube, and help decipher the origin of high-energy cosmic rays. The TRopIcal DEep-sea Neutrino Telescope (TRIDENT) will...
I present a novel mechanism for creating primordial black holes and dark MACHOs. 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...
Scenarios such as the QCD axion with the Peccei-Quinn symmetry broken after inflation predict an enhanced matter power spectrum on sub-parsec scales. These theories lead to the formation of dense dark matter structures known as minihalos, which provide insights into early Universe dynamics and have implications for direct detection experiments. We examine the mass loss of minihalos during...
Cosmic rays can be accelerated both in a source or in intergalactic space, producing gamma rays and neutrinos. Furthermore, all cosmic rays that escape a source can potentially initiate particle cascades through interactions with the background radiation fields such as the cosmic-microwave background and the extragalactic background light. In September 2017, a high-energy neutrino event...
Cosmological observables are particularly sensitive to key ratios of energy densities and rates, both today and at earlier epochs of the Universe. Well-known examples include the photon-to-baryon and the matter-to-radiation ratios. Equally important, though less publicized, are the ratios of pressure-supported to pressureless matter and the Thomson scattering rate to the Hubble rate around...
While nuclei lighter than Fe are fused over the course of typical stellar evolution, about half of the heavier elements are created through the rapid neutron capture process (r-process). These nuclei are thought to be produced in magnetized outflows from neutron-rich explosive events including compact mergers and core-collapse supernovae. I will discuss the potential of neutrino-driven winds...
Dark sector theories naturally lead to multi-component scenarios for dark matter where a sub-component can dissipate energy through self-interactions, allowing efficient dark cooling within galaxies. In this talk, I'll present the first cosmological hydrodynamical simulations of dwarf galaxies where the majority of dark matter is collisionless Cold Dark Matter (CDM), but a sub-component (~6%)...
This work investigates the physics potential of hypothetical large-scale detectors observing the interactions of neutrinos produced in proton-proton collisions at the LHC. We focus on the LHCb interaction point, as the forward neutrino flux from this location passes through Lake Geneva before exiting the Earth's surface. This offers two interesting possibilities: (1) a long pipe-like detector...
Atomic dark matter is a dark sector model including two fermionic states oppositely charged under a dark U(1) gauge symmetry, which can result in rich cosmological signatures. I discuss recent work using cosmological n-body simulations to investigate the impact of an atomic dark matter sector on observables such as the galactic UV luminosity function at redshifts >10, and consider the...
The IceCube Neutrino Observatory has observed a diffuse flux of astrophysical neutrinos of so far unknown origin. The absence of strong individual neutrino sources suggests an extragalactic population of dim sources. Although individual neutrino sources may be faint, the population may trace the underlying large scale matter distribution. In this work, we present a search for the origin of...
Neutron star (NS) mergers are amongst the most promising multimessenger sources in the Universe, as demonstrated by the coincident detection of gravitational waves (GWs) with multi-wavelength electromagnetic (EM) radiation for GW170817. Although it is well-known that short gamma-ray bursts (GRBs) can originate from relativistic jets launched by NS merger remnants, there are still uncertainties...
Atomic dark matter (ADM) is a simple extension to the Standard Model that is motivated by considerations in both particle and astrophysics. ADM can alter structure formation on a variety of astrophysical scales due to the presence of dark baryon acoustic oscillations, and its ability to dissipate energy through cooling mechanisms. While previous work has begun to constrain the ADM parameter...
If dark matter has strong self-interactions, future astrophysical and cosmological observations, together with a clearer understanding of baryonic feedback effects, might be used to extract the velocity dependence of the dark matter scattering rate. To interpret such data, we should understand what predictions for this quantity are made by various models of the underlying particle nature of...
Binary neutron-star (BNS) mergers are accompanied by multi-messenger
emissions, including gravitational wave (GW), neutrino, and
electromagnetic (EM) signals. Some fraction of BNS mergers may result in a
rapidly spinning magnetar as a remnant, which can enhance both the EM
and neutrino emissions. In this talk, I will discuss
the possible neutrino and EM signatures from such systems. I...
