Double-Hit Signature of Millicharged Particles in 3D segmented neutrino detector

TL;DR

This paper investigates the potential to detect millicharged particles using a double-hit signature in neutrino detectors at T2K and T2HK, revealing new sensitivity to previously unexplored charge ranges for sub-GeV MCPs.

Contribution

It introduces a novel double-hit detection method in neutrino experiments to search for millicharged particles, extending the sensitivity to lower charge values.

Findings

Proposes a background-free double-hit signature for MCP detection.

Estimates sensitivity to MCP charges between 5×10^{-4} and 10^{-2} e.

Identifies a new parameter space region accessible to future experiments.

Abstract

We calculate the production of hypothetical millicharged particles (MCPs) of sub-GeV masses by the J-PARC proton beam in the framework of T2K and future T2HK neutrino oscillation experiments. Concentrating on the region of model parameter space, where an MCP can hit the near neutrino detector twice, we adopt this background-free signature to estimate the sensitivity of T2K and T2HK experiments to MCPs. We find that a previously inaccessible in direct searches region of charges 5$\times$$10^{-4}$-$10^{-2}$ $e$ for MCP masses 0.1-0.5 GeV can be probed.