Parton distribution functions, αs , and heavy-quark masses for LHC Run II

Abstract

We determine a new set of parton distribution functions (ABMP16), the strong coupling constant $\alpha_s$ and the quark masses $m_c$, $m_b$ and $m_t$ in a global fit to next-to-next-to-leading order (NNLO) in QCD. The analysis uses the $\overline{\mathrm{MS}}$ scheme for $\alpha_s$ and all quark masses and is performed in the fixed-flavor number scheme for $n_f=3, 4, 5$. Essential new elements of the fit are the combined data from HERA for inclusive deep-inelastic scattering (DIS), data from the fixed-target experiments NOMAD and CHORUS for neutrino-induced DIS, and data from Tevatron and the LHC for the Drell-Yan process and the hadro-production of single-top and top-quark pairs. The theory predictions include new improved approximations at NNLO for the production of heavy quarks in DIS and for the hadro-production of single-top quarks. The description of higher twist effects relevant beyond the leading twist collinear factorization approximation is refined. At NNLO we obtain the value $\alpha_s^{(n_f=5)}(M_Z) = 0.1147 \pm 0.0008$.