Study of the decay K sup + r arrow. pi. sup + e+ e minus

We present results of an experiment in which approximately 500 events of the decay {ital K}{sup +}{r arrow}{pi}{sup +}{ital e+}{ital e{minus}} were observed. We have measured the branching ratio for {ital K}{sub {pi}{ital e}{ital e}}{sup +} to be (2.75{plus minus}0.23{plus minus}0.13){times}10{sup {minus}7} assuming a vector interaction with a form factor of {lambda}=0.105{plus minus}0.035{plus minus}0.015. We have also found the branching ratio times decay probability for {ital K}{sup +}{r arrow}{pi}{sup +}{ital X0}, {ital X}{sup 0}{r arrow}{ital e}{sup +}{ital e{minus}} to be less than 1.5{times}10{sup {minus}8} (99% C.L.) over an {ital X}{sup 0} invariant mass range from 150 to 340 MeV/{ital c}{sup 2}.