论文标题
$ b_s \todexν\barν$在CEPC上的分析
Analysis of $B_s\toϕν\barν$ at CEPC
论文作者
论文摘要
稀有的$ b \ tosν\barν$衰减对新物理学（NP）的贡献很敏感，并有助于解决多个$ b $风味异常的难题。在这项工作中，我们建议在未来的Lepton Collider上研究$ b \ tosν\barν$过渡，该撞机在$ z $ pole中通过$ b_s \ to ϕν \barν$衰减。使用$ b_s \ to ϕ $衰减形式从晶格模拟中进行的形式，我们首先更新br（$ b_s \ to ϕν \barν）_ {\ mathrm {sm}} =（9.93 \ pm 0.72） $ f_ {l，{\ mathrm {sm}}}} = 0.53 \ pm 0.04 $。我们的分析使用完整的CEPC模拟样本，其净统计量为$ \ Mathcal {O}（10^9）$ $ z $衰减。精确的$ ϕ $和$ b_s $重建用于抑制背景。结果表明，可以以$ \ Mathcal {o}（\％）$和$ \ Mathcal {O}（O}（O} $ s/b $比率的统计不确定性），可以测量Br（$ b_s \ to ϕν \barν）$。还得出了事件重建的质量度量。通过将BR（$ b_s \ to ϕν \barν）$和$ f_l $的测量结合起来，给出了低能时有效理论耦合的约束。
The rare $b\to sν\barν$ decays are sensitive to contributions of new physics (NP) and helpful to resolve the puzzle of multiple $B$ flavor anomalies. In this work, we propose to study the $b\to sν\barν$ transition at a future lepton collider operating at the $Z$ pole through the $B_s \to ϕν\barν$ decay. Using the $B_s\toϕ$ decay form factors from lattice simulations, we first update the SM prediction of BR($B_s \to ϕν\barν)_{\mathrm{SM}}=(9.93\pm 0.72)\times 10^{-6}$ and the corresponding $ϕ$ longitudinal polarization fraction $F_{L,{\mathrm{SM}}}=0.53\pm 0.04$. Our analysis uses the full CEPC simulation samples with a net statistic of $\mathcal{O}(10^9)$ $Z$ decays. Precise $ϕ$ and $B_s$ reconstructions are used to suppress backgrounds. The results show that BR($B_s \to ϕν\barν)$ can be measured with a statistical uncertainty of $\mathcal{O}(\%)$ and an $S/B$ ratio of $\mathcal{O}(1)$ at the CEPC. The quality measures for the event reconstruction are also derived. By combining the measurement of BR($B_s \to ϕν\barν)$ and $F_L$, the constraints on the effective theory couplings at low energy are given.
