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arXiv 2007.11173hep-ph
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排他$B$介子衰变的次首对数阈值计算

Next-to-Leading-logarithm threshold resummation for exclusive $B$ meson decays

Zhi-Qing Zhang, Hsiang-nan Li

摘要:

我们将$x$作为旁观者动量分数的$B$介子衰变因子分解公式中出现的大动量项$\ln x$的阈值重算推广到次首对数(NLL)精度。结果表明,NLL的重定效应提供了抑制在端点区域与$x\sim 0$强于领先的对数(LL)之一,从而改善上述过程的微扰分析。我们重新研究了在NLL再激发下的$B\to Kπ$衰变,发现与LL再激发相比,它引起了20- 25%的直接CP不对称性变化.我们的方法,以避免在逆梅林变换的朗道奇异性引起的理论不确定性很小。

英文摘要:

We extend the threshold resummation of the large logarithms $\ln x$ which appear in factorization formulas for exclusive $B$ meson decays, $x$ being a spectator momentum fraction, to the next-to-leading-logarithm (NLL) accuracy. It is shown that the NLL resummation effect provides suppression in the end-point region with $x\sim 0$ stronger than the leading-logarithm (LL) one, and thus improves perturbative analyses of the above processes. We revisit the $B\to Kπ$ decays under the NLL resummation, and find that it induces 20-25\% variation of the direct CP asymmetries compared to those from the LL resummation. Our way to avoid the Landau singularity in the inverse Mellin transformation causes little theoretical uncertainty.

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