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arXiv 1004.0620hep-phhep-ex
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QCD中味变中性耦合介导的辐射顶夸克次领先级衰变

Flavor Changing Neutral Coupling Mediated Radiative Top Quark Decays at Next-to-Leading Order in QCD

Jure Drobnak, Svjetlana Fajfer, Jernej F. Kamenik

摘要:

我们计算了QCD中次领先阶的有效变味中性耦合所介导的稀有顶夸克衰变t到c γ和t到c Z的分支比,包括算子混合的影响.利用重整化群方法,在主对数水平上对[alpha_slog(Lambda / m_t)]^n阶(Lambda是有效算子产生的尺度)的贡献进行求和,计算有限矩阵元修正,并研究实验运动学切割对提取的分支比的影响.我们发现,t到c的伽马衰变也可以用来探测有效的运营商介导的t到c g过程,因为这些可以naturaly贡献10%或更多的辐射衰变。相反,任何t到cg的实验信号都将指示t到cZ,γ的自然下限。

英文摘要:

We compute the branching ratios for the rare top quark decays t to c gamma and t to c Z mediated by effective flavor changing neutral couplings at the next-to-leading order in QCD including the effects due to operator mixing. After re-suming contributions of order [alpha_s log (Lambda / m_t)]^n, where Lambda is the scale at which the effective operators are generated, at leading log level using renormalization group methods, we compute finite matrix element corrections and study the effects of experimental kinematic cuts on the extracted branching ratios. We find that the t to c gamma decay can be used to probe also the effective operators mediating t to c g processes, since these can naturaly contribute 10% or more to the radiative decay. Conversely, any experimental signal of t to c g would indicate a natural lower bound on t to cZ, gamma.

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