Searching for GeV-scale new Gauge Bosons in QGP thermal dilepton production

TL;DR

This paper proposes using thermal dilepton spectra from the Quark-Gluon Plasma in heavy-ion collisions to search for GeV-scale dark gauge bosons, setting new limits on their couplings and suggesting future experimental prospects.

Contribution

It introduces a novel method to detect GeV-scale dark gauge bosons via resonant enhancement in QGP dilepton spectra and provides the first experimental upper limits in this context.

Findings

Resonant enhancement of dilepton spectrum at gauge boson mass

Upper limit on gauge boson coupling: chi_q chi_e < 10^(-3)

Potential for future detection by ALICE experiment

Abstract

In this paper we propose to use the measurement of the thermal Quark-Gluon Plasma (QGP) dilepton spectra in the Intermediate Mass Region (IMR) of heavy-ion collisions, as a new method to search for GeV-scale dark gauge bosons (gamma' or Z'). Such light mediators are a common feature of light (i.e. low mass) dark matter scenarios, which have been invoked to explain puzzling signals in dark matter indirect and direct detection experiments. First we show that a light gamma' or Z' will generate a resonant enhancement of the dilepton spectrum produced thermally by the QGP, at an energy corresponding to the dark gauge boson mass. Secondly, using data from the PHENIX experiment, we are able to set an upper limit on the combined coupling of this new gauge boson to quarks and leptons (independently of their vectorial or axial nature) chi_q chi_e < 10^(-3) at the 95% confidence level for a gauge boson mass in the range 1.5 - 2.5 GeV. This result complements previous searches for new light gauge bosons and probes a new region of the parameter space, particularly interesting in the case of non-universal couplings to quarks and leptons. Prospects for the discovery of such a boson by the ALICE collaboration are also discussed.