New bounds on neutrino electric millicharge from limits on neutrino magnetic moment

Using the new limit on the neutrino anomalous magnetic moment recently obtained by the GEMMA experiment on measurements of the cross section for the reactor antineutrino scattering on free electrons, we get a new direct upper bound on the neutrino millicharge $\mid q_{\nu} \mid < 1.5 \times 10^{-12} e_0$. This is a factor of 2 more stringent constraint than the previous bound obtained from the TEXONO reactor experiment data that is included to the Review of Particle Properties 2012. We predict that with data from the ongoing new phase of the GEMMA experiment the upper bound on the neutrino millicharge will be reduced to $\mid q_{\nu} \mid < 3.7 \times 10^{-13}e_0$ within two years. We also predict that with the next phase of the considered experiment the upper bound on the millicharge will be reduced by an order of magnitude over the present bound and reach the level $\mid q_{\nu} \mid < 1.8 \times 10^{-13}e_0$ within approximately four years.Using the new limit on the neutrino anomalous magnetic moment recently obtained by the GEMMA experiment on measurements of the cross-section for the reactor antineutrino scattering on free electrons, we get, by comparing the neutrino magnetic moment and millicharge contributions to the total cross-section at the electron recoil energy threshold of the experiment, an order-of-magnitude estimation for a possible new direct upper bound on the neutrino electric millicharge $\mid q_{\nu}\mid \sim 1.5 \times 10^{-12} e_0$ (e(0) is the absolute value of the electron charge). This estimation is confirmed by the performed analysis of the GEMMA data using established statistical procedures and a new direct bound on the neutrino millicharge absolute value $\mid q_{\nu} \mid < 2.7 \times 10^{-12} e_0 \ (90{\%}\ \text{C.L.})$ is derived. This limit is more stringent than the previous one obtained from the TEXONO reactor experiment data that is included to the Review of Particle Properties 2012. We also predict, in an order-of-magnitude estimation, that with data from the ongoing new phase of the GEMMA experiment (GEMMA-II) the upper bound on the neutrino millicharge will reach an expected level of about $\mid q_{\nu} \mid \sim 3.7 \times 10^{-13}e_0$ within two years. We also predict that, with the next phase of the considered experiment (GEMMA-III), the upper bound on the millicharge will be reduced by an order of magnitude over the present bound and reach the level $\mid q_{\nu} \mid \sim 1.8 \times 10^{-13}e_0$ within approximately four years.Original article: EPL, 107 (2014) 21001