EPOS 2 and LHC Results

Transcription

1 EPOS 2 and LHC Results Tanguy Pierog, K. Werner, Y. Karpenko Institut für Kernphysik, Karlsruhe, Germany 46th Rencontres de Moriond, QCD, La Thuile, France March the 24th 2011 T. Pierog, KIT - 1/19

2 Outline Collective effects In AA : ridge@rhic In pp : ridge@lhc T. Pierog, KIT - 2/19

3 The EPOS Model EPOS is a parton model, with many binary parton-parton interactions, each one creating a parton ladder. Energy-sharing : for cross section calculation AND particle production (Parton Based Gribov-Regge Theory) Parton Multiple scattering Outshell remnants Screening and shadowing via unitarization and splitting Collective effects for dense systems EPOS can be used for minimum bias hadronic interaction generation (h-p to A-B) from 100 GeV (lab) to 1000 TeV (cms). EPOS tested with particle physics experiment analysis (LEP, HERA, SPS, RHIC, Tevatron, LHC) and cosmic rays! T. Pierog, KIT - 3/19

4 Approach (1) treated as Multiple scattering approach EPOS (marriage of pqcd and Gribov-Regge) : initial condition for a hydrodynamic evolution if the energy density is high enough event-by-event procedure taking into the account the irregular space structure of single events : ridge structures in two-particle correlations core-corona separation : only a part of the matter thermalizes; 3+1 D hydro evolution conservation of baryon number, strangeness, and electric charge T. Pierog, KIT - 4/19

5 Approach (2) treated as parton-hadron transition realistic equation-of-state, compatible with lattice gauge results cross-over transition from the hadronic to the plasma phase hadronization, Cooper-Frye, using complete hadron table at an early stage (166 MeV, in the transition region) with subsequent hadronic cascade procedure (UrQMD) details see: Phys.Rev. C82 (2010) , arxiv: (accepted for pub. in Phys. Rev. C), arxiv: (ridge in pp) T. Pierog, KIT - 5/19

6 Check with Heavy Ions : AuAu@RHIC (%) Early freeze-out (166MeV) + hadr. cascade Full casc. Elastic casc. Important role of core-corona effect (K. Werner et al. J.Phys.G36:064030,2009) Full casc. Elastic casc. After checking successfully hundreds of particle spectra in AuAu Event-by-event analysis T. Pierog, KIT - 6/19

7 Event-by-Event Energy Density : AuAu Bumpy structure of energy density in transverse plane, but translational invariance pseudorapidity extension of flux tubes T. Pierog, KIT - 7/19

8 Event-by-Event Energy Density : AuAu Bumpy structure of energy density in transverse plane, but translational invariance pseudorapidity extension of flux tubes T. Pierog, KIT - 8/19

9 Event-by-Event Radial Flow : AuAu Leads to translational invariance of transverse flows give the same collective push to particles produced at different values of ηs at the same azimuthal angle T. Pierog, KIT - 9/19

10 AuAu : Di-hadron correlation ridge-structure in the dihadron correlation dn/dδηdδφ for free T. Pierog, KIT - 10/19

11 TeV : Di-hadron correlation Our calculation provides a similar ridge structure in pp@lhc using particles with 1 < pt < 3GeV/c, for high multiplicity events close in form and magnitude compared to the CMS result (5.3 times mean multipl., compared to 7 in CMS) T. Pierog, KIT - 11/19

12 TeV : no Hydro Calculation without hydro => NO RIDGE hydrodynamical evolution makes the effect! HOW? T. Pierog, KIT - 12/19

13 Event-by-Event Energy Density : pp Random azimuthal asymmetries of initial energy density but translationally invariant pseudorapidity extension of flux tubes Initial energy density in the transverse plane for two different ηs T. Pierog, KIT - 13/19

14 Summary Ridge in pp Translational invariance of the flow asymmetry means: The system gives an increased collective push to particles produced at different values of ηs at the same azimuthal angle corresponding to a flow maximum ΔηΔφ correlation More evidence for collective effects Bose-Einstein Correlation Heavy particles pt spectra,... Consequence of collective effect in pp : change spectra of particles with pt < 5-6 GeV/c T. Pierog, KIT - 14/19

