2 research outputs found
General helicity formalism for Single and Double Spin Asymmetries in p p --> pion + X
We consider within a generalized QCD factorization approach, the high energy
inclusive polarized process p p --> pion + X, including all intrinsic partonic
motions. Several new spin and k_T-dependent soft functions appear and
contribute to cross sections and spin asymmetries. We present here formal
expressions for transverse single spin asymmetries and double longitudinal
ones. The transverse single spin asymmetry, A_N, is considered in detail, and
all contributions are evaluated numerically. It is shown that the azimuthal
phase integrations strongly suppress most contributions, leaving at work mainly
the Sivers effect
Sivers and Collins effects in polarized pp scattering processes
We summarize the present phenomenology of Sivers and Collins effects for
transverse single spin asymmetries in polarized proton-proton collisions within
the framework of the generalized parton model (GPM). We will discuss a
reassessment of the Collins effect and some preliminary predictions for SSA's
in p(pol) p -> pi,K + X processes at RHIC obtained using updated information
from SIDIS data and a new set of meson fragmentation functions