用于暗物质和Belle II报道的$B^+\to K^+ν\barν$超出事例的$U(1)_{(B-L)_3}$模型
A $U(1)_{(B-L)_3}$ model for dark matter and the $B^+\to K^+ν\barν$ excess reported by Belle II
AI总结：
该研究构建$U(1)_{(B-L)_3}$模型，引入手征费米子作为热暗物质，利用新规范玻色子对$b$、$s$夸克的非对角耦合，尝试解释Belle II报道的$B^+\to K^+\nu\bar{\nu}$超出事例。
AI中文摘要：
我们研究仅第三代费米子带电的$U(1)_{(B-L)_3}$规范对称性。$[U(1)_{(B-L)_3}]^3$反常的抵消需要一个手征费米子$\tilde{\tau}_L$，它是规范群下的单态但在$U(1)_{(B-L)_3}$下带电。该手征费米子可作为热暗物质，其残余丰度通过与第三代费米子对湮灭的冻结产生场景确定。在夸克质量基下，新规范玻色子会对$b$和$s$夸克产生非对角耦合，这可对$B^+\to K^+\nu_\tau\bar{\nu}_\tau$产生新贡献。我们讨论了来自LHC对新规范玻色子的搜寻、暗物质搜寻、电弱精确数据、$\tau$衰变、CKM矩阵以及$B_s^0-\bar{B}_s^0$混合的相关限制，探讨了在该模型内解释Belle II近期报道的$B^+\to K^+\nu\bar{\nu}$超出事例的可能性。
英文摘要：
We explore the $U(1)_{(B-L)_3}$ gauge symmetry under which only third generation fermions are charged. The cancelation of the $[U(1)_{(B-L)_3}]^3$ anomaly requires a chiral fermion, $χ_L$, singlet under the gauge group but charged under $U(1)_{(B-L)_3}$. This chiral fermion can play the role of thermal dark matter with a relic abundance set via the freeze-out scenario through the annihilation to pairs of the third generation fermions. In the quark mass basis, the new gauge boson will have off-diagonal couplings to the $b$ and $s$ quarks which can lead to a new contribution to $B^+\to K^+ν_τ\barν_τ$. We discuss the relevant bounds from the LHC searches for a new gauge boson, dark matter searches, electroweak precision data, $Υ$ decay, the CKM matrix and the $B_s^0-\bar{B}_s^0$ mixing. We entertain the possibility of explaining the $B^+\to K^+ν\barν$ excess recently reported by Belle II within this model.
