2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/179660We analyse the constraints on scalar leptoquarks coming from radiative corrections to $Z$ physics. We perform a global fitting to the LEP data including the contributions of the most general effective Lagrangian for scalar leptoquarks, which exhibits the $SU(2)_L \times U(1)_Y$ gauge invariance. We show that the bounds on leptoquarks that couple to the top quark are much stronger than the ones obtained from low energy experiments.RevTeX 3.0, 26 pages, 4 postscript figures included as uufileHigh Energy Physics - Phenomenologytext