Standard Model and New Physics contributions to and into four leptons
arXiv:1309.5736 · doi:10.1140/epjc/s10052-013-2678-1
Abstract
We study the and decays into four leptons () where we use a form factor motivated by vector meson dominance, and show the dependence of the branching ratios and spectra from the slopes. A precise determination of short distance contribution to is affected by our ignorance on the sign of the amplitude but we show a possibility to measure the sign of this amplitude by studying and decays in four leptons. We also investigate the effect of New Physics contributions for these decays.
Improvements of the text and references added