Probing top-quark operators with precision electroweak measurements  

作　　者：Yiming Liu Yuhao Wang Cen Zhang Lei Zhang Jiayin Gu 刘一鸣;王昱昊;张岑;张雷;顾嘉荫(Institute of High Energy Physics,Chinese Academy of Sciences,Beijing 100049,China;School of Physics,Nanjing University,Nanjing 210093,China;Department of Physics and Center for Field Theory and Particle Physics,Fudan University,Shanghai 200438,China;Key Laboratory of Nuclear Physics and Ion-beam Application(MOE),Fudan University,Shanghai 200433,China;School of Physical Sciences,University of Chinese Academy of Science,Beijing 100049,China;Center for High Energy Physics,Peking University,Beijing 100871,China)

机构地区：[1]Institute of High Energy Physics,Chinese Academy of Sciences,Beijing 100049,China [2]School of Physics,Nanjing University,Nanjing 210093,China [3]Department of Physics and Center for Field Theory and Particle Physics,Fudan University,Shanghai 200438,China [4]Key Laboratory of Nuclear Physics and Ion-beam Application(MOE),Fudan University,Shanghai 200433,China [5]School of Physical Sciences,University of Chinese Academy of Science,Beijing 100049,China [6]Center for High Energy Physics,Peking University,Beijing 100871,China

出　　处：《Chinese Physics C》2022年第11期118-142,共25页中国物理C（英文版）

基　　金：supported by National Natural Science Foundation of China(NSFC)(12035008);supported by NSFC(12122507)。

摘　　要：In the standard model effective field theory,operators involving the top quark are generally difficult to probe and can generate sizable loop contributions to electroweak precision observables measured by past and future lepton colliders.Could the high precision of electroweak measurements compensate for loop suppression and provide competitive reaches on these operators?Would the inclusion of these contributions introduce too many additional parameters for a meaningful global electroweak analysis to be performed?In this paper,we perform a detailed phenomenological study to address these two important questions.Focusing on eight dimension-6 operators that generate anomalous couplings between electroweak gauge bosons and third-generation quarks,we calculate their one loop contributions to e^(+)e^(-)→ff processes,both on and off the Z-pole,and the e^(+)e^(-)→WW process.A global analysis is performed with these eight operators and those that contribute to the above processes at tree level using measurements at the LEP,SLC,and several low energy experiments.We find that although current electroweak precision measurements are sensitive to the one-loop effects of top-quark operators,it is difficult to separate them from the operators that contribute at tree level,making a global analysis rather challenging.Under further assumptions(for instance,new physics contributes to only third generation quark operators and the S and T parameters),competitive reaches may be obtained in a global fit.Another important finding of our study is that the two operators that generate the dipole interactions of the bottom quark have a significant impact on the Z-pole measurements and should not be omitted.We also discuss the implications of the recently reported W-boson mass measurement at the CDF for our results.Finally,we estimate the reaches of future lepton colliders in probing top-quark operators with precision electroweak measurements.

关 键 词：loop-induced processes effective field theory Monte Carlo generator top quark 

分 类 号：O572.33[理学—粒子物理与原子核物理]