TauPolaris：利用条件归一化流重建τ轻子极化矢量
TauPolaris: reconstructing tau lepton polarimetric vectors with conditional normalizing flows
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中文总结 AI 辅助
TauPolaris工具利用条件归一化流估计逃逸中微子动量以重建τ极化矢量，提升自旋观测量分辨率，在LHC模拟数据中实现希格斯衰变纠缠区分、CP灵敏度提升及本底抑制。
中文摘要 AI 辅助
τ轻子衰变产物的运动学依赖于τ自旋，可用于获取产生τ轻子过程的自旋关联和CP结构。最优自旋观测量是极化矢量，其指向τ自旋最可能的方向。确定该矢量需要τ衰变中产生的中微子动量，而中微子会逃逸探测，因此必须通过推断得到。我们提出TauPolaris工具，用于通过条件归一化流估计未探测到的中微子动量，以重建τ极化矢量。该方法不进行点回归，而是对中微子运动学的完整条件密度进行建模，为每个事例提供最可能的构型及其不确定性估计。与使用均方误差损失训练的网络相比，该方法重建自旋观测量的分辨率更高。我们利用包含探测器分辨率效应的模拟LHC质子-质子碰撞数据，在三个应用中验证了该方法：对于希格斯玻色子衰变产生的τ轻子，在高亮度LHC上可至少以4.3σ的显著性区分量子纠缠的存在与否；在H→ττ衰变中，对CP破坏的灵敏度提升18%；最后，我们引入新变量以抑制希格斯玻色子搜索中的Z→ττ本底。
英文摘要
The kinematics of tau lepton decay products depend on the tau spin, giving access to the spin correlations and CP structure of the process that produced them. The optimal spin observable is the polarimetric vector, which points along the most likely direction of the tau spin. Determining it requires the momenta of the neutrinos produced in the tau decays, which escape detection and must therefore be inferred. We present TauPolaris, a tool for reconstructing tau polarimetric vectors by estimating the undetected neutrino momenta with a conditional normalizing flow. Rather than performing a point regression, the method models the full conditional density of the neutrino kinematics, providing both the most likely configuration for each event and an estimate of its uncertainty. The resolution of the reconstructed spin observables improves on that obtained from networks trained with a mean-squared-error loss. Using simulated LHC proton-proton collisions, including detector resolution effects, we demonstrate the method in three applications. For tau leptons produced in Higgs boson decays, we show that the presence of quantum entanglement can be distinguished from its absence with a significance of at least $4.3σ$ at the High-Luminosity LHC. We demonstrate an 18% improvement in the sensitivity to CP violation in $H\rightarrowττ$ decays. Finally, we introduce new variables for suppressing the $Z\rightarrowττ$ background in Higgs boson searches.
