INSTITUTE OF PHYSICS PUBLISHING JOURNAL OF PHYSICS G: NUCLEAR AND PARTICLE PHYSICS J. Phys. G: Nucl. Part. Phys. 27 (2001) 391–396 www.iop.org/Journals/jg PII: S0954-3899(01)19186-3 Determination of the event centrality in the WA97 and NA57 experiments N Carrer on behalf of the WA97 and NA57 Collaborations: F Antinori 1 , A Badal ` a 2 , R Barbera 2 , W Beusch 3 , I J Bloodworth 4 , G Bruno 5 , R Caliandro 5 , M Campbell 3 , E Cantatore 3 , W Carena 3 , N Carrer 1,3 , A P de Haas 6 , D Di Bari 5 , S Di Liberto 7 , R Divia 3 , D Elia 5 , D Evans 4 , K Fanebust 8 , F Fayazzadeh 9 , J Fedoriˇ sin 10 , G A Feofilov 11 , R A Fini 5 , J Ft ´ aˇ cnik 12 , B Ghidini 5 , G Grella 13 , M Gulino 2 , H Helstrup 14 , M Henriquez 9 , A K Holme 9 , D Huss 15 , A Jacholkowski 5 , G T Jones 4 , P Jovanovic 4 , A Jusko 10 , R Kamermans 6 , J B Kinson 4 , W Klempt 3 , K Knudson 3 , A A Kolojvari 11 , V Kondratiev 11 , I Kr ´ alik 10 , P Kuijer 6 , V Lenti 5 , R Lietava 12 , G Løvhøiden 9 , M Lupt ´ ak 10 , V Manzari 5 , G Martinsk ´ a 10 , M A Mazzoni 7 , F Meddi 7 , A Michalon 16 , M E Michalon-Mentzer 16 , M Morando 1 , D Muigg 6 , E Nappi 5 , F Navach 5 , P I Norman 4 , A Palmeri 2 , G S Pappalardo 2 , B Pastirˇ c´ ak 10 , J Piˇ s´ ut 12 , N Piˇ s´ utov´ a 12 , F Posa 5 , E Quercigh 1,3 , F Riggi 2 ,DR¨ ohrich 8 , G Romano 13 , K ˇ Safaˇ r´ ık 3 ,L ˇ S´ andor 10 , E Schillings 6 , G Segato 1 , M Sen´ e 17 , R Sen´ e 17 , W Snoeys 3 , P Staroba 18 , M Thompson 4 , G D Torrieri 4 , T A Tulina 11 , R Turrisi 1 , T S Tveter 9 , J Urb ´ an 10 , F F Valiev 11 , A van den Brink 6 , P van de Ven 6 , P Vande Vyvre 3 , N van Eijndhoven 6 , L Vannucci 19 , A Vascotto 3 , T Vik 9 , O Villalobos Baillie 4 , L Vinogradov 11 , T Virgili 13 , M F Votruba 4 , J Vrl ´ akov´ a 10 and P Z ´ avada 18 1 Dipartimento di Fisica dell’Universit` a and Sezione INFN, Padua, Italy 2 Dipartimento di Fisica dell’Universit` a and Sezione INFN, Catania, Italy 3 CERN, European Laboratory for Particle Physics, Geneva, Switzerland 4 School of Physics and Astronomy, University of Birmingham, Birmingham, UK 5 Dipartimento I A di Fisica dell’Universit` a e del Politecnico di Bari and Sezione INFN, Bari, Italy 6 Utrecht University and NIKHEF, Utrecht, The Netherlands 7 Dipartimento di Fisica dell’Universit` a ‘La Sapienza’ and Sezione INFN, Rome, Italy 8 Fysisk institutt, Universitetet i Bergen, Bergen, Norway 9 Fysisk institutt, Universitetet i Oslo, Oslo, Norway 10 Institute of Experimental Physics SAS and P J ˇ Saf´ arik University, Koˇ sice, Slovakia 11 State University of St Petersburg, St Petersburg, Russia 12 Comenius University, Bratislava, Slovakia 13 Dipartimento di Scienze Fisiche ‘E R Caianiello’ dell’Universit` a and INFN, Salerno, Italy 14 Høgskolen i Bergen, Bergen, Norway 15 GRPHE, Universit´ e de Haute Alsace, Mulhouse, France 16 Institut de Recherches Subatomiques, IN2P3/ULP, Strasbourg, France 17 Coll` ege de France and IN2P3, Paris, France 18 Institute of Physics, Academy of Sciences of the Czech Republic, Prague, Czech Republic 19 INFN, Laboratori Nazionali di Legnaro, Legnaro, Italy Received 2 November 2000 0954-3899/01/030391+06$30.00 © 2001 IOP Publishing Ltd Printed in the UK 391