Probing top-quark couplings indirectly at Higgs factories  

作　　者：Gauthier Durieux Jiayin Gu Eleni Vryonidou Cen Zhang Gauthier Durieux;顾嘉荫;Eleni Vryonidou;张岑(DESY NotkestraBe 85,D-22607,Hamburg,Germany;PRISMA Cluster of Excellence,Institut fur Physik,Johannes Gutenberg-University,55099 Mainz,Germany;Theoretical Physics Department,CERN,1211 Geneva 23,Switzerland;Institute of High Energy Physics,and School of Physical Sciences,University of Chinese Academy of Sciences,Beijing 100049,China)

机构地区：[1]DESY Notkestratle 85,D-22607,Hamburg,Germany [2]PRISMA Cluster of Excellence,Institut ffir Physik,Johannes Gutenberg-Universitgt,55099 Mainz,Germany [3]Theoretical Physics Department,CERN,1211 Geneva 23,Switzerland [4]Institute of High Energy Physics,and School of Physical Sciences,University of Chinese Academy of Sciences,Beijing 100049,China

出　　处：《Chinese Physics C》2018年第12期53-65,共13页中国物理C（英文版）

基　　金：supported by IHEP(Y7515540U1);supported by a Marie Sk lodowska-Curie Individual Fellowship of the European Commission’s Horizon 2020 Programme(704187)

摘　　要：We perform a global effective-field-theory analysis to assess the combined precision of Higgs couplings, triple gauge-boson couplings, and top-quark couplings, at future circular e＋e- colliders, with a focus on runs below the tt-production threshold. Deviations in the top-quark sector entering as one-loop corrections are consistently taken into account in the Higgs and diboson processes. We find that future lepton colliders running at center-of-mass energies below the tt production threshold can still provide useful information on top-quark couplings, by measuring virtual top-quark effects. With rate and differential measurements, the indirect individual sensitivity achievable is better than at the high-luminosity LHC. However, strong correlations between the extracted top-quark and Higgs couplings are also present and lead to much weaker global constraints on top-quark couplings. This implies that a direct probe of top-quark couplings above the t~ production threshold is also helpful for the determination of Higgs and triple-gauge-boson couplings. In addition, we find that below the e＋e- -＋tth production threshold, the top-quark Yukawa coupling can be determined by its loop corrections to all Higgs production and decay channels. Degeneracy with the ggh coupling can be resolved, and even a global limit is competitive with the prospects of a linear collider above the threshold. This provides an additional means of determining the top-quark Yukawa coupling indirectly at lepton colliders.We perform a global effective-field-theory analysis to assess the combined precision of Higgs couplings, triple gauge-boson couplings, and top-quark couplings, at future circular e＋e- colliders, with a focus on runs below the tt-production threshold. Deviations in the top-quark sector entering as one-loop corrections are consistently taken into account in the Higgs and diboson processes. We find that future lepton colliders running at center-of-mass energies below the tt production threshold can still provide useful information on top-quark couplings, by measuring virtual top-quark effects. With rate and differential measurements, the indirect individual sensitivity achievable is better than at the high-luminosity LHC. However, strong correlations between the extracted top-quark and Higgs couplings are also present and lead to much weaker global constraints on top-quark couplings. This implies that a direct probe of top-quark couplings above the t~ production threshold is also helpful for the determination of Higgs and triple-gauge-boson couplings. In addition, we find that below the e＋e- -＋tth production threshold, the top-quark Yukawa coupling can be determined by its loop corrections to all Higgs production and decay channels. Degeneracy with the ggh coupling can be resolved, and even a global limit is competitive with the prospects of a linear collider above the threshold. This provides an additional means of determining the top-quark Yukawa coupling indirectly at lepton colliders.

关 键 词：effective field theory top quark lepton collider 

分 类 号：O572.33[理学—粒子物理与原子核物理]