In this study,we reanalyze the top-quark pair production at next-to-next-to-leading order(NNLO)in quantum chromodynamics(QCD)at future e^(+)e^(−)colliders using the Principle of Maximum Conformality(PMC)method.The PMC...In this study,we reanalyze the top-quark pair production at next-to-next-to-leading order(NNLO)in quantum chromodynamics(QCD)at future e^(+)e^(−)colliders using the Principle of Maximum Conformality(PMC)method.The PMC renormalization scales inαs are determined by absorbing the non-conformalβterms by recursively using the Renormalization Group Equation(RGE).Unlike the conventional scale-setting method of fixing the scale at the center-of-mass energyμ_(r)=√s,the determined PMC scale Q_(⋆)is far smaller than the √sand increases with the √s,yielding the correct physical behavior for the top-quark pair production process.Moreover,the convergence of the pQCD series for the top-quark pair production is greatly improved owing to the elimination of the renormalon divergence.For a typical collision energy of √s=500 GeV,the PMC scale is Q_(⋆)=107 GeV;the QCD correction factor K for conventional results is K∼1+0.1244+0.0102+0.0012−0.0087−0.0011+0.0184−0.0086+0.0002+0.0061−0.0003,where the first error is caused by varying the scaleμr∈[√s/2,2√s]and the second error is from the top-quark massΔm_(t)=±0.7 GeV.After applying the PMC,the renormalization scale uncertainty is eliminated,and the QCD correction factor K is improved to K∼1+0.1507_(−0.0015)^(+0.0015)−0.0057_(−0.0000)^(+0.0001),where the error is from the top-quark massΔm_(t)=±0.7 GeV.The PMC improved predictions for the top-quark pair production are helpful for detailed studies of the properties of the top-quark at future e^(+)e^(−)colliders.展开更多
By applying the Error PDF Updating Method,we analyze the impact of the absolute and normalized single differential cross-sections for top-quark pair production data from the ATLAS and CMS experiments at the Large Hadr...By applying the Error PDF Updating Method,we analyze the impact of the absolute and normalized single differential cross-sections for top-quark pair production data from the ATLAS and CMS experiments at the Large Hadron Collider,at a center-of-mass energy of √s=8TeV,on the CT14HERA2 PDFs.We find that the top quark pair single differential distributions provide minor constraints on the CT14HERA2 gluon PDF when the nominal CT14HERA2 inclusive jet production data are included in the fit.Larger constraints on the gluon distribution are present when the jet data are removed(CT14HERA2mJ)and/or when increased weights are given to the top data in the CT14HERA2 fits.The weighted$t\bar t$data provide significant constraints on the CT14HERA2mJ gluon PDF,which are comparable to those obtained from inclusive jet production data.Furthermore,we examine the top quark mass sensitivity of the top-quark pair single differential distributions.展开更多
In this study,we calculate the tt pQCD production cross-section at the NNLO and determine the top-quark pole mass from recent measurements at the LHC at the center-of-mass energy √S=13 TeV to a high precision by appl...In this study,we calculate the tt pQCD production cross-section at the NNLO and determine the top-quark pole mass from recent measurements at the LHC at the center-of-mass energy √S=13 TeV to a high precision by applying the principle of maximum conformality(PMC).The PMC provides a systematic method that rigorously eliminates QCD renormalization scale ambiguities by summing the nonconformalβcontributions into the QCD coupling constant.The PMC predictions satisfy the requirements of renormalization group invariance,including renormalization scheme independence,and the PMC scales accurately reflect the virtuality of the underlying production subprocesses.By using the PMC,an improved prediction for the tt production cross-section is obtained without scale ambiguities,which in turn provides a precise value for the top-quark pole mass.Moreover,the prediction of PMC calculations that the magnitudes of higher-order PMC predictions are well within the error bars predicted from the known lower-order has been demonstrated for the top-quark pair production.The resulting determination of the top-quark pole mass,m^(pole)_(t)=172.5±1.4 GeV,from the LHC measurement at √S=13 TeV agrees with the current world average cited by the Particle Data Group(PDG).The PMC prediction provides an important high-precision test of the consistency of pQCD and the SM at √S=13 TeV with previous LHC measurements at lower CM energies.展开更多
The Large Hadron Collider at CERN is performing direct searches for top-quark anomalous flavorchanging neutral current(FCNC)processes.However,these processes may be correlated closely with the lowenergy rare B and K m...The Large Hadron Collider at CERN is performing direct searches for top-quark anomalous flavorchanging neutral current(FCNC)processes.However,these processes may be correlated closely with the lowenergy rare B and K meson decays.In this paper,we review the anomalous top-quark coupling effects in these low-energy flavor transitions,summarize the flavor constraints and discuss their implications for direct detection of top-FCNC processes at the Large Hadron Collider.展开更多
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 ...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.展开更多
