A. P. Filin

Search for Heavy Neutrino in

Heavy neutrino nu_h with m_h mu nu_h (nu_h -> nu gamma) decay chain in the following parameter region: 30MeV/c^2 < m_h < 80MeV/c^2; 10^{-11}sec < tau_h < 10^{-9}sec. For the whole region |U_{mu h}|^2 < 5 x 10^{-5} for Majorana type of nu_h and | U_{\mu h}|^2 < 8 x 10^{-5} for the Dirac case.

K^- -> \mu^- \nu_h(\nu_h -> \nu \gamma)

Heavy neutrino nu_h with m_h mu nu_h (nu_h -> nu gamma) decay chain in the following parameter region: 30MeV/c^2 < m_h < 80MeV/c^2; 10^{-11}sec < tau_h < 10^{-9}sec. For the whole region |U_{mu h}|^2 < 5 x 10^{-5} for Majorana type of nu_h and | U_{\mu h}|^2 < 8 x 10^{-5} for the Dirac case.

Decay at ISTRA+ Setup

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.).

Search for heavy neutrino in K−→μ−νh(νh→νγ) decay at ISTRA+ setup

The decay K− → e−νπ0 has been studied using in-flight decays detected with the ISTRA+ setup working at the 25-GeV negative secondary beam of the U-70 PS. About 130K events were used for the analysis. The λ+ parameter of the vector form factor has been measured: λ+=0.0293±0.0015(stat.)±0.002(syst.). The limits on the possible tensor and scalar couplings have been derived: fT/f+(0)=−0.045±0.060(stat.) and fS/f+(0)=−0.019−0.016+0.025(stat.).

Study of the K− → μ−νπ0 decay

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.

Study of the K− → e−νπ0 decay

AbstractResults of study of the

Study of \(K^ - \to \pi ^0 e^ - \overline \nu _e \gamma \) decay with ISTRA+ setup

K^ - \to \pi ^0 e^ - \overline \nu \gamma

Search for light pseudoscalar sgoldstino in K− decays

decay at the ISTRA+ setup are presented. We observed 4476 events of this decay. The branching ratio is found to be