The 3-, 4-, and 5-flavor NNLO Parton from Deep-Inelastic-Scattering Data and at Hadron Colliders

TL;DR

This paper performs a comprehensive NNLO QCD analysis of deep-inelastic scattering data to determine parton distribution functions across 3, 4, and 5 flavors, providing precise measurements of the strong coupling constant and predictions for collider processes.

Contribution

It introduces a detailed NNLO PDF analysis with matching conditions across flavor schemes and compares different schemes for charm-quark contributions, enhancing the accuracy of PDFs and collider predictions.

Findings

NNLO strong coupling constant measured at about 0.113

Derived PDFs for 3, 4, and 5 flavors with matching conditions

Predicted cross sections for key collider processes at Tevatron and LHC

Abstract

We determine the parton distribution functions (PDFs) in a next-to-next-to-leading order (NNLO) QCD-analysis of the inclusive neutral-current deep-inelastic-scattering (DIS) world data combined with the neutri{-}no-nucleon DIS di-muon data and the fixed-target Drell-Yan data. The PDF-evolution is performed in the $N_f = 3$ fixed-flavor scheme and supplementary sets of PDFs in the 4- and 5-flavor schemes are derived from the results in the 3-flavor scheme using matching conditions. The charm-quark DIS contribution is calculated in a general-mass variable-flavor-number (GMVFN) scheme interpolating between the zero-mass 4-flavor scheme at asymptotically large values of momentum transfer $Q^2$ and the 3-flavor scheme prescription of Buza-Matiounine-Smith-van Neerven (BMSN) at the value of $Q^2 = m_c^2$. The results in the GMVFN scheme are compared with those of the fixed-flavor scheme and other prescriptions used in global fits of PDFs. The strong coupling constant is measured at an accuracy of $\approx 1.5%$. We obtain at NNLO $\alpha_s(M_Z^2) = 0.1135 \pm 0.0014$ in the fixed-flavor scheme and $\alpha_s(M_Z^2) = 0.1129 \pm 0.0applying the BMSN-prescription. The implications for important standard candle and hard scattering processes at hadron colliders are illustrated. Predictions for cross sections of $W^{\pm}$- and $Z$-boson, the top-quark pair- and Higgs-boson production at the Tevatron and the LHC based on the 5-flavor PDFs of the present analysis are provided.014$