In this work, we have conducted three-dimensional cosmological magnetohydrodynamical (MHD) simulations of the turbulent intracluster medium (ICM) combined with multi-dimensional Monte Carlo simulations of CR propagation for redshifts ranging from $z \sim 5$ to $z = 0$ to study the multi-messenger emission from these sources. We found that when CRs with a spectral index in the range $1.5 -...
In recent years, the study of Galactic cosmic ray leptons has advanced significantly, largely due to measurements of absolute fluxes of positrons and electrons by AMS-02, and to the direct measurements of the total lepton flux above TeV energies by DAMPE and CALET. In this talk, we discuss how these results refine our models of cosmic ray propagation and contribute to resolving outstanding...
Accelerator experiments, both collider and fixed-target, play a pivotal role in probing the dark sector and uncovering the nature of dark matter. This talk will provide an overview of current efforts and future plans in utilizing accelerators to explore a wide range of dark matter candidates, from WIMPs to light dark sector particles. The synergy and complementarity between accelerator...
How was dark matter produced in the early Universe? There is a growing diversity of particle physics models for dark matter, which can be organized by different mechanisms for dark matter production. In this talk I will chart phase diagrams for thermal and nonthermal production of dark matter, highlighting recent developments.
The High Altitude Water Cherenkov (HAWC) Observatory was officially inaugurated in 2015 and will soon reach 10 years of accumulated data. Of the many discoveries HAWC has made, one of the most scientifically interesting is the detection of many sources emitting gamma rays past 100 TeV. HAWC’s first publication on this topic, in 2020, contained three sources and at the time, was the...
The first catalog (1LHAASO) on very high energy and ultra-high energy gamma-ray sources observed by the Large High Altitude Air Shower Observatory reports about eight new gamma-ray sources exclusively linked with Fermi-LAT detected GeV gamma rays. We searched for gamma-ray counterparts of these sources in the energy range of 100 GeV - 100 TeV using the pass-5-reconstructed data of the...
The GeV gamma-ray sky, as observed by the Fermi Large Area Telescope (Fermi LAT), harbors a plethora of localized point-like sources. At high latitudes ($|b|>30^{\circ}$), most of these sources are of extragalactic origin. The source-count distribution as a function of their flux, $\mathrm{d}N/\mathrm{d}S$, is a well-established quantity to summarize this population. We employ sequential...
SST-1M is a single-mirror small size Cherenkov telescope prototype developed by a consortium among institutes in Switzerland, Poland, and the Czech Republic. With a 4 meter mirror and a 5.6 m focal length, SST-1Ms have a broad 9 degree field of view and aim to detect gamma rays spanning the energy range of 1 to 300 TeV. The DigiCam camera incorporates a compact Photo-Detector Plane comprising...
The James Webb Space Telescope (JWST) is unveiling astounding results about the first few hundred million years of life of the Universe, delivering images of galaxies at very high redshifts. We develop a UV luminosity function model for high-redshift galaxies, considering parameters such as the stellar formation rate, dust extinction, and halo mass function. Testing the model against data at...
The observation of delayed GeV emission after a Gamma Ray Burst (GRB) detected at the very-high energies (VHE) beyond 100 GeV could indicate a non-zero magnetic field in the intergalactic medium. Indeed, VHE photons interact with the Extragalactic Background Light (EBL) to produce electron-positron pairs, which in turn can initiate electromagnetic cascades. An intergalactic magnetic field...
The identification of the sources contributing to the acceleration of Galactic Cosmic Rays (CRs) is a long-standing puzzle. Assuming that CRs originate in the supernovae and winds of massive stars, starburst galaxies should provide an ideal environment for the production of gamma rays via the interaction of CRs with dense gas. Very-high-energy (VHE; E>100 GeV) gamma-ray emission was discovered...
Space-based gamma-ray astronomy, a vital tool for understanding extreme astrophysical phenomena, has significantly contributed to the study of high-energy emissions in the Universe. Gamma rays, linked to gravitational waves, neutrinos, and cosmic rays, are essential in forming a multi-messenger picture of the cosmos. With many current missions nearing their end and only a few future missions...
