Measuring properties of a dark photon from semi-invisible decay of the Higgs boson

TL;DR

This paper explores how properties of a dark photon could be measured at the LHC through Higgs decays, assessing detection prospects, distinguishing signals, and potential decay channels.

Contribution

It provides new methods to estimate dark photon mass limits, distinguish dark photon signals from similar processes, and explores additional decay channels at the LHC.

Findings

Upper limit on massless dark photon established

Feasibility of distinguishing dark photon signals from gravitino-related decays analyzed

Potential observation of Higgs decay to dark photon and Z boson discussed

Abstract

Considerable efforts have been dedicated to discovering a dark photon via the decay of the Higgs boson to a photon and an invisible particle. A subject that is still mostly unexplored is which properties of the dark photon could be measured at the LHC if an excess were to be found in this channel and whether we could determine if this signal is indeed that of a dark photon. In this paper, we seek to address some of these questions for two Higgs production channels: gluon-fusion and $Z$-associated. First, prospects are presented for the upper limit on the mass of a massless dark photon and for the uncertainty on the mass of a massive dark photon. Second, we study the feasibility of distinguishing this signal from that of the Higgs decaying to a gravitino and a neutralino that decays to a photon and another gravitino. Finally, the complementary possibility of observing the decay of the Higgs to a dark photon and a $Z$ boson is studied.