arXiv subjects

Deep Jyoti Das

Publications and source records attributed to Deep Jyoti Das.

3 recordsLinked to original sources

arXiv2026

Not so good $\nu$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

Too Heavy to Hide: Gamma-Ray Constraints on Annihilating Dark Matter beyond Unitarity

The measurement of high energy diffuse gamma rays by various ground-based air shower detectors have opened a new chapter for high energy particle physics and astrophysics. The broad range of viable dark matter candidates motivates extending indirect searches to heavier dark matter masses, opening new opportunities to uncover the nature of dark matter. If dark matter is composite rather than point-like, then the thermal unitarity bound can be relaxed, opening up the possibility of dark matter masses far beyond the electroweak scale. We perform a model agnostic search for heavy annihilating dark matter using the gamma-ray measurements and upper limits from Tibet AS$_\gamma$, LHAASO, KASCADE-Grande, Pierre Auger Observatory, and Telescope Array. These highest energy datasets enable us to probe new regions of parameter space and set world-leading limits on the annihilation cross sections for dark matter masses $10^5$--$10^{12}$ GeV. Our work highlights the power of high energy gamma-ray datasets in discovering heavy dark matter signatures in the near future.

hep-ph↗

arXiv2025

Galaxy Mergers Collectively Illuminate the $γ$-Ray Sky

The origin and acceleration mechanism of cosmic rays (CRs) remain fundamental open questions. Galaxy mergers are proposed as very high-energy CR accelerators, which are expected to produce high-energy (HE) $γ$ rays and neutrinos through interactions with the ambient gas and low-energy background radiation fields. For the first time, we systematically study the HE $γ$-ray emission from galaxy mergers utilising 16.7 years of Fermi Large Area Telescope (Fermi-LAT) data with the sample list compiled from eight survey catalogs. Our analysis finds 8 galaxy mergers that exhibit $γ$-ray emission with significance $\gtrsim5σ$ in the 1-500 GeV energy range. A stacking analysis of the remaining faint galaxy mergers yields a combined $γ$-ray emission detected at $\sim 35σ$ significance, a best-fit spectral index of $Γ\approx 2.07$, and an energy flux of $\sim \rm 2\times10^{-14}~erg~cm^{-2}~s^{-1}$. We compare the stacked spectral energy distributions of the galaxy mergers with the projected sensitivity of the upcoming $γ$-ray telescope Cherenkov Telescope Array (CTA). Furthermore, we find that 18 previously unassociated Fermi-LAT sources are spatially coincident with galaxy mergers. Our findings establish galaxy mergers as a new class of HE $γ$-ray sources. Future neutrino and $γ$-ray observatories will be crucial to discover the particle acceleration mechanism in these newly identified CR sources.

astro-ph.HE↗