Sensitivity of spherical gravitational-wave detectors to a stochastic background of non-relativistic scalar radiation

TL;DR

This paper investigates how spherical gravitational-wave detectors can better detect non-relativistic scalar backgrounds, showing enhanced sensitivity compared to interferometers due to lack of suppression and faster signal growth over time.

Contribution

It demonstrates that spherical detectors have increased sensitivity to non-relativistic scalar gravitational waves, especially for flat spectra, due to unique interaction properties.

Findings

Enhanced signal-to-noise ratio for non-relativistic scalar backgrounds

No suppression of signals for non-relativistic scalars compared to massless particles

Signal growth over observation time is faster than in massless stochastic backgrounds

Abstract

We analyze the signal-to-noise ratio for a relic background of scalar gravitational radiation composed of massive, non-relativistic particles, interacting with the monopole mode of two resonant spherical detectors. We find that the possible signal is enhanced with respect to the differential mode of the interferometric detectors. This enhancement is due to: {\rm (a)} the absence of the signal suppression, for non-relativistic scalars, with respect to a background of massless particles, and {\rm (b)} for flat enough spectra, a growth of the signal with the observation time faster than for a massless stochastic background.