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

The NA38 and NA50 Collaborations:     M.C. Abreu - et al.

doi:doi:10.1007/s100520000373

2022 Impact factor 4.4

Particles and Fields

Eur. Phys. J. C 14, 443-455
DOI 10.1007/s100520000373

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

The NA38 and NA50 Collaborations

M.C. Abreu⁷ - B. Alessandro¹² - C. Alexa⁴ - R. Arnaldi¹² - J. Astruc⁹ - M. Atayan¹⁴ - C. Baglin² - A. Baldit³ - M. Bedjidian¹³ - F. Bellaiche¹³ - S. Beolè¹² - V. Boldea⁴ - P. Bordalo⁷ - A. Borhani¹⁰ - A. Bussière² - L. Capelli¹³ - V. Capony² - L. Casagrande⁷ - J. Castor³ - T. Chambon³ - B. Chaurand¹⁰ - I. Chevrot³ - B. Cheynis¹³ - E. Chiavassa¹² - C. Cicalò⁵ - T. Claudino⁷ - M.P. Comets⁹ - N. Constans¹⁰ - S. Constantinescu⁴ - J. Cruz⁷ - A. De Falco⁵ - N. De Marco¹² - G. Dellacasa¹ - A. Devaux³ - S. Dita⁴ - O. Drapier^13,6 - L. Ducroux¹³ - B. Espagnon³ - J. Fargeix³ - F. Fleuret¹⁰ - P. Force³ - M. Gallio¹² - Y.K. Gavrilov⁸ - C. Gerschel⁹ - P. Giubellino¹² - M.B. Golubeva⁸ - M. Gonin¹⁰ - A.A. Grigorian¹⁴ - J.Y. Grossiord¹³ - F.F. Guber⁸ - A. Guichard¹³ - H. Gulkanyan¹⁴ - R. Hakobyan¹⁴ - R. Haroutunian¹³ - M. Idzik¹² - D. Jouan⁹ - T.L. Karavitcheva⁸ - L. Kluberg¹⁰ - A.B. Kurepin⁸ - Y. Le Bornec⁹ - C. Lourenço⁶ - P. Macciotta⁵ - M. Mac Cormick⁹ - A. Marzari-Chiesa¹² - M. Masera¹² - A. Masoni⁵ - S. Mehrabyan¹⁴ - M. Monteno¹² - S. Mourgues³ - A. Musso¹² - F. Ohlsson-Malek¹³ - P. Petiau¹⁰ - A. Piccotti¹² - J.R. Pizzi¹³ - G. Puddu⁵ - C. Quintans⁷ - C. Racca¹¹ - L. Ramello¹ - S. Ramos⁷ - P. Rato-Mendes⁷ - L. Riccati¹² - A. Romana¹⁰ - I. Ropotar⁶ - P. Saturnini³ - E. Scomparin¹² - S. Serci⁵ - R. Shahoyan⁷ - S. Silva⁷ - M. Sitta¹ - C. Soave¹² - P. Sonderegger⁶ - X. Tarrago⁹ - N.S. Topilskaya⁸ - G.L. Usai⁵ - E. Vercellin¹² - L. Villatte⁹ - N. Willis⁹

¹ Università del Piemonte Orientale, Alessandria and INFN-Torino, Italy
² LAPP, CNRS-IN2P3, Annecy-le-Vieux, France
³ LPC, Université Blaise Pascal and CNRS-IN2P3, Aubière, France
⁴ IFA, Bucharest, Romania
⁵ Università di Cagliari/INFN, Cagliari, Italy
⁶ CERN, Geneva, Switzerland
⁷ LIP, Lisbon, Portugal
⁸ INR, Moscow, Russia
⁹ IPN, Université de Paris-Sud and CNRS-IN2P3, Orsay, France
¹⁰ LPNHE, Ecole Polytechnique and CNRS-IN2P3, Palaiseau, France
¹¹ IRS, Université Louis Pasteur and CNRS-IN2P3, Strasbourg, France
¹² Università di Torino/INFN, Torino, Italy
¹³ IPN, Université Claude Bernard and CNRS-IN2P3, Villeurbanne, France
¹⁴ YerPhI, Yerevan, Armenia

Received: 20 December 1999 / Revised version: 4 February 2000 /
Published online: 14 April 2000 - © Springer-Verlag 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 $\phi$ and the J/ $\psi$ . In p-A collisions we find that, after the subtraction of the combinatorial background due to $\pi$ 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, $A\times B$ , 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.