论文标题
$ b \ to k \ ell^+\ ell^ - $，$ b \ to K \ ell_1^ - \ ell_2^+$和$ b \ tokν\barν$使用$ n_f = 2+1+1+1+lattice qccd的标准模型预测
Standard Model predictions for $B\to K\ell^+\ell^-$, $B\to K\ell_1^- \ell_2^+$ and $B\to Kν\barν$ using form factors from $N_f=2+1+1$ lattice QCD
论文作者
论文摘要
我们使用HPQCD的近期晶格QCD确定$ b \ to K $ stallar，vector和tensor形式的形式来确定$ b \ to K \ ell^+el^+el^+el^ - $，$ b \ to K \ ell_1^+ell_1^+ell_2^+ell_2^ - $ and $ b \ tok k \ ell^+el^$ b \ to K \ ell^+el^$ b \ tok ken的标准模型差异分支的分数。这些形式是在衰减的整个$ q^2 $范围内计算出的，并且比以前的工作更小，尤其是在低$ q^2 $时。对于$ b \至k \ ell^+\ ell^ - $，我们在平方$ j/ψ$质量下方的$ q^2 $区域中找到了标准模型分支分数，超过了LHCB结果，张力高达$4.2σ$ $ b^+\ to K^+μ^+μ^+μ^ - $。对于高$ q^2 $区域，我们看到$2.7σ$张紧。在有效弱的汉密尔顿人中，将转换应用于Wilson系数$ C_9 $和$ C_ {10} $，从而大大降低了紧张局势，从而使它们脱离了与其他$ B $现象学指示的标准模型值相一致的标准模型值。我们还更新了Lepton-Flavour比率的结果$ r^μ_e$和$ r^τ_μ$和`flat farm''，$ f_h^{\ ell} $ in \ ell \ in \ ell \ in \ el \ el {我们对搜索Lepton-flavour-violating所需的依赖形式的贡献的结果损失了$ b \ to k \ ell^-_ 1 \ ell^+_ 2 $达到7％的不确定性。我们还计算分支分数$ \ MATHCAL {B}（b \ toKν\barν）$，不确定性低于10％，以与未来的实验结果进行比较。
We use HPQCD's recent lattice QCD determination of $B \to K$ scalar, vector and tensor form factors to determine Standard Model differential branching fractions for $B \to K \ell^+\ell^-$, $B\to K \ell_1^+\ell_2^-$ and $B \to Kν\overlineν$. These form factors are calculated across the full $q^2$ range of the decay and have smaller uncertainties than previous work, particularly at low $q^2$. For $B \to K \ell^+ \ell^-$ we find the Standard Model branching fraction in the $q^2$ region below the squared $J/ψ$ mass to exceed the LHCb results, with tensions as high as $4.2σ$ for $B^+\to K^+μ^+μ^-$. For the high $q^2$ region we see $2.7σ$ tensions. The tensions are much reduced by applying shifts to Wilson coefficients $C_9$ and $C_{10}$ in the effective weak Hamiltonian, moving them away from their Standard Model values consistent with those indicated by other $B$ phenomenology. We also update results for lepton-flavour ratios $R^μ_e$ and $R^τ_μ$ and the `flat term', $F_H^{\ell}$ in the differential branching fraction for $\ell\in\{e,μ,τ\}$. Our results for the form-factor-dependent contributions needed for searches for lepton-flavour-violating decays $B\to K\ell^-_1\ell^+_2$ achieve uncertainties of 7%. We also compute the branching fraction $\mathcal{B}(B\to Kν\barν)$ with an uncertainty below 10%, for comparison with future experimental results.
