论文标题
仔细检查半左右的新物理学
Scrutinizing New Physics in Semi-leptonic $B_{c}\rightarrow J/ψτν$ Decay
论文作者
论文摘要
我们使用$ b_c \ to j/ψ$向量和轴向向量形式的最新晶格结果对$ b \ tocτν$数据进行全局分析。为了探索除标准模型以外的新物理张量操作员的效果，我们通过使用张量和（轴向 - ）矢量形式的非相关QCD（NRQCD）关系来确定张量形式因素。基于晶格+NRQCD形式，我们通过包括最近测量的$ r（λ_c）$的$ r_2 $，$ s_1 $和$ r_2 $，$ s_1 $和$ u_1 $ leptoquark型号的新物理耦合，并在轻松的约束$ \ mathc b（b_cc \ 30 p（b_cc \ 30）上<30 c）<30 c）<30 c） $ b_c $ lifetime。我们对实验性观察物进行预测，包括$ r（j/ψ）$，$p_τ（j/ψ）$，$ f_l（j/ψ）$和$ \ Mathcal a_ {fb}（fb}（j/ψ）$以及他们的$ q^2 $在新物理风景/模型中的$ q^2 $。我们的结果表明，纵向$τ$极化分数$p_τ（j/ψ）$和前进的不对称$ \ Mathcal a_ {fb}（j/ψ）$对于测试$ r_2 $ leptoquark模型很有用。
We perform a global analysis of the $b\to cτν$ data using the recent lattice results on the $B_c\to J/ψ$ vector and axial-vector form factors. To explore the effects from the tensor operator of new physics beyond the standard model, we determine the tensor form factors by using the non-relativistic QCD (NRQCD) relations between tensor and (axial-)vector form factors. Based on the lattice+NRQCD form factors, we fit the Wilson coefficients and the new physics couplings in $R_2$, $S_1$ and $U_1$ leptoquark models by including the recently measured $R(Λ_c)$ and imposing the relaxed constraint $\mathcal B(B_c\to J/ψ)<30\%$ in light of the recent studies on LEP1 data and $B_c$ lifetime. We give predictions for the experimental observables including $R(J/ψ)$, $P_τ(J/ψ)$, $F_L(J/ψ)$ and $\mathcal A_{FB}(J/ψ)$ as well as their $q^2$ distribution in new physics scenarios/models. Our results suggest that the longitudinal $τ$ polarization fraction $P_τ(J/ψ)$ and the forward-backward asymmetry $\mathcal A_{FB}(J/ψ)$ are useful for testing the $R_2$ leptoquark model.
