Probing muonic forces with neutron star inspirals

2020-01-18T16:48:31Z (GMT) by Laha, Ranjan

We show that gravitational wave emission from neutron star binaries can be used to discover any generic long-ranged muonic force due to the large inevitable abundance of muons inside neutron stars. As a minimal consistent example, we focus on a gauged U(1) $L_\mu L_\tau$ symmetry. In pulsar binaries, such U(1) $L_\mu L_\tau$ vectors induce an anomalously fast decay of the orbital period through the emission of dipole radiation. We study a range of different pulsar binaries, finding the most powerful constraints for vector masses below $\mathcal{O}(10^{−18}$ eV). For merging binaries the presence of muons in neutron stars can result in dipole radiation as well as a modification of the chirp mass during the inspiral phase. We make projections for a prospective search using the GW170817 event and find that current data can discover light vectors with masses below $\mathcal{O}(10^{−10}$ eV). In both cases, the limits attainable with neutron stars reach gauge coupling g′ $\lesssim 10^{−20}$, which are many orders of magnitude stronger than previous constraints. We also show projections for next generation experiments, such as Einstein Telescope and Cosmic Explorer.