Reduction of PDF uncertainty in the measurement of the weak mixing angle at the ATLAS experiment

• 作 者: Yao Fu Siqi Yang Minghui Liu Liang Han Tie-Jiun Hou Carl Schmidt Chen Wang C.-P.Yuan
• 机 构: Department of Modem Physics, University of Science and Technology of China, Jinzhai Road 96, Hefei 2
• 出 处: 中国物理C（英文版）
• 发表日期: 2021年5期
• 关键词: parton distribution function weak mixing angle hadron collider experiment electr

We investigate the parton distribution function (PDF) uncertainty in the measurement of the effective weak mixing angle sin2 θeffe at the CERN Large Hadron Collider (LHC).The PDF-induced uncertainty is large in proton-proton collisions at the LHC due to the dilution effect.The measurement of the Drell-Yan forward-backward asymmetry (AFB) at the LHC can be used to reduce the PDF uncertainty in the sin2 θeffe measurement.However,when including the full mass range of lepton pairs in the AFB data analysis,the correlation between the PDF updating procedure and the sin2 θeffe extraction leads to a sizable bias in the obtained sin2 θeffe value.From our studies,we find that the bias can be significantly reduced by removing Drell-Yan events with invariant mass around the Z-pole region,while most of the sensitivity in reducing the PDF uncertainty remains.Furthermore,the lepton charge asymmetry in the Wboson events as a function of the rapidity of the charged leptons,A±(ηe),is known to be another observable which can be used to reduce the PDF uncertainty in the sin2 θeffe measurement.The constraint from A±(ηe)is complementary to that from AFB,and thus no bias affects the sin2 θeffe extraction.The studies are performed using the error PDF Updating Method Package (ePump),which is based on Hessian updating methods.In this article,the CT14HERA2 PDF set is used as an example.