“School of Particles And Accelerator”

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Paper   IPM / Particles And Accelerator / 14323
School of Particles and Accelerator
  Title:   Next-to-next-to-leading order QCD analysis of spin-dependent parton distribution functions and their uncertainties: Jacobi polynomials approach
1.  Fatemeh Taghavi-Shahri
2.  Hamzeh Khanpour
3.  Shahin Atashbar Tehrani
4.  Zahra Alizadehyazdi
  Status:   Published
  Journal: Phys. Rev. D
  No.:  114024
  Vol.:  93
  Year:  2016
  Supported by:  IPM
We present a first global QCD analysis of next-to-next-leading-order (NNLO) contributions of the spin-dependent parton distribution functions (PPDFs) and their uncertainties using the Jacobi polynomial approach. Having the NNLO contributions of the quark-quark and gluon-quark splitting functions in perturbative QCD (Nucl. Phys. B 889 (2014) 351-400), one can obtain the evolution of longitudinally polarized parton densities of hadrons up to NNLO accuracy of QCD. A very large sets of recent and up-to-date experimental data of spin structure functions of the proton g1p, neutron g1n, and deuteron g1d have been used in this analysis. The predictions for the NNLO calculations of the polarized parton distribution functions as well as the proton, neutron and deuteron polarized structure functions are compared with the corresponding results of the NLO approximation. We form a mutually consistent set of polarized PDFs due to the inclusion of the most available experimental data including the recently published data from COMPASS16 experiments (Phys. Lett. B 753 (2016) 18-28). We have performed a careful estimation of the uncertainties using the most common and practical method, the Hessian method, for the polarized PDFs originating from the experimental errors. The proton, neutron and deuteron structure functions and also their first moments, Γp, n, d, are in good agreement with the experimental data at small and large momentum fraction of x. We will discuss how our knowledge of spin-dependence structure functions may be improved at small and large value of x by the recent COMPASS16 measurements at CERN, the PHENIX and STAR measurements at RHIC, and at the future proposed colliders such as Electron-Ion collider (EIC).

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