ABM11 PDFs and the cross section benchmarks in NNLO

Abstract

We report an updated version of the ABKM09 NNLO PDF fit, which includes the most recent HERA collider data on the inclusive cross sections and an improved treatment of the heavy-quark contribution to deep-inelastic scattering using advantages of the running-mass definition for the heavy quarks. The ABM11 PDFs obtained from the updated fit are in a good agreement with the recent LHC data on the W- and Z-production within the experimental and PDF uncertainties. We also perform a determination of the strong coupling constant α_s in a variant of the ABM11 fit insensitive to the influence of the higher twist terms and find the value of α_s=0.1133(11) which is in good agreement with the nominal ABM11 one and our earlier determination.

Figures (7)

• Figure 1: The data on $F_L$ versus $x$ obtained by the H1 collaboration Collaboration:2010ry confronted with the 3-flavor scheme NNLO predictions based on the different PDFs (solid line: this analysis, dashes: JR09 JimenezDelgado:2008hf, dots: MSTW Martin:2009iq). The NLO predictions based on the 3-flavor NN21 PDFs Ball:2011mu are given for comparison (dashed dots). The value of $Q^2$ for the data points and the curves in the plot rises with $x$ in the range of $1.5 \div 45~{\rm GeV}^2$.
• Figure 2: The charm- (left) and the bottom-quark (right) PDFs obtained in the fit: The dotted (red) lines denote the $\pm 1 \sigma$ band of relative uncertainties (in percent) and the solid (red) line indicates the central prediction resulting from the fit with the running masses taken at the PDG values. For comparison the shaded (grey) area represents the results of ABKM09 Alekhin:2009ni.
• Figure 3: The $\chi^2$-profile versus the value of $\alpha_s(M_Z)$, for the separate data subsets, all obtained in variants of the present analysis with the value of $\alpha_s$ fixed and all other parameters fitted (solid lines: NNLO fit, dashes: NLO fit).
• Figure 4: The ATLAS data of Ref. Aad:2011dm on the rapidity distribution of the charged leptons $l^-$ (left panel), $l^+$ (central panel), and $Z$-boson (right panel) in comparison with the NNLO predictions computed with the ABM11 PDFs taking into account the uncertainties due to PDFs (shaded area). The dashed curves display the ABM11 predictions obtained with the value of $\alpha_s(M_Z)=0.118$.
• Figure 5: The same as Fig. \ref{['fig:atlas']} for the CMS data of Ref. Chatrchyan:2012xt on the electron asymmetry rapidity distribution. The curve corresponding to the ABM11 predictions obtained with the value of $\alpha_s(M_Z)=0.118$ coincides with the nominal one.