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Comparing extractions of Sivers functions

M. Anselmino, M. Boglione, J. C. Collins, U. D'Alesio, A. V. Efremov, K. Goeke, A. Kotzinian, S. Menzel, A. Metz, F. Murgia, A. Prokudin, P. Schweitzer, W. Vogelsang, F. Yuan

TL;DR

The paper compares multiple recent extractions of the Sivers function from HERMES and COMPASS SIDIS data, emphasizing how different treatments of transverse momentum impact the recovered distributions. Despite distinct parameterizations and modeling choices, the approaches yield qualitatively similar Sivers functions within the kinematic region probed by SIDIS, with systematic, model-related uncertainties often larger than statistical ones. The work reinforces the predicted sign change of the Sivers function between SIDIS and Drell-Yan and provides consistent, if method-dependent, predictions for DY SSA in current and future experiments. It also highlights the necessity of more precise data and dedicated tests of factorization to sharpen quantitative conclusions about the Sivers effect.

Abstract

A comparison is given of the various recently published extractions of the Sivers functions from the HERMES and COMPASS data on single-transverse spin asymmetries in semi-inclusive deeply inelastic scattering.

Comparing extractions of Sivers functions

TL;DR

The paper compares multiple recent extractions of the Sivers function from HERMES and COMPASS SIDIS data, emphasizing how different treatments of transverse momentum impact the recovered distributions. Despite distinct parameterizations and modeling choices, the approaches yield qualitatively similar Sivers functions within the kinematic region probed by SIDIS, with systematic, model-related uncertainties often larger than statistical ones. The work reinforces the predicted sign change of the Sivers function between SIDIS and Drell-Yan and provides consistent, if method-dependent, predictions for DY SSA in current and future experiments. It also highlights the necessity of more precise data and dedicated tests of factorization to sharpen quantitative conclusions about the Sivers effect.

Abstract

A comparison is given of the various recently published extractions of the Sivers functions from the HERMES and COMPASS data on single-transverse spin asymmetries in semi-inclusive deeply inelastic scattering.

Paper Structure

This paper contains 5 sections, 14 equations, 1 figure.

Table of Contents

  1. Introduction
  2. The approach of Refs. [ ?, ?]
  3. The approach of Ref. [ ?]
  4. The approach of Refs. [ ?, ?]
  5. Comparison of the results and Conclusions

Figures (1)

  • Figure 1: The first and 1/2-transverse moments of the Sivers quark distribution functions, defined in Eqs. (\ref{['Eq:Def-Siv-transv-mom']}, \ref{['Eq:VY-00']}), as extracted in Refs. [ ?, ?, ?]. The fits were constrained mainly (or solely) by the preliminary HERMES dataDiefenthaler:2005gx in the indicated $x$-range. The curves indicate the 1-$\sigma$ regions of the various parameterizations.