6 research outputs found
Single spin asymmetry for the Drell-Yan process
We calculated the single spin asymmetries for the reaction
in the framework of twist-3 QCD for
HERA energies. The necessary imaginary phase is produced by the on-shell
contribution of the quark propagator, while the long distance part is analogous
to that providing the direct photon asymmetry calculated by J. Qiu and G.
Sterman. The asymmetry turns out to be generally of the order percent.Comment: 7 pages, 4 figures, LaTe
Wandzura-Wilczek approximation from generalized rotational invariance
We present the alternative way of derivation of the Wandzura-Wilczek
relations between the kinematical twist-3 and twist-2 functions, parameterizing
hadronic matrix element in two-photon processes and . The new equations, providing
the independence of the physical cross-sections on the choice of the light-cone
direction, are suggested and explored. The amplitude of
up to genuine twist-3 accuracy is found.Comment: 14 pages, Late
Color gauge invariance in the Drell-Yan process
We consider the color gauge invariance of a factorized description of the
Drell-Yan process cross section. In particular, we focus on the next-to-leading
twist contributions for polarized scattering and on the cross section
differential in the transverse momentum of the lepton pair in the region where
the transverse momentum is small compared to the hard scale. The hadron tensor
is expressed in terms of manifestly color gauge invariant, nonlocal operator
matrix elements and a color gauge invariant treatment of soft gluon poles is
given. Also, we clarify the discrepancy between two published results for a
single spin asymmetry in the Drell-Yan cross section. This asymmetry arises if
such a soft gluon pole is present in a specific twist-three hadronic matrix
element.Comment: 16 pages, Revtex, 2 Postscript figures, uses aps.sty, epsf.sty; error
in revision remove
The twist-3 single spin asymmetries of pion production
Consiglio Nazionale delle Ricerche (CNR). Biblioteca Centrale / CNR - Consiglio Nazionale delle RichercheSIGLEITItal