Electroweak quantum effects in theM w -M z relation

Quantum effects in theM_w-M_z relation are studied in the framework of the standard SU(2)×U(1) electroweak theory. After reviewing this relation in detail, numerical analysis is carried out by using recent data of ALEPH, DELPHI, L3, OPAL and MARK II collaborations onM_z, and those of CDF and UA2 collaborations onM_w. For the weighted averageM_z^exp=91.157±0.032 GeV, theW mass is calculated asM_w⁽⁰⁾=80.90±0.04 GeV,M_w^(l.l)=79.75±0.04±0.02 GeV andM_w=80.21±0.04±0.04 GeV at the tree, leading-log and full correction level (form_top=140 GeV andm_Higgs=100 GeV) respectively. Remarkable is that only the fully correctedM_w is consistent withM_w^exp=80.24±0.37 GeV, which clearly demands the heavy top-quark correction, and therefore gives a strong phenomenological support, independent of the neutral current data, to the electroweak theory as a renormalizable quantum field theory with the spontaneous symmetry breakdown.