K. J. S. Ragan

Ξ− and Ξ− inclusive production in Ξ− Be interactions at 116 GeV/c

The cross sections for Ξ− and Ω− inclusive production in Ξ− Be collisions at 116 GeV/c have been measured in the kinematic domain [0.1<xF<0.9, 0<pT<1.7 GeV/c]. The integrated cross sections per nucleon are found to be about twice as large as in Ξ−p collisions. The invariant cross sections increase by a factor of 70 for the Ξ−s and of 100 for the Ω−s between the central region (xF∼0.2) and the projectile fragmentation region (xF∼0.8). In the central region, they have about the same magnitude as the ones for Ξ− and Ω− inclusive production inp nucleon collisions. The Ξ− and Ω− polarisations have been measured over the same kinematic domain and are found to be compatible with zero.

First observation ofΩ* resonances

In a experiment at the CERN SPS charged hyperon beam using incident Ξ−, we have obtained evidence for the production of two Ω* resonances decaying into Ξ−π+K−, with the following parameters:M1=2251±12,Γ1=48±20 MeV/c2, 78 ±23 events, andM2=2284±12,Γ2=26±23 MeV/c2 45±10 events. The first state is also observed as a 4.2σ effect in a subsample which contains an additionalK+ orK0 in the final state. Production cross sections and branching ratios to Ξ*K− and Ξ−K* are presented.

First measurement of the Λ→nγ branching ratio

In an experiment performed at the CERN-SPS charged hyperon beam, we have observed the radiative decay Λ→nγ, using well identified Λ from the decays of Ο− of 116 GeV/c momentum. Neutrons and photons from the Λ decays were observed in liquid argon and lead glass detectors. From a sample of 31 candidates, containing an estimated background of 7.3 events, the decay branching ratio was measured to be Γ(Λ→nγ)/Γ(Λ→all)=(1.02±0.33)×10−3.

Ξ Resonances in Ξ− Be interactions II. Properties of Ξ(1820) and Ξ(1960) in the\(\Lambda \bar K^0 \) and\(\Sigma ^0 \bar K^0 \) channels

AbstractIn an experiment at the CERN-SPS charged hyperon beam, we have investigated the inclusive

Inclusive Ξ0, Ξ(1530)- and Ξ(1530)0 production in Ξ--Be interactions at 116 GeV/c

\Lambda \bar K^0

Ξ* resonances inΞ−be interactions

and

First measurement of the (Ξ−→∑−γ)/(Ξ−→Λπ−) branching ratio

\Sigma ^0 \bar K^0