1 / 29

Search for the Critical Point of Strongly Interacting Matter at the CERN SPS

Tatranská Štrba, June 27th - July 1st, 2011. Search for the Critical Point of Strongly Interacting Matter at the CERN SPS. G.Melkumov (JINR Dubna) for NA49 collaboration. QCD prediction of quark-gluon deconfinement. Pb+Pb at SPS energies:

lucio
Download Presentation

Search for the Critical Point of Strongly Interacting Matter at the CERN SPS

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Tatranská Štrba, June 27th - July 1st, 2011 Search for the Critical Point of Strongly Interacting Matter at the CERN SPS G.Melkumov (JINR Dubna) for NA49 collaboration

  2. QCD prediction of quark-gluon deconfinement Pb+Pb at SPS energies: Energy density exceeds the critical value ( ≈ 1 GeV / fm3 ) Signatures for deconfinement • radial & anisotropic flow • strangeness enhancement • J/Ψ,Ψ’ yield suppression • di-lepton enhancement & ρ0 modification Search for the onset of deconfinement by the energy scan at the SPS Comprehensive study of the phase diagram of strongly interacting matter

  3. NA49 experiment at CERN SPS Hadron measurements in large acceptance (yCM > y > ybeam) Tracking by large-volume TPCs in SC magnet field PID by dE/dx,TOF, decay topology, invariant mass Centrality determination by Forward Calorimeter Operating 1994-2002; p+p, C+C, Si+Si and Pb+Pb interactions at center of mass energy 6.3 – 17.3GeVfor N+N interaction

  4. Tracking and particle identification Tracking PID by dE/dx PID by TOF + dE/dx

  5. Search for the onset of deconfinement What is the energy threshold for deconfinement? (the lowest energy sufficient to create a partonic system)  Motivation: Statistical Model of the Early Stage (SMES) Gaździcki, Gorenstein, Acta Phys. Polon. B30, 2705 (1999) “kink” “horn” “step” HG cont. entropy S  4 Np QGP QGP QGP HG cont. HG HG mixed phase mixed phase HG 1st order phase transition to QGP between top AGS and top SPS energies sNN 7 GeV number of internal degrees of freedom (NDF) increases HG QGP (activation of partonic degrees of freedom) total entropy and total strangeness are the same before and after hadronization (cannot decrease QGP  HG) mass of strangeness carriers decreases HG QGP (mL, K, ...> ms) constant temperature and pressure in mixed phase

  6. Pion energy dependence - 4π yields Final NA49 results on the onset of deconfinemet: C.Alt et al., PRC77,024903 (2008) Full phase space (4p) Pions measure early stage entropy. InSMES: <π>/Nw~ NDF1/4  A+Adatachangefrom "suppression" (AGS) to "enhancement" atlowSPSenergies  Changeofslopearound30AGeV; slope in A+A increases from ≈1 (AGS) to ≈ 1.3 (top SPS+RHIC) - consistent with increase x 3 in NDF Nochangeofslopeinp+p data M. Gazdzicki and M. Gorenstein, Acta Phys.Pol. B30 (1999) 2705

  7. Onset of deconfinement Pion yield per participant Ratio of strange particles to pions NA49,C.Alt et al.,PRC77,024903(2008) Horn central PbPb/AuAu Kink • πyield related to entropy production • steeper increase in A+A suggests • 3-fold increase of initial d.o.f • Es related to strangeness/entropy ratio • plateau consistent with prediction for • deconfinement (SMES model, M.Gazdzicki and M.Gorenstein, Acta Phys. Pol.30,2705(1999))

  8. Strangeness to entropy ratio Peaks sharply at the SPS AGS SPS mixed partonic SMES explanation: - entropy, number of s, s quarks conserved from QGP to freeze-out - ratio of (s + s) / entropy rises rapidly with T in the hadron gas - Es drops to the predicted constant QGP level above the threshold of deconfinement : hadronic Proposed as measure of strangeness to entropy ratio (SMES) Es shows distinct peak at 30A GeV Described (predicted) by model assuming phase transition (SMES)

  9. Kaon inverse slope parameter Step Step Hydro+PT Hydro+PT • The step-like feature observed at SPS energies, not seen • for p+p collisions and in models without phase transition • Consistent with approximately constant temperature and pressure in mixed phase (latent heat)(softest point of EoS) • Hydrodynamical model with deconfinement phase transition starting at lower SPS energies describes data M. Gorenstein et al., Phys. Lett. B 567 (2003) 175 S. Hama et al., Braz. J. Phys. 34 (2004) 322

