Parton

About: Parton is a research topic. Over the lifetime, 13484 publications have been published within this topic receiving 368877 citations.

Testing the Universality of Fragmentation Functions

Abstract: Using fragmentation functions for charged pions, charged kaons, and (anti)protons recently extracted from experimental data of e^+e^- annihilation at the Z-boson resonance and at centre-of-mass energy root(s) = 29 GeV, we perform a global study of inclusive charged-hadron production in p anti-p, gamma p, and gamma gamma collisions at next-to-leading order in the parton model of quantum chromodynamics. Comparisons of our results with p anti-p data from CERN S p anti-p S and the Fermilab Tevatron, gamma p data from DESY HERA, and gamma gamma data from CERN LEP2 allow us to test the universality of the fragmentation functions predicted by the factorization theorem. Furthermore, we perform comparisons with (e^+e^-)-annihilation data from LEP2 so as to test the scaling violations predicted by the Altarelli-Parisi evolution equations.

Sivers effect in semiinclusive deeply inelastic scattering

Abstract: The Sivers function is extracted from HERMES data on single spin asymmetries in semi-inclusive deeply inelastic scattering. Our analysis use a simple Gaussian model for the distribution of transverse parton momenta, together with the flavor dependence given by the leading 1/N{sub c} approximation and a neglect of the Sivers antiquark distribution. We find that within the errors of the data these approximations are sufficient.

Nuclear parton distribution functions from neutrino deep inelastic scattering

Abstract: We study nuclear effects in charged current deep inelastic neutrino--iron scattering in the framework of a chi^2-analysis of parton distribution functions. We extract a set of iron PDFs and show that under reasonable assumptions it is possible to constrain the valence, light sea and strange quark distributions. We compare our results with nuclear parton distribution functions from the literature and find good agreement. Our iron PDFs are used to compute nuclear correction factors which are required in global analyses of free nucleon PDFs.

Single soft gluon emission at two loops

Abstract: We study the single soft-gluon current at two loops with two energetic partons in massless perturbative QCD, which describes, for example, the soft limit of the two-loop amplitude for gg → Hg. The results are presented as Laurent expansions in ϵ in D = 4 − 2ϵ spacetime dimension. We calculate the expansion to order ϵ 2 analytically, which is a necessary ingredient for Higgs production at hadron colliders at next-to-next-to-next-to-leading order in the soft-virtual approximation. We also give two-loop results of the single soft-gluon current in $ \mathcal{N}=4 $ Super-Yang-Mills theory, and find that it has uniform transcendentality. By iteration relation of splitting amplitudes, our calculations can determine the three-loop single soft-gluon current to order ϵ 0 in $ \mathcal{N}=4 $ Super-Yang-Mills theory in the limit of large N c .