Production of Lambda and Sigma^0 hyperons in proton-proton collisions

TL;DR

This study measures hyperon production in proton-proton collisions at various energies, revealing insights into the reaction mechanisms, resonance contributions, and the role of kaon exchange, providing benchmarks for theoretical models.

Contribution

It offers detailed experimental data on hyperon production cross sections and angular distributions, highlighting the significance of nucleon resonances and kaon exchange in the processes.

Findings

High energy limit of cross section ratio nearly reached at 200 MeV excess energy

Interfering nucleon resonances significantly contribute to bLambda production

Kaon exchange plays a minor role in bLambda but an important role in bSigma^0 production

Abstract

This paper reports results on simultaneous measurements of the reaction channels pp -> pK+\Lambda and pp -> pK+\Sigma^0 at excess energies of 204, 239, and 284 MeV (\Lambda) and 127, 162, and 207 MeV (\Sigma^0). Total and differential cross sections are given for both reactions. It is concluded from the measured total cross sections that the high energy limit of the cross section ratio is almost reached at an excess energy of only about 200 MeV. From the differential distributions observed in the overall CMS as well as in the Jackson and helicity frames, a significant contribution of interfering nucleon resonances to the \Lambda production mechanism is concluded while resonant \Sigma^0-production seems to be of lesser importance and takes place only through specific partial waves of the entrance channel. The data also indicate that kaon exchange plays a minor role in the case of \Lambda- but an important role for \Sigma^0-production. Thus the peculiar energy dependence of the \Lambda-to-\Sigma^0 cross section ratio appears in a new light as its explanation requires more than mere differences between the p\Lambda and the p\Sigma^0 final state interaction. The data provide a benchmark for theoretical models already available or yet to come.