Predictions for single spin asymmetries in lepton + p(transv. polarized) -> pion + X and gamma^* + p(transv. polarized) -> pion + X

TL;DR

This paper predicts single spin asymmetries in semi-inclusive deep inelastic scattering, attributing observed effects primarily to the Collins fragmentation mechanism, with discussions on the Sivers effect's potential role.

Contribution

It provides predictions for asymmetries based solely on the Collins effect, assuming it is the main cause of observed single spin asymmetries in polarized proton collisions.

Findings

Non-negligible asymmetries predicted in semi-inclusive DIS.

Predictions based on Collins effect fitted from previous data.

Discussion of possible Sivers effect contributions.

Abstract

Predictions for the single transverse spin asymmetry A_N in semi-inclusive DIS processes are given; non negligible values of A_N may arise from spin effects in the fragmentation of a polarized quark into a final hadron with a transverse momentum k_T with respect to the jet axis, the so-called Collins effect. The elementary single spin asymmetry of the fragmenting quark has been fixed in a previous paper, by fitting data on p(transv. polarized) + P -> pion + X, and the predictions given here are uniquely based on the assumption that the Collins effect is the only cause of the observed single spin asymmetries in p(transv. polarized) + p -> pion + X. Eventual spin and k_T dependences in quark distribution functions, the so-called Sivers effect, are also discussed.