Inclusive Σ− and Λ(1520) production in hadronic Z decays

Production of Σ − and Λ(1520) in hadronic Z decays has been measured using the Delphi detector at Lep. The Σ − is directly reconstructed as a charged track in the Delphi microvertex detector and is identified by its Σ→n π decay leading to a kink between the Σ − and π-track. The reconstruction of the Λ(1520) resonance relies strongly on the particle identification capabilities of the barrel Ring Imaging Cherenkov detector and on the ionisation loss measurement of the TPC. Inclusive production spectra are measured for both particles. The production rates are measured to be 〈N Σ − /N Z had 〉=0.081±0.002±0.010 , 〈N Λ(1520)/N Z had 〉=0.029±0.005±0.005 . The production rate of the Λ(1520) suggests that a large fraction of the stable baryons descend from orbitally excited baryonic states. It is shown that the baryon production rates in Z decays follow a universal phenomenological law related to isospin, strangeness and mass of the particles.