Related papers: Proton spin in double-logarithmic approximation
We present a next-to-next-to-leading order (NNLO) global QCD analysis of the proton's helicity parton distribution functions (PDFs), the first of its kind. To obtain the distributions, we use data for longitudinal spin asymmetries in…
We present a measurement of the double longitudinal spin asymmetry in inclusive pi^0 production in polarized proton-proton collisions at sqrt(s)=200 GeV. The data were taken at the Relativistic Heavy Ion Collider with average beam…
The prompt photon production in p-p collisions at high energies is studied. Double-spin asymmetry of the process is calculated by using Monte Carlo code SPHINX. A possibility to discriminate the spin-dependent gluon distributions and to…
Jet production in polarized $p+p$ collisions at $\sqrt{s} = 200$ GeV and $\sqrt{s} = 500$ GeV provides a powerful probe to study gluons inside the proton. The Solenoidal Tracker at RHIC (STAR) has the capability, with nearly full azimuthal…
The differential cross-sections are calculated for proton-proton and proton-antiproton elastic scattering using the phenomenological model based on the analytic parameterizations for global scattering parameters (total cross-section and…
The parton distributions in the proton are evaluated dynamically using a nonlinear QCD evolution equation - the DGLAP equation with twist-4 (the GLR-MQ-ZSR) corrections - starting from a low scale $\mu^2$, where the nucleon consists of…
The production of jets in polarized proton collisions at STAR is dominated by quark-gluon and gluon-gluon scattering processes. The dijet longitudinal double-spin asymmetry $(A_{LL})$ is sensitive to the helicity distributions and may be…
Measurements of double helicity asymmetries for inclusive hadron production in polarized proton-proton collisions are sensitive to spin-dependent parton distribution functions, in particular to the gluon distribution function. This study…
We present expressions for electromagnetic helicity amplitudes and spin observables for any elastic spin 1/2 - spin 1/2 scattering to first order in QED. In particular all electromagnetic helicity amplitudes and spin observables for elastic…
We report on a lattice QCD estimate of the quark spin fraction of the proton spin. The estimate is arrived at by means of a lattice QCD simulation of the polarized proton matrix element of the Adler-Bell-Jackiw anomaly. The preliminary…
We have utilized the concept of valon model to calculate the spin structure functions of proton, neutron and deuteron. The valon structure itself is universal and arises from the perturbative dressing of the valence quark in QCD. Our…
Nontrivial $q \bar q$ sea effects have their origin in the low-$Q^2$ dynamics of strong QCD. We present here a quark model calculation of the contribution of $s \bar s$ pairs arising from a {\it complete} set of OZI-allowed strong $Y^*K^*$…
The contribution to the spin of the proton from the gluon helicity is starting to come into focus: for gluons carrying a large fraction $x$ of the proton momentum, evidence of positive gluon polarization has been observed, via measurements…
We present a Monte Carlo based analysis of the combined world data on polarized lepton-nucleon deep-inelastic scattering at small Bjorken $x$ within the polarized quark dipole formalism. We show for the first time that double-spin…
The spin structure of the proton has revealed itself to be extremely complex and is an area of ongoing research. The Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL) inaugurated its operation as the first…
We recall our recent description of quark parton densities of the proton at $Q^2=4 GeV^2$ in terms of Fermi-Dirac distributions parametrized with very few free parameters. We have also proposed some simple assumptions to relate unpolarized…
We report measurements of the longitudinal double spin asymmetry for inclusive jet production using polarized p+p collisions at sqrt{s} = 200 GeV at RHIC. Results from the 2005 and 2006 runs are presented. These results set substantial new…
We report on recent results of the longitudinal double-spin asymmetry A_LL from the STAR and PHENIX experiments. Data were collected in longitudinally polarized proton-proton collisions at a center-of-mass energy of 200 GeV. The results…
Since the announcement of the proton spin crisis by the European Muon Collaboration there has been considerable progress in unravelling the distribution of spin and orbital angular momentum within the proton. We review the current status of…
This talk consists of four parts. In part one, I give an elementary discussion on constructing a Lorentz-invariant spin sum rule for the nucleon. In part two, I discuss a gauge-dependent spin sum rule, explore its relation with the…