High p T particle production, hard scattering and correlations from the PHENIX Experiment Vlad islav Pantuev, INR Moscow

2 Outline Jet quenching. Current status Inclusive yields. Reaction plane dependence Correlations. Two-particle, vs. reaction plane Conclusions

3 Why hard scattering? Jet “tomography” Capability to calculate in pQCD for p+p Cross sections are small – should follow NN-collisions scaling Process at very early stage of the collision. Can illuminate the whole AA collision in time Direct photons can easy penetrate through color matter Fragmentation functions could be parameterized There is a believe that energy loss of colored parton in color medium could be calculated (?)

4 Some questions remains from RHIC to LHC What are the energy loss mechanisms? Can we discriminate between them and quantify relevant parameters? How does energy loss depend on quark mass? How can we study the energy loss dependence on path length, pT, jet energy? Is the medium modified by the probes? How to extract properties of the colored medium from hard scattering observables?

5 One of the major RHIC discovery – jet quenching

6 R AA energy scan, Cu+Cu Transition happens at beam energy somewhere between 22 and 62 GeV. LHC is well above – more clear signals. New features?

7 R AA for identified particles

8 Old question: Is Raa rising with p T ?  extends p T range Phys. Rev. C 82, (2010)

9 Experimental data on jet suppression, RAA constrains model parameters PQM – Arnold, Moore, Yaffe

10 Very different models with different parameters CAN explain RAA !

11 R AA. Jet quenching. Current status Current understanding of jet quenching faces several challenges pQCD vs. AdS/CFT  Energy loss mechanisms ? Large discrepancies among pQCD models for jet quenching parameter: GLV : 2.8 GeV 2 /fm ASW: 10.0 GeV 2 /fm HT : 2.3 GeV 2 /fm AMY: 4.1 GeV 2 /fm Need observables with more discriminating power

12 Reaction plane – another “knob” PHENIX has wide range of capabilities to determine reaction plane  Beam-Beam counters, BBC  Zero degree calorimeters, ZDC  Reaction plane detectors, 3 rings, RXN  Muon Piston Calorimeters, MPC

13 BBC MPC PbW0 4 2cm Pb converter in front RXN (zero degree n calorimeter ZDC/SMD /shower max detector) (reaction plane detector) (muon piston EM-calorimeter) (beam-beam quartz- Cherenkov detector) 05-5  dN/d  CNT (PHENIX central tracking arm)

14 Results with different detectors are consistent within few % Resolution good worse

15 So, “difficult” (to explain) result – large anisotropy at high p T : v2 is non-zero at high pT v2 is flat above 6 GeV/c Phys. Rev. Lett. 105, (2010)

16 pQCD models doing well with R AA but can’t explain large v 2 radiativeAdS/CF T  o =1.5-2 fm/c

17 R AA (  ): In many models, e-loss scales as: radiativeAdS/CFT JJ and R. Wei, PRC82,024902,2010 Better scaling with m=2, Accidental? AdS/CFT is static, our system is rapidly changing. Be aware! Different colors and sets correspond to different centrality and angles, PRC80  o =1.5-2 fm/c

18 My non-PHENIX slide In previous slides with reference J.Jia and R.Wei PRC82, (2010), where they use ~L 3, there is an additional parameter  0 =1.5-2 fm/c In 2005 (arXiv:hep-ph/ , JETP Lett.85,104 ) I use formation time 2.3 fm/c in peripheral zone of the collision and describe R AA AND v 2 My the only statement is that the energy loss mechanism is still not fully understood Formation time dependence vs. distance from the center for Au+Au 5% central collisions. Depends on distance between hard scattering vertexes At LHC RAA and v2 about two times smaller, “Last call for predictions”

19 Correlations at high p T  0 – hadron  – hadron Correlations vs. reaction plane e – hadron

20 At low p T of secondary particle there is definite response from the medium

21 0.5

22 Again, My personal “back on the envelop” slide: Transforming Atlas/CMS parameter “A j ” to RHIC “style”: GeV and I AA E_T1>100 GeV I use =150 GeV PS. Errors ~10% are not shown pp PbPb ratio 0.5!

23  – hadron correlations. Very hard to measure! Phys. Rev. C 80, (2009) The first PHENIX attempt:

24 With better statistics, Run7: No surprise that  – hadron I AA = R AA for hadrons, But  -h have advantage – energy is roughly known, see Aneta talk

25  0 – h correlations. Away side vs. reaction plane, yet another “knob” arXiv: Better control of geometry and thickness of the reaction zone

26 Mid-central 20-60% centrality Near – side trigger jet fragments are consistent with no energy loss and no dependence on orientation wrt. reaction plane. Surface bias, fluctuations? Away – side jet demonstrates significantly larger suppression for out-of-plane trigger particle, where energy loss is bigger for the larger system size

27 Most central collisions Near and away – side jet have no dependence on the orientation of trigger particle. Interaction zone is almost symmetric.

28 Ratio out-of-plane to in-plane In mid-central collisions, where in-plane and out-of- plane system sizes are very different we see factor 4-5 larger suppression for out-of-plane

29 Heavy flavor e-hadron correlation. Near side Away side Recoil jet from heavy (c, b) quark demonstrates the same suppression as a light quark/hadron trigger PHENIX already demonstrate that c- and b- quarks suppression is almost the same as for light quarks

30 Summary At RHIC formation of new type of matter was discovered PHENIX, as well as other RHIC experiments developed set of “tools” to investigate properties of the new matter LHC opens new, more precise, more sensitive capabilities and methods: full jet reconstruction, direct photons… Some fundamental questions should be posted and solved at LHC We still well far away from the answer to the question on the origin of color confinement (but this was one of our “banner” 20 years ago ). Any hope from parton fragmentation?