Search for Ultraheavy Dark Matter from Observations of Dwarf Spheroidal Galaxies with VERITAS

TL;DR

This study used VERITAS gamma-ray observations of dwarf galaxies to search for signals from ultraheavy dark matter particles, setting new constraints on their annihilation properties in the mass range up to 30 PeV.

Contribution

First search for ultraheavy dark matter annihilation signals using gamma-ray data from dwarf galaxies with VERITAS, extending the mass range beyond previous WIMP-focused studies.

Findings

No gamma-ray signals detected from UHDM annihilation.

Constraints placed on the annihilation cross section for masses 1 TeV to 30 PeV.

Limits on the size of composite UHDM particles.

Abstract

Dark matter is a key piece of the current cosmological scenario, with weakly interacting massive particles (WIMPs) a leading dark matter candidate. WIMPs have not been detected in their conventional parameter space (100 GeV $\lesssim M_{\chi} \lesssim$ 100 TeV), a mass range accessible with current Imaging Atmospheric Cherenkov Telescopes. As ultraheavy dark matter (UHDM; $M_{\chi} \gtrsim$ 100 TeV) has been suggested as an under-explored alternative to the WIMP paradigm, we search for an indirect dark matter annihilation signal in a higher mass range (up to 30 PeV) with the VERITAS gamma-ray observatory. With 216 hours of observations of four dwarf spheroidal galaxies, we perform an unbinned likelihood analysis. We find no evidence of a $\gamma$-ray signal from UHDM annihilation above the background fluctuation for any individual dwarf galaxy nor for a joint-fit analysis, and consequently constrain the velocity-weighted annihilation cross section of UHDM for dark matter particle masses between 1 TeV and 30 PeV. We additionally set constraints on the allowed radius of a composite UHDM particle.