# Light dark matter in a gauged $U\left(1{\right)}_{{L}_{\mu }-{L}_{\tau }}$ model

Foldenauer, Patrick (Institut für Theoretische Physik, Universität Heidelberg, Philosophenweg 16, 69120 Heidelberg, Germany)

08 February 2019

Abstract: As experimental null results increase the pressure on heavy weakly interacting massive particles (WIMPs) as an explanation of thermal dark matter (DM), it seems timely to explore previously overlooked regions of the WIMP parameter space. In this work we extend the minimal gauged $U\left(1{\right)}_{{L}_{\mu }-{L}_{\tau }}$ model studied in [M. Bauer, P. Foldenauer, and J. Jaeckel, J. High Energy Phys. 07 (2018) 094.] by a light (MeV-scale) vectorlike fermion $\chi$. Taking into account constraints from cosmology, direct and indirect detection we find that the standard benchmark of ${M}_{V}=3{m}_{\chi }$ for DM coupled to a vector mediator is firmly ruled out for unit DM charges. However, exploring the near-resonance region ${M}_{V}\gtrsim 2{m}_{\chi }$ we find that this model can simultaneously explain the DM relic abundance $\Omega {h}^{2}=0.12$ and the $\left(g-2{\right)}_{\mu }$ anomaly. Allowing for small charge hierarchies of $\lesssim O\left(10\right)$, we identify a second window of parameter space in the few-GeV region, where $\chi$ can account for the full DM relic density.

Published in: Physical Review D 99 (2019)