基金the Natural Science Foundation of China(12175025,12147102,12265011)by the Projects of Guizhou Provincial Department(YQK[2023]016,ZK[2023]141,[2020]1Y027,GZMUZK[2022]PT01)。
文摘In this study,we reanalyze the top-quark pair production at next-to-next-to-leading order(NNLO)in quantum chromodynamics(QCD)at future e^(+)e^(−)colliders using the Principle of Maximum Conformality(PMC)method.The PMC renormalization scales inαs are determined by absorbing the non-conformalβterms by recursively using the Renormalization Group Equation(RGE).Unlike the conventional scale-setting method of fixing the scale at the center-of-mass energyμ_(r)=√s,the determined PMC scale Q_(⋆)is far smaller than the √sand increases with the √s,yielding the correct physical behavior for the top-quark pair production process.Moreover,the convergence of the pQCD series for the top-quark pair production is greatly improved owing to the elimination of the renormalon divergence.For a typical collision energy of √s=500 GeV,the PMC scale is Q_(⋆)=107 GeV;the QCD correction factor K for conventional results is K∼1+0.1244+0.0102+0.0012−0.0087−0.0011+0.0184−0.0086+0.0002+0.0061−0.0003,where the first error is caused by varying the scaleμr∈[√s/2,2√s]and the second error is from the top-quark massΔm_(t)=±0.7 GeV.After applying the PMC,the renormalization scale uncertainty is eliminated,and the QCD correction factor K is improved to K∼1+0.1507_(−0.0015)^(+0.0015)−0.0057_(−0.0000)^(+0.0001),where the error is from the top-quark massΔm_(t)=±0.7 GeV.The PMC improved predictions for the top-quark pair production are helpful for detailed studies of the properties of the top-quark at future e^(+)e^(−)colliders.
基金The work of S.Dulat was supported by the National Natural Science Foundation of China(11965020,11847160)。
文摘By applying the Error PDF Updating Method,we analyze the impact of the absolute and normalized single differential cross-sections for top-quark pair production data from the ATLAS and CMS experiments at the Large Hadron Collider,at a center-of-mass energy of √s=8TeV,on the CT14HERA2 PDFs.We find that the top quark pair single differential distributions provide minor constraints on the CT14HERA2 gluon PDF when the nominal CT14HERA2 inclusive jet production data are included in the fit.Larger constraints on the gluon distribution are present when the jet data are removed(CT14HERA2mJ)and/or when increased weights are given to the top data in the CT14HERA2 fits.The weighted$t\bar t$data provide significant constraints on the CT14HERA2mJ gluon PDF,which are comparable to those obtained from inclusive jet production data.Furthermore,we examine the top quark mass sensitivity of the top-quark pair single differential distributions.
基金Supported in part by the Natural Science Foundation of China (11625520, 11705033, 11905056, 11947406)the Project of Guizhou Provincial Department(KY[2021]003)the Department of Energy Contract (DE-AC02-76SF00515. SLAC-PUB-17567)
文摘In this study,we calculate the tt pQCD production cross-section at the NNLO and determine the top-quark pole mass from recent measurements at the LHC at the center-of-mass energy √S=13 TeV to a high precision by applying the principle of maximum conformality(PMC).The PMC provides a systematic method that rigorously eliminates QCD renormalization scale ambiguities by summing the nonconformalβcontributions into the QCD coupling constant.The PMC predictions satisfy the requirements of renormalization group invariance,including renormalization scheme independence,and the PMC scales accurately reflect the virtuality of the underlying production subprocesses.By using the PMC,an improved prediction for the tt production cross-section is obtained without scale ambiguities,which in turn provides a precise value for the top-quark pole mass.Moreover,the prediction of PMC calculations that the magnitudes of higher-order PMC predictions are well within the error bars predicted from the known lower-order has been demonstrated for the top-quark pair production.The resulting determination of the top-quark pole mass,m^(pole)_(t)=172.5±1.4 GeV,from the LHC measurement at √S=13 TeV agrees with the current world average cited by the Particle Data Group(PDG).The PMC prediction provides an important high-precision test of the consistency of pQCD and the SM at √S=13 TeV with previous LHC measurements at lower CM energies.
基金supported by the National Natural Science Foundation of China (11225523 and 11221504)supported by the CCNU-QLPL Innovation Fund (QLPL2011P01)the Excellent Doctorial Dissertation Cultivation Grant from Central China Normal University
文摘The Large Hadron Collider at CERN is performing direct searches for top-quark anomalous flavorchanging neutral current(FCNC)processes.However,these processes may be correlated closely with the lowenergy rare B and K meson decays.In this paper,we review the anomalous top-quark coupling effects in these low-energy flavor transitions,summarize the flavor constraints and discuss their implications for direct detection of top-FCNC processes at the Large Hadron Collider.
基金supported by IHEP(Y7515540U1)supported by a Marie Sk lodowska-Curie Individual Fellowship of the European Commission’s Horizon 2020 Programme(704187)
文摘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.
