Extraction of kaon formfactors from K−→μ−νγ decay at ISTRA+ setup

The radiative decay K−→μ−νμγ has been studied at ISTRA+ setup in a new kinematic region. About 22K events of K−→μ−νμγ have been observed. The sign and value of FV−FA have been measured for the first time. The result is FV−FA=0.21±0.04(stat)±0.04(syst).