Dark hyperCharge Symmetry

TL;DR

This paper introduces a novel class of chiral $U(1)_X$ symmetries called dark hyperCharge, which include dark fermions for anomaly cancellation, with implications for dark matter and collider phenomenology.

Contribution

It systematically constructs chiral solutions for dark hyperCharge symmetries with anomaly cancellation and explores their phenomenological implications, including dark matter candidates.

Findings

Dark fermions can serve as viable dark matter candidates.

The $Z'$ gauge boson mediates interactions between dark and visible sectors.

Models satisfy current dark matter constraints across various masses.

Abstract

We introduce a new class of $U(1)_X$ symmetries where all Standard Model fermions are ``chiral," i.e., the left- and right-handed components have different charges under the $U(1)_X$ symmetry. Gauge anomaly cancellation is achieved by introducing three Standard Model gauge singlet dark fermions ($f^i$; $i=1,2,3$) charged under this symmetry. We systematically present chiral solutions for cases in which (a) one, (b) two, or (c) all three generations of Standard Model fermions are charged under the $U(1)_X$ symmetry. The $U(1)_X$ charges of these dark fermions are uniquely determined by anomaly cancellation conditions. These new fermions belong to the dark sector, with the lightest of them being a good dark matter candidate. Additionally, the $Z'$ gauge boson mediates interactions between the dark and visible sectors, and we call this $U(1)_X$ symmetry as the ``dark hyperCharge" symmetry. Using a benchmark model, we explore phenomenological implications in the heavy $Z'$ case ($M_{Z'} > M_Z$), analyzing collider constraints and examining the lightest dark fermion's viability as dark matter. Our analysis shows that it satisfies all current dark matter constraints over a wide range of dark matter mass.