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arXiv 0802.3241hep-ph
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弱电标度右手中微子模型中轻子味破坏μ子衰变

Lepton Flavor Violating Muon Decays in a Model of Electroweak-Scale Right-Handed Neutrinos

Jian-Ping Bu, Yi Liao, Ji-Yuan Liu

摘要:

在中微子振荡中观察到的小中微子质量可以用跷跷板机制很好地解释。如果重中微子不比电弱标度重得多,则通常会有丰富的现象学。一个模型与此功能内置已建议最近由洪。该模型保留了标准规范群,但为费米子引入了手征翻转的伙伴。特别是,右手中微子与带电的重轻子形成一个弱偶线,因此是活跃的。我们分析了规范相互作用中的轻子味结构。荷电电流中的混合矩阵通常是非幺正的,它们偏离幺正性会导致味变中性电流。我们计算了稀有衰变μ \to eγ和μ \to ee \bar e由于规范相互作用引起的分支比.虽然前者通常比后者小三个数量级,但即使考虑到μ \to ee \bar e的当前严格界限,也存在μ \to eγ在下一代实验中可达的参数区域。如果轻中微子在μ \to eγ中占主导地位,则由于CC和FCNC贡献之间的显著抵消,后者不能对轻轻子混合矩阵中的幺正性破坏设定有意义的界限。相反,该作用由衰变μ \to ee \bar e接管。

英文摘要:

The small neutrino mass observed in neutrino oscillations is nicely explained by the seesaw mechanism. Rich phenomenology is generally expected if the heavy neutrinos are not much heavier than the electroweak scale. A model with this feature built in has been suggested recently by Hung. The model keeps the standard gauge group but introduces chirality-flipped partners for the fermions. In particular, a right-handed neutrino forms a weak doublet with a charged heavy lepton, and is thus active. We analyze the lepton flavor structure in gauge interactions. The mixing matrices in charged currents (CC) are generally non-unitary, and their deviation from unitarity induces flavor changing neutral currents (FCNC). We calculate the branching ratios for the rare decays μ\to eγand μ\to ee\bar e due to the gauge interactions. Although the former is generally smaller than the latter by three orders of magnitude, parameter regions exist in which μ\to eγis reachable in the next generation of experiments even if the current stringent bound on μ\to ee\bar e is taken into account. If light neutrinos dominate for μ\to eγ, the latter cannot set a meaningful bound on unitarity violation in the mixing matrix of light leptons due to significant cancelation between CC and FCNC contributions. Instead, the role is taken over by the decay μ\to ee\bar e.

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