Σ−-antihyperon correlations in Z0 decay and investigation of the baryon production mechanism

Abstract

Data collected around √ s = 91 GeV by the OPAL experiment at the LEP e + e − collider are used to study the mechanism of baryon formation. As the signature, the fraction of − hyperons whose baryon number is compensated by the production of a − , or − antihyperon is determined. The method relies entirely on quantum number correlations of the baryons, and not rapidity correlations, making it more model independent than previous studies. Within the context of the JETSET implementation of the string hadronization model, the diquark baryon production model without the popcorn mechanism is strongly disfavored with a significance of 3.8 standard deviations including systematic uncertainties. It is shown that previous studies of the popcorn mechanism with and pπp cora

Signal propagation in long wire chambers

“…For high momentum kaons, this happens at cos θ * π = −0.61, where θ * π is the pion emission angle in the the kaon rest frame. In the backward region cos θ * π < −0.61 the reconstructed masses differ from the Σ mass at most by 8%, if the kaons are reconstructed as Σ hyperons [22], irrespective of the kaon momentum. A finite resolution introduces a phase space overlap between kaons and Σ − hyperons [22] and any improvement of the z resolution helps to reduce the region of confusion.…”

“…In the backward region cos θ * π < −0.61 the reconstructed masses differ from the Σ mass at most by 8%, if the kaons are reconstructed as Σ hyperons [22], irrespective of the kaon momentum. A finite resolution introduces a phase space overlap between kaons and Σ − hyperons [22] and any improvement of the z resolution helps to reduce the region of confusion. Fortunately, the resolution problem turned out to be much less severe in the interior of the chamber, where the z resolution of the Σ − decay vertex was only 40% larger [22] than the statistical error of the Monte Carlo prediction [23], based on independent hits.…”

“…A finite resolution introduces a phase space overlap between kaons and Σ − hyperons [22] and any improvement of the z resolution helps to reduce the region of confusion. Fortunately, the resolution problem turned out to be much less severe in the interior of the chamber, where the z resolution of the Σ − decay vertex was only 40% larger [22] than the statistical error of the Monte Carlo prediction [23], based on independent hits. Equation (5.2) for the final z coordinates uses hit information only and does not depend explicitly on global track parameters.…”