Low mass dimuon production in p–A collisions at GeV with NA60

Abstract

The NA60 experiment has studied low-mass muon pair production in proton–nucleus collisions with a system of Be, Cu, In, W, Pb and U targets using a 400 GeV/c proton beam at the CERN SPS. The mass spectrum is well described by the superposition of the two-body and Dalitz decays of the light neutral mesons η, ρ, ω, η′ and ϕ. A new high-precision measurement of the electromagnetic transition form factors of the η and ω mesons is presented, complemented with a measurement of the temperature parameter of the ρ meson in cold nuclear matter. The pT spectra for the ω and ϕ mesons are extracted in the full pT range accessible, up to pT = 2 GeV/c. The nuclear dependence of the production cross sections for the η, ω and ϕ mesons has been investigated in terms of the power law σpA∝Aα, and the α parameter was studied as a function of pT.