Study of Rapidity Gap Events in Hadronic Z Decays with the L3 Detector

TL;DR

This paper investigates rapidity gap events in hadronic Z decays to detect colour singlet exchange and colour reconnection effects, setting upper limits on their occurrence using data from the L3 detector.

Contribution

It provides the first experimental limits on colour singlet exchange and reconnection effects in Z decays, testing specific QCD predictions.

Findings

Upper limit of 7-9% for colour singlet exchange fraction.

Upper limit of 0.93% for the Rathsman model's colour reconnection parameter.

Asymmetries in particle flow are sensitive indicators of these effects.

Abstract

A search is performed in symmetric 3-jet hadronic Z decay events for evidence of colour singlet exchange and for colour reconnection effects predicted by the Rathsman model. Asymmetries in particle flow and the angular separation of particles are found to be sensitive to such effects. 95% upper limits of 7-9% are found for the fraction of colour singlet exchange, and of 0.93% for the colour reconnection parameter $R_0$ (default value 0.1) of the Rathsman model.