Higgs Decays as a Window into the Dark Sector

TL;DR

This paper investigates Higgs boson decays into a dark sector gauge boson Z_d and other particles, estimating decay rates and exploring how LHC measurements can reveal properties of the dark sector and distinguish underlying physics.

Contribution

It provides theoretical estimates of Higgs decay rates into dark sector particles and discusses how LHC measurements can probe dark sector interactions and distinguish different models.

Findings

Decay rates depend on Z_d coupling and mixing mechanisms.

LHC can potentially measure these rare Higgs decays.

Z_d polarization analysis helps identify underlying physics.

Abstract

A light vector boson, Z_d, associated with a "dark sector" U(1)_d gauge group has been introduced to explain certain astrophysical observations as well as low energy laboratory anomalies. In such models, the Higgs boson may decay into X+Z_d, where X=Z, Z_d or \gamma. Here, we provide estimates of those decay rates as functions of the Z_d coupling through either mass-mixing (e.g. via an enlarged Higgs mechanism) or through heavy new fermion loops and examine the implied LHC phenomenology. Our studies focus on the higher m_{Z_d} case, > several GeV, where the rates are potentially measurable at the LHC, for interesting regions of parameter spaces, at a level complementary to low energy experimental searches for the Z_d. We also show how measurement of the Z_d polarization (longitudinal versus transverse) can be used to distinguish the physics underlying these rare decays.