Data di Pubblicazione:
2000
Abstract:
Muon pair production in p-A, S-U and Pb-Pb collisions has been studied by the NA38 and NA50 collaborations at the CERN SPS. In this paper we present an analysis of the dimuon invariant mass region between the φ and the J/ ψ . In p-A collisions we find that, after the subtraction of the combinatorial background due to π and K decays, the superposition of dimuons from semi-leptonic decays of D mesons and from the Drell-Yan process reproduces well the measured mass and transverse momentum spectra. The yield of open charm dimuons required to fit our data leads to a charm production cross section in good agreement with previous measurements. A linear extrapolation of the p-A sources with the product of the mass numbers of the projectile and target nuclei, A× B, underestimates the dimuon yield measured in S-U and Pb-Pb collisions. The excess increases with the number of participant nucleons, and the ratio between the observed dimuon yield and the expected sources reaches a factor 2 for central Pb-Pb interactions. The kinematical distributions of the measured dimuon excess are compatible with those expected from the open charm contribution.
Tipologia CRIS:
03A-Articolo su Rivista
Elenco autori:
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; L. 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; Fairouz 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; N. Willis
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