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Sivers and Collins Effects: from SIDIS to Proton-Proton Inclusive Pion Production

M. Anselmino, M. Boglione, U. D'Alesio, E. Leader, S. Melis, F. Murgia, A. Prokudin

Abstract

We consider the Sivers, Collins and transversity functions as extracted from SIDIS and e+e- experimental data and investigate to what extent they might explain the large Single Spin Asymmetries (SSA) observed in proton-proton inclusive processes. This phenomenological study is performed within the TMD factorization scheme. As the SIDIS data cover only a limited range of x values (x < 0.3), we allow for different large $x$ behaviours of the SIDIS Sivers functions and transversity distributions. We conclude that, within the available experimental constraints, one cannot observe any clear universality breaking effect for the Sivers functions.

Sivers and Collins Effects: from SIDIS to Proton-Proton Inclusive Pion Production

Abstract

We consider the Sivers, Collins and transversity functions as extracted from SIDIS and e+e- experimental data and investigate to what extent they might explain the large Single Spin Asymmetries (SSA) observed in proton-proton inclusive processes. This phenomenological study is performed within the TMD factorization scheme. As the SIDIS data cover only a limited range of x values (x < 0.3), we allow for different large behaviours of the SIDIS Sivers functions and transversity distributions. We conclude that, within the available experimental constraints, one cannot observe any clear universality breaking effect for the Sivers functions.

Paper Structure

This paper contains 6 equations, 3 figures.

Figures (3)

  • Figure 1: The Sivers, transversity and Collins density functions as determined by fitting SIDIS and $e^+e^-$ data Anselmino:2008sga,Anselmino:2008jk.
  • Figure 2: The Sivers (upper panel) and Collins (lower panel) effects, evaluated according to Eq. (\ref{['AN']}) by using the Sivers, transversity and Collins functions extracted in Anselmino:2008sgaAnselmino:2008jk, are compared to the experimental data from STAR star. The shaded bands are obtained by scanning over the $\beta$ parameters, as described in the text.
  • Figure 3: The Sivers (upper panel) and Collins (lower panel) effects, evaluated according to Eq. (\ref{['AN']}) by using the Sivers, transversity and Collins functions extracted in Anselmino:2008sgaAnselmino:2008jk, are compared to the experimental data from BRAHMS brahms.