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Highlights of the BNL press release

Highlights of the BNL press release. after the end of the d+Au run at RHIC. Results of BRAHMS, PHENIX, PHOBOS and STAR collaborations summarized by Tamás Csörgő. Introduction to high energy heavy ion physics Conceptual similarities with modern cosmology Suppression in Au+Au at high pt

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Highlights of the BNL press release

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  1. Highlights of the BNL press release after the end of the d+Au run at RHIC Results of BRAHMS, PHENIX, PHOBOS and STAR collaborations summarized by Tamás Csörgő • Introduction to high energy heavy ion physics • Conceptual similarities with modern cosmology • Suppression in Au+Au at high pt • “Absence of suppression” in d+Au • Highlights from BRAHMS, PHENIX, PHOBOS, STAR • Summary and interpretation T. Cs. & A. Ster, http://arXiv.org/abs/nucl-th/0207016 <- Allegory of Hung. Acad. Sci: „From darkness, the light”, painting by P. Endel

  2. Some recent “papers”: • In a Lab on Long Island, a Visit to the Big Bang - New York Times, Jan. 14,2003 http://www.phy.bnl.gov/users/ • 'Little' Big Bang stumps scientist (CNN, Nov. 20, 2002) http://www.cnn.com/2002/TECH/space/11/13/little.bang/ • Big Bang machine gets down to work (MSNBC News, June 14, 2000) http://www.msnbc.com/news/314049.asp?cp1=1 Major goals of high energy heavy ion physics: i) Study of the collective properties of matter at the highest experimentally available temperatures in the largest available volumes ii) Collision of heavy ions (almost fully ionized atoms, ~ atomic nuclei), with max. mass number and energy iii) Experimentally prepare and identify the quark-gluon plasma which is predicted by theory to exist

  3. Overview of the Big Bang basic facts about our Universe Age: 13.7 x 109 (billion|milliard) years Shape: flat Age when light first appeared: 200 million years Contents: 4% ordinary matter 23% „dark matter”, nature unknown 73% „dark energy”, nature unknown Expansion rate (or Hubble Constant): H0 = 71 km/sec/Megaparsec New Scientist, 15.2 2003 p. 12-13 SI Units: Age: 4.3 x 1017 sec Expansion rate: H0= (2.3 ± 0.2)x10-12 sec-1 Hubble law: v =H0 r velocity ~ distance 1 parsec = 3.26 lightyear ~ 3.1 x1016 m

  4. Overview of the Big Bang Experimental signals of inflation: Universe is homogeneous The region of thermal equilibrium is larger, than the particle horizont

  5. Big Bang and Little Bang (2) heavy ion collisions • Early Universe: hot and expanding system • High energy heavy ion collisions: hot and expanding systems • Expansion velocity is proportional to distance (Hubble law) • Protons and neutrons may melt down, phase transition • Quark Matter, Quark Gluon Plasma

  6. We have strong interaction analogues of familiar phases Nuclei behave like a liquid Nucleons are like molecules Quark Gluon Plasma “Ionize” nucleons with heat “Compress” them with density New state of matter! Phases of QCD Matter Fodor and Katz: Tc~ 170 MeV ~ 140x1012 K, at finite baryon density. Using Poor Man’s Supercomputer in Hungary. Crossover like phase transition, e.g. in case of ionization of atoms…

  7. Accelerators and Experiments: CERN (1) • Pb+Pb @ Elab = 158 AGeV @ CERN SPS • O +Pb, S+Pb, h+p, p+p, p+A collisions • 7 big experiments took data: NA44, NA45, NA49, NA50, NA52, NA57, WA98 • Collaboration of European countries with observer states from outside.

  8. Accelerators and Experiments (2): Brookhaven, RHIC, USA • Au+Au @ Ecms = 100+100 AGeV @ run2 • polarized p +polarized p, p+A collisions • 4 experimental collaborations: BRAHMS, PHENIX, PHOBOS, STAR • Hundreds of scientists/experiment, countries from all over the world are participating • Visible from space! Manhattan, New York RHIC, Brookhaven

  9. 4 RHIC experiments

  10. Goals of the RHIC experiments The broadest possible investigations studying A+B, p+p and p+A collisions - study of strongly interacting matter - leptonic and hadronic signals, both „collective” and „individual” - systematic studies with variation of bombarding energy and system size - study of the structure of the spin of the proton

  11. Thermally-shaped Soft Production “Well Calibrated” Hard Scattering The Medium and the Probe p+p->p0 + X • At RHIC energies different mechanisms are responsible for different regions of particle production. • The rare process (Hard Scattering or “Jets”) probes whether the soft production products form a medium. • Calibrated Probe • “The tail that wags the dog” (M. Gyulassy) hep-ex/0305013 S.S. Adler et al.

