2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/179168We present the leading unpolarized and single spin asymmetries in inclusive two-hadron production in electron-positron annihilation at the Z pole. The azimuthal dependence in the unpolarized differential cross section of almost back-to-back hadrons is a leading cos(2 phi) asymmetry, which arises solely due to the intrinsic transverse momenta of the quarks. An extensive discussion on how to measure this asymmetry and the accompanying time-reversal odd fragmentation functions is given. A simple estimate indicates that the asymmetry could be of the order of a percent.8 pages, Revtex, 2 Postscript figures, uses epsf.sty. Some typos corrected, minor clarifying changes, one reference added, including a comment at the endHigh Energy Physics - Phenomenologytext