Double-hit signature of millicharged particles in 3D segmented neutrino detector

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