Transition radiation induced by nonrelativistic electron bunches

The experiments showed that the Bernstein – Green – Kruskal (BGK)-waves can be used to form short electron bunches with time durations ranging between 50 and 100 ps. Experiments on generating electromagnetic pulses (EMPs) by using nonrelativistic electron bunches passing through diaphragms of various radii and complex geometries are described. Results obtained may also be used in designing devices for generating EMPs with tunable characteristics.Розглядається можливість генерації коротких електронних згустків тривалістю від 50 до 100 пс хвилями Бернштейна-Гріна-Крускала (БГК) і формування електромагнітних імпульсів (ЕМІ) з керованими характеристиками на діафрагмах різної геометрії. Експерименти продемонстрували, що БГК-хвилі можуть бути використані для формування коротких електронних згустків з керованими характеристиками.Рассматривается возможность генерации коротких электронных сгустков протяженностью от 50 до 100 пс волнами Бернштейна-Грина-Крускала (БГК) и формирования электромагнитных импульсов (ЭМИ) с управляемыми характеристиками на диафрагмах разных геометрий. Эксперименты продемонстрировали, что БГК-волны могут использоваться для формирования коротких ЭМИ с управляемыми характеристиками

On the analysis of the pi -> e nu gamma experimental data

The most general amplitude for the radiative pion decay pi -> e nu gamma including terms beyond V-A theory is considered. The experimental constraints on the decay amplitude components are discussed. A model independent presentation of the results of high statistics and high resolution experiments is suggested.Comment: 5 pages, 2 figure

Measurement of the Dalitz plot slope parameters for K- -> pi0 pi0 pi- decay using ISTRA+ detector

The Dalitz plot slope parameters g, h and k for the K- -> pi0 pi0 pi- decay have been measured using in-flight decays detected with the ISTRA+ setup operating in the 25 GeV negative secondary beam of the U-70 PS. About 252 K events with four-momenta measured for the pi- 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.Comment: LaTeX, 10 pages, 8 eps-figures, update of IHEP 2002-1

T-Odd Correlations in pi->e nu_e gamma and pi->mu nu_mu gamma Decays

The transverse lepton polarization asymmetry in pi_l2gamma decays may probe T-violating interactions beyond the Standard Model. Dalitz plot distributions of the expected effects are presented and compared to the contribution from the Standard Model final state interactions. We give an example of a phenomenologically viable model, where a considerable contribution to the transverse lepton polarization asymmetry arises.Comment: 19 pages, 5 figures. To be published in Phys.Rev.D. Fixed sign in FSI contribution figure, fixed formulas in K-bar{K} mixing analysis, added some minor comment

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

The radiative decay K->mu nu gamma has been studied at ISTRA+ setup in a new kinematical region. About 22K events of K^- -> mu^- nu_mu gamma have been observed. The sign and value of Fv-Fa have been measured for the first time. The result is Fv-Fa=0.21(4)(4).Comment: 11 pages, 21 figures, submitted to Phys. Lett.

Search for light pseudoscalar sgoldstino in K- decays

A search for the light pseudoscalar sgoldstino production in the three body K- decay K-->pipi0P has been performed with the ISTRA+ detector exposed to the 25 GeV negative secondary beam of the U70 proton synchrotron. No signal is seen. An upper limit for the branching ratio Br(K->pipi0P), at 90% confidence level, is found to be around 9*10**-6 in the effective mass m(P) range from 0 till 200 MeV, excluding the region near m(pi0) where it degrades to 3.5*10**-5.Comment: 10 pages, LATEX, 8 EPS figures, revised version, to be published in Phys.Lett.

High statistic measurement of the K- -> pi0 e- nu 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$(syst), f_{S}/f_{+}(0)=-0.0037^{+0.0066}_{-0.0056}(stat) +- 0.0041(syst).Comment: 11 pages, 8 figures. Accepted by Phys.Lett.

Aspects of radiative K^+_e3 decays

We re-investigate the radiative charged kaon decay K+- --> pi0 e+- nu_e gamma in chiral perturbation theory, merging the chiral expansion with Low's theorem. We thoroughly analyze the precision of the predicted branching ratio relative to the non-radiative decay channel. Structure dependent terms and their impact on differential decay distributions are investigated in detail, and the possibility to see effects of the chiral anomaly in this decay channel is emphasized.Comment: 15 pages, 6 figure