[en] Recent ARGUS measurements of charmed baryon semileptonic decay branching ratios are presented, that have been observed in the channels Λ⁺_c → Λl⁺ν_l, Ξ⁰_c → Ξ^-l⁺ν_l and Λ⁺_c → Λ^*e⁺ν_e. Measurements of the form factor structure of Λ⁺_c → Λl⁺ν_l decay is also presented. These results are compared with various semileptonic charmed baryon decay models and with Heavy Quark Effective Theory (HQET) predictions. (author). 21 refs., 2 figs., 3 tabs

[en] The MiniBooNE experiment at Fermilab searches for ν^¯_μ→ν^¯_e oscillations using a data sample corresponding to 5.66×10²0 protons on target. An excess of events is observed which, when constrained by the observed ν^¯_μ a probability for consistency with the background-only hypothesis of 0.5% in the energy range of 475< E_ν^QE<1250MeV. Fitting for ν^¯_μ→ν^¯_e oscillations, the probability of the ratio of the likelihood of the background-only fit to the likelihood of the best oscillation fit is 0.6%. The data are consistent with ν^¯_μ→ν^¯_e oscillations in the 0.1 to 1.0 eV²Δm² range and with the evidence for antineutrino oscillations from the Liquid Scintillator Neutrino Detector at Los Alamos National Laboratory.

[en] The Sudbury Neutrino Observatory is a 1000 T D₂O Cerenkov detector that is sensitive to ⁸B solar neutrinos. The energy, radius, and direction with respect to the sun is measured for each neutrino event; these distributions are used to separately determine the rates of the charged current, neutral current and electron scattering reactions of neutrinos on deuterium. Assuming an undistorted ⁸B spectrum, the ν_e component of the ⁸B solar flux is phi_e = 1.76^+0.05_-0.05(stat.)^+0.09_-0.09 (syst.) x 10⁶ cm^-2s^-1 based on events with a measured kinetic energy above 5 MeV. The non-ν_e component is phi_μτ 3.41^+0.45_-0.45(stat.)^+0.48_-0.45 (syst.) x 10⁶ cm^-2s^-1, 5.3σ greater than zero, providing strong evidence for solar ν_e flavor transformation. The total flux measured with the NC reaction is phi_NC = 5.09^+0.044_-0.43(stat.)^+0.46_-0.43 (sy st.) x 10⁶ cm^-2s^-1, consistent with solar models. The night minus day rate is 14.0% ± 6.3%^+1.5_-1.4% of the average rate. If the total flux of active neutrinos is additionally constrained to have no asymmetry, the ν_e asymmetry is found to be 7.0% ± 4.9%^+1.3_-1.2%. A global solar neutrino analysis is terms of matter-enhanced oscillations of two active flavors strongly favors the Large Mixing Angle (LMA) solution

[en] A search has been performed for rare B meson decays into D_s⁺ mesons arising from b→u transitions, W exchange modes, B⁺ annihilation processes, and decays where the D_s⁺ is not produced via a W→c anti s quark pair coupling, using the ARGUS detector operating on the Y(4S) resonance at the e⁺e^- storage ring DORIS II. Upper limits for individual decay modes are obtained. In addition, from a study of D_s⁺l^- correlations an upper limit of BR(B→D_s⁺l^-X)<1.2%(90% CL) is determined. (orig.)

[en] An analysis of the decay τ^-→π^-π⁰ν_τ has been performed using the ARGUS detector at the DORIS II storage ring. The branching ratio has been determined to the Br(τ^-→π^-π⁰ν_τ=(22.6±0.4±0.9)%. The shape of the π^-π⁰ invariant mass spectrum is found to be in good agreement with the predictions obtained using the conserved vector current (CVC) hypothesis, suggesting that the π^-π⁰ system is produced in J^P=1^- state. An analysis of the measured decay angular distribution of the pions with respect to the flight direction of the π^-π⁰ system demonstrates the fector nature of the coupling at the τν_τ vertex. With the assumption of the zero ν_τ mass tha ν_τ spin has been shown to be J_ντ=1/2. (orig.)

[en] Using the ARGUS detector at the DORIS II storage ring, a new measurement of the mass of the τ lepton has been obtained. An analysis of the tan pseudomass spectrum for decays of the type τ^- → π^-π^-π⁺ν_τ finds m_τ = (1776.3 ± 2.4 ± 1.4) MeV/c². This result also leads to an improvement of the upper limit on the ν_τ mass to m_ντ < 31 MeV/c² at the 95% confidence level. (orig.)

[en] Using the ARGUS detector at the e⁺e^- storage ring DORIS II, we have studied Cabibbo-suppressed D⁰ decay modes resulting in the K⁺K^-π⁺π^-final state and two-body D⁰ decay modes with a Φ meson in the final state. The BR(D⁰→ K_S⁰K_S⁰π⁺π^-) was measured for the first time. We also present a measurement of the D⁺ → K_S⁰K_S⁰K⁺ branching ratio. The values are compared with other experimental results and model predictions. (orig.)

[en] Using the ARGUS detector at the DORIS-II electron-positron storage ring at DESY, we have investigated the exclusive decay D^*+ → D⁰ π⁺, D⁰ → K⁰_sπ⁺π^-. From a partial wave analysis of the K⁰_s π^+π-system we find that (71.8± 4.2±3.0)% are D⁰ → K^*- π⁺ and (22.7±3.2±0.9)% are D⁰→ anti K⁰ p⁰ with a relative phase of (-137±7±3)⁰ between the channels. The remaining fraction can be described by several channels involving excited resonances, but not by a three-body phase space decay, thus giving first evidence for D⁰ decays into K^*₀ (1430)^-π⁺, anti K⁰ f₀(975), anti K⁰f₂ (1270), and anti K⁰f₀(1400). (orig.)

[en] Using the ARGUS detector at the e⁺e^- storage ring DORIS II at DESY, we have studied lepton energy spectra in τ decays. We present a 'pseudo-rest-frame' technique in which the second τ in the event, decaying into a heavy hadronic system, is used as reference. This method allows for the first measurement of the Michel Parameter η in τ decays. We also determine the Michel Parameter ρ in τ→e anti νν decays with a precision comparable to the present world average. The measured values of the parameters ρ=0.735±0.036±0.020 and η=0.03±0.18±0.12 are in good agreement with standard V-A coupling at the τ-ν-W vertex. (orig.)

[en] Using the ARGUS detector at the e⁺e^- storage ring DORIS II at DESY we have observed a new decay channel for the excited charm-strange meson D_s1(2536)⁺ → D^*0K⁺. The production cross section for the D_s1(2536)⁺ decaying via this channel is measured to be σ(D_s1(2536)⁺)xBR(D_s1(2536)⁺ → D^*K⁺) = (18 ± 4 ± 3) pb at E_CM = 10.4 GeV. The mass of the D_s1(2536)⁺ is found to be (2535.2 ± 0.5 ± 1.5) MeV/c² in agreement with the value obtained from an analysis of the D_s1(2536)⁺ → D^*K_s⁰ decay channel. The natural width is determined to be less than 3.9 MeV/c² at 90% CL. (orig.)