The role of different schemes in the QCD analysis and determination of the strong coupling

Abstract

In this article, we present a Next-to-Leading Order (NLO) QCD analysis to study the role and influence of different schemes on simultaneous determination of the Parton Distribution Functions (PDFs) and strong coupling, α s (M 2 Z ). We perform our analysis based on three different data sets, HERA I and II combined data, H1-ZEUS charm combined data, and H1 and ZEUS beauty production cross sections data, in two different Thorne-Roberts (TR or RT) and Thorne-Roberts Optimal (RT OPT) schemes. We show in going from RT scheme to RT OPT scheme, in addition of reduction the uncertainty of some PDFs, specially for the gluon distribution, we get ∼ 0.4 % and ∼ 0.7 % improvement in the fit quality and ∼ 0.9 % and ∼ 1.6 % improvement for the strong coupling, α s (M 2 Z ), without and with heavy flavor contributions, respectively.

Impact of beauty and charm H1-ZEUS combined measurements on PDFs and determination of the strong coupling

“…A discussion about the three normalization parameters A uv , A dv and A g and some additional constraints which we imposed to Eqs. (9-13) have been reported in Ref [41].…”

“…where α is the fine-structure constant at zero momentum transfer, Y ± = 1 ± (1 − y) 2 , a helicity factor and the photon propagator are absorbed in the definitions of σ ± r,N C and finally,F 2 , xF 3 andF L are the generalized structure functions. Some details about these generalized structure functions have been reported in Ref [41].…”

QCD analysis of structure functions in deep inelastic neutrino-nucleon scattering without using the orthogonal polynomials approach

“…[20], NuTeV [21], CHORUS [22], and CDHSW [23] data sets. [89], BBG [80], MRST03 [92], H1 [93], ZEUS [94], NMC [95], KKT [49], VK17 [60], ABM11 [2], MSTW [5], NNPDF2.1 [96], ABKM09 [97], CT14 [88], ABMP16 [98], HERAPDF [99], and NNLO A02 [90], A06 [91], MRST03 [92], ABMP16 [98], BBG [80], MMMHT [89], NNPDF [100], JR [101], ABKM09 [97], ABM11 [2], H1 and ZEUS [102], MSTW [5], NMC [95], KKT [49], CT14 [88] approximations. The dotted line with yellow band indicates the preaverage results of the strong coupling constant α s (M 2 Z ) in the DIS subfield [81].…”

“…Refs. [60][61][62][63][64][65], we have used the xFitter package for different QCD analyses. Very recently, we presented also a new set of PDFs considering the intrinsic charm content of the proton using this package [66].…”

Impact of recent COMPASS data on polarized parton distributions and structure functions

“…Although these values are extracted from data in the range 1 Figure 9. The strong coupling constant αs(M 2 Z ) values as compared with different QCD analyses at NLO [16,26,37,44,45,48,[87][88][89][90], NNLO [91][92][93][94][95][96][97], and NNNLO [91,98]. The dashed line and yellow band shows the world average αs(M 2 Z ) = 0.1181 ± 0.0011 [99].…”