1. 1 - Onset of deconfinement NA60+ - Existence (or non existence) of QCD critical point - Chiral symmetry restoration  Measuring dimuons at different energies in the range 20- 160 AGeV and with different collision systems:  Simulation studies for the apparatus setup (PRIN 2009): - acceptances - rec eff - mass resolution - rates

2. First order transition and onset of deconfinement  Full circles: early stage of systems created in central Pb-Pb collisions at different energies at √s NN = 6.3, 7.6, 8.7 and 12.3 GeV (NA49 PbPb, AGS AuAu)  Systems cool and expand evolving along the solid lines to the freeze- out points (squares and triangles)  The magenta circle might lie on the first order transition line marking the onset of deconfinement QCD phase diagram poorly known in the region of highest baryon densities and moderate temperatures – is there a critical point?

3. Critical point(s) search Search for the critical point  Energy interval covered by SPS: fundamental for search of CP  Requires a bidimensional scan in energy and collision system Accelerator landscape

4. Beam conditions: CERN vs. GSI/FAIR Luminosity at the SPS comparable to that of SIS100/300 No losses of beam quality at lower energies except for emittance growth RP limits at CERN in EHN1, not in (former) NA60 cave < 11 – 35 (45) SPS SIS100/300 beam target interaction intensity thickness rate 2.5×10 6 5×10 5 [λi ][λi ] [Hz] 20% NA60 (2003) new injection scheme 10 8 10% 10 7 10 8 1% 10 6 interaction rate [Hz] 10 5 - 10 7 Energy range: 10 – 158 [AGeV] LHC AA 5×10 4 Pb beams scheduled for the SPS in 2016-2017, 2019-2021 H.J.Specht, ECT* Trento 2013

5. q Characteristic regimes in invariant  +   mass, M 2 =(p e+ + p e  ) 2 : Drell-Yan: power law ~ M n thermal ~ exp(-M/T): - QGP - HG (4  processes) Measuring dileptons in the IMR region

6. ~ exponential fall-off  ‘Planck-like’ M>1 GeV fit to T>T c : partons dominate range 1.1-2.0 GeV: T=205±12 MeV 1.1-2.4 GeV: T=230±10 MeV Evolution of yield and T vs beam energy QGP spectrum using a lattice-QCD constrained rate (Rapp et al.) hadronic spectrum using the in- medium  +  +4  spectral function (Rapp et al.) PbPb 40 AGeV 0-5% central collisions  QGP fraction still relevant even at 20-40 AGeV?  Measure evolution of yield and temperature vs beam energy In-In 160 AGeV dN ch /d  >30

7.  p T spectra nearly thermal  Fit with dN/dp T =p T exp(-M T /T) in 50 MeV mass bins (using 10 7 ev MC sample) HG radiation QGP radiation mass spectrum: T = 205 ± 12 MeV p T spectra: = 190 ± 12 MeV M >1 GeV T = 205 MeV > T c = 170 (MeV) - T eff independent of mass within errors - same values within errors negligible flow  soft EoS above T c all consistent with partonic phase Transverse momentum spectra: evolution of T eff vs beam energy PbPb 40 AGeV 0-5% central collisions (Rapp et al.)  Measure the evolution of T eff vs mass vs beam energy

8. Phys. Rev. Lett. 91 (2003) 042301 Higher baryon density at 40 than at 158 AGeV Enhancement factor: 5.9±1.5(stat.)±1.2(syst.) (published ±1.8 (syst. cocktail) removed due to the new NA60 results on the η and ω FFs) Larger enhancement in support of the decisive role of baryon interactions Measuring the rho region Large enhancement: might not be just coincidental with expectation of emergence of CP Only one exisiting measurement at 40 AGeV with very low statistics

9. Muon spectrometer Toroid field (R=160 cm) beam 5 m 9 Compress the spectrometer reducing the absorber and enlarge transverse dimensions dimuons@160 GeV (NA60) rapidity coverage 2.9<y<4.5 beam 2.4 m Longitudinally scalable setup for running at different energies From the high energy to a low energy apparatus layout dimuons@20 GeV rapidity coverage 1.9<y< 4 3m 9 m Muon spectrometer Toroid field (R≈230 cm) toroid Vertex spectrometer Dipole field

10. Pixel plane: - 400  m silicon + 1 mm carbon substrate - material budget ≈0.5% X 0 - 10-15  m spatial resolution Required rapidity coverage @20 GeV starting from =1.9 ( ϑ ~ 0.3 rad) 3 T dipole field along x 40 cm x z 5 silicon pixel planes at 7<z<38 cm The vertex spectrometer

11. The muon spectrometer Muon Tracker 4 tracking stations (z=295, 360, 550, 650 cm) Trigger stations 2 trigger stations placed after muon wall (ALICE-like) at z = 840, 890 cm No particular topological and p T constraints introduced contrary to NA60 hodo system (muons required in different sextants) z x R=290 cm Muon wall (120 or 180 cm) Muon spectrometer field toroid magnet B 0 /r – B 0 = 0.5 Tm 380<z<530 cm; r<180 cm

12. Rates 40 AGeV Pb-Pb central collisions : first look Reconstructed signal rate is evaluated as L = beam intensity = 10 7 /s int = target interaction length = 0.15 Centrality class = 0.05 most central collisions This leads to ≈5x10 6 rec signal pairs in few day!

13. Signal: 5x10 6 events sampled from signal rec yield histogram Bkg: sampled from rec bkg yield histogram and normalized according to S/B Combinatorial bkg subtraction: 0.5% systematic uncertainty Experimental spectrum Events/50 MeV T measurable with a precision at MeV level 40 AGeV Pb-Pb 0-5% central collisions

14. On-going studies  Beam conditions, triggering and rates at different energies  J/psi and Chi_c measurement  Preparation of a “white” paper