Leptobaryons as Majorana Dark Matter

TL;DR

This paper investigates a minimal gauged $U(1)_B$ model where a Majorana fermion naturally emerges as a dark matter candidate, analyzing its collider signatures and constraints from dark matter observations.

Contribution

It introduces a minimal $U(1)_B$ model with a Majorana dark matter candidate and explores its phenomenology, including collider signals and dark matter constraints.

Findings

Dark matter candidate is a Majorana fermion stabilized by a $Z_2$ symmetry.

Constraints on symmetry breaking scale from LHC dijet searches.

Potential collider signatures from Higgs mixing and fermion loops.

Abstract

We explore the dark matter and collider phenomenology of the minimal gauged $U(1)_B$ model, consisting of a leptophobic $Z_B$ gauge boson, and an accompanying Higgs $S_B$. By requirement of anomaly cancellation, the fermion sector naturally contains a dark matter candidate---a Majorana isosinglet $\chi$ stabilized by an inherent $Z_2$ symmetry. The absence of evidence for $Z$ prime dijet resonances at the LHC suggests that the scale of symmetry breaking $\Lambda_{B}\gtrsim 500$ GeV. Saturation of dark matter abundance together with limits on the direct detection cross section (dominated by Higgs exchange) constrains the Higgs mixing angle to $|\theta|\lesssim 0.22$. For small mixing angles of $|\theta| \lesssim 10^{-3}$, the $\mathcal{O}(10\%)$ branching fractions of the fermion loop-mediated $S_B\rightarrow\gamma \gamma$, $Z\gamma$, $ZZ$ modes may provide clues about the fermion content of the model at the LHC.