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Recent Results from RHIC

Recent Results from RHIC. David Hofman University of Illinois at Chicago. EPS 2003 July 17-24, 2003 Aachen. Relativistic Heavy Ions. AGS: fixed target, 4.8 GeV/u pair SPS: fixed target, 17 GeV/u pair RHIC: collider, 200 GeV/u pair LHC: collider, 5.4 TeV/u pair. RHIC.

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Recent Results from RHIC

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  1. Recent Results from RHIC David Hofman University of Illinois at Chicago EPS 2003July 17-24, 2003 Aachen

  2. Relativistic Heavy Ions • AGS: fixed target, 4.8 GeV/u pair • SPS: fixed target, 17 GeV/u pair • RHIC: collider, 200 GeV/u pair • LHC: collider, 5.4 TeV/u pair RHIC • Two concentric superconducting magnet rings, 3.8 km circum. • Funded by U.S. Dept. of Energy ($616 million) • Construction began Jan. 1991, first collisions June 2000 • Au + Au √sNN = (19.6, 56) 130, 200 GeV • p + p √sNN = 200 GeV • d + Au √sNN = 200 GeV (Just finished spring 2003!) EPS2003 - Aachen

  3. Relativistic Heavy Ions EPS2003 - Aachen

  4. STAR Four Complementary Experiments ~303 collaborators ~307 collaborators Large solid angle tracking ~ Complete events Leptons, (+h’s, g’s) High rate, Sophisticated triggering ~52 collaborators ~68 collaborators ~4p accept. Good vtx. resolution (All Si det.) Tracking & PID at high y EPS2003 - Aachen

  5. p + p Collisions “Participant” Scaling Npart/2= # of participating pairs of nucleons: = 1 Binary “Collision” Scaling Ncoll = # of NN collisions: = 1 EPS2003 - Aachen

  6. Au+Au Collisions “Participant” Scaling Head-On Collision Npart/2= # of participating pairs of nucleons: ~ A Binary “Collision” Scaling Head-On Collision A L~A1/3 Ncoll = # of NN collisions: ~ A4/3 EPS2003 - Aachen

  7. Number of Binary Collisions vs. Centrality and Energy Glauber Monte Carlo for Au + Au Collisions sinel=42 mb (RHIC) nmax ~ 6 (RHIC) Au+Au nmax ~ 5 (SPS) n = Ncoll/(Npart/2) sinel=33 mb (SPS) nmax ~ 3 (AGS) sinel=21 mb (AGS) nmax = 1 (p+p) Peripheralcollisions Centralcollisions <Npart> (√sNN=200) ~ 100 EPS2003 - Aachen

  8. Charged Particle Density near Midrapidity EPS2003 - Aachen

  9. RHIC SPS AGS Charged Particle Density near Midrapidity Most Naïve Model Possible: A+A = Incoherent Superposition of binary p+p collisions Au+Au Min-bias (n~3.6) (n~3.1) EPS2003 - Aachen

  10. RHIC SPS AGS Charged Particle Density near Midrapidity Central Collisions (for Heavy Ion data) RHIC - combined EPS2003 - Aachen

  11. RHIC SPS AGS Charged Particle Density near Midrapidity Central Collisions (for Heavy Ion data) dN/dyT (for e+e- data) RHIC - combined EPS2003 - Aachen

  12. RHIC Results for Au + Au Charged Particles mid-rapidity • Multiplicities at the very low end of model expectation. • (√s = 200 GeV) • Energy-density estimates: • εBJ ~ 4.6 GeV/fm3(√s = 130 GeV)(PHENIX; PRL 87 (2001) 052301) • εBJ ~ 5.5 GeV/fm3(√s = 200 GeV)(PHENIX: preliminary) • Expectation for a “new form of matter” at energy-densities: • ε > 1 GeV/fm3 Mid-Rapidity Density EPS2003 - Aachen

  13. Charged Particle Production at Midrapidity p + p Energy and Centrality Dependence Data is normalized by p+p value for each energy. Binary collision scaling 200 GeV Au+Au 130 GeV 19.6 GeV preliminary Participant scaling peripheral central  Very “flat” particle production with centrality!  Importance of comparing results to proton “baseline”. EPS2003 - Aachen

  14. Suppression in Au+Au Hadron Spectra Binary collision scaling Picture From:T. Peltzmann, QM02 Central collisions at midrapidity BRAHMSSTARPHOBOS h± h±p0 PHENIX 0-10% Participant scaling  High pT yields in Au+Au are strongly suppressed for central collisions relative to p+p data and collision scaling expectation.  Trend is seen in all four RHIC experiments. EPS2003 - Aachen