  12. absorption Jet quenching in Au + Au observed. Why? Initial conditions? New matter? Compressed gluons, color glass How to distinquish? Swich off the medium d+Au collisions

  13. Nuclear Modification Factor: RAA • We define the nuclear modification factor as: • RAA is what we get divided by what we expect. • By definition, processes that scale with the number of underlying nucleon-nucleon collisions (aka Nbinary) will produce RAA=1. Au+Au->p0+X RAA is well below 1 for both charged hadrons and neutral pions. The neutral pions fall below the charged hadrons since they do not contain contributions from protons and kaons. nucl-ex/0304022 S.S. Adler et al.

  14. What happens at RHIC? New form of matter Jets suppressed and decorrelated in Au+Au at RHIC, but not in d+Au at RHIC! Press release, BNL, June 18, 2003 Title page of PRL, Aug 15, 2003,

  15. PHENIX results: Particle Spectra Evolution “Central” Nuclear Physics Particle Physics K. Adcox et al, Phys Lett B561 (2003) 82-92 “Peripheral”

  16. Proton/deuteron nucleus collision Nucleus- nucleus collision d+Au Control Experiment • Collisions of small with large nuclei were always foreseen as necessary to quantify cold nuclear matter effects. • Recent theoretical work on the “Color Glass Condensate” model provides alternative explanation of data: • Jets are not quenched, but are a priori made in fewer numbers. • Color Glass Condensatehep-ph/0212316; Kharzeev, Levin, Nardi, Gribov, Ryshkin, Mueller, Qiu, McLerran, Venugopalan, Balitsky, Kovchegov, Kovner, Iancu • Small + Large distinguishes all initial and final state effects.

  17. d+Au Spectra • Final spectra for charged hadrons and identified pions. • Data span 7 orders of magnitude.

  18. RAA vs. RdA for Identified p0 Initial State Effects Only d+Au Initial + Final State Effects Au+Au d-Au results rule out CGC as the explanation for Jet Suppression at Central Rapidity and high pT

  19. “PHENIX Preliminary” results, consistent with PHOBOS data in submitted paper Centrality Dependence Au + Au Experiment d + Au Control Experiment • Dramatically different and opposite centrality evolution of Au+Au experiment from d+Au control. • Jet Suppression is clearly a final state effect. Final Data Preliminary Data

  20. Escaping Jet “Near Side” Lost Jet “Far Side” “PHENIX Preliminary” results, consistent with STAR data in submitted paper The “Away-Side” Jet • Jets produced on the periphery of the collision zone coming out should survive. • However, their partner jet will necessarily be pointed into the collision zone and be absorbed. d+Au Au+Au 60-90% Min Bias 0-10% Near Far Near Far PHENIX Preliminary PHENIX Preliminary • Peripheral Au+Au similar to d+Au • Central Au+Au shows distinct reduction in far side correlation. • Away-side Jet is missing in Au+Au

  21. Relative to UA1 p+p 0.2<yp<1.4 Data: PHOBOS, nucl-ex/0302015 Submitted to Phys Lett B PHOBOS results: pT Spectra for Au+Au @ 200 GeV

  22. Initial State Coherence? Interaction in Dense Medium? Centrality Dependence vs pT PHOBOS, nucl-ex/0302015 Similar centrality dependence at pT = 0.5 and 4 GeV/c !

  23. Predictions for d+Au pQCD Parton Saturation Vitev, nucl-th/0302002, Phys.Lett.B in press Vitev and M.Gyulassy, Phys.Rev.Lett. 89 (2002) Kharzeev, Levin, McLerran, hep-ph/021332 “~30%suppression of high pT particles” (central vs peripheral) Central Nuclear ModificationFactor RdAu Peripheral 16% increase central vs peripheral

  24. PHOBOS Detector 2003 T0 T0 mini-pCal SPECTRIG • Moved TOF walls back • 5 m from interaction point • New on-line high pT Spectrometer Trigger • New “time-zero” (T0) Cerenkov detectors • On-line vertexing and ToF start time • Forward proton calorimeters on Gold and Deuteron sides • DAQ upgrade (x10) pCal

  25. Compare to p+p reference… 41mb (same as for Glauber) From Glauber (HIJING 1.383) From UA1, using Pythia to go from |h| < 2.5 to 0.2 < h < 1.4 …for each centrality bin d+Au pT Spectra PHOBOS d+Au: nucl-ex/0306025

  26. RdAu vs pT PHOBOS d+Au: nucl-ex/0306025 central Au+Au All syst. uncertainties: 90% C.L.

  27. Centrality dependence of RdAu PHOBOS d+Au: nucl-ex/0306025 Data disfavor initial state interpretation of Au+Au high-pT suppression N.B. Smaller sppinel would increase RdAu central vs RdAu peripheral All syst. uncertainties: 90% C.L.

