Fourth quark-lepton generation and precision measurements

Abstract

Precise measurements of Z-boson parameters and W-boson and t-quark masses put strong constraints on non SU(2) * U(1) singlet New Physics. We demonstrate that one extra generation passes electroweak constraints even when all new particle masses are well above their direct mass bounds.

Comments: Comments: Presented at XXIst Rencontres de Blois "Windows on the Universe" 21-26 June 2009 in Blois, France and "Progress and Challenges in Flavour Physics" 29 Sep- 3 Oct 2009 in Primosten, Croatia, 4 pages, 3 figures. 2 references added