1304.5037 (Peng Sun et al.)
Peng Sun, Feng Yuan
We investigate the energy evolution of the azimuthal spin asymmetries in semi-inclusive hadron production in deep inelastic scattering (SIDIS) and Drell-Yan lepton pair production in $pp$ collisions.The scale dependence is evaluated by applying an approximate solution to the Collins-Soper-Sterman (CSS) evolution equation at one-loop order which shall be adequate for moderate $Q^2$ variations. This describes well the spin and azimuthal angular average cross sections for SIDIS and Drell-Yan process in the $Q^2$ range of 2.4-100GeV$^2$. A combined analysis of the Sivers asymmetries in SIDIS from HERMES and COMPASS experiments, and the predictions for the Drell-Yan process at RHIC at $\sqrt{S}=200$GeV are presented with the CSS evolution. This corrects previous over-estimated energy evolution effects. We further extend to the Collins asymmetries, and emphasize an important test of the evolution effects by studying di-hadron azimuthal asymmetry in $e^+e^-$ annihilation at moderate energy range, such as at BEPC at $\sqrt{S}=4.6$GeV.
View original:
http://arxiv.org/abs/1304.5037
No comments:
Post a Comment