QCD analysis of DIS and SIDIS data with two alternative methods

• Published in: Physics of particles and nuclei 2014-01, Vol.45 (1), p.40-42
• Main Authors: Shevchenko, O. Yu, Akhunzyanov, R. R.
• Format: Article
• Language: English
• Subjects: DISTRIBUTION; Particle and Nuclear Physics; PARTICLE PRODUCTION; Physics; Physics and Astronomy; PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; PROTONS; QUANTUM CHROMODYNAMICS; S QUARKS; SEAS; Session 1. Spin Structure of Hadrons; SPIN
• ISSN: 1063-7796; 1531-8559
• DOI: 10.1134/S1063779614010936

The global fit analysis of all published data on DIS and semi-inclusive DIS (SIDIS) asymmetries is performed in the next to leading (NLO) QCD order. The respective parameterization on polarized PDFs is constructed. The especial attention is paid to the impact of novel SIDIS data on the polarized distributions of light sea and strange quarks as well as on the polarized gluon distributions. The first moments of these distributions entering the nucleon spin are found to be surprisingly small quantities. The alternative direct (free of any fitting procedure) method of NLO QCD analysis is elaborated. Method is especially important for analysis of SIDIS data because it allows to avoid the problems arising in the conventional fitting procedure: functional arbitrariness at initial scale and ambiguities in the error band calculation. Within the alternative method the central values and uncertainties of the measured asymmetries directly propagate to the central values and uncertainties of the polarized PDFs we are interested in. The method is applied to all existing SIDIS data on pion production for an estimation in NLO QCD of the valence and sea quark contributions to the proton spin. As a result one arrives at the conclusion that, contrary to the valence contributions, the sea contributions to the proton spin are compatible with zero within the errors.