2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/104559The GUT value of Weinberg's angle is also the value that minimises the total square matrix elements of $Z^0$ decay, independently of any GUT consideration, and thus the one that maximises the neutrino branching ratio against total width. We review the proof of this result and some related facts.5 pages, 1 figureHigh Energy Physics - Phenomenologytext