Measurement of Leading Particle Effects in Decays of Z0 Bosons into Light Flavors

TL;DR

This study provides experimental evidence for leading particle effects in Z0 boson decays into light-flavor jets, showing that high-momentum particles tend to carry the original quark flavor, with implications for understanding fragmentation processes.

Contribution

First direct evidence of leading particle effects in Z0 decays into light-flavor jets using polarized beams and advanced particle identification techniques.

Findings

High-momentum particles in quark jets are more likely to carry the primary quark flavor.

Asymmetries observed between particles and antiparticles support leading particle production.

s-s(bar) production is suppressed in the fragmentation process.

Abstract

We present evidence for leading particle production in hadronic decays of the Z0 boson to light-flavor jets. A polarized electron beam was used to tag quark and antiquark jets, and a vertex detector was employed to reject heavy-flavor events. Charged hadrons were identified with a Cherenkov ring imaging detector. In the quark jets, more high-momentum p, Lambda, K-, and anti-K*0 were observed than their antiparticles, and vice versa for antiquark jets, providing direct evidence that the higher-momentum particles in jets are more likely to carry the primary quark or antiquark from the Z0 decay, and that s-s(bar) production is suppressed in fragmentation.