Abstract
Small discrete family symmetries such as S4, A4 or A5 may lead to simple leading-order predictions for the neutrino mixing matrix such as the bimaximal, tribimaximal or golden ratio mixing patterns, which may be brought into agreement with experimental data with the help of corrections from the charged-lepton sector. Such scenarios generally lead to relations among the parameters of the physical leptonic mixing matrix known as solar lepton mixing sum rules. In this article, we present a simple derivation of such solar sum rules, valid for arbitrary neutrino and charged lepton mixing angles and phases, assuming only {\theta}13^{\nu} = {\theta}13^e = 0. We discuss four leading-order neutrino mixing matrices with {\theta}13^{\nu} = 0 which are well motivated from family symmetry considerations. We then perform a phenomenological analysis of the scope to test the resulting four solar sum rules, highlighting the complementarity between next-generation neutrino oscillation experiments such as the reactor experiment JUNO and a superbeam experiment.
Highlights
Subgroups of an underlying discrete family symmetry
Atmospheric sum rules [11] arise from a variety of “semi-direct” models in which only half of the Klein symmetry emerges from the discrete family symmetry, classified in terms of finite von Dyck groups, with charged lepton mixing controlled by the T generator [12,13,14]
We have presented a succinct derivation of solar lepton mixing sum rules, arising from simple patterns of neutrino mixing with θ1ν3 = 0, enforced by discrete family symmetry and corrected by a rather generic charged lepton mixing matrix, assuming only that θ1e3 = 0
Summary
We present a simple derivation of the solar sum rule of eq (1.6). In later subsections we discuss the leading-order mixing patterns which one encounters in the considered class of models. We shall find that there are only four well-motivated patterns of interest, whose relation to model building will be discussed
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