[en] CP violation experiments, new measurements of the parameters of the neutral K system and searches for rare decays are summarized. Perspectives for the near future are presented

[en] The authors report results for measurements of the decay branching fractions of B⁰ to the charmless final states ηω and ηK⁰, and of B⁺ to ηρ⁺ and η'π⁺. None of these decays have been observed definitively. Measurements of the related decays B⁺ --> ηK⁺, B⁺ --> ηπ⁺, and B --> η'K were published recently. Charmless decays with kaons are usually expected to be dominated by b --> s loop (''penguin'') transitions, while b --> u tree transitions are typically larger for the decays with pions and ρ mesons. However the B --> ηK decays are especially interesting since they are suppressed relative to the abundant B --> η'K decays due to destructive interference between two penguin amplitudes. The CKM-suppressed b --> u amplitudes may interfere significantly with penguin amplitudes, possibly leading to large direct CP violation in B⁺ --> ηρ⁺ and B⁺ --> η'π⁺; numerical estimates are available in a few cases. The authors search for such direct CP violation by measuring the charge asymmetry A_ch (equivalent_to) (Γ^- - Γ⁺)/(Γ^- + Γ⁺) in the rates Γ^± = Γ(B^± --> f^±), for each observed charged final state f^±. Charmless B decays are becoming useful to test the accuracy of theoretical predictions. Phenomenological fits to the branching fractions and charge asymmetries can be used to understand the importance of tree and penguin contributions and may provide sensitivity to the CKM angle γ

[en] The analysis of data from CLAS is a multi-step process. After the detectors for a given running period have been calibrated, the data is processed in the so called pass-1 cooking. During the pass-1 cooking each event is reconstructed by the program a1c which finds particle tracks and computes momenta from the raw data. The results are then passed on to several data monitoring and filtering utilities. In CLAS software, a filter is a parameterless function which returns an integer indicating whether an event should be kept by that filter or not. There is a main filter program called g1-filter which controls several specific filters and outputs several files, one for each filter. These files may then be analyzed separately, allowing individuals interested in one reaction channel to work from smaller files than using the whole data set would require. There are several constraints on what the filter functions should do. Obviously, the filtered files should be as small as possible, however the filter should also not reject any events that might be used in the later analysis for which the filter was intended

[en] A measurement of the H(e, e′ K⁺) reaction was performed at Hall A, TJNAF as part of the hypernuclear experiment E94-107. Data was taken at very low Q² (~ 0.07 (GeV/c)²) and W = 2.2 GeV. Kaons were detected along the direction of q-vector, the momentum transferred by the incident electron (θ_CM = 6°). These measurements provide data about the Σ⁰/Λ ratio which drops rapidly with Q², the angular dependence of the cross sections as Q² → 0, and the dependence of the cross section with respect to Q² ,W and θ_CM. The dependence of the cross section at very forward angles has been poorly known. Available models are inadequate to describe the results. The measurement of the elementary cross section will constrain models for the elementary reaction which are inadequate to describe these results. It is also a key ingredient in the hypernuclear spectroscopy studies performed at the same kinematics. Details of the calculations and results will be shown. (author)

[en] We report a new measurement of A_b using data obtained by SLD in 1997-98. This measurement uses a vertex tag technique, where the selection of a b hemisphere is based on the reconstructed mass of the bottom hadron decay vertex. The method uses the 3D vertexing capabilities of SLD's CCD vertex detector and the small and stable SLC beams to obtain a high b-event tagging efficiency and purity of 78% and 97%, respectively. Charged kaons identified by the CRID detector provide an efficient quark-antiquark tag, with the analyzing power calibrated from the data. We obtain a preliminary result of A_b = 0.997 ± 0.044 ± 0.067

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[en] The status of present experiments and future projects with kaons is reviewed, focusing on prospects for discrete symmetries tests

[en] We report a new measurement of A_b using data obtained by SLD in 1997-98. This measurement uses a vertex tag technique, where the selection of a b hemisphere is based on the reconstructed mass of the bottom hadron decay vertex. The method uses the 3D vertexing capabilities of SLD's CCD vertex detector and the small and stable SLC beams to obtain a high b-event tagging efficiency and purity of 78% and 97%, respectively. Charged kaons identified by the CRID detector provide an efficient quark-antiquark tag, with the analyzing power calibrated from the data. We obtain a preliminary result of A_b = 0.997 ± 0.044 ± 0.067

[en] It is used the 1/N_c expansion within the effective chiral lagrangian for pseudoscalar mesons and compute the hadronic matrix elements at leading and next-to-leading order in the chiral and the 1/N_c expansions. Numerically, our calculation reproduces the dominant ΔI = 1/2 K→ ππ amplitude. The result depends only moderately on the choice of the cutoff scale in the chiral loops. The ΔI = 3/2 amplitude emerges sufficiently suppressed but shows a significant dependence on the cutoff. The B_K parameter turns out to be smaller than the value previously obtained in the 1/N_c approach. It also shows a significant dependence on the choice of the cutoff scale. The results indicate that corrections from higher order terms and/or higher resonances are large for the ΔI = 3/2 K → ππ amplitude and the (|ΔS| = 2) K⁰ - K⁰ transition amplitude