Speaker
Steven Heppelmann
(Penn State University for the STAR Collaboration)
Description
The STAR collaboration has collected two large data sets for measurement of forward π^0 transverse single spin asymmetries (SSA) in polarized pp collisions. Preliminary results and analysis progress will be presented for data from two RHIC runs, from RHIC Run 11 (2011) with energy √s=500 GeV and with luminosity of 22 pb-1 and from RHIC Run 12 (2012) with √s=200 GeV and with luminosity of 18 pb-1. Neutral pions are measured with the STAR forward electromagnetic calorimeter (called FMS) with nearly full azimuthal acceptance over the range of pseudo-rapidity from 2.65 to 4.0. Large transverse SSA is now seen over a much greater range of transverse momentum, up to 10 GeV/c, than reported in previous publications. The analysis of the underlying event structure raises important questions about the overall jet-like nature of events associated with the spin asymmetry of the π^0. These results may provide new insight into the 30 year old puzzle as to the nature of large SSAs in forward hadron production.
Author
Steven Heppelmann
(Penn State University for the STAR Collaboration)