  28. Connection to QCD Initial State ‘Intermediate State’ Interactions Interaction of fast partons with dense medium has been observed Quantitative diagnostic tool now established Multiplicity systematics connected to initial state Consistent with parton saturation picture

  29. The STAR detector E-M Calorimeter Projection           Chamber Time of    Flight

  30. Partonic energy loss in dense matter Bjorken, Baier, Dokshitzer, Mueller, Pegne, Schiff, Gyulassy, Levai, Vitev, Zhakarov, Wang, Wang, Salgado, Wiedemann,… Multiple soft interactions: Gluon bremsstrahlung Opacity expansion: • Strong dependence of energy loss on gluon density glue: • measure DE color charge density at early hot, dense phase

  31. jet parton nucleon nucleon Jets at RHIC Find this……….in this p+p jet+jet (STAR@RHIC) Au+Au ??? (STAR@RHIC)

  32. Binary collision scaling p+p reference Partonic energy loss via leading hadrons Energy loss  softening of fragmentation  suppression of leading hadron yield

  33. Au+Au and p+p: inclusive charged hadrons nucl-ex/0305015 PhysRevLett 89, 202301 p+p reference spectrum measured at RHIC

  34. Suppresion of inclusive hadron yield RAA Au+Au relative to p+p RCP Au+Au central/peripheral nucl-ex/0305015 • central Au+Au collisions: factor ~4-5 suppression • pT>5 GeV/c: suppression ~ independent of pT

  35. trigger Jets and two-particle azimuthal distributions p+p  dijet • trigger: highest pT track, pT>4 GeV/c • Df distribution: 2 GeV/c<pT<pTtrigger • normalize to number of triggers Phys Rev Lett 90, 082302 N.B. shifted horizontally by p/2 relative to previous STAR plots!

  36. ? Azimuthal distributions in Au+Au Au+Au peripheral Au+Au central pedestal and flow subtracted Phys Rev Lett 90, 082302 Near-side: peripheral and central Au+Au similar to p+p Strong suppression of back-to-back correlations in central Au+Au

  37. Is suppression an initial or final state effect? Initial state? Final state? partonic energy loss in dense medium generated in collision strong modification of Au wavefunction (gluon saturation)

  38. RCP nucl-ex/0305015 pQCD-I: Wang, nucl-th/0305010 pQCD-II: Vitev and Gyulassy, PRL 89, 252301 Saturation: KLM, Phys Lett B561, 93 Inclusive suppression: theory vs. data Final state Initial state pT>5 GeV/c: well described by KLM saturation model (up to 60% central) and pQCD+jet quenching

  39. Inclusive spectra RAB If Au+Au suppression is final state 1.1-1.5 1 If Au+Au suppression is initial state (KLM saturation: 0.75) ~2-4 GeV/c pT High pT hadron pairs broadening? pQCD: no suppression, small broadening due to Cronin effect saturation models: suppression due to mono-jet contribution? 0 suppression? /2  0  (radians) d+Au vs. p+p: Theoretical expectations All effects strongest in central d+Au collisions

  40. Inclusive charged particle spectra

  41. Inclusive yield relative to binary-scaled p+p • d+Au : enhancement • Au+Au: strong suppression • pT=4 GeV/c: • cent/minbias= 1.110.03 • central collisions enhanced wrt minbias Suppression of the inclusive yield in central Au+Au is a final-state effect

  42. pedestal and flow subtracted Azimuthal distributions Near-side: p+p, d+Au, Au+Au similar Back-to-back: Au+Au strongly suppressed relative to p+p and d+Au Suppression of the back-to-back correlation in central Au+Au is a final-state effect

  43. Conclusion from STAR, BNL, June 18, 2003 The strong suppression of the inclusive yield and back-to-back correlations at high pT previously observed in central Au+Au collisions are due to final-state interactions with the dense medium generated in such collisions. Comment (~Bo Andersson): Can you discover something by observing the absence of the suppression of an effect? What would be a positive signal for QGP? Young experimentalists are welcome to find the answer!

  44. Have we found the Quark Gluon Plasma at RHIC? We now know that Au+Au collisions generate a medium that • is dense (pQCD theory: many times cold nuclear matter density) • is dissipative • exhibits strong collective behavior This represents significant progress in our understanding of strongly interacting matter We have yet to show that: • dissipation and collective behavior both occur at the partonic stage • the system is deconfined and thermalized • a transition occurs: can we turn the effects off ? Not yet, there is still work to do We have developed the tools necessary to complete this program

  45. p+A: What happens at lower energies, at CERN SPS? Central Pb+Pb (SPS): Did the vikings have a „Vinland map” ?? “Cronin effekt”, increase instead of decrease, multiple scattering szó Now new matter at CERN SPS?

  46. Overview and Outlook A deeper meaning of the analogy CERN SPS <-> Viking age, BNL RHIC <-> Age of Columbus? Personal view: A new world discovered. But is it India or America? Is it QGP or some other new form of matter? Need to make the map. (All information soft spectra, correlations, high pt are needed)

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