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arXiv 0812.0001hep-ph
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B -> Xsl + l-观测量中的非微扰m_X切割效应

Nonperturbative m_X cut effects in B -> Xs l+ l- observables

Keith S. M. Lee, Frank J. Tackmann

摘要:

最近,研究表明,在包含B -> Xs l+ l-衰变中,角分解提供了三个独立(q^2相关)的可观测量。我们制定了一个策略,从低q^2区域的这些观测量的几个简单积分中提取B -> Xsl + l-中的所有可测量威尔逊系数。在低q^2区域的实验测量需要对强子不变质量进行切割,这就引入了对非微扰b夸克分布函数的依赖性。相关的强子不确定性可能会限制这些衰变对新物理的敏感性。在Λ QCD/mb中,我们计算了在幂展开式中首阶和次首阶三个观测量的非微扰修正。我们发现,次主导功率修正给出了相当大的修正,数量级为-5%到-10%,这取决于可观测的强子质量切割的精确值。它们在前后不对称的零点处引起了-0.05 GeV^2到-0.1 GeV^2量级的位移。

英文摘要:

Recently, it was shown that in inclusive B -> Xs l+ l- decay, an angular decomposition provides three independent (q^2 dependent) observables. A strategy was formulated to extract all measurable Wilson coefficients in B -> Xs l+ l- from a few simple integrals of these observables in the low q^2 region. The experimental measurements in the low q^2 region require a cut on the hadronic invariant mass, which introduces a dependence on nonperturbative b quark distribution functions. The associated hadronic uncertainties could potentially limit the sensitivity of these decays to new physics. We compute the nonperturbative corrections to all three observables at leading and subleading order in the power expansion in Λ_QCD/m_b. We find that the subleading power corrections give sizeable corrections, of order -5% to -10% depending on the observable and the precise value of the hadronic mass cut. They cause a shift of order -0.05 GeV^2 to -0.1 GeV^2 in the zero of the forward-backward asymmetry.

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