Related papers: Gluon Spin in a Quark Model
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 calculate polarization asymmetries in photoproduction of high transverse momentum mesons, focusing on charged pions, considering the direct, fragmentation, and resolved photon processes. The results at very high meson momentum measure…
We suggest a method of constructing gauge invariant quark and gluon distributions that describe an abstract QCD observable and apply this method to analyze angular momentum of a hadron. In addition to the known quark and gluon polarized…
The fundamental program in high energy spin physics focuses on the spin structure of the nucleon. The gluon and orbital angular momentum components of the nucleon spin are virtually unknown. The J_z=1/2 sum rule involves the integrated…
We present a preliminary measurement of the gluon polarization Delta G/G in the nucleon, based on the spin asymmetry of quasi-real photoproduction events for which a pair of large transverse momentum hadrons is produced. The data were…
Determination of the orbital angular momentum of the proton is a difficult but important part of understanding fundamental structure. Insight can be gained from suitable models of the gluon asymmetry applied to the Jz = 1/2 sum rule. We…
We report a state-of-the-art lattice QCD calculation of the total gluon helicity contribution to the proton spin, $\Delta G$. The calculation is done on ensembles with three different lattice spacings $a=\{0.08, 0.09, 0.11\}$ fm. By…
The gluon polarization $\Delta G$ in a nucleon can be defined in a gauge invariant way as the integral over the Ioffe-time distribution of polarized gluons. We argue that for sufficiently regular polarized gluon distributions $\Delta G$ is…
In order to determine polarized parton densities in nucleon we have made fits using all experimental data on spin asymmetries measured in the deep inelastic scattering on different nucleon targets. We have used in our analysis next to…
The absence of "valence-gluon" degrees of freedom combined with an examination of radiative QCD diagrams leads to an implication that the gluon spin asymmetry in a proton, defined as A_G(x,Q^2) = (Delta G)/G, should be approximately Q^2…
The double helicity asymmetry in neutral pion production for p_T = 1 to 12 GeV/c has been measured with the PHENIX experiment in order to access the gluon spin contribution, Delta-G, to the proton spin. Measured asymmetries are consistent…
We present a determination of the gluon polarisation Delta g/g in the nucleon, based on the longitudinal double-spin asymmetry of DIS events with a pair of large transverse-momentum hadrons in the final state. The data were obtained by the…
Measurements involving the gluon spin density, Delta G=G++ - G+-, can play an important role in the quantitative understanding of proton structure. To demonstrate this, we show that the shape of the gluon asymmetry, A(x,t)=Delta…
We present a calculation of Wigner distributions for gluons in light-front dressed quark model. We calculate the kinetic and canonical gluon orbital angular momentum and spin-orbit correlation of the gluons in this model.
The orbital angular momentum is one of the least understood of the spin characteristics of a proton. There are no direct ways to model the orbital angular momentum. However, the Jz=1/2 sum rule includes an angular momentum component and can…
We have measured the spin-dependent structure function $g_1^p$ in inclusive deep-inelastic scattering of polarized muons off polarized protons, in the kinematic range $0.003 < x < 0.7$ and $1 GeV^2 < Q^2 < 60 GeV^2$. A next-to-leading order…
In the past few years, a lot of evidences have been accumulated, which indicate that the gluon polarization inside the nucleon is likely to be small at least at the low renormalization scales. On the other hand, the recent lattice QCD…
Longitudinal double-spin asymmetries of charged hadrons with high transverse momentum $p_T$ have been measured in electroproduction using the \hermes\ detector at \hera. Processes involving gluons in the nucleon have been enhanced relative…
We present a measurement of the longitudinal spin cross section asymmetry for deep inelastic muon-nucleon interactions with two high transverse momentum hadrons in the final state. Two methods of event classification are used to increase…
We calculate the quark orbital angular momentum of the nucleon from the quark energy-momentum tensor form factors on the lattice. The disconnected insertion is estimated stochastically which employs the $Z_2$ noise with an unbiased…