论文标题
在$ {\ bar b} \ to d^{*+} \ ell^ - {\barν} $中搜索标准模型以外的物理的新工具
A new tool to search for physics beyond the Standard Model in ${\bar B}\to D^{*+}\ell^- {\barν}$
论文作者
论文摘要
Belle，Babar和LHCB的$ B $物理学的最新实验结果表明，弱$ b \ to C $充电 - 电流中的新物理（NP）以及$ b \ to $ b \ to s $中性流动过程。在这里，我们将重点放在充电的情况下，特别是衰减模式$ b \ to d^{*+} \ ell^ - \barν$带有$ \ ell = e，μ，$，$和$τ$。当前的世界平均值$ r_d $和$ r_d^{*} $当前与标准型号（SM）差异为$3.4σ$，而$ΔA_{fb} = a_ {fb}（b \ to d^{*}μν） - 预测2019年Belle数据。这些有趣的结果表明，迫切需要在$ b \ to d^{*+} \ ell^ - \barν$衰减中改进模拟和分析技术。在这里，我们描述了基于开发的EVTGEN的蒙特卡洛事件生成工具，以允许在$ b \ to d^*\ ell^ - ν$中模拟NP签名，这是由于SM和NP振幅之间的干扰而产生的。为了证明所提出的方法，我们展示了一些与当前数据一致的NP耦合示例，并且可以解释$ b \ in $ b \ in $ b \ to d^*\ ell^ - ν$的$ΔA_{fb} $异常，同时与其他约束保持一致。我们表明，$δ$ -Type可观察值，例如$ΔA_{fb} $和$ΔS_5$消除了形式的大多数QCD不确定性，并允许对NP进行清洁测量。我们引入了相关的可观察物，以提高对NP的敏感性。我们讨论了对NP耦合敏感的可观察到的前景，其预期的50 AB $^{ - 1} $的Belle II数据似乎非常适合这类测量。
Recent experimental results in $B$ physics from Belle, BaBar and LHCb suggest new physics (NP) in the weak $b\to c$ charged-current and the $b\to s$ neutral-current processes. Here we focus on the charged-current case and specifically on the decay modes $B\to D^{*+}\ell^- \barν$ with $\ell = e, μ,$ and $τ$. The world averages of the ratios $R_D$ and $R_D^{*}$ currently differ from the Standard Model (SM) by $3.4σ$ while $ΔA_{FB} = A_{FB}(B\to D^{*} μν) - A_{FB} (B\to D^{*} e ν)$ is found to be $4.1σ$ away from the SM prediction in an analysis of 2019 Belle data. These intriguing results suggest an urgent need for improved simulation and analysis techniques in $B\to D^{*+}\ell^- \barν$ decays. Here we describe a Monte Carlo Event-generator tool based on EVTGEN developed to allow simulation of the NP signatures in $B\to D^*\ell^- ν$, which arise due to the interference between the SM and NP amplitudes. As a demonstration of the proposed approach, we exhibit some examples of NP couplings that are consistent with current data and could explain the $ΔA_{FB}$ anomaly in $B\to D^*\ell^- ν$ while remaining consistent with other constraints. We show that the $Δ$-type observables such as $ΔA_{FB}$ and $ΔS_5$ eliminate most QCD uncertainties from form factors and allow for clean measurements of NP. We introduce correlated observables that improve the sensitivity to NP. We discuss prospects for improved observables sensitive to NP couplings with the expected 50 ab$^{-1}$ of Belle II data, which seems to be ideally suited for this class of measurements.
