Study of the K− → μ−νπ0 decay

The decay K− → μ−νπ0 has been studied using in-flight decays detected with the ISTRA+ setup operating in the 25-GeV negative secondary beam of the U-70 PS. About 112K events were used for the analysis. The λ+ and λ0 slope parameters of the decay form factors f+(t) and f0(t) have been measured: λ+=0.0321±0.004(stat.)±0.002(syst.), λ0=0.0209±0.004(stat.)±0.002(syst.); the correlation dλ0/dλ+=−0.46. The limits on the possible tensor and scalar couplings have been derived: fT/f+(0)=−0.021±0.028(stat.)±0.014(theor.), fS/f+(0)=0.004±0.005(stat.)±0.005(theor.).