Ds Asymmetry in Photoproduction

Asymmetry in Photoproduction

Considering of the possible difference in strange and antistrange quark distributions inside nucleon, we investigate the D s −D − s asymmetry in photoproduction in the framework of heavy-quark recombination mechanism. We adopt two distribution models of strange sea, those are the light-cone mesonbaryon fluctuation model and the effective chiral quark model. Our results show that the asymmetry i...

Polarization Asymmetry Zero in Heavy Quark Photoproduction and Leptoproduction

We demonstrate two novel features of the sea-quark contributions to the polarized structure functions and photoproduction cross sections, a zero sum rule and a zero crossing point of the polarization asymmetry, which can be traced directly to the dynamics of the perturbative tree-graph gluon-splitting contributions. In particular, we show that the Born contribution of massive quarks arising fro...

Two–Spin Asymmetry for ψ Photoproduction with Color–Octet Mechanism

We studied the photoproduction of ψ in the forward regions in polarized γp collisions at relevant HERA energies. We found that this reaction is very effective to test the color–octet mechanism which is based on the NRQCD factorization formalism. Furthermore we found that the value of the NRQCD matrix elements can be severely constrained by measuring the two–spin asymmetry, though the process de...

Measurement of the helicity asymmetry e in ω→π+πˉπo photoproduction

The spin asymmetry in the photoproduction of pairs of high transverse momentum hadrons at HERMES

Results from the HERMES experiment at the DESY Laboratory in Germany are presented on the longitudinal asymmetry in the photoproduction of pairs of oppositely charged hadrons with high transverse momentum. A negative asymmetry is determined in contrast to the positive asymmetries typically measured in deep-inelastic scattering from protons. Monte Carlo studies indicate that the photon-gluon pro...