Probing light mediators at ultra-low threshold energies with coherent elastic neutrino-nucleus scattering

TL;DR

This paper explores how ultra-low threshold detectors combined with neutrino sources can significantly improve constraints on light neutral mediators, especially through nuclear scattering channels.

Contribution

It demonstrates the potential of terrestrial neutrino experiments with low-threshold detectors to set stronger bounds on light mediators than previous methods.

Findings

Nuclear scattering provides the most stringent bounds on light mediators.

Low-threshold detectors improve sensitivity to mediator masses above 0.1 GeV.

Complementary sensitivity from neutrino-nucleus and neutrino-electron channels.

Abstract

Light neutral mediators, with mass $\lesssim 1$ GeV, are common features of extensions to the Standard Model (SM). Current astrophysical and terrestrial experiments have constrained the model parameter space, and planned experiments around the world promise continued improvement in sensitivity. In this paper we study the prospects for probing light neutral mediators using terrestrial stopped pion and reactor sources in combination with ultra-low threshold nuclear and electron recoil detectors. We show that the coherent neutrino-nucleus and neutrino-electron scattering channels provide complementary sensitivity to light mediators. With low threshold detectors, we show that most stringent bounds on models arise from the nuclear scattering process, improving upon previous bounds from electron scattering of solar neutrinos by nearly an order of magnitude for mediator masses $\gtrsim 0.1$ GeV.