A study of the semi-leptonic decays of K/sup +/ mesons

The form factors of the semi-leptonic decays K/sup +/ to pi /sup 0/e /sup +/ nu and K/sup +/ to pi /sup 0/ mu /sup +/ nu have been investigated using a sample of events detected in the CERN 1.1 m/sup 3 / heavy liquid bubble chamber. Analyses have been carried out using methods independent of any assumption of the q/sup 2/ dependence of the form factors in addition to the usual linear parametrizations. Consistent results have been obtained from separate studies of both Dalitz plot density distributions and the branching ratio. A parametrized global analysis of both decay modes gives the values xi (0)=-1.3+or-0.7 and xi (4.4M/sub pi //sup 2/)=-0.45+or-0.13, or lambda /sub 0/=-0.017+or-0.011 both for a fitted value of lambda /sub + /=0.025+or-0.007. (56 refs).