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BRAHMS overview

BRAHMS overview. Paweł Staszel, Marian Smoluchowski Institute of Physics Jagiellonian University for the BRAHMS Collaboration. Quark Matter Budapest, 4 – 9 August, 2005. PHOBOS. BRAHMS. PHENIX. STAR. Au+Au. Cu+Cu. d+Au. energies:  s NN =200GeV,  s NN =62GeV. BRAHMS. p+p.

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BRAHMS overview

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  1. BRAHMS overview Paweł Staszel, Marian Smoluchowski Institute of Physics Jagiellonian University for the BRAHMS Collaboration Quark Matter Budapest, 4 – 9 August, 2005

  2. PHOBOS BRAHMS PHENIX STAR Au+Au Cu+Cu d+Au energies: sNN=200GeV, sNN=62GeV BRAHMS p+p The Relativistic Heavy Ion Collider

  3. Outline Detector setup. General (bulk) characteristics of nucleus-nucleus reactions. Elliptic flow (for AuAu @ 200). Baryon to meson ratios. High pT suppression. Summary.

  4. Flow Ring 2 Si Ring 1 Tile Ring 1 Broad Range Hadron Magnetic Spectrometers

  5. 0<<1 1.5<<4 2 cut TOFW TOFW2 TOF1 TOF2 K/ 2.0 GeV/c 2.5 GeV/c 3.0 GeV/c 4.5 GeV/c K / p 3.5 GeV/c 4.0 GeV/c 5.5 GeV/c 7.5 GeV/c • C4 Threshold (MRS): •  / K separation 9 GeV/c • RICH (FS): •  / K separation 20 GeV/c • Proton ID up to 35 GeV/c Particle identification summary

  6. Charged Particle Multiplicity Energy density: Bjorken 1983 eBJ = 3/2 (<Et>/ pR2t0) dNch/d assuming formation time t0=1fm/c: >5.0 GeV/fm3 for AuAu @ 200 GeV >4.4 GeV/fm3 for AuAu @ 130 GeV >3.7 GeV/fm3 for AuAu @ 62.4 GeV

  7. K/ energy dependence, AuAu Ionat Arsene, poster #126 200GeV 62GeV

  8. Chemical freeze-out Anti-particle to particle ratios BRAHMS PRELIMINARY It is not true for p+p BRAHMS PRELIMINARY • pbar/p verus K-/K+ : good statistical model description with B= B(y) with T~170MeV • But this describes also energy depencency at y=0  only B controls the state of matter • STAR and NA47 measures pbar/p versus • -/+ • At 200 GeV: -/+ = 1.0, K-/K+ = 0.95, pbar/p = 0.75 • At 62 GeV: -/+ = 1.0, K-/K+ = 0.84, pbar/p = 0.45, • At |y|<1 matterantimatter

  9. Flow velocity increases with centrality. • Temperature decreases with centrality. • the same anti-correlation is observed • versus y: • Flow velocity decreases with rapidity. • Temperature increases with rapidity Kinetic freeze-out: AuAu @ 200GeV BRAHMS preliminary Comparing 200GeV and 62GeV data In the same Npart bin, we see reduction in flow by ~10% and no change in T Lower density  lower pressure  less flow faster freeze out  higher temperature Oana Ristea poster #50

  10. AuAu @200GeV dN ddptd dN 1 ddpt 2 = (1 + 2v1cos + 2v2(,pt)cos2) =0 No v2(pT) rapidity dependence =1 =3.2 Elliptic flow (v2) Hiro Ito, parallel sem. 2b, Fri.

  11. pbar/- ratios vs. centrality and  (parton recombination) • Smooth increase from peripheral to central in AuAu at sNN = 200 GeV • Centrality dependence is stronger at midrapidity than forward rapidity • The maximum is shifted to low pT at forward rapidity

  12. p/pi ratios vs pt (parton recombination, hydro) • no significant difference between y=0 and y~1 • flow/mass effect ?

