Results on open charm from NA50

Masera, Massimo; Abreu, M. C.; Alessandro, B.; Alexa, C.; Arnaldi, Roberta; Atayan, M.; Baglin, C.; Baldit, A.; Bedjidian, M.; Beole', Stefania; Boldea, V.; Bordalo, P.; Bussière, A.; Capelli, L.; Casagrande, L.; Castor, J.; Chambon, T.; Chaurand, B.; Chevrot, I.; Cheynis, B.; Chiavassa, Emilio Luciano; Cicalò, C.; Claudino, T.; Comets, M. P.; Constans, N.; Constantinescu, S.; De Falco, A.; De Marco, N.; Dellacasa, Giuseppe; Devaux, A.; Dita, S.; Drapier, O.; Ducroux, L.; Espagnon, B.; Fargeix, J.; Force, P.; Gallio, Mauro; Gavrilov, Y. K.; Gerschel, C.; Giubellino, P.; Golubeva, M. B.; Gonin, M.; Grigorian, A. A.; Grossiord, J. Y.; Guber, F. F.; Guichard, A.; Gulkanyan, H.; Hakobyan, R.; Haroutunian, R.; Idzik, M.; Jouan, D.; Karavitcheva, T. L.; Kluberg, L.; Kurepin, A. B.; Le Bornec, Y.; Lourenço, C.; Macciotta, P.; Mac Cormick, M.; Marzari Chiesa, A.; Masera, Massimo; Masoni, A.; Mehrabyan, S.; Monteno, M.; Musso, A.; Petiau, P.; Piccotti, A.; Pizzi, J. R.; Prino, F.; Puddu, G.; Quintans, C.; Ramos, S.; Ramello, Luciano; Rato Mendes, P.; Riccati, L.; Romana, A.; Ropotar, I.; Saturnini, P.; Scomparin, E.; Serci, S.; Shahoyan, R.; Silva, S.; Sitta, Mario; Soave, C.; Sonderegger, P.; Tarrago, X.; Topilskaya, N. S.; Usai, G. L.; Vercellin, Ermanno; Villatte, L.; Willis, N.

doi:10.1088/0954-3899/27/3/353

The NA50 and NA38 experiments have studied muon pair production in p-A and nucleus-nucleus collisions at the CERN SPS. Results on dimuons in the invariant mass region between the phi and the J/ψ masses (IMR) are presented. The standard sources of muon pairs in the IMR are the Drell-Yan process and the semileptonic decay of charmed mesons. A new four-dimensional unfolding method is applied to the data. The p-A results are well described in terms of these known sources, which, in contrast, fail to explain nucleus-nucleus data: an extra yield of muon pairs is observed. Although this excess is compatible with an enhanced production of charmed hadrons, other possible sources cannot be excluded. In particular, a comparison between data and predictions from a theoretical model which calculates the production of thermal dimuons is presented in this paper.