15 Pseudorapidity and Multiplicity Distribution Little effect of hydro in MinBias dn/deta but not negligible (~10%) small reduction of multiplicity Preliminary results with EPOS 2 T. Pierog, KIT - 15/19

16 PT Distributions Small effect in average (all charged min bias) Big effect for pt distributions of baryons or for high multiplicity events Preliminary results with EPOS 2 T. Pierog, KIT - 16/19

17 pp Distributions at 200 GeV (RHIC) No visible effect of hydro Data well described without hydro (same parameters as for LHC) Preliminary results with EPOS 2 T. Pierog, KIT - 17/19

18 Mean PT Distribution Summarized in <pt> versus multiplicity (here 900 GeV) T. Pierog, KIT - 18/19

19 Summary EPOS 2 : Complete integrated treatment of microscopic parton multiple interaction scheme and 3D hydrodynamical calculation Hydro on event-by-event basis : explains naturally nontrivial features as ridge correlations, elliptical flow, BE correlations, in both heavy ions and pp results. Influence of collective effects on pt spectra below 6 GeV/c for proton-proton collisions : reference spectra for HI : pt > 6 GeV/c or Nch < 2x<Nch> On-going developments : Test all Min Bias LHC data Improvement of hard events (jets) in MB Selection of hard processes (specific born pt) Both at the same time : underlaying events T. Pierog, KIT - 19/19

20 Radius of Particle Emission Space-time structure strongly affected (here 900 GeV) T. Pierog, KIT - 20/19

21 Bose-Einstein Correlations Consequences for Bose-Einstein correlations ALICE data. Radii R from exponential fit. KT1= [100, 250], KT3= [400, 550], KT5= [700, 1000] T. Pierog, KIT - 21/19

22 Event-by-Event Energy Density : pp Random azimuthal asymmetries of initial energy density but translationally invariant pseudorapidity extension of flux tubes Initial energy density in the transverse plane for two different ηs T. Pierog, KIT - 22/19

23 Event-by-Event Radial Flow : pp Elliptical initial shapes leads to asymmetric flows as well translationally invariant (in ηs) Radial flow velocity at a later time in the transverse plane T. Pierog, KIT - 23/19

24 Initial Conditions T. Pierog, KIT - 24/19

25 EoS T. Pierog, KIT - 25/19

26 AuAu : Kaon T. Pierog, KIT - 26/19

27 AuAu : Lambda T. Pierog, KIT - 27/19

28 Pt distribution CDF TeV with Hydro T. Pierog, KIT - 28/19

29 Pt distribution CDF TeV without Hydro T. Pierog, KIT - 29/19

30 <pt> vs multiplicity TeV : EPOS 2 Using small flux tube size Very good description of CDF data No additional parameter Hadron mass dependence hydro+hadronic cascade No collective effects λ Ks Charged T. Pierog, KIT - 30/19

31 Elementary scatterings - flux tubes AA - even pp: many elementary collisions happening in parallel elementary scattering = parton ladder Parton evolutions from the projectile and the target side towards the center (small x) Evolution equation DGLAP Parton ladder = quasilongitudinal color field ( flux tube ) relativistic string Intermediate gluons kink singularities in relativistic strings Fragmentation : production of quark-antiquark pairs fragments identified with hadrons T. Pierog, KIT - 31/19

32 Kinky Strings mainly longitudinal object (here parallel to the z-axis) due to the kinks there are string pieces moving transversely (in y-direction in the picture). But despite these kinks, most of the string carries only little transverse momentum! T. Pierog, KIT - 32/19

33 High Density Core Formation Heavy ion collisions or very high energy proton-proton scattering: the usual procedure has to be modified, since the density of strings will be so high that they cannot possibly decay independently : core Each string splitted into a sequence of string segments, corresponding to widths δα and δβ in the string parameter space If energy density from segments high enough segments fused into core If low density (corona) segments remain hadrons T. Pierog, KIT - 33/19

34 Energy Density Initial conditions at proper time τ=τ0 Energy tensor : Flavor flow : Evolution according to the equations of ideal hydrodynamics: with k = B, S, Q referring to respectively baryon number, strangeness, and electric charge. T. Pierog, KIT - 34/19