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Title: Predictions for Sivers single spin asymmetries in one- and two-hadron electroproduction at CLAS12 and EIC

The study of the Sivers effect, describing correlations between the transverse polarization of the nucleon and its constituent (unpolarized) parton's transverse momentum, has been the topic of a great deal of experimental, phenomenological and theoretical effort in recent years. Semi-Inclusive Deep Inelastic Scattering measurements of the corresponding single spin asymmetries (SSA) at the upcoming CLAS12 experiment at JLab and the proposed Electron-Ion Collider will help to pinpoint the flavor structure and the momentum dependence of the Sivers parton distribution function describing this effect. Here we describe a modified version of the $$\tt{PYTHIA}$$ Monte Carlo event generator that includes the Sivers effect. Then we use it to estimate the size of these SSAs, in the kinematics of these experiments, for both one and two hadron final states of pions and kaons. For this purpose we utilize the existing Sivers parton distribution function (PDF) parametrization extracted from HERMES and COMPASS experiments. Furthermore, we also show that the the leading order approximation commonly used in such extractions provides significantly underestimated values of Sivers PDFs, as the omitted parton showers and non-DIS processes play an important role in these SSAs at lower light-cone momentum fraction, for example in the COMPASS kinematics.
 [1] ;  [2] ;  [3] ;  [4] ;  [1]
  1. Univ. of Adelaide, Adelaide (Australia)
  2. Yerevan Physics Inst. (YerPhI), Yerevan (Armenia); Sezione di Torino, Torino (Italy)
  3. Brookhaven National Lab. (BNL), Upton, NY (United States)
  4. Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
Publication Date:
OSTI Identifier:
Report Number(s):
JLAB-PHY--15-2026; DOE/OR/23177--3330; arXiv:1502.02669
Journal ID: ISSN 1550-7998; PRVDAQ
Grant/Contract Number:
FL0992247 (AWT); CE110001004 (CoEPP); SC0012704; AC05-06OR23177
Accepted Manuscript
Journal Name:
Physical Review. D, Particles, Fields, Gravitation and Cosmology
Additional Journal Information:
Journal Volume: 92; Journal Issue: 5; Journal ID: ISSN 1550-7998
American Physical Society (APS)
Research Org:
Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)
Sponsoring Org:
USDOE Office of Science (SC)
Country of Publication:
United States