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arXiv 1208.4053hep-ph
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强子对撞机上离壳ttbar产生的NLO QCD修正

NLO QCD corrections to off-shell ttbar production at hadron colliders

Ansgar Denner, Stefan Dittmaier, Stefan Kallweit, Stefano Pozzorini

摘要:

在强子对撞机上产生顶-反顶-夸克对,不仅作为信号过程本身很有趣,而且作为许多新物理学探索的背景也很有趣。相应的预测目标是百分之几的精度水平,不仅包括强相互作用和电弱相互作用的辐射修正,而且包括源于顶夸克衰变t -> bW-> bl ν_l /qq '的离壳效应和有限宽度效应。本文报道了次-首阶QCD下pp -> W^+ W^- b \bar{b} -> v_ee ^+ μ^-v_μb \bar{b}的全过程计算,并讨论了顶夸克和W玻色子的有限宽度对所选观测量的影响。一般来说,当顶夸克共振占主导地位时,有限顶宽效应处于百分比水平,但这些效应在离壳尾中可以达到百分之几十。另一方面,只要顶夸克可以共振,并且只有在特殊情况下才变得相当大,那么夸克-W-宽度效应就会被抑制到小于0.5%。然而,底夸克和相应的带电轻子的不变质量就是这样一种情况,它们是由同一个顶夸克衰变产生的--这是一个与精确测量顶夸克质量相关的可观测量。

英文摘要:

The production of top-antitop-quark pairs at hadron colliders is interesting both in its own right as signal process, but also as background to many searches for new physics. The corresponding predictions aim at the precision level of few per cent, rendering not only the inclusion of radiative corrections of the strong and electroweak interactions relevant, but also of off-shell and finite-width effects originating from the top-quark decays t -> b W -> b l ν_l / qq'. We report on a calculation for the full process pp -> W^+ W^- b \bar{b} -> ν_e e^+ μ^- ν_μb \bar{b} at next-to-leading order QCD and discuss the effects of the finite widths of the top quarks and of the W bosons for selected observables. Generically it turns out that finite-top-width effects are at the per-cent level whenever the top-quark resonances dominate, but those effects can reach tens of per cent in off-shell tails. Finite-W-width effects, on the other hand, are suppressed to less than 0.5% whenever the top quarks can become resonant and only become sizeable in exceptional cases. One such case, however, is the invariant mass of a bottom quark and the corresponding charged lepton, which result from the same top-quark decay - an observable that is relevant for precision measurements of the top-quark mass.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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