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Dimuon and charm production in nucleus-nucleus collisions at the CERN-SPS

By M.C. Abreu, B. Alessandro, C. Alexa, R. Arnaldi, J. Astruc, M. Atayan, C. Baglin, A. Baldit, M. Bedjidian, F. Bellaiche, S. Beole, V. Boldea, P. Bordalo, A. Borhani, A. Bussiere, Laurent Capelli, V. Capony, L. Casagrande, J. Castor, T. Chambon, B. Chaurand, I. Chevrot, B. Cheynis, E. Chiavassa, C. Cicalo, T. Claudino, M.P. Comets, N. Constans, S. Constantinescu, J. Cruz, A. De Falco, N. De Marco, G. Dellacasa, A. Devaux, S. Dita, O. Drapier, L. Ducroux, B. Espagnon, J. Fargeix, F. Fleuret, P. Force, M. Gallio, Y.K. Gavrilov, C. Gerschel, P. Giubellino, M.B. Golubeva, M. Gonin, A.A. Grigorian, J.-Y. Grossiord, F.F. Guber, A. Guichard, H. Gulkanyan, R. Hakobyan, R. Haroutunian, M. Idzik, D. Jouan, T.L. Karavitcheva, L. Kluberg, A.B. Kurepin, Y. Le Bornec, C. Lourenco, P. Macciotta, M. Mac Cormick, A. Marzari-Chiesa, M. Masera, A. Masoni, S. Mehrabyan, M. Monteno, S. Mourgues, A. Musso, F. Ohlsson-Malek, P. Petiau, A. Piccotti, J.-R. Pizzi, G. Puddu, C. Quintans, C. Racca, L. Ramello, S. Ramos, P. Rato-Mendes, L. Riccati, A. Romana, I. Ropotar, P. Saturnini, E. Scomparin, S. Serci, R. Shahoyan, S. Silva, M. Sitta, C. Soave, P. Sonderegger, X. Tarrago, N.S. Topilskaya, G.L. Usai, E. Vercellin, L. Villatte and N. Willis

Abstract

NA50Muon pair production in \mbox{p-A}, \mbox{S-U} and \mbox{Pb-Pb}collisions has been studied by the NA38 and NA50 collaborations at theCERN SPS. In this paper we present an analysis of the dimuon invariantmass region between the $\phi$ and the \jpsi. After subtraction ofthe combinatorial background due to $\pi$ and K decays, we find thatthe superposition of dimuons from semi-leptonic decays of D mesons andfrom the Drell-Yan process reproduces well the mass and transversemomentum spectra measured in \mbox{p-A} collisions. From the yield ofopen charm dimuons required to fit our data we extract a charmproduction cross section in good agreement with previous measurements.A linear extrapolation of the \mbox{p-A} sources with the product ofthe mass numbers of the projectile and target nuclei, $A\times B$, underestimates the yield measured in \mbox{S-U} and \mbox{Pb-Pb}collisions. The excess increases with the number of participantnucleons, and the ratio between the observed dimuon yield and theexpected sources reaches a factor 2 for central \mbox{Pb-Pb}interactions. The kinematical distributions of the measured dimuonexcess are compatible with those expected from the open charmcontribution

Topics: [ PHYS.HPHE ] Physics [physics]/High Energy Physics - Phenomenology [hep-ph]
Publisher: Springer Verlag (Germany)
Year: 2000
OAI identifier: oai:HAL:in2p3-00009703v1
Provided by: HAL-IN2P3

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