Supernova Limits on Muonic Dark Forces

TL;DR

This paper investigates how supernova observations constrain models of muonic dark forces, showing that supernova cooling limits can surpass current laboratory bounds on new physics involving muons and dark fermions.

Contribution

It provides the first detailed calculation of supernova constraints on light dark fermions coupled via a new vector boson, extending to effective operators and applying to the $L_-L_ au$ model.

Findings

SN 1987A constrains dark fermion models up to ~7 TeV.

Supernova limits exclude significant parameter space for future experiments.

Constraints are stronger than current laboratory bounds.

Abstract

Proto-neutron stars formed during core-collapse supernovae are hot and dense environments that contain a sizable population of muons. If these interact with new long-lived particles with masses up to roughly 100 MeV, the latter can be produced and escape from the stellar plasma, causing an excessive energy loss constrained by observations of SN 1987A. In this article we calculate the emission of light dark fermions that are coupled to leptons via a new massive vector boson, and determine the resulting constraints on the general parameter space. We apply these limits to the gauged $L_\mu-L_\tau$ model with dark fermions, and show that the SN 1987A constraints exclude a significant portion of the parameter space targeted by future experiments. We also extend our analysis to generic effective four-fermion operators that couple dark fermions to muons, electrons, or neutrinos. We find that SN 1987A cooling probes a new-physics scale up to $\sim7$ TeV, which is an order of magnitude larger than current bounds from laboratory experiments.