Constraints on millicharged particles by neutron stars

Abstract: We have constrained the charge-mass ($\varepsilon-m$) phase space of millicharged particles through the simulation of the rotational evolution of neutron stars, where an extra slow-down effect due to the accretions of millicharged dark matter particles is considered. For a canonical neutron star of $M=1.4~M_{\odot}$ and $R=10~{\rm km}$ with typical magnetic field strength $B_{0}=10<sup>{12}$ G, we have shown an upper limit of millicharged particles, which is compatible with recently experimental and observational bounds. Meanwhile, we have also explored the influences on the $\varepsilon-m$ phase space of millicharged particles for different magnetic fields $B_{0}$ and dark matter density $\rho_{\rm{DM}}$ in the vicinity of the neutron star.