We propose to search for millicharged particles in electron colliders operated with the center-of-mass energies at O(1-10) GeV, which include Belle II, BESIII, BaBar, and also the proposed experiment STCF. We use the monophoton final state at electron colliders to probe the parameter space of millicharged particles, that is spanned by millicharge ϵ and mass m. We find that electron colliders have sensitivity to the previously unexplored parameter space for millicharged particles with MeV-GeV mass: ϵ≲O(10−1) for 0.5 GeV ≲m≲3.5 GeV in BaBar, ϵ≲O(10−3) for 0.1 GeV ≲m≲1.5 GeV in BESIII, ϵ≲10−3−10−2 for 0.1 GeV ≲m≲4 GeV in Belle II, and ϵ≲O(10−4) for 1 MeV ≲m≲1 GeV in STCF.
@article{arxiv.1909.06847,
title = {Millicharged particles at electron colliders},
author = {Jinhan Liang and Zuowei Liu and Yue Ma and Yu Zhang},
journal= {arXiv preprint arXiv:1909.06847},
year = {2021}
}