We study the impact of recent measurements of charm cross section H1-ZEUS combined data on simultaneous determination of parton distribution functions（PDFs） and the strong coupling,α_s（M_Z^2）,in two different sch...We study the impact of recent measurements of charm cross section H1-ZEUS combined data on simultaneous determination of parton distribution functions（PDFs） and the strong coupling,α_s（M_Z^2）,in two different schemes.We perform several fits based on Thorne-Roberts（RT） and Thorne-Roberts optimal（RTOPT） schemes at next-to-leading order（NLO）.We show that adding charm cross section H1-ZEUS combined data reduces the uncertainty of the gluon distribution and improves the fit quality up to ～0.4% and ～0.9%,without and with the charm contribution,from the RT scheme to the RTOPT scheme,respectively.We also emphasise the central role of the strong coupling,α_s（M_Z^2）,in revealing the impact of charm flavour contribution,when it is considered as an extra free parameter.We show that in going from the RT scheme to the RT OPT scheme,we get ～0.9% and ～2.0% improvement in the value of α_s（M_Z^2）,without and with the charm flavour contribution respectively.展开更多
We determine the strong coupling constant α s up to 4-loop in perturbative QCD.Testing QCD requires the measurement of α s over ranges of energy scales.In this analysis,the value of α s is determined from the unpol...We determine the strong coupling constant α s up to 4-loop in perturbative QCD.Testing QCD requires the measurement of α s over ranges of energy scales.In this analysis,the value of α s is determined from the unpolarized structure functions data points by minimizing the χ ^2 function between the theory result and experimental data.Using perturbative QCD calculations from threshold corrections,we obtain α s （M 2 Z ） = 0.1139±0.0020 at N ^3 LO which is in good agreement with the very recently results from the inclusive jet cross section in pp collisions at√ s=1.96 TeV.展开更多
文摘We study the impact of recent measurements of charm cross section H1-ZEUS combined data on simultaneous determination of parton distribution functions（PDFs） and the strong coupling,α_s（M_Z^2）,in two different schemes.We perform several fits based on Thorne-Roberts（RT） and Thorne-Roberts optimal（RTOPT） schemes at next-to-leading order（NLO）.We show that adding charm cross section H1-ZEUS combined data reduces the uncertainty of the gluon distribution and improves the fit quality up to ～0.4% and ～0.9%,without and with the charm contribution,from the RT scheme to the RTOPT scheme,respectively.We also emphasise the central role of the strong coupling,α_s（M_Z^2）,in revealing the impact of charm flavour contribution,when it is considered as an extra free parameter.We show that in going from the RT scheme to the RT OPT scheme,we get ～0.9% and ～2.0% improvement in the value of α_s（M_Z^2）,without and with the charm flavour contribution respectively.
文摘We determine the strong coupling constant α s up to 4-loop in perturbative QCD.Testing QCD requires the measurement of α s over ranges of energy scales.In this analysis,the value of α s is determined from the unpolarized structure functions data points by minimizing the χ ^2 function between the theory result and experimental data.Using perturbative QCD calculations from threshold corrections,we obtain α s （M 2 Z ） = 0.1139±0.0020 at N ^3 LO which is in good agreement with the very recently results from the inclusive jet cross section in pp collisions at√ s=1.96 TeV.
