[en] We study the Υ(3S, 2S) → ηΥ(1S) and Υ(3S, 2S) → π⁺π^-Υ(1S) transitions with 122 x 10⁶ Υ(3S) and 100 x 10⁶ Υ(2S) mesons collected by the BABAR detector at the PEP-II asymmetric-energy e⁺e^- collider. We measure Β[Υ(2S) → ηΥ(1S)] = (2.39 ± 0.31(stat.) ± 0.14(syst.)) x 10^-4 and Λ[Υ(2S) → ηΥ(1S)]/Λ[Υ(2S) → π⁺π^-Υ(1S)] = (1.35 ± 0.17(stat.) ± 0.08(syst.)) x 10^-3. We find no evidence for Υ(3S) → ηΥ(1S) and obtain Β[Υ(3S) → ηΥ(1S)] < 1.0 x 10^-4 and Λ[Υ(3S) → ηΥ(1S)]/Λ[Υ(3S) → π⁺π^-Υ(1S)] < 2.3 x 10^-3 as upper limits at the 90% confidence level. We also provide improved measurements of the Υ(2S)-Υ(1S) and Υ(3S)-Υ(1S) mass differences, 562.170 ± 0.007(stat.) ± 0.088(syst.)MeV/c² and 893.813 ± 0.015(stat.) ± 0.107(syst.)MeV/c², respectively.

No abstract available

[en] Recent data on neutrino mass differences are consistent with a hierarchical neutrino mass structure strikingly similar to what is observed for the other fermionic masses. (author)

[en] The decay width and mass of the D_s1(2536)⁺ meson are measured via the decay channel D_s1⁺ → D*⁺ K_S⁰ using 385 fb^-1 of data recorded with the BABAR detector in the vicinity of the Υ(4S) resonance at the PEP-II asymmetric-energy electron-positron collider. The result for the decay width is Γ(D_s1⁺) = 0.92 ± 0.03 (stat.) ± 0.04 (syst.)MeV. For the mass, a value of m(D_s1⁺) = 2535.08 ± 0.01 (stat.) ± 0.15 (syst.)MeV/c² is obtained. The mass difference between the D_s1⁺ and the D*⁺ is measured to be m(D_s1⁺)-m(D*⁺) = 524.83 ± 0.01 (stat.) ± 0.04 (syst.)MeV/c², representing a significant improvement compared to the current world average. The unnatural spin-parity assignment for the D_s1⁺ meson is confirmed.

[en] A method is proposed for the determination of Δ⁺⁺-Δ⁰ pole parameters. The method is free of ambiguity due to the pole-backgroud separation and takes into account all available information about the partial wave amplitudes. The method is tested by two model amplitudes with pole positions known beforehand. Three different approaches are presented based on the same method and the corresponding pole shifts in model amptitudes are calculated. (author)

[en] The microcausality condition allowing to express amplitudes Tsub(i)(ν, q²) of the virtual photon forward scattering by a hadron in terms of the Wsub(i)(ν, q²) functions for the electroproduction process, is applied to explain the mass differences between particles forming the isotopic multiplet. The doublet mass differences are shown to be independent on electroproduction. Various explanations of the mass differences observed are discussed

[en] The nuclear dependence of the neutron-proton mass difference is examined in a relativistic harmonic quark model with the assumption of a swelling of the individual nucleon originated by a decrease of the spring constant inside the nuclear medium. A decrease of the neutron-proton mass difference is obtained which is reasonably small and in the right direction to cope with the Nollenn-Schiffer anomaly in mirror nuclei. (author)

[en] A progress report of the CDHS and CHARM experiments measuring ν-oscillations at the CERN PS is presented. Expected rates and upper limits for the ν-mass differences and mixing angles are also given

[en] Short communication

[en] A new measurement of the Ξ⁰ mass verifies the accuracy of the Coleman-Glashow relation at the level predicted by the 1/N_c expansion. Values for other baryon isospin mass splittings are updated, and continue to agree with the 1/N_c hierarchy. (c) 2000 The American Physical Society