  13. Strong rapidity dependence CuCu data consistent with AuAu for the same Npart pbar/-scaling with Npart sNN=200GeV pp Eun-Joo Kim, parallel sem. 1b Fri. pp

  14. K/ ratios at =3.1, Au+Au @200GeV

  15. Schematic view of jet production hadrons leading particle q q leading particle High pt Suppression  Jet Quenching • Particles with high pt’s (above ~2GeV/c) are primarily produced in hard scattering processes early in the collision • p+p experiments  hard scattered partons fragment intojets of hadrons • In A-A, partons traverse the medium  Probe of the dense and hot stage • If QGP partons will lose a large part of their energy (induced gluon radiation)  suppression of jet production  Jet Quenching Experimentally  depletion of the high pt region in hadron spectra

  16. Nuclear Modification Factor Yield(AA) RAA = NCOLL(AA)  Yield(NN) Scaled N+N reference AuAu @200GeV Yield(0-10%)/NCOLL(0-10%) RCP = Yield(40-60%)/NCOLL(40-60%) Charged hadron invariant spectra RAA<1 Suppression relative to scaled NN reference • SPS: data do not show suppression enhancement (RAA>1) due to initial state multiple scattering (“Cronin Effect”)

  17. Au+Au: comparison 200 GeV between 62 GeV Brahms preliminary 200 GeV Catalin Ristea, poster #4 62 GeV (pp reference is based on ISR collider data)

  18. Two systems comparison @ 62.4GeV Brahms preliminary Cu+Cu Truls M. Larsen, parallel sem. 3a Fri. Au+Au

  19. RCP dependence on  for AuAu @200 GeV and 62.4 GeV weak  dependence at 200 GeV… …but greater suppression approaching beam rapidity at 63 GeV. peripheral collision  pp collision

  20. RCP and RAA for identified hadronsat y~3.1, Au+Au @ 200GeV protons pions kaons

  21. RAA versus centrality for identified hadrons

  22. ….more on RAA rapidity dependence Au+Au @200GeV Radek Karabowicz parallel sem. 1b Fri.

  23. Strong energy absorption model from a static 2D matter source. (Insprired byA.Dainese (Eur.Phys.J C33,495) and A.Dainese , C.Loizides and G.Paic (hep-ph/0406201) ) • Parton spectrum using pp reference spectrum • Parton energy loss DE ~ q.L**2 • q adjusted to give observed RAA at h~1. The change in dN/dh will result in slowly rising RAA . The modification of reference pp spectrum causes the RAA to be approximately constant as function of h .

  24. RdAu and RAA for anti-protons and pions @200 BRAHMS PRELIMINARY • suppression for p- but stronger for AuAu • both RdA and RAA show enhancement for p-bar

  25. Summary • Large hadron multiplicities  Almost a factor of 2 higher than at SPS energy( higher )  Much higher than pp scaled results( medium effects) • Identified hadron spectra Good description by statistical model  Large transverse flow consistent with high initial density • v2(pt) is seem to not depend on rapidity • p/ show strong  dependency  for given energy depend only on Npar • High-pT suppression increases with energy for given centrality bin  weak dependency on rapidity of RAA which is consistent with surface jet emission  RCP can hide or enhance nuclear effects  At y=3.2 RAA shows larger suppression than RdA

  26. The BRAHMS Collaboration I.Arsene7, I.G. Bearden6, D. Beavis1, S. Bekele6 , C. Besliu9, B. Budick5, H. Bøggild6 , C. Chasman1, C. H. Christensen6, P. Christiansen6, R. Clarke9, R.Debbe1, J. J. Gaardhøje6, K. Hagel7, H. Ito10, A. Jipa9, J. I. Jordre9, F. Jundt2, E.B. Johnson10, C.E.Jørgensen6, R. Karabowicz3, E. J. Kim4, T.M.Larsen11, J. H. Lee1, Y. K. Lee4, S.Lindal11, G. Løvhøjden2, Z. Majka3, M. Murray10, J. Natowitz7, B.S.Nielsen6, D. Ouerdane6, R.Planeta3, F. Rami2, C. Ristea6, O. Ristea9, D. Röhrich8, B. H. Samset11, D. Sandberg6, S. J. Sanders10, R.A.Sheetz1, P. Staszel3, T.S. Tveter11, F.Videbæk1, R. Wada7, H. Yang6, Z. Yin8,and I. S. Zgura9 1Brookhaven National Laboratory, USA, 2IReS and Université Louis Pasteur, Strasbourg, France 3Jagiellonian University, Cracow, Poland, 4Johns Hopkins University, Baltimore, USA, 5New York University, USA 6Niels Bohr Institute, University of Copenhagen, Denmark 7Texas A&M University, College Station. USA, 8University of Bergen, Norway 9University of Bucharest, Romania,10University of Kansas, Lawrence,USA 11 University of Oslo Norway 48 physicists from 11 institutions

  27. 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%)

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