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arXiv 2409.13249hep-ph
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带单电荷标量的最大味破坏$U(1)_{L_μ-L_τ}$模型

Maximal flavor violating $U(1)_{L_μ-L_τ}$ model with singly-charged scalar

Fei Huang, Jin Sun

AI总结:

本研究针对$U(1)_{L_μ-L_τ}$ $Z'$模型中味守恒约束及味破坏情形下$(g-2)_μ$与$τ\toμν\barν$的参数冲突,引入单电荷标量,发现仅弱三重态对应的标量可缓解该张力并解释电子$(g-2)_e$反常,为$U(1)$框架研究提供新思路。

摘要:

$U(1)_{L_μ-L_τ}$ $Z'$模型已成为解决长期存在的μ子$(g-2)_μ$反常问题的颇具潜力的候选方案。味守恒的$Z'$相互作用受到中微子三叉戟过程和NA64$μ$实验的严格约束,这些约束将$Z'$质量限制在$m_{Z'}<40$ MeV。为规避这些约束,可通过离散交换对称性将味守恒的$Z'$相互作用转化为最大味破坏相互作用。最大味破坏的$Z'$相互作用会通过中性流对$τ\toμν\barν$过程产生贡献,但该过程的参数空间与$(g-2)_μ$的允许区域存在冲突。为解决这一冲突,我们提出引入一种通过带电流相互作用介导的单电荷标量。该标量预计会对轻子$(g-2)_l$产生负贡献,同时会诱发τ衰变$τ\toμν\barν$。单电荷标量的引入会产生三种不同的情形:由弱单态和三重态驱动的$\ncal{O}_{LL}$算符,以及由弱二重态驱动的$\ncal{O}_{LR}$算符。我们对这三种情形的唯象学分析表明,只有来自弱三重态的单电荷标量才能有效缓解大$Z'$质量下μ子$(g-2)_μ$反常与$τ\toμν\barν$之间的张力,而单态和二重态情形无法做到这一点。此外,来自弱三重态的单电荷标量还能为电子$(g-2)_e$反常提供额外解释。我们的研究结果表明,弱三重态可能在$Z'$模型中发挥关键作用,有望为未来$U(1)$框架的研究提供有价值的见解。

英文摘要:

The $U(1)_{L_μ-L_τ}$ $Z'$ model has emerged as a promising candidate to address the longstanding muon $(g-2)_μ$ anomaly. Flavor-conserving $Z'$ interactions are subject to stringent constraints from the neutrino trident process and NA64$μ$ experiments, which limit the $Z'$ mass to $m_{Z'}<40$ MeV. To circumvent these constraints, flavor-conserving $Z'$ interactions can be converted into maximal flavor-violating interactions through a discrete exchange symmetry. Maximal flavor-violating $Z'$ interactions contribute to $τ\toμν\barν$ via the neutral current, yet the parameter space for this process conflicts with the $(g-2)_μ$ allowed regions. To resolve this conflict, we propose introducing a singly-charged scalar that mediates via charged current interactions. This scalar is anticipated to produce a negative contribution to the lepton $(g-2)_l$ while concurrently inducing the tau decay $τ\toμν\barν$. Three distinct scenarios arise from the introduction of singly-charged scalars: the $\mathcal{O}_{LL}$ operator, driven by weak singlet and triplet, and the $\mathcal{O}_{LR}$ operator, driven by weak doublet. Our analysis of the phenomenology in these three cases reveals that the tension between the muon $(g-2)_μ$ anomaly and $τ\toμν\barν$ for large $Z'$ masses can be effectively alleviated only by the singly-charged scalars from the weak triplet, whereas the singlet and doublet scenarios fall short. Furthermore, the singly-charged scalars from the weak triplet offer an additional explanation for the electron $(g-2)_e$ anomaly. Our findings indicate that weak triplets could play a crucial role in $Z'$ models, potentially providing valuable insights for future research into $U(1)$ frameworks.

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