Radiative corrections to the lepton flavor mixing in dense matter

Abstract

One-loop radiative corrections will lead to a small difference between the matter potentials developed by $\nu_\mu^{}$ and $\nu_{\tau}$ when they travel in a medium. By including such radiative corrections, we derive the exact expressions of the corresponding effective mass-squared differences and the moduli square of the lepton flavor mixing matrix elements $|\widetilde U_{\alpha i}^{}|^2$ (for $\alpha=e,\mu,\tau $ and $i=1,2,3$) in matter in the standard three-flavor mixing scheme and focus on their asymptotic behaviors when the matter density is very big (i.e., the matter effect parameter $A\equiv 2\sqrt{2} G_{\rm F}^{} N_e^{}E$ is very big). Different from the non-trivial fixed value of $|\widetilde U_{\alpha i}^{}|^2$ in the $A\to \infty$ limit in the case without radiative corrections, we get $|\widetilde U_{\alpha i}^{}|^2=0~{\rm or}~1$ under this extreme condition. The radiative corrections can significantly affect the lepton flavor mixing in dense matter, which are numerically and analytically discussed in detail. Furthermore, we also extend the discussion to the $(3+1)$ active-sterile neutrino mixing scheme.