2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/87190This paper studies the possibility to measure the centre of mass energy using e+e- -> Z,gamma -> mu+mu-,gamma events at the ILC. With L = 100 fb^-1 at sqrt(s) = 350 GeV a relative error of around 10^{-4} is possible. The potentially largest systematic uncertainty comes from the knowledge of the aspect ratio of the detector.Talk presented at LCWS05, Stanford, March 2005Instrumentation and DetectorsHigh Energy Physics - Experimenttext