Novel Transversity Properties in SIDIS

We consider a rescattering mechanism to calculate a leading twist T -odd pion fragmentation function, a candidate for filtering the transversity properties of the nucleon. We evaluate the single spin azimuthal asymmetry for a transversely polarized target in semi-inclusive deep inelastic scattering (for HERMES kinematics) and the double T -odd cos2φ asymmetry in this framework. Introduction The transversity distribution, h1 which measures the probability to find a transversely polarized quark in the transversely polarized nucleon, is as important for the description of the internal nucleon spin structure as the more familiar helicity distribution function, g1. However, it still remains unmeasured, unlike the spin-average and helicity distribution functions, which are known experimentally and extensively modeled theoretically. The difficulty is that h1 is chiral odd, and consequently suppressed in inclusive deep inelastic scattering (DIS) processes [1]; it has to be accompanied by a second chiral-odd quantity. Semi-inclusive deep inelastic scattering (SIDIS) on polarized nucleons is one of several [2, 3, 4] promising methods proposed to access transversity. It relies on just such a quantity the so called Collins fragmentation function [5], which correlates the transverse spin of the fragmenting quark to the transverse momentum of the produced hadron. Beside being chiral-odd, this fragmentation function is also time-reversal odd (T -odd) [6, 7] which makes its calculation challenging. In this context, the non-zero single spin asymmetries in recent measurements [3] may signal the existence of a nontrivial T -odd effects which are intimately tied to our understanding of transversity. Here we explore [8] a one-gluon exchange mechanism, for the fragmentation of a transversely polarized quark into a spinless hadron similar to the approach we applied [9, 10] to the distribution of the transversely polarized quarks in the both unpolarized and transversely polarized nucleons. The non-perturbative information about the quark content of the target and the fragmentation of quarks into hadrons in SIDIS is encoded in the general form of the factorized cross sections in terms of the quark distributions Φ(p) and fragmentation functions ∆(k), entering the hadronic tensor. To leading order in 1/Q2 [11] the fragmentation functions are projected from ∆(k,Ph)=∑ X ∫ dξ dξ⊥ 2z(2π)3 eik·ξ 〈0 |G[ξ+,−∞]ψ(ξ )|X ;Ph〉〈X ;Ph|ψ(0)G † [0,−∞]|0〉 ∣