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PL9902547

THE ALICE EXPERIMENT LABORATORY

Head of Laboratory: Prof. Jerzy Bartke telephone: (48) (12) 633-33-66 fax: (48) (12) 633-38-84 e-mail: [email protected]

PERSONNEL:

Research Staff: Jerzy Bartke, Prof. Andrzej Rybicki, M.Sc, Ph.D. Student, Ewa Gladysz-Dziadus, Ph.D. Piotr Stefanski, Ph.D. Marek Kowalski, Ph.D.

Technical Staff: Ewa Bukala Maria Mielnik, M.A. Danuta Filipiak Maria Pieczora Danuta Krzyszton Tadeusz Wojas

OVERVIEW:

The Laboratory is involved in research with ultrarelativistic heavy ions: the NA49 experiment at the CERN SPS and the preparation of the ALICE experiment at the CERN LHC. The aim of the NA49 experiment is to study the production of charged and charged and neutral strange in collisions of ultrarelativistic nuclei with nuclear targets. The production of strangeness (A and E-hyperons, -mesons, and both, neutral and charged, ), single spectra as well as two- correlations (boson interferometry) are investigated in a search for the phase transition of nuclear matter to the - Plasma predicted by Lattice QCD. The NA49 experiment1 is a continuation of NA35 using the beam of 158 GeV/ (the NA35 experiment used oxygen and sulphur beams). The major components of the detector are two large volume, fine granularity time projection chambers (MTPC), and two smaller high resolution time projection chambers (VTPC) placed in a magnetic field. The identification system is completed by high resolution time of flight walls. The new additions to the setup are the time of flight system based on Pestov counters and a small "forward" TPC with the new readout scheme. The forward angle calorimeters measure the directional energy flow and provide a trigger on the "centrality" of the collisions. Large acceptance of the detector allows the study of global dynamical observables to be done at the event-by-event level. NA49 is seen by the CERN Management as the only fixed-target heavy ion experiment to remain on the floor until the year 2000, and perhaps even beyond it.

1 Participating laboratories: Athens, Berkeley, Birmingham, Bratislava, Budapest, CERN, Darmstadt, Davis, JINR, Frankfurt, Houston, Krakow, Los Angeles, Marburg, Miinchen, Yale, Seattle, Warszawa, Zagreb. 210

In 1998 interactions of with various nuclear targets were recorded with a new "centrality" trigger as well as Pb+Pb interactions at 158 A GeV and at 40 A GeV. Two people from Krakow participated in data taking runs. Our group was responsible for the maintenance of the TPC low- voltage system, built in Krakow in 1994-95. The NA49 physics data analysis was continued in 1998, leading to several publications and con- ference reports. The Krakow group took part in two NA49 workshops, during which the prepared papers were discussed. ALICE (A Large Ion Collider Experiment)2 is a dedicated detector for heavy ion physics at the LHC whose goal is to pursue similar research at much higher energies. The experiment was approved by the CERN Management on February 6, 1997 and should be on the floor in the year 2005 when the LHC is expected to enter into operation. The main tracking detector of ALICE is the large cylindrical (TPC). Its task will be track finding, momentum measurement and particle identification by energy loss dE/dx. Simulations of the TPC performance have been carried out in Krakow. The fragmentation regions of colliding heavy ions seem to be also interesting from the point of view of "exotic" events observed so far only in cosmic ray experiments: "centauros" and "strangelets". An additional, special detector, named CASTOR has been proposed to look for these phenomena. After having been reviewed by the panel of CERN experts, the CASTOR detector was approved in 1998, at least in its calorimeter part, the multiplicity detectors needing some further studies. Our group performed some calorimeter simulations for this proposal. The six subsequent short reports summarize our activities in 1998.

Professor Jerzy Bartke

REPORTS ON RESEARCH: PL9902548

Baryon Stopping in p+p, P+Pb and Pb+Pb Collisions at 158 A GeV Projectile Energy H.G. Fischer1, A. Rybicki, and F. Sikler2 1CERN, Geneva,, Switzerland, 2KFKI Research Institute for Particle and Nuclear Physics, Budapest, Hungary

Baryon stopping in hadronic interactions can be studied by investigating longitudinal momentum spectra (or xp spectra) of observed in the collision. Especially useful is a comparative study of such spectra for various types of collisions, e.g. hadron-nucleon, hadron-nucleus, and nucleus- nucleus interactions. Such a study is possible in the NA49 experiment for various projectile and target types, and for a large fraction of the available phase space. Moreover, the addition of the Centrality Detector [l] to the NA49 setup allows a more detailed study of hadron-nucleus interactions as a function of collision centrality.

Participating laboratories: Alessandria, Aligarh, Athens, Attikis, Ban, Bijing, Bergen, Birmingham, Bombay, Bratislava, Budapest, Cagliari, Calcutta, Catania, CERN, Chandigahr, Clermont-Ferrand, Copenhagen, Darmstadt, Frankfurt, Gatchina, Heidelberg, Ioannina, Jaipur, Jammu, JINR, Kharkov, Kiev, Kosice, Krakow, Legnaro, Lund, Lyon, Marburg, Mexico City, Minsk, Moscow, Minister, Nantes, Novosibirsk, Oak Ridge, Ohio, Orsay, Oslo, Padua, Prague, Protvino, Rehovot, Re2, Rome, Salerno, Sarov, St. Petersburg, Strasbourg, Trieste, Turin, Utrecht, Warszawa, Wuhan, Yerevan, Zagreb.