Millicharged cosmic rays and low recoil detectors

We consider the production of a ``fast flux'' hypothetical millicharged particles (mCPs) in interstellar medium. two possible sources induced by cosmic rays: (a) $pp\ensuremath{\rightarrow}(\mathrm{meson})\ensuremath{\rightarrow}\phantom{\rule{0ex}{0ex}}(\mathrm{mCP})$, which adds to atmospheric mCPs, and (b) cosmic-ray upscattering on component dark matter. notice that galactic magnetic fields retain mCPs for long time, leading an enhancement fast flux many orders magnitude. In both scenarios, we calculate expected signal direct matter detection aimed at electron recoil. observe scenario neutrino detectors (ArgoNeuT Super-Kamiokande) still provide superior sensitivity compared (XENON1T). However, scenarios with boosted component, perform better, given upscattered low velocities. Given uncertainties, generation model actual atomic physics recoil, it is XENON1T-reported excess may come from mCP flux, will be decisively tested future experiments.