C. Berat

Measurement of the lifetime

We present the measurement of the lifetime of the Omega_c we have performed using three independent data samples from two different decay modes. Using a Sigma- beam of 340 GeV/c we have obtained clean signals for the Omega_c decaying into Xi- K- pi+ pi+ and Omega- pi+ pi- pi+, avoiding topological cuts normally used in charm analysis. The short but measurable lifetime of the Omega_c is demonstrated by a clear enhancement of the signals at short but finite decay lengths. Using a continuous maximum likelihood method we determined the lifetime to be tau(Omega_c) = 55 +13-11(stat) +18-23(syst) fs. This makes the Omega_c the shortest living weakly decaying particle observed so far. The short value of the lifetime confirms the predicted pattern of the charmed baryon lifetimes and demonstrates that the strong interaction plays a vital role in the lifetimes of charmed hadrons.

Xi- production by Sigma-, pi- and neutrons in the hyperon beam experiment at CERN

Inclusive cross sections for Ξ- hyperon production in high-energy Σ-, π- and neutron induced interactions were measured by the experiment WA89 at CERN. Secondary Σ- and π- beams with average momenta of 345 GeV/c and a neutron beam of 260 GeV/c were produced by primary protons of 450 GeV/c from the CERN SPS. The influence of the target mass on the Ξ- cross section is explored by comparing reactions on copper and carbon nuclei. Both single and double differential cross sections are presented as a function of the transverse momentum and the Feynman variable xF. A strong leading effect for Σ- produced by Σ- is observed.

First observation of the

Abstract. We report the first observation of the

\Xi^{-} \pi^{+}

\Xi^- \pi^+

decay mode of the

scattering mode of the

\Xi^{0}(1690)

\Xi^0

hyperon

(1690), confirming the existence of this resonance. The

Upper limit on the diffuse flux of UHE tau neutrinos

\Xi^0

Observation of a resonance in the K(s)p decay channel at a mass of 1765 MeV/c**2

(1690) were produced by

宇宙線スペクトルの「くるぶし」での混合質量組成の証拠

\Sigma^-