Search for exotic neutrino-electron interactions using solar neutrinos in XMASS-I

Abstract

We have searched for exotic neutrino-electron interactions that could be produced by a neutrino millicharge, by a neutrino magnetic moment, or by dark photons using solar neutrinos in the XMASS-I liquid xenon detector. We observed no significant signals in 711 days of data. We obtain an upper limit for neutrino millicharge of 5.4$\times$10${}^{-12}e$ at 90\% confidence level assuming all three species of neutrino have common millicharge. We also set flavor dependent limits assuming the respective neutrino flavor is the only one carrying a millicharge, $7.3\times 10^{-12}e$ for $\hat{I}{½}_e$, $1.1\times 10^{-11}e$ for $\hat{I}{½}_{\hat{I}}¼$, and $1.1\times 10^{-11}e$ for $\hat{I}{½}_{\ddot{I}}„$. These limits are the most stringent yet obtained from direct measurements. We also obtain an upper limit for the neutrino magnetic moment of 1.8$\times$10${}^{-10}$ Bohr magnetons. In addition, we obtain upper limits for the coupling constant of dark photons in the $U(1{)}_{B-L}$ model of 1.3$\times$10${}^{-6}$ if the dark photon mass is 1$\times 10^{-3}$ MeV$/c^2$, and 8.8$\times$10${}^{-5}$ if it is 10 MeV$/c^2$.