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Recent Results from the BRAHMS Experiment at RHIC Paweł Staszel, Jagellonian University for the BRAHMS Collaboration Eighth Workshop on Non-Perturbative QCD Paris, 7 – 11 June, 2004 The Relativistic Heavy Ion Collider BRAHMS Top energy: sNN=200GeV BRAHMS Au+Au P. Staszel - Jagellonian University, Kraków Eighth Workshop on Non-Perturbative QCD, Paris 2004 d+Au p+p BRAHMS 2 The BRAHMS Collaboration I.G. Bearden7, D. Beavis1, C. Besliu10, B. Budick6, H. Bøggild7 , C. Chasman1, C. H. Christensen7, P. Christiansen7, J.Cibor4, R.Debbe1, E. Enger12, J. J. Gaardhøje7, M. Germinario7, K. Hagel8, O. Hansen7, A.K. Holme12, H. Ito11, A. Jipa10, J. I. Jordre10, F. Jundt2, C.E.Jørgensen7, R. Karabowicz3, E. J. Kim5, T. Kozik3, T.M.Larsen12, J. H. Lee1, Y. K.Lee5, G. Løvhøjden2, Z. Majka3, A. Makeev8, B. McBreen1, M. Mikkelsen12, M. Murray8, J. Natowitz8, B.S.Nielsen7, K. Olchanski1, D. Ouerdane7, R.Planeta4, F. Rami2, D. Röhrich9, B. H. Samset12, D. Sandberg7, S. J. Sanders11, R.A.Sheetz1, P. Staszel3,7, T.S. Tveter12, F.Videbæk1, R. Wada8, Z. Yin9, and I. S. Zgura10 1Brookhaven National Laboratory, USA, 2IReS and Université Louis Pasteur, Strasbourg, France 3Jagiellonian University, Cracow, Poland, 4Institute of Nuclear Physics, Cracow, Poland 5Johns Hopkins University, Baltimore, USA, 6New York University, USA 7Niels Bohr Institute, University of Copenhagen, Denmark 8Texas A&M University, College Station. USA, 9University of Bergen, Norway 10University of Bucharest, Romania, 11University of Kansas, Lawrence,USA 12 University of Oslo Norway 50 physicists from 12 institutions P. Staszel - Jagellonian University, Kraków Eighth Workshop on Non-Perturbative QCD, Paris 2004 BRAHMS 3 Agenda of this talk General Characteristics of the Au+Au sNN=200GeV - particle production - nuclear stopping - statistical model description (particle ratios) - transvers dynamics (particle pt spectra) Nuclear modification of spectra Au+Au (QGP) Rapidity evolution of nuclear modification for d+Au (CGC) Summary P. Staszel - Jagellonian University, Kraków Eighth Workshop on Non-Perturbative QCD, Paris 2004 BRAHMS 4 Charged Particle Multiplicity 0-5% 5-10% 10-20% 20-30% 30-40% 0-5% central Au+Au: Total charged particle multiplicity: 4630370 (PRL 88, 202301(2002)) 50% increase over p+pbar (UA5) 40-50% p+p Energy density: Bjorken 1983 eBJ = 3/2 (<Et>/ pR2t0) dNch/dh 4.0 GeV/fm3 (<Et>=0.5GeV, t0=1fm/c) P. Staszel - Jagellonian University, Kraków Eighth Workshop on Non-Perturbative QCD, Paris 2004 BRAHMS 5 Limiting Fragmentation Shift the dNch/d distribution by the beam rapidity, and scale by Npart. Lines up with lower energy limiting fragmentation Au+Au sNN=200GeV (0-5% and 30-40%) Au+Au sNN=130GeV (0-5%) Pb+Pb sNN=17GeV (9.4%) P. Staszel - Jagellonian University, Kraków Eighth Workshop on Non-Perturbative QCD, Paris 2004 BRAHMS 6 Baryon stopping y = yb - y y = 2.03 0.16 y = 2.00 0.1 Gaussians in pz 6 order polynomial yp yp mT dN( B B ) y dy cosh y dy Total E=25.72.1TeV 72GeV per participant P. Staszel - Jagellonian University, Kraków Eighth Workshop on Non-Perturbative QCD, Paris 2004 BRAHMS 7 Baryon stopping II y =0.58yp LHC ? y = 2.2, E/A=2800GeV broken Sscaling NN=63 GeV (Ebeam/A=3500GeV, yp=8.9) ??? 8.9 P. Staszel - Jagellonian University, Kraków Eighth Workshop on Non-Perturbative QCD, Paris 2004 BRAHMS 8 Chemical freeze-out Kinetic freeze-out PRL90,102301 (2003) •At y=0: p-/p+ = 1.0, K-/K+ = 0.95 ±0.05 pbar/p = 0.75 ±0.04 •Good statistical model description with B= B(y), • At |y|<1 materanti-matter Phys. Rev. Lett. 90, 102301(2003) T115 Mev, T0.7c at y=0 • Flow velocity decreases with rapidity. Lower density lower pressure less flow • Temperature increases with rapidity. Lower density faster freeze out higher temperature P. Staszel - Jagellonian University, Kraków Eighth Workshop on Non-Perturbative QCD, Paris 2004 BRAHMS 9 High pt Suppression Jet Quenching Particles with high pt’s (above ~2GeV/c) are primarly produced in hard scattering processes early in the collision