arXiv 0707.07732007-07hep-phhep-ex

W对产生阈附近的四费米子产生

Four-fermion production near the W pair production threshold

Martin Beneke, Pietro Falgari, Christian Schwinn, Adrian Signer, Giulia Zanderighi

备注：: 53 pages, v2: version to be published, inessential modifications
发表信息：: Nucl.Phys.B792:89-135,2008
DOI：: 10.1016/j.nuclphysb.2007.09.030

摘要：

考虑到四费米子产生过程对精确测量W玻色子质量的重要性，我们对W对产生阈值附近的四费米子产生过程e-e + -> mu- nubar_mu udbar X进行了专门的研究。对这一过程的精确理论预测需要系统地处理有限宽度效应。我们使用不稳定粒子有效场论（EFT）对耦合常数γ W/MW和W玻色子的非相对论速度v进行了展开，直到次领先级γ W/MW ~ alpha_ew ~ v ^2。我们发现，占主导地位的理论不确定性MW目前是由于不完整的治疗初始状态辐射。NLO EFT计算的剩余不确定性转化为Δ MW ~ 10-15 MeV，并且在完整理论中具有来自NLO四费米子计算的额外输入的情况下转化为约5 MeV。

英文摘要：

We perform a dedicated study of the four-fermion production process e- e+ -> mu- nubar_mu u dbar X near the W pair-production threshold in view of the importance of this process for a precise measurement of the W boson mass. Accurate theoretical predictions for this process require a systematic treatment of finite-width effects. We use unstable-particle effective field theory (EFT) to perform an expansion in the coupling constants, GammaW/MW, and the non-relativistic velocity v of the W boson up to next-to-leading order in GammaW/MW ~ alpha_ew ~ v^2. We find that the dominant theoretical uncertainty in MW is currently due to an incomplete treatment of initial-state radiation. The remaining uncertainty of the NLO EFT calculation translates into delta MW ~ 10-15 MeV, and to about 5 MeV with additional input from the NLO four-fermion calculation in the full theory.

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