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arXiv 1010.2402hep-phhep-ex
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QCD中t-> b W次领先衰变的新物理

New physics in t-> b W decay at next-to-leading order in QCD

Jure Drobnak, Svjetlana Fajfer, Jernej F. Kamenik

摘要:

考虑了非标准tbW有效算符对QCD中非极化顶夸克衰变为底夸克和次领先级W规范玻色子的贡献。我们发现,在底夸克质量不为零的情况下,偶极算符O_{LR}对横正W螺旋度分数F+的贡献比首阶结果显著增强.尽管如此,目前对直接O_{LR}贡献最敏感的观测是纵向W螺旋度分数F_L。特别是,最新的CDF测量F_L已经提供了最严格的上限O_{LR}的贡献,即使与间接的边界从罕见的衰变B -> X_s γ。

英文摘要:

We consider contributions of non-standard tbW effective operators to the decay of an unpolarized top quark into a bottom quark and a W gauge boson at next-to-leading order in QCD. We find that the dipole operator O_{LR} contribution to the transverse-plus W helicity fraction F_+ is significantly enhanced compared to the leading order result at non-vanishing bottom quark mass. Nonetheless, presently the most sensitive observable to direct O_{LR} contributions is the longitudinal W helicity fraction F_L. In particular, the most recent CDF measurement of F_L already provides the most stringent upper bound on O_{LR} contributions, even when compared with indirect bounds from the rare decay B -> X_s gamma.

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