Title: Measuring the CP property of Higgs coupling to tau leptons in the VBF channel at the LHC Show Chinese title

Title: 在LHC的VBF通道中测量希格斯粒子与陶轻子耦合的CP性质

Abstract: We study the prospects of measuring the CP property of the Higgs ($h$) coupling to tau leptons using the vector boson fusion (VBF) production mode at the high-luminosity LHC. Utilizing the previously proposed angle between the planes spanned by the momentum vectors of the $(\pi^+\pi^0)$ and $(\pi^- \pi^0)$ pairs originating in $\tau^\pm$ decays as the CP-odd observable, we perform a detailed Monte Carlo analysis, taking into account the relevant standard model backgrounds, as well as detector resolution effects. We find that excluding a pure CP-odd coupling hypothesis requires $\mathcal{O}(400 {~\rm fb}^{-1})$ luminosity at the 14 TeV LHC, and values of the CP-mixing angle larger than about $25^\circ$ can be excluded at $95\%$ confidence level using $3 {~\rm ab}^{-1}$ data. It is observed that the uncertainty in the angular resolution of the neutral pion momenta does not constitute a significant hurdle. Achieving a signal to background ratio ($S/B$) close to one, while keeping a high enough signal yield required to study the angular distributions selects out VBF as a promising mode to probe the CP nature of the $h\tau\tau$ coupling, with gluon fusion suffering from a low $S/B$, and the $W^\pm h/Zh$ mode (with leptonically decaying $W^\pm /Z$) having a much smaller signal rate. Show Chinese abstract

Abstract: 我们研究在高亮度LHC上使用矢量玻色子融合（VBF）产生模式测量希格斯（$h$）与τ轻子耦合的CP性质的可能性。 利用之前提出的由源自$\tau^\pm$衰变的$(\pi^+\pi^0)$和$(\pi^- \pi^0)$对的动量矢量所张开的平面之间的角度作为CP奇数可观测量，我们进行了一项详细的蒙特卡罗分析，考虑了相关的标准模型背景以及探测器分辨率效应。 我们发现，排除纯CP奇耦合假设需要14 TeV LHC上的$\mathcal{O}(400 {~\rm fb}^{-1})$亮度，使用$3 {~\rm ab}^{-1}$数据，在$95\%$置信水平下，可以排除CP混合角大于约$25^\circ$的值。 观察到中性π介子动量的角度分辨率的不确定性并不构成重大障碍。 实现接近于一的信号与背景比（$S/B$），同时保持足够的信号产率以研究角分布，使VBF成为探测$h\tau\tau$耦合CP性质的一种有前景的模式，而胶子融合由于较低的$S/B$而受到限制，以及$W^\pm h/Zh$模式（带轻子衰变的$W^\pm /Z$）具有较小得多的信号速率。