Related papers: Spin Effects In Diffractive $J/\Psi$ And $Q \Bar Q…
We present microscopic QCD calculation of the cross section of diffractive DIS and of the partonic structure of the pomeron from the dipole approach to the generalized BFKL pomeron. We show that the pomeron can not be treated as a particle…
Exclusive production of $\rho^0$ mesons was studied at the COMPASS experiment by scattering 160 GeV/$c$ muons off transversely polarised protons. Five single-spin and three double-spin azimuthal asymmetries were measured as a function of…
The observation of beam spin asymmetries in two-pion production in semi-inclusive deep inelastic scattering off an unpolarized proton target is reported. The data presented here were taken in the fall of 2018 with the CLAS12 spectrometer…
It is shown how the single spin asymmetry observed in inclusive pion production is related, in the helicity basis, to the imaginary part of the product of two different distribution amplitudes, rather than to the usual quark and gluon…
We investigate the single-spin asymmetries in inclusive and exclusive processes of electron-proton scattering and electron-positron annihilation. In the decomposition of hadronic tensor, a Lorentz symmetric spin-dependent term is generally…
Central pseudoscalar production in $pp$ scattering is suppressed at small values of $Q_\perp$. Such a behavior is expected if the production occurs through the fusion of two vectors. We argue that an extension of the experiment could probe…
Soft diffraction phenomena in elastic nucleon scattering are considered from the viewpoint of the spin dependence of the interaction potential. Spin-dependent pomeron effects are analyzed for elastic $pp$ scattering, spin-dependent…
We show that a large anomalous contribution due to nonperturbative instanton-like gluonic field configurations to the axial charge of the proton implies high-energy spin effects in $p-p$ elastic scattering. This is the same mechanism which…
Recent preliminary PHENIX data are consistent with a negative and sizable longitudinal double-spin asymmetry A_LL^pi for pi^0 production at moderate transverse momentum p_perp \simeq 1 - 4 GeV and central rapidity. By means of a systematic…
A single-spin asymmetry was measured in the azimuthal distribution of pi+pi- pairs produced in semi-inclusive deep-inelastic scattering on a transversely polarized hydrogen target. For the first time, evidence is found for a correlation…
In this paper we propose to investigate the transverse single spin asymmetry in the inelastic $J/\Psi$ photoproduction in $p^\uparrow p$ and $p^\uparrow A$ collisions at RHIC energies. At leading order this process probes the gluon Sivers…
We report new STAR measurements of the single-spin asymmetries $A_L$ for $W^+$ and $W^-$ bosons produced in polarized proton--proton collisions at $\sqrt{s}$ = 510 GeV as a function of the decay-positron and decay-electron pseudorapidity.…
This paper contains three parts relating to the nucleon spin structure in a simple picture of the nucleon: (i) The polarized gluon distribution in the proton is dynamically predicted starting from a low scale by using a nonlinear QCD…
At the leading twist, the transversity distribution function, $h^{q}_{1}(x)$, where $x$ is the longitudinal momentum fraction of the proton carried by quark $q$, encodes the transverse spin structure of the nucleon. Extraction of it is…
We discuss the production of polarized hadrons in polarized lepton nucleon interactions and show that the helicity density matrix of the hadron, when measurable, can give information on the spin structure of the nucleon and the spin…
Presented here is a study of the large p_T J/psi production in hard diffractive process by the pomeron exchange at the Fermilab Tevatron. We find that this process (p\bar p \to p+J/psi+X) can be used to probe the gluon content of the…
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…
We perform a global leading-order QCD fit to recent polarized structure function data in order to extract a consistent set of spin-dependent parton distributions. Assuming that there is no significant intrinsic polarization of the quark…
We present a precise measurement of the proton longitudinal double-spin asymmetry $A_1^{\rm p}$ and the proton spin-dependent structure function $g_1^{\rm p}$ at photon virtualities $0.006~({\rm GeV}/c)^2<Q^2 < 1~({\rm GeV}/c)^2$ in the…
Absorptive corrections, which are known to suppress proton-neutron transitions with a large fractional momentum z -> 1 in pp collisions, become dramatically strong on a nuclear target, and they push the partial cross sections of leading…