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- Onset of deconfinement

NA60+. Measuring dimuons at different energies in the range 20-160 AGeV and with different collision systems :. - Onset of deconfinement. - Existence (or non existence ) of QCD critical point. - C hiral symmetry restoration.

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- Onset of deconfinement

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  1. NA60+ • Measuringdimuonsatdifferentenergiesin the range 20-160 AGeV and with differentcollisionsystems: - Onset of deconfinement - Existence (or non existence) of QCD criticalpoint - Chiralsymmetryrestoration • Simulationstudies for the apparatussetup (PRIN 2009): • - acceptances • - receff • - mass resolution • - rates

  2. First order transition and onset of deconfinement QCD phase diagram poorly known in the region of highest baryon densities and moderate temperatures – is there a critical point? • Full circles: earlystage of systemscreated in central Pb-Pb collisionsatdifferentenergiesat √sNN= 6.3 , 7.6, 8.7 and 12.3 GeV(NA49 PbPb, AGS AuAu) • Systems cool and expandevolvingalong the solidlines to the freeze-out points (squares and triangles) • The magenta circlemightlie on the first ordertransition line marking the onset of deconfinement

  3. Critical point(s) search Search for the criticalpoint Accelerator landscape • Energy intervalcovered by SPS: fundamental for search of CP • Requires a bidimensionalscan in energy and collisionsystem

  4. Beam conditions: CERN vs. GSI/FAIR SPS SIS100/300 < 11 – 35 (45) Energy range: 10 – 158 [AGeV] interaction rate beam target interaction intensity thickness rate [Hz] [Hz] [λi] [Hz] NA60 (2003) 20% 5×105 2.5×106 new injection scheme 105 - 107 108 10% 107 5×104 LHC AA 108 1% 106 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 Pb beams scheduled for the SPS in 2016-2017, 2019-2021 H.J.Specht, ECT* Trento 2013

  5. qq Measuring dileptons in the IMR region • Characteristic regimes in invariant m+m-mass, M2=(pe++ pe- )2 : • Drell-Yan: power law ~ Mn • thermal ~ exp(-M/T): - QGP • - HG(4p processes)

  6. Evolution of yield and T vs beam energy hadronicspectrumusing the in-medium r+w+4pspectralfunction (Rapp et al.) QGP spectrumusing a lattice-QCD constrained rate (Rapp et al.) M>1 GeV PbPb 40 AGeV 0-5% centralcollisions In-In 160 AGeVdNch/dh>30 ~ exponential fall-off  ‘Planck-like’ fit to range 1.1-2.0 GeV: T=205±12 MeV • QGP fractionstillrelevantevenat20-40 AGeV? • Measureevolution of yield and temperature vs beamenergy 1.1-2.4 GeV: T=230±10 MeV T>Tc: partons dominate

  7. Transverse momentum spectra: evolution of Teffvs beam energy PbPb 40 AGeV 0-5% centralcollisions (Rapp et al.) HG radiation QGP radiation M >1 GeV - Teff independent of mass within errors • pTspectranearlythermal • Fit with dN/dpT=pTexp(-MT/T) in 50 MeV mass bins (using 107ev MC sample) mass spectrum: T= 205±12 MeV pTspectra: <Teff> = 190±12 MeV - same values within errors • Measure the evolution of Teff vs mass vs beamenergy T = 205 MeV > Tc= 170 (MeV) negligible flow  soft EoS above Tc all consistent with partonic phase

  8. Measuring the rho region Onlyoneexisitingmeasurementat 40 AGeV with verylowstatistics Phys. Rev. Lett. 91 (2003) 042301 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) Higher baryon density at 40 than at 158 AGeV Larger enhancement in support of the decisive role of baryon interactions Large enhancement: might not be just coincidental with expectation of emergence of CP

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

  10. The vertex spectrometer 3 T dipolefieldalong x 40 cm • Requiredrapiditycoverage @20 GeVstarting from <y>=1.9 (ϑ~0.3 rad) x • 5 silicon pixel planesat 7<z<38 cm • Pixel plane: • - 400 mm silicon + 1 mm carbon substrate • - material budget ≈0.5% X0 • - 10-15 mm spatialresolution z

  11. The muon spectrometer Muonwall (120 or 180 cm) • MuonTracker • 4 trackingstations (z=295, 360, 550, 650 cm) R=290 cm x z • Muonspectrometerfield • toroidmagnet B0/r – B0 = 0.5 Tm • 380<z<530 cm; r<180 cm • Trigger stations • 2 trigger stationsplacedaftermuonwall (ALICE-like) atz = 840, 890 cm • No particulartopologicaland pTconstraintsintroducedcontrary to NA60 hodosystem (muonsrequired in differentsextants)

  12. Rates 40 AGeVPb-Pb central collisions : first look Reconstructedsignal rate isevaluatedas • L = beamintensity = 107/s • lint = target interactionlength = 0.15 • Centralityclass = 0.05 mostcentralcollisions Thisleads to ≈5x106recsignalpairsin fewday!

  13. Experimental spectrum • Signal: 5x106eventssampled from signalrecyieldhistogram • Bkg: sampled from recbkgyieldhistogram and normalizedaccording to S/B • Combinatorialbkgsubtraction: 0.5% systematicuncertainty 40 AGeVPb-Pb 0-5% centralcollisions 40 AGeVPb-Pb 0-5% centralcollisions Events/50 MeV Events/50 MeV • T measurable with a precisionatMeVlevel

  14. On-going studies • Beamconditions, triggering and ratesatdifferentenergies • J/psi and Chi_cmeasurement • Preparation of a “white” paper

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