Low mass dimuon production in proton-nucleus collisions with the NA60 apparatus

Abstract

During the June 2002 run NA60 collected around 600 000 dimuon triggers in proton-nucleus collisions at 400 GeV. We show that the collected dimuon mass spectra can be understood in terms of known sources. The specific target setup, consisting of Beryllium, Indium and Lead targets, simultaneously exposed to the beam, allowed us to study the nuclear dependence of the production cross-section of the \(\omega\) and \(\phi\) resonances. The elementary nucleon-nucleon production cross-sections at 400 GeV for the \(\rho\), \(\omega\) and \(\phi\) mesons are also presented. By using the \(\eta\)-Dalitz decay, dominating the mass range below 450 MeV, we, furthermore, extracted the \(\eta\) production cross-section and its nuclear dependence. The results are discussed in the framework of previous measurements, mostly obtained in different decay channels, performed by NA27, HELIOS-1 and CERES-TAPS.