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arXiv 2004.10942hep-ph
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重介子衰变中自旋$1/2$不可见粒子

Spin-$1/2$ invisible particles in heavy meson decays

Geng Li, Tianhong Wang, Yue Jiang, Jing-Bo Zhang, Guo-Li Wang

摘要:

研究了末态含有自旋$1/2$粒子的$B$和$B_c$介子的味变中性流衰减过程.考虑到标准模型中$ν\barν$贡献了丢失能量的背景和分支分数的实验上界,我们得到了夸克-反夸克和假设的不可见粒子$χ\barχ$的耦合常数的约束。利用耦合常数的约束条件研究了$B_c$介子的类似过程。在$m_χ$的某些特定区域,BR($B_c\to D_{(s)}χ\barχ$)的上限为$10^{-6}$的数量级,而BR($B_c\to D^\ast_{(s)}χ\barχ$)的上限为$10^{-5}$。讨论了用微分分支分数区分$χ$是Majorana费米子还是Dirac费米子的可能性。

英文摘要:

The flavor-changing neutral current decay processes of the $B$ and $B_c$ mesons with the final states involving spin-$1/2$ particles are investigated. By considering the background of the Standard Model where $ν\barν$ contributes the missing energy and the experimental upper bounds for the branching fractions, we get the constraints of the coupling constants of the quark-antiquark and the assumed invisible particles $χ\barχ$. The constraints of the coupling constants are then used to study the similar processes of the $B_c$ meson. At some specific region of $m_χ$, the upper limit of BR($B_c\to D_{(s)}χ\barχ$) is of the order of $10^{-6}$, while for BR($B_c\to D^\ast_{(s)}χ\barχ$), it is $10^{-5}$. The possibility of distinguishing $χ$ to be a Majorana or Dirac fermion by the differential branching fractions is also discussed.

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