arXiv subjects

Abhijeet Singh

Publications and source records attributed to Abhijeet Singh.

3 recordsLinked to original sources

arXiv2026

Not so good $ν$s for Higgsino dark matter as LZ excess: stringent limits from Super-Kamiokande and IceCube

The LUX-ZEPLIN (LZ) collaboration has recently reported a single nuclear recoil event at a high recoil energy of about 250 keV. This has been interpreted as inelastic scattering of dark matter that is a supersymmetric Higgsino with a mass splitting between the neutral states of a few 100 keV. Such dark matter may be captured at high recoil in the Sun through scattering on heavy elements in it, and annihilate to $W^+W^-$ and $ZZ$, in turn giving rise to a neutrino flux detectable on Earth. Using measurements of atmospheric electron- and muon-neutrino fluxes by Super-Kamiokande and IceCube, we constrain thermal and non-thermal Higgsino dark matter, excluding inter-state mass splittings $\lesssim 557$ keV. This disfavors Higgsino-like interpretations of the LZ event for standard halo velocities.

hep-ph↗

arXiv2026

Dark Secrets of Baryons: Illuminating Dark Matter-Baryon Interactions with JWST

The James Webb Space Telescope (JWST) has discovered bright galaxies at high redshifts ($z\approx 10-14$) and various galaxy candidates extending to even higher redshifts ($z\approx 15-30$). Many astrophysical and beyond the Standard Model physics scenarios have been proposed to explain these observations. We investigate, {\it for the first time}, the implications of dark matter (DM) scattering with baryons (protons and electrons) in light of the JWST UV luminosity function (UVLF) observations. These interactions suppress structure formation on galactic scales, which may have an observable effect on the UVLF measurements at high redshifts. Using a recent galaxy formation model designed to explain high redshift observations, we obtain strong upper limits on DM-baryon scattering cross-sections and explore new regions of the parameter space. For DM-proton scattering with cross-section $\propto v^{-2}$ velocity dependence, we obtain the strongest limit for DM masses of $\sim$ 1 -- 500 MeV. For other cases that we study (DM-proton scattering cross-section $\propto v^{0},\,v^{-4}$ and DM-electron scattering cross-section $\propto v^{0},\,v^{-2},\,v^{-4}$, our limits are competitive with those obtained from other cosmological observables. Our study highlights the potential of JWST observations as a novel and powerful probe of non-gravitational interactions of DM.

hep-ph↗

arXiv2025

Hunting Primordial Black Hole Dark Matter in Lyman-$α$ Forest

A very pressing question in contemporary physics is the identity of Dark Matter (DM). Primordial Black Holes (PBHs) are one of the most well-motivated DM candidates. Light PBHs have been constrained by either the non-detection of their Hawking radiation itself, or by the non-observation of any measurable effects of this radiation on astrophysical and cosmological observables. We constrain the PBH contribution to the DM density by non-detection of their Hawking radiation's effect on the intergalactic medium (IGM) temperature evolution. We use the latest deductions of IGM temperature from Lyman-$α$ forest observations. We put constraints on the fraction of DM as PBHs with masses $5 \times 10^{15}$ g - $10^{17}$ g, separately for spinning and non-spinning BHs. We derive constraints by dealing with the heating effects of the astrophysical reionization sources on the IGM in two ways. In one way, we completely neglect this heating due to astrophysical sources, thus giving us weaker constraints, but completely robust to the reionization history of the universe. In the second way, we utilise some modelling of the ionization and temperature history, and use it to derive more stringent constraints. We find that for non-spinning PBHs of mass $10^{16}$ g, the current measurements can constrain the PBH-density to be $\lesssim$ 0.1\% of the total DM. We find that these constraints are competitive, and hence provide a new observable to probe the nature of PBH DM. The systematics affecting Lyman-$α$ forest measurements are different from other constraining observations, and thus this is a complementary probe.

astro-ph.CO↗