Four-jet final state production in e+e- collisions at centre-of-mass energies ranging from 130 to 184 GeV

European Organization for Nuclear Research
Sezione di Milano Istituto Nazionale di Fisica Nucleare
Sezione di Catania Istituto Nazionale di Fisica Nucleare
Sezione di Bari Istituto Nazionale di Fisica Nucleare
Service de Physique des Particules
Santa Cruz Institute for Particle Physics
Laboratoire de l'Accélérateur Linéaire
Johannes Gutenberg Universität Mainz
Università di Pisa
Institute of High Energy Physics Chinese Academy of Science
Los Angeles University of California
IN2P3 Institut National de Physique Nucleaire et de Physique des Particules
Lancaster University
Universität Siegen
Universitat Autònoma de Barcelona
Rutherford Appleton Laboratory
Consiglio Nazionale delle Ricerche
Università degli Studi di Firenze
Université de la Méditerranée Aix-Marseille II
Royal Holloway University of London

Abstract

The four jet topology is analysed in the ALEPH data taken between November 1995 and October 1997, at centre-of-mass energies ranging from 130 to 184 GeV. While an unexpected accumulation of events with a dijet mass sum around 105 GeV/c 2 had been observed during the first run in 1995 at 130/136 GeV, corresponding to an integrated luminosity of 5.7 pb1 , no significant dierences between data and standard model prediction is seen, either in the high energy runs (81.1 pb1 taken at centre-of-mass energies from 161 to 184 GeV) or in the 7.1 pb1 recorded during a new short run at 130/136 GeV in 1997. We have found no other explanation for the earlier reported \four jet anomaly" than a statistical uctuat