Download or read book Charged-pion Cross Sections and Double-helicity Asymmetries in Polarized [math Display written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In this paper, 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 s=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. Lastly, the charge-separated pion asymmetries presented here sample an x range of ~0.03-0.16 and provide unique information on the sign of the gluon-helicity distribution.