1. Probing the properties of dense partonic matter at RHIC Y. Akiba (RIKEN) for PHENIX collaboration

2. PHENIX White paper conclusion The last paragraph of Formation of dense partonic matter in nucleus-nucleus collisions at RHIC: Experimental evaluation by the PHENIX collaboration (NPA757, 184, 2005) In conclusion, there is compelling experimental evidence that heavy ion collisions at RHIC produce a state of matter characterized by very high energy densities,......additional incisive experimental measurements combined with continued refinement of the theoretical description is needed to achieve a complete understanding of the state of matter created at RHIC. What Additional Incisive Experimental measurements do we have in QM2005?

3. The matter is so opaque that even a 20 GeV  0 is stopped. Suppression is very strong (R AA =0.2!) and flat up to 20 GeV/c Common suppression for  0 and  it is at partonic level  > 15 GeV/fm 3 ; dN g /dy > 1100

4. The matter is so dense that even heavy quarks are stopped Even heavy quark (charm) suffers substantial energy loss in the matter The data provide a strong constraint on the energy loss models. The data suggest large c-quark-medium cross section; evidence for strongly coupled QGP? (3) q_hat = 14 GeV 2 /fm (2) q_hat = 4 GeV 2 /fm (1) q_hat = 0 GeV 2 /fm (4) dN g / dy = 1000

5. The matter is so strongly coupled that even heavy quarks flow Charm flows, but not as strong as light mesons. Drop of the flow strength at high p T. Is this due to b-quark contribution ? The data favors the model that charm quark itself flows at low p T. Charm flow supports high parton density and strong coupling in the matter. It is not a weakly coupled gas. v 2 (D)=0.3 v 2 (  ) v 2 (D)=0.6 v 2 (  ) v 2 (D)=v 2 (  ) Greco,Ko,Rapp: PLB595(2004)202

6. The first promising result of direct photon measurement at low p T from low-mass electron pair analysis. Are these thermal photons? The rate is above pQCD calculation. The method can be used in p+p collisions. If it is due to thermal radiation, the data can provide the first direct measurement of the initial temperature of the matter. T 0 max ~ 500-600 MeV !? T 0 ave ~ 300-400 MeV !? The matter is so hot that it emits (thermal?) photon copiously PHENIX preliminary

7. The matter is so dense that it melts(?) J/  (and regenerates it ?) CuCu  200 GeV/c AuAu  200 GeV/c dAu  200 GeV/c AuAu ee 200 GeV/c CuCu ee 200 GeV/c J/  ’s are clearly suppressed beyond the cold nuclear matter effect The preliminary data are consistent with the predicted suppression + re- generation at the energy density of RHIC collisions. Can be tested by v 2 (J/  )?

8. The matter is so dense that it modifies the shape of jets The shapes of jets are modified by the matter. –Mach cone? –Cerenkov? Can the properties of the matter be measured from the shape? –Sound velocity –Di-electric constant Di-jet tomography is a powerful tool to probe the matter PHENIX preliminary

9. The matter may melt but regenerate J/  ’s Put the results together The matter is dense The matter is strongly coupled The matter is hot Can we determine the properties of the matter? We look forward to working with the theory community to extract the properties of the matter The matter modifies jets  > 15 GeV/fm 3 dN g /dy > 1100 T ave = 300 - 400 MeV (?) Vs = ?  (dielec) = ? PHENIX preliminary

10. Summary: Probing partonic state of dense matter RHIC has produced a strongly interacting, partonic state of dense matter We now have started probing the properties of the matter –The energy loss mechanism and initial parton density from jet suppression and flow data of light and heavy quarks  >15 GeV/fm 3 and dN g /dy > 1100 –the initial state temperature from thermal radiation T 0 ave = 300-400 MeV? These high densities and temperatures are unprecedented We look forward to working with the theory community to relate the wealth of experimental observables to the properties of matter.

12. The matter may melt but regenerate J/  ’s Probing Partonic State of Matter The matter is dense The matter is strongly coupled The matter is hot We look forward to working with the theory community to extract the properties of the matter The matter modifies jets PHENIX preliminary

13. backup

14. PHENIX: Reaction Plane Angle –Study (di)jet correlations vs angle of trigger hadron relative to reaction plane J. Bielcikova et al, Phys. Rev. C69:021901, 2004  trig =  trig -  6 bins from 0 to  /2. –Flow systematics change completely vs  trig –Can study dependence of distortion on geometry.  Shoulder and dip seen in all  trig bins.  trig ? From Poster by J. Jia