Status of the CHORUS neutrino oscillation experiment

The CHORUS experiment is designed to search for ν_μ → ν_τ oscillation with a hybrid detector system containing 800 kg nuclear emulsions as target and vertex detector. Run I (320 000 recorded ν_μCC in 1994/5) and more than half of the run II (460 000 ν_μCC in 1996/7) data taking have been successfully completed. Approximately 80 000 events have been analyzed so far, searching for and τ⁻ → h⁻ (nπ⁰) ν_τ decays. No candidate has been found, leading to a limit sin² 2θ_μτ ≤ 4.5 10⁻³ for large Δm².     

Double-β decays with the NEMO experiment: final results of NEMO-2 with various nuclei and status of NEMO-3

The NEMO-2 prototype, built for background measurements and located in the Fréjus Underground Laboratory (4800 m w.e.) has provided results with three ββ decay sources, ¹⁰⁰Mo, ¹¹⁶Cd and ⁸²Se with data accumulated over a total of 23000 h. Final results of ββ2ν half-lives measurements and limits on 0ν modes are given here. The NEMO-3 detector which will be able to accomodate sources of 10 kg is now under construction. The aim of the experiment is to reach a half-life measurement of 10²⁵y for ββ0ν decay, which corresponds to a Majorana neutrino mass of 0.1 eV for ¹⁰⁰Mo.     

Search for scalar fermions and long-lived scalar leptons at centre-of-mass energies of 130 GeV to 172 GeV

Data taken by DELPHI during the 1995 and 1996 LEP runs have been used to search for the supersymmetric partners of electron, muon and tau leptons and of top and bottom quarks. The observations are in agreement with standard model predictions. Limits are set on sfermion masses. Searches for long lived scalar leptons from low scale supersymmetry breaking models exclude stau masses below 55 GeV/c at the 95% confidence level, irrespective of the gravitino mass. Received: 13 July 1998 / Published online: 19 November 1998     

New Suppression Mode of the ψ(2S) Hadronic Decay

The hadronic decays ,and ωf2(1270) have been studied in a sample of 1.27 million produced.Measurements of their branching fractions are presented. While obeys the "14% rule" predicted by theory, →ωf2 (1270) is suppressed comparing with the corresponding decay. As a vector-tensor pair combination, the ωf2 mode is the first example of a non-vector-pseudoscalar decay of charmonium which violates the above mentioned rule.     

Measurement of J/ψ Resonance Parameters

The cross sections of e⁺e^－→hadrons,e⁺e^－,μ⁺μ^－have been measured in the vicinity of J/ψresonance at BES/BEPC.The fit of the observed cross sections gives the new results of J/ψ resonance parameters:the partial widths to hadrons,electrons and muous are Γh=74.1±8.1keV,Γe= 5.14±0.39keV and Γμ=5.13±0.52keV respectively;the total width Γ=84.4±8.9keV;the branching fractions Γh/Γ=(87.8±0.5)%,Γe/Γ=(6.09± 0.33)%,and Γμ/Γ=(6.08±0.33) %.