11th International Conference on Hard and Electromagnetic Probes of High-Energy Nuclear Collisions

The high-intensity beams provided by the CERN SPS in a wide energy interval offer a unique opportunity to investigate the region of the QCD phase diagram at high baryochemical potential. The NA60+ experiment, proposed for taking data with heavy-ion collisions at the SPS in the next years, has a strong potential for investigating the QCD phase diagram via measurements of rare probes in a beam-energy scan of Pb-Pb and p-A collisions in the interval √s${}_{NN}$ = 6-17 GeV.
In this talk the physics program of the NA60+ on thermal dimuons will be described.
At beam energies below top SPS energy, the baryon density becomes maximal and its effect on $\rho$ meson broadening can be measured by NA60+ with utmost precision.
NA60+ will have sensitivity to the $\rho -a_1$ chiral mixing mechanism, which provides access also to the properties of the $a_1$ by exploring the thermal dimuon mass spectrum in the range 1 < M < 1.4 GeV.
For dimuon masses above 1.5 GeV, the temperature of the emitting source can be directly extracted by a fit of the mass spectrum. The experimental program of NA60+ plans to determine for the first time a caloric curve by measuring the temperature vs beam energy, with particular focus on √s${}_{NN}$ < 10 GeV, which is believed to be essential to map out the phase transition regime at high ${\mu }_B$.
Finally, the competitiveness and complementarity of NA60+ in the landscape of the experiments foreseen at other facilities in the next decade will be discussed.