  15. Suppression in Au+Au Hadron Spectra STAR: nucl-ex/0305015 0 2 4 6 8 10 12 pT (GeV/c) pQCD: Wang, nucl-th/0305010 (see also Vitev and Gyulassy, PRL 89, 252301) Saturation: KLM, Phys Lett B561, 93 Initial state effect Final state effect EPS2003 - Aachen

  16. jet STAR parton Jets at RHIC From: P. Jacobs, RHIC special colloquium Find this… …in this p+p jet+jet (STAR@RHIC) Au+Au ??? (STAR@RHIC) Select highest pT(>4 GeV/c) “trigger jet” nucleon nucleon → create Df distribution for 2 < pT < pT(trigger) EPS2003 - Aachen

  17. STAR Azimuthal Jet Distributions in Au+Au STAR: PRL 90, 082302 Figs From:P. Jacobs Au+Au peripheral Au+Au central pedestal and flow subtracted pedestal and flow subtracted Near-side: peripheral and central Au+Au similar to p+p Far-side: strong suppression of back-to-back correlations in central Au+Au EPS2003 - Aachen

  18. Suppression: Initial or Final State Effect? Pics From:P. Jacobs Initial state? Final state? partonic energy loss gluon saturation High pT suppression in Au + Au explained by both models. EPS2003 - Aachen

  19. Suppression: Initial or Final State Effect? Pics From:P. Jacobs Initial state? Final state? partonic energy loss gluon saturation High pT suppression in Au + Au explained by both models. How to discriminate? Turn off final state. d+Au collisions ? EPS2003 - Aachen

  20. Charged Hadron Results @ RHIC PHOBOS d+Au: nucl-ex/0306025 2.5 2.0 d+A (0-20%) 1.5 1.0 0.5 Au+Au (central) 0 2 4 6 pT (GeV/c) d+Au vs. Au+Au at √sNN = 200 GeV STAR d+Au: nucl-ex/0306024 PHENIX d+Au: nucl-ex/0306021 d+Au Au+Aucentral 0 1 2 3 4 5 6 7 8 9 10 pT (GeV/c) BRAHMS d+Au: nucl-ex/0307003 d+Au Au+Aucentral (BRAHMS: same in Au+Au for h=2) pT (GeV/c) EPS2003 - Aachen

  21. p0 Yields Relative to Binary Scaled p+p Color Fig From:T. Hemmick d+Au Binary Collision Scaling Au+Au Au+Au: strong suppression d+Au: no suppression EPS2003 - Aachen

  22. STAR Azimuthal Jet Distributions in d+Au Fig From:P. Jacobs pedestal and flow subtracted D f (radians) Near-side: similar result for p+p, d+Au and Au+Au. Far-side: strong suppression of back-to-back correlations only in central Au+Au; NOT in d+Au, p+p nor peripheral Au+Au. EPS2003 - Aachen

  23. June 18th 2003 RHIC special symposium • Evidence for ‘jet quenching’ in central Au+Au at RHIC • Evidence of ‘jet non-quenching’ in d+Au (and peripheral Au+Au) Data suggest we have observed a final state effect produced in a hot dense medium. • A few (of many) other hot topics at RHIC: • Statistical model and particle ratios • – Everything fits with T ~ 176 MeV. • HBT Radii • – No change in Rside and Rout! • Elliptic Flow • – Saturates hydrodynamics limit at low pT! • – Interesting mass, pT and h dependence! • First glimpses of J/Y at RHIC EPS2003 - Aachen

  24. Particle Ratios: Fit Beautifully in Statistical Model Fig From:B. Norman → Statistical/Thermal model represents data well. → No change in freezeout temperature from 130 to 200 GeV, but decreasing baryon chemical potential. EPS2003 - Aachen

  25. Two pion correlations at RHIC √sNN = 130 GeV • Source dimensions by measuring HBT radii. • Essentially no change (in Rside and Rout) from AGS (√sNN~4.7) to RHIC (√sNN~200)! • Short lived source. • Not described in current dynamical models. PHENIX: PRL 88 (2002) 192302 STAR: PRL 87 (2001) 082301 EPS2003 - Aachen

  26. Elliptic Flow: a Collective Effect Initial spatial anisotropy z z Reaction plane (YR) y f x y y x x (defines YR) Final momentum anisotropy dN/d(f -YR ) = N0 (1 + 2v1cos (f-YR) + 2v2cos (2(f-YR)) + ... ) py px Anisotropy parameter v2 EPS2003 - Aachen

