标题： 使用 gg -> 2e 2μ 的完整解析结果在 LHC 上限制希格斯宽度 显示英文标题

标题： Bounding the Higgs width at the LHC using full analytic results for gg -> 2e 2μ

摘要： 我们重新研究了通过初始态胶子的融合产生四轻子末态 e^- e^+\mu ^-\mu ^+ 的强子过程。 该过程由夸克环介导，我们提供了首次完整的解析结果，用于计算考虑了环中夸克质量效应和非定域矢量玻色子的螺旋振幅。 解析结果已实现于蒙特卡罗程序 MCFM 中，在低 Z 传递动量区域中既快速又数值稳定。 我们利用这些结果研究了由希格斯介导和连续态产生四轻子末态之间的干涉，这对于在希格斯共振区外获得准确的理论预测是必要的。 我们确认并扩展了 Caola 和 Melnikov 最近的一项分析，该分析提出通过测量非定域区域来约束希格斯玻色子的总宽度。 使用简单的截断计数方法，现有的 LHC 数据应能将宽度限制在标准模型预期的 25-45 倍水平。 我们研究了使用矩阵元方法构建运动学判据以增强约束的能力。 在我们的分析中，相比使用不变质量截断 m_{4l}> 300 GeV，通过在 MEM 判据上使用简单截断，希格斯宽度的限制提高了约 1.6 倍。 显示英文摘要

摘要： We revisit the hadronic production of the four-lepton final state, e^- e^+ \mu^- \mu^+, through the fusion of initial state gluons. This process is mediated by loops of quarks and we provide first full analytic results for helicity amplitudes that account for both the effects of the quark mass in the loop and off-shell vector bosons. The analytic results have been implemented in the Monte Carlo program MCFM and are both fast, and numerically stable in the region of low Z transverse momentum. We use our results to study the interference between Higgs-mediated and continuum production of four-lepton final states, which is necessary in order to obtain accurate theoretical predictions outside the Higgs resonance region. We have confirmed and extended a recent analysis of Caola and Melnikov that proposes to use a measurement of the off-shell region to constrain the total width of the Higgs boson. Using a simple cut-and-count method, existing LHC data should bound the width at the level of 25-45 times the Standard Model expectation. We investigate the power of using a matrix element method to construct a kinematic discriminant to sharpen the constraint. In our analysis the bound on the Higgs width is improved by a factor of about 1.6 using a simple cut on the MEM discriminant, compared to an invariant mass cut m_{4l} > 300 GeV.