Inclusive Sigma- and Lambda(1520) production in hadronic Z decays

TL;DR

This paper measures the production rates of Sigma- and Lambda(1520) baryons in hadronic Z decays using the DELPHI detector, revealing insights into baryon production mechanisms and their relation to particle properties.

Contribution

It provides the first detailed measurements of Sigma- and Lambda(1520) production in Z decays and demonstrates a universal law governing baryon production rates.

Findings

Lambda(1520) production suggests many baryons originate from excited states.

Baryon production rates follow a universal phenomenological law.

Measured production rates are consistent with theoretical expectations.

Abstract

Production of Sigma- and Lambda(1520) in hadronic Z decays has been measured using the DELPHI detector at LEP. The Sigma- is directly reconstructed as a charged track in the DELPHI microvertex detector and is identified by its Sigma -> n pi decay leading to a kink between the Sigma- and pi-track. The reconstruction of the Lambda(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_{Sigma-}/N_{Z}^{had}> = 0.081 +/- 0.002 +/- 0.010, <N_{Lambda(1520)}/N_{Z}^{had}> = 0.029 +/- 0.005 +/- 0.005. The production rate of the Lambda(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.