  27. RHIC Results Reach Hydro at low pT (PHENIX: nucl-ex/0305013) STAR: nucl-ex/0306007 • STAR & PHENIX have similar results for the mass and pT dependence of elliptic flow (v2). • Reach hydro limit only at low pT. Different particles deviate from this limit at different values of pT. • Mass and pT dependence removed if scale by number of constituent quarks (n). • Quark coalescence? → More detailed studies needed. EPS2003 - Aachen

  28. Charged Particle v2 vs. h and Energy PHOBOS: PRL 89, 222301 (2002) Anisotropy parameter v2 Hydrodynamic limit illustration √sNN = 130 GeV (PRL 89) √sNN = 200 GeV (preliminary) h (pseudorapidity)  Lack of boost invariance. Poses a challenge for theory. EPS2003 - Aachen

  29. J/y from PHENIX • The suppression of J/y yields in heavy-ion collisions at SPS is believed to be an important signal for a de-confined state of matter. • Important to measure at RHIC. • PHENIX has successfully measured J/y at RHIC for p+p collisions. • Full story in the next talk! p+p collisions at √s= 200 GeV (In case you forgot: Mass J/y ~ 3.1 GeV) EPS2003 - Aachen

  30. Conclusion: Recent Results from RHIC • Clear signatures of high pT suppression (“jet quenching”) in central Au + Au collisions at RHIC that are not present in d + Au. • Indication of final state interactions in bulk dense matter. • Much more data exists than I had time to show.(Stay in session today and tomorrow for more results.) • Many exciting puzzles remain… EPS2003 - Aachen

  31. More RHIC Experimental Talks to Follow • J/y production (PHENIX) • Nichelle Bruner • Charged particle production (PHOBOS) • Gerrit van Nieuwenhuizen • Freeze-out temperatures and transverse flow (BRAHMS) • Oana Ristea • Identified Low pT spectra (PHOBOS) • Adam Trzupek • Identified High pT production (BRAHMS) • Zhongbao Yin • Charged particle pT spectra (PHOBOS) • Rachid Nouicer • Strangeness production at RHIC (BRAHMS) • Jens I. Jordre EPS2003 - Aachen

  32. Backup Slides

  33. b b Peripheral Central Reminder: Centrality in Au+Au Data Paddle: Multiplicity in 3 < |h| < 4.5 • HIJING +GEANT • Glauber calculation • Model of paddle trigger Paddle signal Data+MC Npart EPS2003 - Aachen

  34. Charged Particle Production at Midrapidity Energy and Centrality Dependence PRC 65, 061901(R) (2002); 19.6 GeV in Preparation Midrapidity |h|<1 Au+Au 200 GeV dNch/dh 130 GeV 19.6 GeV preliminary pp two component fit with x~ 0.1  See same fraction of about 10% collision scaling fits all energies. EPS2003 - Aachen

  35. Charged Particle Production at Midrapidity p + p Energy and Centrality Dependence → Data described by model with: Data is normalized by corresponding pp value for each energy. 200 GeV 130 GeV Au+Au 19.6 GeV preliminary Kharzeev, Levin, McLerran (KLM)(e.g. PLB 561 (2003) 93)  Initial state (KLM) saturation model also describes full dN/dh shapes; including new effect seen by PHOBOS in the fragmentation region. EPS2003 - Aachen

  36. PT Distribution of Charged Particles “Soft” part of spectrum Phobos Preliminary Systematic Errors not shown  What about high pT? Have a quick look at the “Hard” part of the spectrum. EPS2003 - Aachen

  37. Energy evolution of B Using measured <K–>/<K+>,<p>/<p> and statistical model of F. Becattiniet al.,(PRC64,024901,2001) with Tch 160 – 170 MeV Estimated baryochemical potential at sNN = 200 GeV: B = 26  2 MeV • LHC ~ 1 MeV? Fit: P.Braun-Munzinger NP. A697,902,2002 EPS2003 - Aachen

  38. Theory Calculations Energy loss applied: M. Gyulassy, I. Vitev, X.N Wang and B.W. Zhang; nucl-th/0302007 dE/dxo is the only free parameter. It is determined by fitting to STAR central RAA(pt) Cronin Effect: X.N. Wang, Phys. Rev C61, 064910 (2000). Attributed to initial state multiple scattering. Implemented by Q2(pt) dependent Gaussian kt broadening EPS2003 - Aachen

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