Abstract: It is widely accepted that supernova (SN) shocks can accelerate particles to very high energies, although the maximum energies are still unclear. These accelerated particles can interact with other particles to produce gamma-ray emission. Details of the process are not well characterized, including the dynamics and kinematics of the SN shock wave, the nature and magnitude of the...
Compact symmetric objects (CSOs) are sources with radio lobe emission on both sides of an active nucleus and an overall size of less than one kpc.
From the detection of 3 CSOs by the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope, we know that the emission from these objects can extend into the GeV band. Surprisingly, the first LHAASO catalog reported a TeV source,...
The IceCube Neutrino Observatory measures astrophysical and atmospheric neutrinos from the entire sky via the Cherenkov light emitted when these neutrinos interact in the ice and produce secondary particles like leptons or hadrons. The Medium Energy Starting Events (MESE) data sample selects events with vertices contained inside the detector volume and have energies from 1 TeV and above. This...
The Peccei-Quinn mechanism addresses the strong charge-parity problem in particle physics by postulating the existence of the QCD axion, a heretofore undetected particle that would interact with known particles. In particular, axion-photon coupling would enable axion-photon conversion in the presence of a magnetic field. Detecting axions requires strong magnetic fields, dense dark matter...
In 2017, the Event Horizon Telescope (EHT) imaged the black-hole shadow of M87* for the first time. This achievement was paralleled by an extensive multi-wavelength (MWL) observational campaign involving ground- and space-based facilities spanning radio waves to very high-energy (VHE) gamma rays. During this initial campaign, M87's core and its innermost knot, HST-1, were observed to be in...
Arrays of Imaging Atmospheric Cherenkov Telescopes (IACTs), like the High Energy Stereoscopic System (H.E.S.S.), observe extensive air showers initiated by gamma rays and cosmic rays when interacting with the Earth’s atmosphere. IACTs image the distribution of Cherenkov light emitted by air shower particles as they propagate through Earth's atmosphere. The traditional reconstruction of...
Recent measurements of astrophysical neutrinos have expanded our understanding of their nature and origin. However, very little is still known about the astrophysical $\nu/\bar{\nu}$ ratio. The only direct measurement is the recent, single Glashow event at IceCube. Understanding the astrophysical $\nu/\bar{\nu}$ ratio has a bearing on multiple questions, including the astrophysical spectral...
As the stellar analogs of extragalactic quasars, microquasars have been recognized as powerful Galactic particle accelerators that emit gamma rays exceeding multi-TeV energies since the first detection of SS 433. Interest in these objects has surged over the last decade. Recently, several have been observed emitting gamma rays above tens of TeV. The High Altitude Water Cherenkov (HAWC)...
Galactic PeVatrons are astrophysical sources accelerating particles up to a few PeV (~10^15 eV), which are believed to be located within our Galaxy. The primary identification of both electron and proton PeVatrons is gamma-ray radiation at ultra-high energies (UHE, E>100 TeV). In 2021, LHAASO detected 14 steady gamma-ray sources with photon energies above 100 TeV and up to 1.4 PeV. Most...
In 2021, the Tibet ASγ experiment achieved the first detection of Galactic diffuse gamma rays at Sub-PeV energies (E > 100 TeV = 10^14 eV), ensuring the presence of PeVatrons in the Galaxy. On the other hand, in 2024, the LHAASO observatory claimed the detection of 43 Sub-PeV gamma-ray sources with one- order-of-magnitude better sensitivity than other sub-PeV gamma-ray observatories. To...
The Cherenkov Telescope Array Observatory (CTAO), the new transformational ground-based instrument for the study of high-energy phenomena in the Universe, is currently under construction, with the first Large Size Telescopes (LSTs) already operational in the Canary Islands, Spain. A significant component of the U.S. effort in CTAO consortium, along with those of international partners, has...
I will review the important progress made in recent years towards understanding the origin of ultra-high-energy cosmic rays from a theoretical perspective.
Located in the southern field of view of the High Altitude Water Cherenkov (HAWC) observatory, the eHWC J1825-134 region is one of the most complicated gamma-ray emission sites on the galactic plane. The region contains a few PeVatron candidates that can accelerate particles up to PeV energies. Disentangling the overlapping gamma-ray emission and associating it with accelerators is crucial to...
