I. Ya. Korolkov

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.).

Observation of the radiative kaon decay K − → µ−π0γν

Using data collected with the ISTRA+ spectrometer during the 2001 run of the U-70 proton synchrotron in Protvino, the first observation of the radiative kaon decay K− → µ−π0γν is reported. The ratio Br(Kµ3γ, 5 < E*γ < 30 MeV)/Br(Kµ3) is found to be [0.270 ± 0.029(stat.) ± 0.026(syst.)]% and the ratio Br(Kµ3γ, 30 < E*γ < 60 MeV)/Br(Kµ3) = [0.0448 ± 0.0068(stat.) ± 0.0099(syst.)]%. These ratios are consistent with the theoretical predictions 0.21 and 0.047%, respectively. The measured angular distribution asymmetry for the region 5 < E*γ < 30 MeV, A(cos ϑ*µγ) = 0.093 ± 0.141, is two standard deviations away from the theoretical prediction of 0.354. The measured asymmetry in the T-odd variable ξ = pγ · (pµ × pπ)/mK3 is −0.03 ± 0.13.Using data collected with the ISTRA+ spectrometer during the 2001 run of the U-70 proton synchrotron in Protvino, we report the first observation of the radiative kaon decay K- -->mu-pi0gammanu. We find Br(Kmu3g)/Br(Kmu3) for two regions 5<Eg<30 and 30<Eg<60 MeV consistent with theoretical predictions. The measured angular distribution asymmetry for the first region, 0.093+/-0.141, is two standard deviations away from the theoretical prediction of 0.354. The measured asymmetry in the T-odd variable is -0.03+/-0.13.

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

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

Experimental study of direct photon emission in K/it− → π−π0γ decay using ISTRA+ detector

The branching ratio in the charged-pion-kinetic-energy region of 55 to 90 MeV for the direct photon emission in the K− → π−π0γ decay has been measured using in-flight decays detected with the ISTRA+ setup operating in the 25-GeV/c negative secondary beam of the U-70 PS. The value Br(DE)=[0.37±0.39(stat.)±0.10(syst.)]×10−5 obtained from the analysis of 930 completely reconstructed events is consistent with the average value of two stopped-kaon experiments, but it differs by 2.5 standard deviations from the average value of three in-flight-kaon experiments. The result is also compared with recent theoretical predictions.The branching ratio in the charged-pion-kinetic-energy region of 55 to 90 MeV for the direct photon emission in the K{sup -} {sup {yields}} {pi}{sup -}{pi}{sup 0}{gamma} decay has been measured using in-flight decays detected with the ISTRA+ setup operating in the 25-GeV/c negative secondary beam of the U-70 PS. The value Br(DE)=[0.37{+-}0.39(stat.){+-}0.10(syst.)]x10{sup -5} obtained from the analysis of 930 completely reconstructed events is consistent with the average value of two stopped-kaon experiments, but it differs by 2.5 standard deviations from the average value of three in-flight-kaon experiments. The result is also compared with recent theoretical predictions.

Extraction of Kaon Formfactors from K->mu nu gamma Decay at ISTRA+ Setup

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

Extraction of Kaon Formfactors from K^- -> mu^- nu_mu gamma Decay at ISTRA+ Setup

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

Experimental study of direct photon emission in K/it{sup -} {sup {yields}} {pi}{sup -}{pi}{sup 0}{gamma} decay using ISTRA+ detector

The branching ratio in the charged-pion-kinetic-energy region of 55 to 90 MeV for the direct photon emission in the K− → π−π0γ decay has been measured using in-flight decays detected with the ISTRA+ setup operating in the 25-GeV/c negative secondary beam of the U-70 PS. The value Br(DE)=[0.37±0.39(stat.)±0.10(syst.)]×10−5 obtained from the analysis of 930 completely reconstructed events is consistent with the average value of two stopped-kaon experiments, but it differs by 2.5 standard deviations from the average value of three in-flight-kaon experiments. The result is also compared with recent theoretical predictions.The branching ratio in the charged-pion-kinetic-energy region of 55 to 90 MeV for the direct photon emission in the K{sup -} {sup {yields}} {pi}{sup -}{pi}{sup 0}{gamma} decay has been measured using in-flight decays detected with the ISTRA+ setup operating in the 25-GeV/c negative secondary beam of the U-70 PS. The value Br(DE)=[0.37{+-}0.39(stat.){+-}0.10(syst.)]x10{sup -5} obtained from the analysis of 930 completely reconstructed events is consistent with the average value of two stopped-kaon experiments, but it differs by 2.5 standard deviations from the average value of three in-flight-kaon experiments. The result is also compared with recent theoretical predictions.