Physics and Astronomy
Journal or Book Title
Physical Review D
We present midrapidity charged-pion invariant cross sections, the ratio of the pi(-) to pi(+) cross sections and the charge-separated double-spin asymmetries in polarized p + p collisions at root s = p + 200 GeV. While the cross section measurements are consistent within the errors of next-to-leading-order (NLO) perturbative quantum chromodynamics predictions (pQCD), the same calculations overestimate the ratio of the charged-pion cross sections. This discrepancy arises from the cancellation of the substantial systematic errors associated with the NLO-pQCD predictions in the ratio and highlights the constraints these data will place on flavor-dependent pion fragmentation functions. The charge-separated pion asymmetries presented here sample an x range of similar to 0.03-0.16 and provide unique information on the sign of the gluon-helicity distribution.
American Physical Society
Adare, Andrew; Dion, Alan; Hill, John C.; Kempel, Todd; Lajoie, John G.; Lebedev, Alexandre; Ogilvie, Craig; Pei, H.; Rosati, Marzia; Silva, C. L.; Wei, Feng; et al.; and PHENIX Collaboration, "Charged-pion cross sections and double-helicity asymmetries in polarized p plus p collisions at root s=200 GeV" (2015). Physics and Astronomy Publications. 232.