  10. Onset of deconfinement Shape of transverse mass spectra Estimate of sound velocity (H.Petersen and M.Bleicher, nucl-th/0611001) NA49,C.Alt et al., PRC77,024903 (2008) Step Dale SPheRIO Softening of transverse (step) and longitudinal (minimum of cs) features of EoS due to mixed phase (soft point of EoS) Rapid changes of hadron production properties at low SPS energy most naturally explained by onset of deconfinement NA49,C.Alt et al.,PRC77,024903(2008); M.Gazdzicki et al.,arXiv:1006.1765

  11. More signals : Estimate of sound velocity width of rapidity distribution Dale sound velocity Landau hydro-dynamical model (E.Shuryak,Yad.Fiz.16, 395(1972)) → sound velocity can be derived from measurements H.Petersen and M.Bleicher, nucl-th/0611001 Minimum of sound velocity cs (softest point of EoS) around 30A GeV

  12. SPS(NA49) , RHIC(STAR) and LHC(ALICE) Horn Step 400 T(MeV) 200 Verification of SPS(NA49) results by RHIC(STAR) and LHC(ALICE) Horn- and Step- like features in hadron gas ->mixed phase->QGP transitions

  13. Exploration of phase diagram RHIC • QCD considerations suggest a • 1st order phase boundary • ending in a critical point • Hadro-chemical freeze-out points • are obtained from statistical model • fits to measured particle yields • T and μB approach phase boundary • and estimated critical point at SPS critical end point Fodor,Katz JHEP 04,50(2004) SPS • Evidence of the onset of deconfinement from rapid changes of hadron • production properties • Search for indications of the critical point as a maximum in fluctuations

  14. Quark number susceptibilities

  15. Effects (singularities) at critical point hydro predicts that evolution of the system is attracted to critical point effects of critical point are expected over a range of T,µB m = mB/3 M.Asakawa et al.,PRL 101,122302(2008) Y.Hatta and T.Ikeda, PRD67,014028 (2003) For a given chemical freeze-out point three isentropic trajectories (nB/s = const.) are shown We do not need to hit precisely the critical point because a large region can be affected The presence of the critical point can deform the trajectories describing the evolution of the expanding fireball in the (T,mB) phase diagram

  16. Event-by-event multiplicity & transverse momentum fluctuations pT- measures transverse momentum fluctuations on event-by-event basis • - measures multiplicity fluctuations on event-by-event basis If A+A is a superposition of independent N+N pT (A+A) = pT (N+N) w (A+A) = w (N+N) + < n> wpart pT is independent of Npart fluctuations < n> - mean multiplicity of hadrons from a single N+N wpart - fluctuations in Npart w is strongly dependent on Npart fluctuations For a system of independentlyemittedForPoissonianmultiplicitydistribution particles(no inter-particle correlations) pT = 0 w=1

  17. Search for the critical point A (system size) sNN F. (2006) I.Kraus et al., Phys.Rev.C76, 064903 (2007)

  18. Event-by-event <pT> & multiplicity fluctuations Energy dependence for central Pb+Pb collisions NA49 C.Alt et al., PRC78,034914 (2008) NA49 T.Anticic et al., PRC79,044904 (2009) CP1 location: B(CP1) = 360 MeV T(CP1)  147 (chemical freeze-out temperature for Pb+Pb at B = 360 MeV) CP estimates based on: M. Stephanov, K.Rajagopal,E.Shuryak, PRD60,114028(1999) Y.Hatta and T.Ikeda, PRD67,014028(2003) base-lines for CP1 predictions (curves) are mean pT and w values for 5 energies No significant energy dependence at SPS energies Data show no evidence for critical point fluctuations

  19. System size dependence of fluctuatios Pt data: PRC70,034902 (2004) data: pp - PRC75,064904 (2007) Pb+Pb - PRC78,034914 (2008) CC,SiSi - B.Lungwitz (PhD) CP2 location: B(CP2)  250 MeV = B (A+A at 158A GeV) T (CP2)= 178 MeV = Tchem (p+p) CP2 predictions (curves) normalized to reproduce pT and w value for central Pb+Pb collisions Data are consistent with the CP2 predictions Maximum of pT and w observed for C+C and Si+Si

  20. Higher moments of <pT> fluctuation Higher moments of measure (K.Grebieszkow, M.Bogusz) Higher moments have been advertised as a probe for the phase transition and critical point effects St. MrówczykiPhys. Lett. B465, 8 (1999) M.A.Stepanov, Phys.Rev.Lett. 102, 032301 (2009) Advantage: the amplitude of critical point peak is proportional to higher powers of the correlation length. Examples for second and fourth moments: Definition: Single particle variable - inclusive avarage Event variable (summation runs over particles in a given event) - averaging over events Higher moments: So far we were using second moment: F(2)pT 1. In a superposition model F(2)pT (A+A) = F(2)pT (N+N) 2. For independently emitted particles F(2)pT = 0 According to S. Mrówczyński Phys. Lett. B465, 8 (1999) only the 3rd moment preserves the above (1. and 2.) properties of the 2nd moment (higher moments not). In particular only F(2)pT and F(3)pT are intensive as thermodynamic quantities.

