Signatures of a flavor changing Z′ boson in Bq → γ Z′
Signatures of a flavor changing Z′ boson in Bq → γ Z′
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Bq 中改变风味的 Z 玻色子的特征 - γ Z 2
DOI：
10.1016/j.nuclphysb.2020.115237
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发表时间：
2021
影响因子：
2.8
通讯作者：
Yoshihiro Shigekami
中科院分区：
文献类型：
--
作者：
Shao-Long Chen;Amit Dutta Banik;Zhaofeng Kang;Qin Qin;Yoshihiro Shigekami
罕见的B介子衰变提供了一个机会，以探测一个轻隐藏的Z '玻色子。在这项工作中，我们探索了一个新的通道B → γ Z′（q= d，s），随后Z′级联衰变为不可见的（中微子或暗物质）或带电轻子对<$+<$−（<$= e，μ）。该研究基于一个简化的有效模型，其中下夸克扇区与Z′具有微小的变味中性流耦合。首次计算了1/m B和1/E γ的超前幂下的BR（B q→ γ Z′）.面对B介子半不可见衰变的强约束，我们发现B d→不可见+ γ的分支比可以大于其标准模型背景预言，这为新物理，特别是轻暗物质的研究留下了很大的空间。此外，当与夸克的味破坏Z′耦合是轴矢量型时，B d→ e+ e− γ的分支比也可以是相当大的。另一方面，B d→ μ+ μ− γ和B s→ μ + μ − γ的预测分支比受到实验测量的严重限制。
Rare B meson decays offer an opportunity to probe a light hidden Z′ boson. In this work we explore a new channel B q→ γ Z′(q= d, s) followed by a cascade decay of Z′ into an invisible (neutrino or dark matter) or charged lepton pair ℓ+ ℓ−(ℓ= e, μ). The study is based on a simplified effective model where the down quark sector has tiny flavor-changing neutral current couplings with Z′. For the first time, we calculate BR (B q→ γ Z′) at the leading power of 1/m b and 1/E γ. Confronting with the strong constraints from semi-invisible decays of B meson, we find that the branching ratio for B d→ invisible+ γ can be larger than its Standard Model background prediction, leaving a large room for new physics, in particular for light dark matter. Additionally, the branching ratio for B d→ e+ e− γ can also be sizable when the corresponding flavor violating Z′ coupling to quarks is of the axial-vector type. On the other hand, the predicted branching ratios of B d→ μ+ μ− γ and B s→ ℓ+ ℓ− γ are severely constrained by the experimental measurements.