Digital Object Identifier (DOI) 10.1140/epjcd/s2004-03-1705-3 Eur Phys J C 33, s01, s618–s620 (2004) EPJ C direct electronic only Hyperon production in lead–lead interactions at 40 and 160 A GeV/c Presented by H. Helstrup 4 , for the NA57 Collaboration: F. Antinori 12 , P.A. Bacon 5 , A. Badal` a 7 , R. Barbera 7 , A. Belogianni 1 , A. Bhasin 5 , I.J. Bloodworth 5 , M. Bombara 9 , G.E. Bruno 2 , S.A. Bull 5 , R. Caliandro 2 , M. Campbell 8 , W. Carena 8 , N. Carrer 8 , R.F. Clarke 5 , A. Dainese 12 , A.P. de Haas 19 , P.C. de Rijke 19 , D. Di Bari 2 , S. Di Liberto 15 , R. Divi` a 8 , D. Elia 2 , D. Evans 5 , K. Fanebust 4 , G.A. Feofilov 17 , R.A. Fini 2 , P. Ganoti 1 , B. Ghidini 2 , G. Grella 16 , H. Helstrup 4 , A.K. Holme 11 , A. Jacholkowski 2 , G.T. Jones 5 , P. Jovanovic 5 , A. Jusko 5 , R. Kamermans 19 , J.B. Kinson 5 , K. Knudson 8 , A.A. Kolozhvari 17 , V. Kondratiev 17 , I. Kr´ alik 9 , A. Kravˇ c´akov´ a 10 , P. Kuijer 19 , V. Lenti 2 , R. Lietava 5 , G. Løvhøiden 11 , V. Manzari 2 , G. Martinsk´ a 10 , M.A. Mazzoni 15 , F. Meddi 15 , A. Michalon 18 , M. Morando 12 , E. Nappi 2 , F. Navach 2 , P.I. Norman 5 , A. Palmeri 7 , G.S. Pappalardo 7 , B. Pastirˇ c´ak 9 , J. Piˇ s´ ut 6 , N. Piˇ s´ utova 6 , F. Posa 2 , E. Quercigh 12 , F. Riggi 7 , D. R¨ ohrich 3 , G. Romano 16 , K. ˇ Safaˇ r´ ık 8 , L. ˇ S´ andor 8, 9 , E. Schillings 19 , G. Segato 12 , M. Sen´ e 13 , R. Sen´ e 13 , W. Snoeys 8 , F. Soramel 12a , M. Spyropoulou-Stassinaki 1 , P. Staroba 14 , T.A. Toulina 17 , R. Turrisi 12 , T.S. Tveter 11 , J. Urb´ an 10 , F. Valiev 17 , A. van den Brink 19 , P. van de Ven 19 , P. Vande Vyvre 8 , N. van Eijndhoven 19 , J. van Hunen 8 , A. Vascotto 8 , T. Vik 11 , O. Villalobos Baillie 5 , L. Vinogradov 17 , T. Virgili 16 , M.F. Votruba 5 , J. Vrl´ akov´ a 10 , and P. Z´ avada 14 1 Physics Department, University of Athens, Athens, Greece 2 Dipartimento IA di Fisica dell’Universit`a e del Politecnico and INFN, Bari, Italy 3 Fysisk Institutt, Universitetet i Bergen, Bergen, Norway 4 Høgskolen i Bergen, Bergen, Norway 5 School of Physics and Astronomy, University of Birmingham, Birmingham, UK 6 Comenius University, Bratislava, Slovakia 7 University of Catania and INFN, Catania, Italy 8 CERN, European Laboratory for Particle Physics, Geneva, Switzerland 9 Institute of Experimental Physics, Slovak Academy of Science, Koˇ sice, Slovakia 10 P.J. ˇ Saf´arikUniversity,Koˇ sice, Slovakia 11 Fysisk Institutt, Universitetet i Oslo, Oslo, Norway 12 University of Padua and INFN, Padua, Italy 13 Coll` ege de France, Paris, France 14 Institute of Physics, Academy of Sciences of the Czech Republic, Prague, Czech Republic 15 University “La Sapienza” and INFN, Rome, Italy 16 Dip. di Scienze Fisiche “E.R. Caianiello” dell’Universit`a and INFN, Salerno, Italy 17 State University of St. Petersburg, St. Petersburg, Russia 18 Institut de Recherches Subatomique, IN2P3/ULP, Strasbourg, France 19 Utrecht University and NIKHEF, Utrecht, The Netherlands Received: 14 October 2003 / Accepted: 9 February 2004 / Published Online: 26 February 2004 – c  Springer-Verlag / Societ`a Italiana di Fisica 2004 Abstract. The NA57 experiment has measured strange baryon and antibaryon production in Pb-Pb colli- sions at 40 A GeV/c and 160 A GeV/c beam momenta. This presentation covers strangeness enhancement and transverse spectra from the 160 A GeV/c data, and energy dependence of the particle yields. En- hancement factors increase with increasing strangeness content of the particle, when production yields from Pb-Pb collisions are compared with those observed in p-Be and p-Pb interactions. The transverse mass spectra have been analysed both with exponential fits and using a transverse flow model. 1 Introduction The NA57 experiment has been designed to study the production of strange baryons and antibaryons in heavy a Permanent address: University of Udine, Udine, Italy ion collisions. The experiment has extended the WA97 [1] measurements to a wider centrality range and to lower beam momentum. The NA57 results on hyperon produc- tion at 160 A GeV/c confirm the pattern observed by WA97, where the enhancement factor increases with in- creasing strangeness content of the particle. The largest