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Forward and high pt physics at RHIC with BRAHMS

Forward and high pt physics at RHIC with BRAHMS. Stopping in Au+Au at √s=200, 62.4 GeV Rapidity dependence of high pt suppression of hadrons at √s=200 GeV Au+Au and d+Au at η =0 Au+Au at η =2.2, 3.2 d+Au at η = 0 to 3.2 (CGC?)

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Forward and high pt physics at RHIC with BRAHMS

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  1. Forward and high pt physics at RHIC with BRAHMS • Stopping in Au+Au at √s=200, 62.4 GeV • Rapidity dependence of high pt suppression of hadrons at √s=200 GeV • Au+Au and d+Au at η=0 • Au+Au at η=2.2, 3.2 • d+Au at η= 0 to 3.2 (CGC?) • Energy dependence of high pt suppression of hadrons at √s=62.4 GeV in Au+Au at η= 0, 1 • Flavor dependence in Au+Au and d+Au • Rapidity dependence of particle production in p+p collisions Ericeira Jens Jørgen Gaardhøje, Niels Bohr Institute

  2. The BRAHMS experiment Ericeira Jens Jørgen Gaardhøje, Niels Bohr Institute

  3. FS 4 deg m2=p2( t2 / L2 -1) Excellent Hadron Identification by TOF and RICH p D D K  Ericeira Jens Jørgen Gaardhøje, Niels Bohr Institute

  4. Transparency and beam energy loss at RHIC BRAHMS PRL 93 (2004) 102301 Ericeira Jens Jørgen Gaardhøje, Niels Bohr Institute

  5. Net Protons at 62.4 GeV BRAHMS preliminary dN(p-pbar)/dy 0-5% y Ericeira Jens Jørgen Gaardhøje, Niels Bohr Institute

  6. Rapidity and energy loss at RHIC Relative rapidity loss : 35% < y/yb < 44% Rapidity loss saturates! But Energy loss increases strongly dE(baryon)=75GeV ΔE(tot)=26TeV Out of available 35 TeV Ericeira Jens Jørgen Gaardhøje, Niels Bohr Institute

  7. Total relativistic energy E = mt cosh(y) mt=(pt2+m2)1/2 Produced particles in -3<y<+3 carry about 9 TeV of total energy Ericeira Jens Jørgen Gaardhøje, Niels Bohr Institute

  8. BRAHMS: PRL 91 (2003) 072305 RAA 1 pt 2 0 The smoking gun of QGP? Jet Quenching, high pt suppression. Soft Hard (jets) Ericeira Jens Jørgen Gaardhøje, Niels Bohr Institute

  9. PRL 91 (2003) 072305 Au D q q Absence of high pt suppression at midrapidity rules out initial state effects .  1/5 Test: Absence of suppression at midrapidity in d+Au? Ericeira Jens Jørgen Gaardhøje, Niels Bohr Institute

  10. What does theory have to say? HIJING: pQCD (hard) + strings (soft), shadowing, very schematic jet quenching (1992) Vitev-Gyulassy: pQCD (hard), no soft Cronin kT broadening, shadowing and (GLV) jet quenching Cassing et al: pQCD (hard) + strings (soft) kT broadening, shadowing and energy loss (pre-hadronic and hadronic) Hirano-Nara: pQCD (hard) + hydro (soft) Cronin kT broadening, shadowing and (GLV) jet quenching Ericeira Jens Jørgen Gaardhøje, Niels Bohr Institute

  11. High pt suppression persists at forward rapidity Large high pt suppression also at forward rapidity. Longitudinally extended medium, boost invariance, CGC or …? Not quantitatively understood. Ericeira Jens Jørgen Gaardhøje, Niels Bohr Institute

  12. q q q q Energy loss by stimulated gluon emission in QGP ? QCD: <E>g ln(1/L) dz  <L2> Ericeira Jens Jørgen Gaardhøje, Niels Bohr Institute

  13. RAuAu for hadrons at η=3.2 (4degrees)RHIC run IV BRAHMS: preliminary RCP= RdAu (0-20%) / (60-80%) RdAu (30-50%) / (60-80%) RCP indicates strong high pt suppression at very forward rapidities in Au+Au Ericeira Jens Jørgen Gaardhøje, Niels Bohr Institute

  14. RAuAu @ 62.4 GeVη=0 and η=0.95 Ericeira Jens Jørgen Gaardhøje, Niels Bohr Institute

  15. No sudden transition….. ? √Snn (GeV) Ericeira Jens Jørgen Gaardhøje, Niels Bohr Institute

  16. Au D detector Measure at large y on D side: Probes small x in Au Color Glass CondensateThe fundamental state of the colliding nuclei? X= p(parton) /p(nucleon) Ericeira Jens Jørgen Gaardhøje, Niels Bohr Institute

