arXiv 1306.04462013-06-03hep-lathep-ph

静态b夸克格点量子色动力学的$Λ_b \to p l^- \barν$形状因子

$Λ_b \to p l^- \barν$ form factors from lattice QCD with static b quarks

William Detmold, C. -J. David Lin, Stefan Meinel, Matthew Wingate

备注：: 14 pages, 5 figures
发表信息：: Phys. Rev. D 88, 014512 (2013)
DOI：: 10.1103/PhysRevD.88.014512

摘要：

我们提出了一个格点量子色动力学计算$Λ_b \to p μ^- \barν$衰变的形状因子，这是一个有前途的通道，确定CKM矩阵元$|V_{ub}|$在大型强子对撞机。在这个初步的研究中，我们的工作在静态的b夸克的限制，独立的形状因子的数量减少到两个。我们使用动力学域壁费米子的轻夸克，并在两个不同的晶格间距和在一个单一的大体积的轻夸克质量的多个值进行计算。使用我们的形状因子的结果，我们计算的$Λ_b \to p μ^- \barν$微分衰减率的范围$14 GeV^2 \leq q^2 \leq q^2_{max}$，并获得积分$\int_{14 GeV^2}^{q^2_{max}} [dΓ/dq^2] dq^2 / |V_{ub}|^2 = 15.3 \pm 4.2 ps^{-1}$。结合今后的实验数据，提出了一种新的测定$|V_{ub}|$的方法，理论不确定度约为15%。不确定性主要是由使用的静态近似的b夸克，并可以进一步减少通过执行一个更复杂的重夸克作用的晶格计算。

英文摘要：

We present a lattice QCD calculation of form factors for the decay $Λ_b \to p μ^- \barν$, which is a promising channel for determining the CKM matrix element $|V_{ub}|$ at the Large Hadron Collider. In this initial study we work in the limit of static b quarks, where the number of independent form factors reduces to two. We use dynamical domain-wall fermions for the light quarks, and perform the calculation at two different lattice spacings and at multiple values of the light-quark masses in a single large volume. Using our form factor results, we calculate the $Λ_b \to p μ^- \barν$ differential decay rate in the range $14 GeV^2 \leq q^2 \leq q^2_{max}$, and obtain the integral $\int_{14 GeV^2}^{q^2_{max}} [dΓ/dq^2] dq^2 / |V_{ub}|^2 = 15.3 \pm 4.2 ps^{-1}$. Combined with future experimental data, this will give a novel determination of $|V_{ub}|$ with about 15\% theoretical uncertainty. The uncertainty is dominated by the use of the static approximation for the b quark, and can be reduced further by performing the lattice calculation with a more sophisticated heavy-quark action.

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