Angular dependences in inclusive two-hadron production at BELLE

A collection of results is presented relevant for the analysis of azimuthal asymmetries in inclusive twohadron production at BELLE. The aim of this overview is to provide theoretical ingredients necessary to extract the Collins effect fragmentation function. The latter arises within the Collins–Soper factorization formalism, which describes both the transverse momentum and Q2 dependence of the cross section and its angular dependences at low and moderate transverse momentum. Since the Collins effect is not the only source of angular dependences, a discussion of various other effects is included. This concerns higher twist contributions, photon–Z-boson interference effects, radiative corrections, beam polarization and weak decays. Furthermore, different frames, transverse momentum weighting and ratios of asymmetries are discussed. These issues are all of relevance for the unambiguous measurement of the Collins effect. © 2008 Elsevier B.V. All rights reserved. PACS: 13.66.Bc; 13.87.Fh; 13.88.+e