V. A. Uvarov

High statistic measurement of the K−→π0e−ν decay form-factors

The decay K- ->pi0 e- nu is studied using in-flight decays detected with the ISTRA+ spectrometer. About 920K events are collected for the analysis. The lambda+ slope parameter of the decay form-factor f+(t) in the linear approximation (average slope) is measured: lambda+(lin)= 0.02774 +- 0.00047(stat) +- 0.00032(syst). The quadratic contribution to the form-factor was estimated to be lambda+ = 0.00084 +- 0.00027(stat) +- 0.00031(syst). The linear slope, which has a meaning of df+(t)/dt|_{t=0} for this fit, is lambda+ = 0.02324 +- 0.00152(stat) +- 0.00032(syst). The limits on possible tensor and scalar couplings are derived: f_{T}/f_{+}(0)=-0.012 +- 0.021(stat) +- 0.011

High statistics study of the K−→π0μ−ν decay

(syst), f_{S}/f_{+}(0)=-0.0037^{+0.0066}_{-0.0056}(stat) +- 0.0041(syst).

Measurement of the Dalitz plot slope parameters for K−→π0π0π− decay using ISTRA+ detector

The decay K ! � 0 ehas been studied using in-flight decays detected with the ISTRA+ spectrometer operating in the 25-GeV negative secondary beam of the U-70 PS. About 550K events were collected for the analysis. The �+ parameter of the vec- tor form-factor has been measured: �+ = 0.0286 ± 0.0008(stat) ± 0.0006(syst). The limits on the possible tensor and scalar couplings have been obtained: fT/f+(0) = 0.021 +0.064 0.075 (stat) ± 0.026(syst); fS/f+(0) = 0.002 +0.020 0.022 (stat) ± 0.003(syst)

Search for Heavy Neutrino in

Abstract The Dalitz plot slope parameters g, h and k for the K−→π0π0π− decay have been measured using in-flight decays detected with the ISTRA+ setup operating in the 25xa0GeV negative secondary beam of the U-70 PS. About 252xa0K events with four-momenta measured for the π− and four involved photons were used for the analysis. The values obtained g=0.627±0.004(stat)±0.010(syst), h=0.046±0.004(stat)±0.012(syst), k=0.001±0.001(stat)±0.002(syst) are consistent with the world averages dominated by K+ data, but have significantly smaller errors.

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

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.

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

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.

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

AbstractResults of study of the n

Study of the K−→π0e−ν decay

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