论文标题
$λ_b\toλ^*（1520）\ ell^+\ ell^ - $ for lattice qcd
$Λ_b \to Λ^*(1520)\ell^+\ell^-$ form factors from lattice QCD
论文作者
论文摘要
我们介绍了$λ_b\ \至λ^*（1520）$ vector，轴向向量和张量形式的第一个晶格QCD确定与稀有衰减相关的$λ_b\toλ_b\toλ^*（1520）\ ell^+el^+\ ell^ell^ - $。晶格计算以$λ^*（1520）$ rest框架执行，其nonzero $λ_b$ momenta，并且仅限于高$ q^2 $区域。具有协变量衍生物的插值字段用于获得与$λ^*（1520）$的良好重叠。该分析将$λ^*（1520）$视为稳定粒子，预计这对于此狭窄的共鸣是合理的近似值。域壁动作用于轻夸克和奇怪的夸克，而$ b $ quark则使用各向异性三叶草动作实施，其系数调整了可产生正确的$ b_s $动力学质量，静息质量和超精细分解。我们使用RBC和UKQCD协作产生的三个不同集合的晶格量规场配置，并将外形量的外推到连续性极限和物理锥度质量。我们给出了$λ_b\ \的标准模型预测至λ^*（1520）\ ell^+\ ell^ - $差异分支分数和高$ q^2 $区域中的Angular分支分数和Angular可观察力。
We present the first lattice QCD determination of the $Λ_b \to Λ^*(1520)$ vector, axial vector, and tensor form factors that are relevant for the rare decays $Λ_b \to Λ^*(1520)\ell^+\ell^-$. The lattice calculation is performed in the $Λ^*(1520)$ rest frame with nonzero $Λ_b$ momenta, and is limited to the high-$q^2$ region. An interpolating field with covariant derivatives is used to obtain good overlap with the $Λ^*(1520)$. The analysis treats the $Λ^*(1520)$ as a stable particle, which is expected to be a reasonable approximation for this narrow resonance. A domain-wall action is used for the light and strange quarks, while the $b$ quark is implemented with an anisotropic clover action with coefficients tuned to produce the correct $B_s$ kinetic mass, rest mass, and hyperfine splitting. We use three different ensembles of lattice gauge-field configurations generated by the RBC and UKQCD collaborations, and perform extrapolations of the form factors to the continuum limit and physical pion mass. We give Standard-Model predictions for the $Λ_b \to Λ^*(1520)\ell^+\ell^-$ differential branching fraction and angular observables in the high-$q^2$ region.
