Study of the sign change of the Sivers function from STAR Collaboration   W/Z production data
  Recent data on the transverse single spin asymmetry $A_N$ measured by the STAR Collaboration for $p^\uparrow \, p \to W^\pm/Z^0 \, X$ reactions at RHIC allow the first investigation of the Sivers function in Drell-Yan processes and of its expected sign change with respect to SIDIS processes. A new extraction of the Sivers functions from the latest SIDIS data is performed and a critical assessment of the significance of the STAR data is attempted. 
M. Anselmino (1,2), M. Boglione (1,2), U. D'Alesio (3,4), F. Murgia   (4), A. Prokudin (5,6) ((1) University of Torino, Ital...
hep-ph