Probe of the dense and hot stage p+p experiments hard scattered Schematic view of jet production hadrons leading particle q partons fragment into jets of hadrons q In A-A, partons traverse the medium If QGP partons will lose a large part of their energy (induced gluon radiation) Suppression of jet production Jet Quenching leading particle Experimentally depletion of the high pt region in hadron spectra P. Staszel - Jagellonian University, Kraków Eighth Workshop on Non-Perturbative QCD, Paris 2004 BRAHMS 10 Charged hadron invariant spectra BRAHMS, PRL91(2003)072305 Nuclear Modification Factor RAA = h= 0 h= 2. 2 Yield(AA) NCOLL(AA) Yield(NN) Scaled N+N reference RAA<1 Suppression relative to scaled NN reference Reference spectrum p+pbar spectra (UA1) SPS: data do not show suppression enhancent (RAA>1) due to initial state multiple scatering (“Cronin Effect”) P. Staszel - Jagellonian University, Kraków Eighth Workshop on Non-Perturbative QCD, Paris 2004 BRAHMS 11 High pt suppression in Au+Au @ SNN=200 GeV BRAHMS, PRL91(2003)072305 mid-rapidity (=0) At central collisions clear suppression At peripheral no suppression (as expected) forward rapidity (=2.2) the same trend no p+p reference large sys. errors RCP= Yield(0-10%)/NCOLL(0-10%) Yield(40-60%)/NCOLL(4060%) RCP shows suppression at both =0 and =2.2 P. Staszel - Jagellonian University, Kraków Eighth Workshop on Non-Perturbative QCD, Paris 2004 BRAHMS 12 Control measurement: d+Au @ SNN=200 Suppression in AuAu due to Jet Quenching or due to Initial State Parton Saturation (CGC)? What about d+Au? - Jet Quenching – No - CGC - Yes/No? Excludes alternative interpretation in terms of Initial State Effects Supports the Jet Quenching for central Au+Au collisions + back-to-back azimuthal correlation by STAR P. Staszel - Jagellonian University, Kraków Eighth Workshop on Non-Perturbative QCD, Paris 2004 BRAHMS 13 Hirano & Nara (nucl-th/0307087) Data versus Hydro-Jet Model i Hydro description of the soft part of the produced matter ii Hard part use a pQDC model (PYTHIA) i+ii – generation of jets is evolving medium Reasonable description of data at both =0 and =2.2 P. Staszel - Jagellonian University, Kraków Eighth Workshop on Non-Perturbative QCD, Paris 2004 BRAHMS 14 Evolution of RdAu with rapidity nucl-ex/0403005 Cronin like enhancement at =0 Clear suppression at =3.2 Low pt consistent with measured dNch/d P. Staszel - Jagellonian University, Kraków Eighth Workshop on Non-Perturbative QCD, Paris 2004 BRAHMS 15 pQCD versus data @ = 3.2 A. Accardi, M. Gyulassy, nucl-th/0402101 Geometrical shadowing with opacity from fit to PHENIX (y~0, p0) P. Staszel - Jagellonian University, Kraków Eighth Workshop on Non-Perturbative QCD, Paris 2004 BRAHMS 16 Color Glass Condensate explanation =0 =1 D. Kharzeev at al. hep-ph/0405045 quark dipole-nucleus scattering amplitude Two free parameters fitted to data: y0 – onset of saturation c - onset of quantum regime =2.2 =3.2 Overal good description of RdAu With general trend of RdAu 1/Npart, this model accounts also for resonable description of RCP P. Staszel - Jagellonian University, Kraków Eighth Workshop on Non-Perturbative QCD, Paris 2004 BRAHMS 17 Rapidity dependence for d+Au Submitted to PRL nucl-ex/0401025 Curves: Saturation Model from Kharzeev, Levin, Nardi NPA730 (2004) 448 P. Staszel - Jagellonian University, Kraków Eighth Workshop on Non-Perturbative QCD, Paris 2004 BRAHMS 18 Summary Large hadron multiplicies Almost a factor of 2 higher than at SPS ( higher ) Much higher than in pp ( medium effects) Identified hadron spectra Broken lower energy scaling of rapidity loss Good description by statistical model large transvers flow Suppression of high pt particles in central Au+Au collisions observed at =0 and 2.2 Consistent with a Jet Quenching scenario Evolution of nuclear modification in d+Au data absence of the suppression in d+Au data at =0 supports Jet Quenching scenario forward data consistent with onset of suppression in the Color Glass Condensate P. 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