Prospects for the NA60+ experiment at the CERN SPS

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In this talk, the prospects and the physics goals of a new fixed-target experiment, NA60+, which has been proposed for taking data with heavy-ion collisions at the CERN SPS in the next years, will be presented. The competitiveness and complementarity of the NA60+ physics program in the landscape of the experiments foreseen at other facilities in the next decade will also be discussed.

The high-intensity beams provided by the CERN SPS in a wide energy interval provide a unique opportunity to investigate the region of the QCD phase diagram at high baryochemical potential, $\mu_{\rm B}$, via measurements of rare signals. In particular, the main goals of the NA60+ experiment will be focused on precision studies of heavy quark and thermal dimuon production in Pb-Pb collisions via a beam-energy scan in the centre-of-mass energy interval $\sqrt{s_{\rm NN}}=5-17$~GeV. The proposed experimental apparatus consists of a vertex telescope located close to the target, and a muon spectrometer located downstream of a hadron absorber. The vertex telescope will consist of several planes of monolithic active pixel sensors embedded in a dipole magnetic field. The muon spectrometer will utilize GEM and RPC detectors for muon tracking and trigger, and a toroidal magnet based on a new light-weight and general-purpose concept. This apparatus, based on state-of-the-art technologies, will allow a very broad and ambitious physics program.

The high-precision measurements of dimuon invariant mass distributions will open the possibility to investigate the order of the phase transition from the quark-gluon plasma to the hadron gas in the interval $\mu_{\rm B}\approx 200-400$~MeV via the first measurement of the caloric curve. In addition, the first direct measurement of $\rho-{\rm a}_1$ chiral mixing could be achieved by a precision measurement of the dimuon yield in the ${\rm a}_1$ mass region. Furthermore, a simultaneous precision study of hidden and open charm will be carried out, by…