SESZIONE DI TORINO
The transverse momentum dependent generalized parton model at leading twist level may be proved by considering higher twist collinear factorization. Transverse momentum dependent distributions correspond to partial resummation of infinite tower of collinear higher twists. The moment of Sivers function is related to soft gluon twist 3 matrix element. The factorization in terms of twist 3 is complementary to the breaking of factorization in terms of Sivers function by calculable colour factors. The applicability of generalized parton model for high transverse momentum processes is justified.

DATA: 24-10-2008