Dear guys, first of all I want to appologize if this question was already answered in this forum. I tried the search enginge and did not get the right results. According to the Wikipedia article (http://en.wikipedia.org/wiki/Standard_Model#Theoretical_aspects) about the SM, the values at 91 GeV are g(U1) = 0.357 g(SU2) = 0.652 (the table says "minimial substraction scheme" was used for renomalization) As I am a beginner and do not have the knowledge to do the renormalization calculations on my own, I am looking for a source, which I can quote .. (and afaik the authors of the wiki-article dont quote their source). As I am a little bit under time pressure, I would be very very glad, if someone would know a source. I tried google, arxiv etc. but all I find are the LEP measurements from which those coupling constants could be calculated .. but no paper which did this ..