Abstract
We present, for the first time, an abinitio calculation of the individual up, down, and strange quark helicity parton distribution functions for the proton. The calculation is performed within the twisted mass clover-improved fermion formulation of lattice QCD. The analysis is performed using one ensemble of dynamical up, down, strange, and charm quarks with a pion mass of 260MeV. The lattice matrix elements are nonperturbatively renormalized and the final results are presented in the MS[over ¯] scheme at a scale of 2GeV. We give results for Δu^{+}(x), Δd^{+}(x) Δu^{-}(x), Δd^{-}(x), including disconnected quark loop contributions, as well as for Δs^{+}(x) and Δs^{-}(x). For the latter we achieve unprecedented precision compared to the phenomenological estimates.
Highlights
For the first time, an ab initio calculation of the individual up, down, and strange quark helicity parton distribution functions for the proton
The cross section of such processes can be factorized into a component calculated in perturbative quantum chromodynamics (QCD), and a nonperturbative part expressed in terms of the partonic densities
The latter are the parton distribution functions (PDFs), generalized parton distributions (GPDs), and transverse momentum distribution functions (TMDs), which are necessary for the threedimensional mapping of the hadrons
Summary
Constantia Alexandrou ,1,2 Martha Constantinou, Kyriakos Hadjiyiannakou, Karl Jansen, and Floriano Manigrasso 1,5,6. Introduction.—The theory of the strong interaction, quantum chromodynamics (QCD), describes the structure of hadrons in terms of their constituent quark and gluons (partons), via distribution functions. These are universal quantities and, can be accessed by a variety of high-energy scattering processes. The cross section of such processes can be factorized into a component calculated in perturbative QCD, and a nonperturbative part expressed in terms of the partonic densities The latter are the parton distribution functions (PDFs), generalized parton distributions (GPDs), and transverse momentum distribution functions (TMDs), which are necessary for the threedimensional mapping of the hadrons.
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