Related papers: Status of the Proton Spin Problem
The anomalous magnetic and electric dipole moments in spin motion equation acquire pseudoscalar corrections if the $T(CP)$-noninvariance is admitted. It allows to explain the discrepancy between experimental and theoretical values of muon…
We consider spin asymmetries for prompt photon production in collisions of longitudinally polarized hadrons. This reaction will be a key tool at the BNL-RHIC pp collider for determining the gluon spin density in a polarized proton. We study…
The operation of HERA with polarized proton and electron beams will allow to study a wide variety of observables in polarized electron-proton collisions at $\sqrt s=300$ GeV. The physics prospects of this project have been elaborated in…
The STAR experiment at the Relativistic Heavy-Ion Collider at Brookhaven National Laboratory is carrying out a spin physics program in high-energy polarized proton collisions at $\sqrt{s}=200\,$GeV and $\sqrt{s}=500\,$GeV to gain a deeper…
More than three decades has passed since the European Muon Collaboration published the first surprising result on the spin structure of the proton. Much theoretical and experimental progress has been made in understanding the origins of the…
One of the primary goals of the RHIC Spin program is to determine the gluon polarization distribution within the proton. At leading order, $pp$ collisions involve a mixture of quark-quark, quark-gluon, and gluon-gluon scattering. In RHIC,…
The inclusive double-spin asymmetry, A_1^p, has been measured at COMPASS in deepinelastic polarised muon scattering off a large polarised NH3 target. The data, collected in the year 2007, cover the range Q2 > 1 (GeV/c)^2, 0.004 < x < 0.7…
Understanding the spin structure of the proton is one of the main challenges in hadronic physics. While the concepts of spin and orbital angular momentum are pretty clear in the context of non-relativistic quantum mechanics, the…
The real, interacting elementary particle always consits of a 'bare' particle and a cloud of virtual particles mediating a self-interaction and/or the bond inside a composite object. In this letter we discuss the question of spin content of…
We study the contribution to the proton's magnetic moment from a heavy quark sea in quantum chromodynamics. The heavy quark is integrated out perturbatively to obtain an effective dimension-6 magnetic moment operator composed of three gluon…
It is pointed out that the meson cloud model predicts a substantial polarization of the sea quarks of the nucleon due to interference of $\pi$ and $\rho$ exchanges. This polarization is strongly flavour dependent. The model gives an…
The object of this brief review is to reconcile different points of view on how the spin of proton is made up from its constituents. On the basis of naive quark model with flavour symmetry such as isospin or SU(3) one finds a static…
After the EMC and subsequent experiments at CERN, SLAC and DESY on the deep inelastic scattering of polarized leptons on polarized nucleons, it is now established that the Q^2=0 value of the axial strange form factor of the nucleon, a…
It is shown that existence of a large anomalous chromomagnetic moment of quark induced by non-perturbative structure of QCD leads to the additional contribution to exclusive $\rho$-meson electroproduction off proton target. The significant…
The model considered in the paper is used nowadays to describe spin dynamics of quantum dots after optical excitation. Based on the exact diagonalization of a model Hamiltonian, we solve the problems of the electron spin polarization decay…
We derive the consequences of the Myhrer-Thomas explanation of the proton spin problem for the distribution of orbital angular momentum on the valence and sea quarks. After QCD evolution these results are found to be in very good agreement…
We present the first simultaneous global QCD analysis of spin-dependent parton distribution functions alongside their spin-averaged counterparts and pion, kaon, and unidentified hadron fragmentation functions. This analysis includes all…
We have made next to leading order QCD fit to the deep inelastic spin asymmetries on nucleons and we determined polarised quark and gluon densities. The functional form for such distributions was inspired by the Martin, Roberts and Stirling…
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…
The proton spin puzzle has inspired a vast programme of experiments and theoretical work challenging our understanding of QCD and its role in the structure of hadrons.The proton's internal spin structure is connected to chiral symmetry and,…