论文标题
识别中微子振荡背后的最小风味对称性
Towards identifying the minimal flavor symmetry behind neutrino oscillations
论文作者
论文摘要
当前的中微子振荡数据表明$ 3 \ times 3 $ Pontecorvo-Maki-Nakagawa-sakata矩阵$ u $ u $ u $展示$μ$ - $μ$ - $τ$ floes interchange symmetry $ | u^{} _ {μi} _ {μi} | = | u^{} _ {τi} | $（对于$ i = 1，2，3 $）作为一个很好的近似值。特别是，T2K测量意味着最大的中微子混合角$θ^{} _ {23} $和CP-violation阶段$δ$应分别接近$π/4 $和$-π/2 $。这些观察的背后是最小的风味对称性 - - 有效的主要中微子质量术语在转换下保持不变性$ν^{} _ {e \ rm l} \ to（ν^{} {} _ {e \ rm l}） （ν^{} _ {τ\ rm l}）^c $和$ν^{} _ {τ\ rm l} \ to（ν^{} _ {μ\ rm l}）^c $。将这种风味对称性扩展到规范的Seesaw机制，我们发现$ r $ -matrix描述了弱充电相互作用的强度，重物较大的主要中微子可以满足$ | r^{} _ {μii} | = | r^{} _ {τi} | $，因为$ | u^{} _ {μi} | = | u^{} _ {τi} | $。该结果可用于设置一个新的上限，该界限比以前更严格三个数量级，与带电的lepton-fravor-lover-lover-violation衰减模式$τ^ - \ to e^ - +γ$相关的风味混合因子。
Current neutrino oscillation data indicate that the $3\times 3$ Pontecorvo-Maki-Nakagawa-Sakata matrix $U$ exhibits a $μ$-$τ$ flavor interchange symmetry $|U^{}_{μi}| = |U^{}_{τi}|$ (for $i = 1, 2, 3$) as a good approximation. In particular, the T2K measurement implies that the maximal neutrino mixing angle $θ^{}_{23}$ and the CP-violating phase $δ$ should be close to $π/4$ and $-π/2$, respectively. Behind these observations lies a minimal flavor symmetry -- - the effective Majorana neutrino mass term keeps invariant under the transformations $ν^{}_{e \rm L} \to (ν^{}_{e \rm L})^c$, $ν^{}_{μ\rm L} \to (ν^{}_{τ\rm L})^c$ and $ν^{}_{τ\rm L} \to (ν^{}_{μ\rm L})^c$. Extending this flavor symmetry to the canonical seesaw mechanism, we find that the $R$-matrix describing the strength of weak charged-current interactions of heavy Majorana neutrinos satisfies $|R^{}_{μi}| = |R^{}_{τi}|$ as a consequence of $|U^{}_{μi}| = |U^{}_{τi}|$. This result can be used to set a new upper bound, which is about three orders of magnitude more stringent than before, on the flavor mixing factor associated with the charged-lepton-flavor-violating decay mode $τ^- \to e^- + γ$.
