1. Materia a alta densidad (de SPS y RHIC a LHC) Carlos Pajares Universidade de Santiago de Compostela Multiplicity Parton Saturation Elliptic Flow. sQGP, Perfect Liquid. EoS Transverse Momentum Suppression Charm, J/Ψ suppression Fluctuations (Multiplicity, Transverse momentum, Balance, LONG range) Percolation of Color Sources Color Glass Condensate XXXI Bienal Real Sociedad Española de Física. Granada. Sept. 2007

2. Energy density versus T/T C. Curve 1-2 quark flavours, curve 2-2 light plus one Heavy flavour and curve 3-3 quark flavours.

3. MULTIPLICITY Extrapolation From lepton-Nucleon and p-A scaling on At LHC energy gives 9.5, i.e. 1800 charged particles per unit rapidity Linear energy data extrapolation gives 6.5, 1200 charged particles String percolation in between Most of the models over 2500.

4. SATURATION OF PARTONS Number of gluons. Size gluons Total Area New Scale Q S

5. The whole gluon cascade, (ordered in longitudinal momenta) gives

6. A more detailed treatment, is the BFKL eq i.Grows as a power of the energy (Violation unitarity) ii.Diffusive behaviour, gluons can go inside non-perturbative region

7. BK equation Small x, interaction among gluon sources

8. Solution – At lower x (higher energy) N is large but lower than 1 (solving the unitarity problem) – At small r T, N is small (color transparency) BFKL is OK. – The transition between small r T takes place at a characteristic value r T ~1/Q S (τ). (solving the infrared diffusion problem) NEW SCALE Q S (depends on y an A)

9. ELLIPTIC FLOW

10. We expect Hydrodynamics perfect fluid result is for full thermalized system and a soft EoS LHC?

11. Perfect fluid should have scaling properties Limiting fragmentation Centrality dependence

13. This scaling suggests that the collective flow is at the partonic stage OK with coalescence models

14. Evidence Perfect fluid (interacting at partonic stage, soft EoS, low viscosity, fast thermalization) scaling properties

15. Transverse Momentum Suppression Energy loss by medium induced gluon radiation Photons in agreement with perturbative QCD

16. O.K. with Energy loss dependence on N part Problems: Equally supressed as charged hadrons contrary to predictions (less supressed) Non photonic electrons Q=14 GeV 2 /fm

17. Azimuthal distribution of away-side charged hadrons For central collisions, suppression of the back jet The widths of the back-to-back peaks are independent of centrality (for p T (asso c)>6 and 4<p T <6) Possibilities to look for supersonic jets

18. J/Ψ SUPPRESSION hA

19. Data requires smaller σ abs at most 3mb (usually σ abs = 4.2 mb) No additional suppression seen at RHIC 0 mb 3 mb Low x 2 ~ 0.003 (shadowing region) σ ab =1mb 3 4

20. Regeneration models fit the data. They predict, an increase of J/Ψ at LHC. Lattice studies indicate no suppression of J/Ψ at T=T C, only at T≥2T C. Ψ’ and are supressed at Defining S J/Ψ,Ψ’ the survival probabilities once is substracted the absorption, as 60% J/Ψ are directly produced and 40% J/Ψ come from decays of Ψ’ and Grandchamp, Rapp, Brown PRL 92, 212301 (2004) Thews Eur.Phys.J C43, 97 (2005)

21. The prediction for LHC is a large suppression of J/Ψ corresponding to the directly produced J/ Ψ. Clear difference at LHC between regeneration and sequential models

22. Narrowing of the Balance function with Centrality The width sensitive to hadronization time. Delayed hadronization narrow balance function (stronger correlation in rapidity for the charged particles) number of identified charged pion pairs in Caveat: In PyTHIA and other models with short hadronization time are able to describe data. The narrowing is only observed at midrapidity

23. N P Targ fluctuations contribute in target hemisphere (most string hadronic models) Different Extreme Reaction Scenarios MULTIPLICITY FLUCTUATIONS N P Targ fluctuations contribute in both hemispheres (most statistical models) N P Targ fluctuations contribute in Projectile hemisphere Multiplicity fluctuations sensitive to reaction scenario M. Bleicher M. Gazkzicki, M. Gorenstein arXiv:hep-ph/0511058

24. Reflection, Mixing and Transparency Significant amount of mixing of particles projectile and target sources

25. String Hadronic Models String hadronic models shown (UrQMD, HSD, HIJING) belong to transparency class They do not reproduce data on multiplicity fluctuations Projectile hemisphere HSD, UrQMD: V. Konchakovskyi et al. Phys. Rev. C 73 (2006) 034902 HIJING: M. Gyulassy, X. N. Wang Comput. Phys. Commun. 83 (1994) 307 Simulation performed by: M. Rybczynski

26. PERCOLATION COLOR SOURCES Results for the scaled variance of negatively charged particles in Pb+Pb collisions at Plab=158 AGeV/c compared to NA49 experimental data. The dashed line corresponds to our results when clustering formation is not included, the continuous line takes into account clustering. L.Cunqueiro,E.G.Ferreiro,F del Moral,C.P.

27. FLUCTUATIONS AT RHIC %

28. Color strings are stretched between the projectile and target Strings = Particle sources: particles are created via sea qq production in the field of the string Color strings = Small areas in the transverse space filled with color field created by the colliding partons With growing energy and/or atomic number of colliding particles, the number of sources grows So the elementary color sources start to overlap, forming clusters, very much like disk in the 2-dimensional percolation theory In particular, at a certain critical density, a macroscopic cluster appears, which marks the percolation phase transition CLUSTERING OF COLOR SOURCES

29. (N. Armesto et al., PRL77 (96); J.Dias de Deus et al., PLB491 (00); M. Nardi and H. Satz). How?: Strings fuse forming clusters. At a certain critical density η c (central PbPb at SPS, central AgAg at RHIC, central SS at LHC ) a macroscopic cluster appears which marks the percolation phase transition (second order, non thermal). Hypothesis: clusters of overlapping strings are the sources of particle production, and central multiplicities and transverse momentum distributions are little affected by rescattering.

30. LONG RANGE CORRELATIONS A measurement of such correlations is the backward–forward dispersion D 2 FB = - where n B (n F ) is the number of particles in a backward (forward) rapidity In a superposition of independent sources model, is proportional to the fluctuations on the number of independent sources (It is assumed that Forward and backward are defined in such a way that there is a rapidity window to eliminate short range correlations). Cluster formation implies a decreasing number of independent sources. Therefore D BF decreases.

31. Sometimes, it is a measured with b in pp increases with energy. In hA increases with A Clustering of strings implies a suppression of b

33. Color Glass Condensate As the centrality increases, Q s increases, α s decreases an b increases

34. Particle production in high energy is considered as a gluon production in background classical field. The spectrum becomes thermal with Kharzeev, Levin, Satz during

35. If you can not get rid of the noise…. study the noise Penzias and Wilson RHIC II FAIR LHC