Speaker
Description
The excess in electron recoil events reported recently by the XENON1T experiment may be interpreted as evidence for a sizable transition magnetic moment of Majorana neutrinos. We show the consistency of this scenario when a single component transition magnetic moment takes values ϵ (1.65 - 3.42) × $10^{-11}$ $\mu_B$. Such a large value typically leads to unacceptably large neutrino masses. We show that new leptonic symmetries can solve this problem and demonstrate this with several examples. We first revive and then propose a simplified model based on SU(2)$_H$ horizontal symmetry and also generalize to a three-family SU(3)$_H$ -symmetry. Collider and low energy tests of these models are analyzed. We have also analyzed implications of the XENON1T data for the Zee model and its extensions which naturally generate a large neutrino magnetic moment with suppressed m$_\nu$ via a spin symmetry mechanism, but found that it is not large enough to explain recent data. We also propose a mechanism to evade stringent astrophysical limits on neutrino magnetic moments arising from stellar evolution by inducing a medium-dependent mass for the neutrino. Results will be discussed in this talk.
| Working group | WG5 |
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