Probing SUSY at Gravitational Wave Observatories

TL;DR

This paper explores how gravitational wave observatories can detect signs of supersymmetry (SUSY) through changes in particle degrees of freedom, potentially revealing SUSY effects even at very high particle masses.

Contribution

It demonstrates that future GW detectors could identify SUSY signatures via the doubling of degrees of freedom, beyond collider reach, even with entropy dilution effects.

Findings

SUSY signatures could be detected at Einstein Telescope and Cosmic Explorer for particles up to 10^4 TeV.

Detection is possible despite entropy dilution from late-decaying fields.

Any theory predicting increased particle degrees of freedom could be probed through GW observations.

Abstract

Under the assumption that the recent pulsar timing array evidence for a stochastic gravitational wave (GW) background at nanohertz frequencies is generated by metastable cosmic strings, we analyze the potential of present and future GW observatories for probing the change of particle degrees of freedom caused, e.g., by a supersymmetric (SUSY) extension of the Standard Model (SM). We find that signs of the characteristic doubling of degrees of freedom predicted by SUSY could be detected at Einstein Telescope and Cosmic Explorer even if the masses of the SUSY partner particles are as high as about $10^4$ TeV, far above the reach of any currently envisioned particle collider. We also discuss the detection prospects for the case that some entropy production, e.g. from a late decaying modulus field inducing a temporary matter domination phase in the evolution of the universe, somewhat dilutes the GW spectrum, delaying discovery of the stochastic GW background at LIGO-Virgo-KAGRA. In our analysis we focus on SUSY, but any theory beyond the SM predicting a significant increase of particle degrees of freedom could be probed this way.