Sensitivity to sub-GeV dark matter in forthcoming spallation-source neutrino experiments

TL;DR

This paper explores how upcoming neutrino experiments at spallation sources can detect sub-GeV dark matter via neutral pion decays, offering new avenues for probing elusive dark matter models beyond traditional methods.

Contribution

It introduces a novel sensitivity analysis of future neutrino detectors to light dark matter produced in pion decays, comparing simulation approaches and highlighting potential for new discoveries.

Findings

Upcoming neutrino detectors can test unexplored dark matter parameter space.

GEANT4 and Sandford-Wang approaches yield consistent predictions.

Facilities like ESS, J-PARC, and CSNS can enhance the search for secluded sectors.

Abstract

Sub-GeV thermal dark matter weakly interacting with the Standard Model through vector-portal mediators provides a well-motivated and predictive framework that remains challenging to probe with conventional direct detection experiments. Motivated by the rapid development of neutrino facilities based on spallation neutron sources, we study the sensitivity of future coherent elastic neutrino-nucleus scattering experiments to light dark matter produced in neutral pion decays. We consider scalar dark matter interactions mediated by two different vector portals, a generic dark photon and a baryophilic vector mediator. The neutral pion yield is calculated through a GEANT4 simulation and the results are compared with those obtained with the Sandford-Wang parametrization. We show that predictions based on either approach do not produce significant differences. Our results demonstrate that upcoming low-threshold neutrino detectors at the European Spallation Source (ESS), the Japan Proton Accelerator Research Complex (J-PARC) and the China Spallation Neutron Source (CSNS) may test regions in parameter space not yet explored, or be competitive with existing bounds. We point out that these facilities will strengthen the global experimental program searching for secluded sectors.