  21. ΦpT(3): 3rd moment <pT> fluctuations ΦpT(3) has strongly intensive property like ΦpT (S.Mrowczynski,Phys.Lett.B465,8(1999)) NA49 preliminary Higher moments are expected to be more sensitive to fluctuations Pb+Pb 7% central Systematic errors are large NA49 preliminary No indication of CP fluctuations K.Grebieszkow and M.Bogusz, NA49 preliminary

  22. Critical phenomena and density fluctuations Critical phenomena give rise to density fluctuations which obey the power laws. These power laws describe the density fluctuations of zero mass sigma particles abundantly produced in AA collisions at CP as well as the density fluctuations of net-baryons. The critical fluctuations (power laws) in sigma and proton sectors is motivated by the hypothesis that sigma and net-protons densities are a magnitudes of the order parameters for the second order phase transition associated with the QCD CP. For strongly interacting matter long range baryon density fluctuations expected A picture supported by lattice calculations Baryon density fluctuations appear to diverge for some critical value of the baryochemical potential C. R. Allton, Phys. Rev. D68 (2003), 014507 quark number susceptibility: q ≡ ∂nq/∂μq, T0 – critical temperature for μq = 0 (mB = 3mq)

  23. Intermittency in low mass π+π- pair density N.Antoniou et al.,Nucl.Phys.A693,799(2001);A761,149(2005) • critical point predicted to lead to power-law density fluctuations of σ field • observation via density fluctuations of low mass π+π- pairs in pT space • power law behavior of F2(M) factorial moment expected (intermittency) NA49 data indicate intermittency signal for Si+Si (T.Anticicetal.,PRC81,064907(2010)). Similar critical fluctuations for Si+Si interactions observed in proton sector. QCD Critical point close to freeze-out point of Si+Si system ?

  24. Critical point search in fluctuations first hint on the hill of fluctuations? first hint on the hill of fluctuations? T.Anticic et al., PRC70, 034902 (2004) C.Alt et al., PRC75, 064904 (2007) C.Alt et al,. PRC78, 034914 (2008) T.Anticic et al., PRC79, 044904 (2009) B.Lungwitz, NA49 thesis (2008)

  25. NA61  Search for the QCD critical point Critical point of strongly interacting matter by an observation of a hill of fluctuations in two dimensional plane (energy)-(system size) New data to be registered by NA61 The critical point should lead to an increase of multiplicity and transverse momentum fluctuations

  26. NA61  Study of the onset of deconfinement Establish the system size dependence of the anomalies observed in Pb+Pb collisions-further test interpretation as due to the onset of deconfinement New data to be registered by NA61 In+In ? S+S C+C p+p 10 20 30 40 80 158 energy (A GeV) 10 20 30 40 80 158 energy (A GeV) It is expected that the ''horn'' like structure should be the same for S+S and Pb+Pb collisions and then rapidly disappear for smaller systems

  27. Ion physics program NA61Scan in energy and system size A Search for hill of fluctuations as signature of critical point Pb+Pb extrapolation µB T NA49 Study onset of deconfinement: disappearance of “horn” etc.

  28. Progress and revised plans in data taking NA61 Pb+Pb NA49 (1996-2002) Au+Au STAR (2008-10) NA61 ion program Xe+La 2015 2014 Ar+Ca 2010/11/12 T T Be+C p+p P 2009/10/11 p+p 158 p+Pb 2012/14 13 20 30 40 80 158 T energy (A GeV) -test of secondary ion beams P -pilot data taken

  29. Summary Onset of deconfinement indicated in inclusive observables in central Pb+Pb colisions at lower SPS energies of about 30A GeV: Results are not reproduced by hadron-string models (RQMD, UrQMD, HSD). • Described (predicted) by model assuming phase transition (SMES) • No indications of the critical point in the energy dependence of multiplicity • and mean transverse momentum fluctuations in central Pb+Pb collisions System size dependence of the critical point at 158A GeV shows: • a maximum of mean pT and multiplicity fluctuations in the complete pT range  consistentwiththepredictions • an increase (from p+p up to Pb+Pb) of mean pT fluctuations in the low pT region; high pT particles show no fluctuation signal Higher moment of Pt fluctuations measure : analysis of the 3rd moment of Pt fluctuations for the energyand system size dependence is in progress A detailed energy and system-size scan is necessary to investigate the properties of the onset of deconfinement and to establish the existence of the critical point  NA61/SHINE

More Related