Transversity distributions in the nucleon in the large – N c limit

We compute the quark and antiquark transversity distributions in the nucleon at a low normalization point (μ≈600MeV) in the large–Nc limit, where the nucleon can be described as a soliton of an effective chiral theory (chiral quark–soliton model). The flavor–nonsinglet distributions, δu(x)−δd(x) and δū(x)−δd̄(x), appear in leading order of the 1/Nc–expansion, while the flavor–singlet distributions, δu(x)+δd(x) and δū(x)+ δd̄(x), are non-zero only in next–to–leading order. The transversity quark and antiquark distributions are found to be significantly different from the longitudinally polarized distributions ∆u(x)±∆d(x) and ∆ū(x)±∆d̄(x), respectively, in contrast to the prediction of the naive non-relativistic quark model. We show that this affects the predictions for the spin asymmetries in Drell–Yan pair production in transversely polarized pp and pp̄ collisions. PACS: 13.60.Hb, 12.38.Lg, 11.15.Kc, 12.39.Ki