Sivers effect for pion and kaon production in semi-inclusive deep inelastic scattering

Abstract

We study the Sivers effect in the transverse single spin asymmetries (SSA) for pion and kaon production in semi-inclusive deep inelastic scattering (SIDIS) processes. We perform a fit of Awhich, by including recent high statistics experimental data for pion and kaon production from HER-MES and COMPASS Collaborations, allows a new determination of the Sivers distribution functions for quarks and antiquarks with u, d and s flavours. Estimates for forthcoming SIDIS experiments at COMPASS and JLab are given.

Exploring the structure of the proton through polarization observables inlp→jetX

“…For both parameterizations we obtain a healthy asymmetry in the forward region, with effects at the level 5 − 10 %. (Note also that, for the parameterization taken from [51], our numerical results in the collinear approach are similar to those obtained in Ref. [52] by using factorization in terms of transverse momentum dependent parton correlators and the same input for the Sivers function.)…”

“…Despite the small effect, measuring A LL could provide complementary information on the quark helicity distributions of the proton. On the other hand, for the longitudinal double spin asymmetry in l p → jet X one faces the same problems one has in [51] and using the relation in (22), while the dashed line is computed with T F from [9,70].…”

“…For the ETQS matrix element T F we explore two choices: (1) we use the relation (22) between T F and the Sivers function, and take f ⊥ 1T from the recent fit provided in Ref. [51]; (2) we use T F from the parameterization obtained in [9] -taking into consideration the recently discovered sign change [70] -by fitting transverse SSAs measured in hadronic collisions.…”

“…This also applies to A LT when using the approximations (25) and (26). Since both the parameterization of the Sivers function in [51] as well as the one for the ETQS matrix element T F in [9,70] are related to the unpolarized distribution f 1 , also the scale dependence of A U T is quite mild.…”

“…As pointed out in [41,42], the ETQS matrix element is related to the transverse momentum dependent Sivers function [43]. (For experimental studies of the Sivers effect in semi-inclusive DIS we refer to [44,45], while extractions of the Sivers function from data were discussed in [46][47][48][49][50][51]). Thus, measuring A U T in l p → jet X would give a direct (complementary) handle on the Sivers effect.…”