尋找電荷宇稱破壞在質子對撞後頂夸克對的產生與衰變

Abstract

此論文發表第一個尋找頂夸克對的電荷宇稱(CP)破壞現象。此研究利用 T-odd 三重乘積組合之可觀測量來做非對稱量測，其T為時間反轉運算子。此實驗是基於 8 TeV中心質量的質子對撞資料數據而進行分析，而數據量為 19.7 fb-1 並由緊湊緲子線圈偵測器(CMS)所收集。此分析關注於對撞結果的事件含有至少四個噴流以及一個電子或渺子。其 T-odd 可觀測量均由頂夸克對衰變粒子的線性獨立四動量而組成。最後的非對稱量測結果顯示沒有CP 破壞效應的徵兆，並吻合標準模型的預測。

We present the first search for CP violation in top quark-antiquark pair events. The search is based on asymmetries in T-odd triple product correlation observables, where T is the time reversal operator. The analysis is based on a sample of proton-proton collisions at sqrt(s)=8TeV collected by the CMS experiment, corresponding to an integrated luminosity of 19.7fb^-1. The analysis is performed with events having exactly one electron or muon and at least four jets. The T-odd observables are measured using the linearly independent four-momentum vectors associated with top quark production and decay. The measured asymmetries exhibit no evidence for CP-violating effects, in agreement with the standard model prediction.