Sivers Effect in Two-Hadron Electroproduction

Abstract

The Sivers effect in single hadron semi-inclusive deep inelastic scattering (DIS) on a transversely polarized nucleon describes the modulation of the cross section with the sine of the azimuthal angle between the produced hadron's transverse momentum and the nucleon spin ($\boldsymbol{P}_h$ and $\varphi_S$ respectively). This effect is attributed to the so-called Sivers parton distribution function of the nucleon. We employ a simple phenomenological parton model to derive the relevant cross section for two-hadron production in semi-inclusive deep inelastic scattering including the Sivers effect. We show that the Sivers effect can be observed in such process as sine modulations involving the azimuthal angles $\varphi_T$ and $\varphi_R$ of both the total and the relative transverse momenta of the hadron pair. The existence of the modulation with respect to $\varphi_R$ is new. Finally, we employ a modified version of the $\tt{LEPTO}$ Monte Carlo event generator that includes the Sivers effect to estimate the size of single spin asymmetries corresponding to these modulations. We show that $\sin(\varphi_R-\varphi_S)$ modulations can be significant, especially if we impose asymmetric cuts on the momenta of the hadrons in the pairs.Comment: 4 pages, 3 figures. In v2 small changes are made to comply with the version published in PRL. arXiv admin note: text overlap with arXiv:1405.505

Sivers Effect in Dihadron Electroproduction

“…In our recent work [1,2], we proposed a new approach for measuring the Sivers function in the 2h SIDIS process. We presented the results for the relevant cross section calculation that involve the Sivers PDF, with two non-vanishing SSAs with respect to sin(ϕ R − ϕ S ) and sin(ϕ T − ϕ S ), respectively.…”

“…The explicit expressions for σ T and σ R with adopted parametrization of PDFs and DiFFs are given in [2], where it is also shown that in general σ R 0 for asymmetric pair production.…”

“…(16). In our studies [1,2] of the Sivers effect in 2h SIDIS we have chosen the first definition of the relative transverse momentum. As for the previous choice, we can rewrite the Eq.…”

“…The explicit expressions for structure functions σ U , σ 1 and σ 2 are presented in Ref. [2] using Gaussian parameterizations for PDFs, similar to Ref. [7], and the following form for DiFFs:…”

Azimuthal correlations in the structure functions of polarized dihadron semi-inclusive deep inelastic scattering

“…The one hadron single spin asymmetries (SSAs) in two hadron SIDIS samples are then discussed for both Sivers-like (SL) and CL modulations. Finally, similar to [5,6], we use the LEPTO Monte Carlo (MC) event generator [7], that has been modified to include the Sivers effect [8,9] to explore the transverse momenta correlations in the kinematical region of the COMPASS experiment in a framework that is independent of the assumptions employed in deriving the analytical expressions for the SSAs.…”