Dark gauge boson production from neutron stars via nucleon-nucleon bremsstrahlung

TL;DR

This paper investigates how dark gauge bosons could be emitted from neutron stars through nucleon-nucleon bremsstrahlung, deriving new constraints on their properties based on stellar cooling observations and improving previous bounds.

Contribution

It provides a rigorous derivation of dark gauge boson couplings in medium and revisits constraints from supernova observations, including effects of polarization modes.

Findings

Enhanced constraints on gauge coupling from transverse polarization emission.

Newly excluded parameter space due to longitudinal polarization emission.

Revised bounds on $U(1)_{B-L}$ gauge boson from SN1987A data.

Abstract

We discuss the dark gauge boson emission from neutron stars via nucleon-nucleon bremsstrahlung. Through the rigorous treatment of the effective field theory prescription and the thermal effect, we derive the relevant couplings of dark gauge bosons to hadrons in medium. As a specific example, the $U(1)_{\rm B-L}$ gauge boson scenario is chosen to investigate dark gauge boson emissivities during supernovae and cooling of young neutron stars. From the stellar cooling argument, we obtain the constraints on the $\rm B-L$ gauge coupling for given gauge boson masses in two observations: the duration of the supernova neutrino signal of SN1987A, and the inferred x-ray luminosity of the compact object in the remnant of SN1987A (NS1987A). In particular, the constraint from SN1987A on the $U(1)_{\rm B-L}$ gauge boson scenario is revisited. The excluded gauge coupling due to the emission of transverse polarizations is an order of magnitude enhanced compared to the previous derivation. There is also a newly excluded parameter space due to the emission of longitudinal polarizations.