  17. Color Glass Condensate in d+Au collisions? BRAHMS accepted PRL nucl-ex / 0403005 Ericeira Jens Jørgen Gaardhøje, Niels Bohr Institute

  18. RCP= RdAu (0-20%) / (60-80%) RdAu (30-50%) / (60-80%) Most central to peripheral ratio is most enhanced atmidrapidity and most suppressed at forward rapidity This centrality inversion is consistent with the CGC model. Centrality dependence … in d+Au Ericeira Jens Jørgen Gaardhøje, Niels Bohr Institute

  19. ’High pt’ spectra are different for baryons and mesons in Au+Au Very different from p+p and e++e- Hadronic flow or partonic mechanism? Qualitative agreement with parton recombination models, but need results from run IV for higher pt Ericeira Jens Jørgen Gaardhøje, Niels Bohr Institute

  20. How does it look in d+Au ? Identified hadrons at 4 degrees (η=3.2) π PID with RICH At eta= 3.2 P-bar : 10% Π- : 80% p K Ericeira Jens Jørgen Gaardhøje, Niels Bohr Institute

  21. RdAu at η=3.2(min.bias) Baryon meson difference in d+Au Strong Difference between mesons (pions) and Baryons (anti-p) persists at forward rapidity in d+Au collisions BRAHMS preliminary Flow? Isospin? Need to understand Ericeira Jens Jørgen Gaardhøje, Niels Bohr Institute

  22. But many protons at forward rapidity The hadron spectrum for d+Au at η=3.2 Excess of h+ over h- Ericeira Jens Jørgen Gaardhøje, Niels Bohr Institute

  23. Difference understandable from relative abundances h+ = 0.8h-( 1 + p/+ + K/+) Ericeira Jens Jørgen Gaardhøje, Niels Bohr Institute

  24. p+p at 200GeVParticle ratios vs rapidity PYTHIA misses 200GeV protons BRAHMS, nucl-ex/0409002, Submitted to Phys. Lett. B (2004) Ericeira Jens Jørgen Gaardhøje, Niels Bohr Institute

  25. Proton/pion in p+p at η=3.2vs. Pythia (vs. 6.303) Ericeira Jens Jørgen Gaardhøje, Niels Bohr Institute

  26. Summary • Large high pt suppression at midrapidity in Au+Au. Gluon radiation energy loss? • No suppression in d+Au => no initial state effects. Large effect (factor 5). • Strong high pt suppression in Au+Au persists at forward rapidities- need quantitative understanding. • Reduced high pt suppression in Au+Au at 62.4 GeV • Decrease in R(dAU) from η=0 to η=3.2 and centrality dependence inversion. Consistency with CGC picture. • Baryon/mesons difference sseen at midrapidty in Au+Au is also present in d+Au at forward rapidity. • Pythia does not reproduce protons in p+p. • === > BRAHMS whitepaper on RHIC discoveries: Nucl-ex/0410020, subm. Nucl. Phys. A Ericeira Jens Jørgen Gaardhøje, Niels Bohr Institute

  27. Extra material Ericeira Jens Jørgen Gaardhøje, Niels Bohr Institute

  28. Is a unified picture emerging? Ericeira Jens Jørgen Gaardhøje, Niels Bohr Institute

  29. New Physics? Ericeira Jens Jørgen Gaardhøje, Niels Bohr Institute

  30. BRAHMS Intl. collaboration I.G. Bearden7, D. Beavis1, C. Besliu10, Y. Blyakhman6, J. Bondorf7, J.Brzychczyk4, B. Budick6, H. Bøggild7, C. Chasman1, C. H. Christensen7, P. Christiansen7, J.Cibor4, R.Debbe1, J. J. Gaardhøje7, M. Germinario7, K. Grotowski4, K. Hagel8, O. Hansen7, A. Holm7, A.K. Holme12, H. Ito1, E. Jacobsen7, A. Jipa10, J. I. Jordre9, F. Jundt2, E. Johnson11, C. E. Jørgensen7,T. Keutgen9, E. J. Kim11, T. Kozik3, T.M.Larsen12, J. H. Lee1, Y. K.Lee5, G. Løvhøjden12, Z. Majka3, A. Makeev8, B. McBreen1, M. Murray11, J. Natowitz8, B.S.Nielsen7, K. Olchanski1, D. Ouerdane7, R.Planeta4, F. Rami2, D. Roehrich9, B. H. Samset12, S. J. Sanders11, D. Sandberg7,I. S. Sgura10, R.A.Sheetz1, Z.Sosin3, P. Staszel7,3, T.S. Tveter12, F.Videbæk1, R. Wada8 and A.Wieloch3. 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, Blegdamsvej 17, University of Copenhagen, Denmark8Texas A&M University, College Station. USA 9University of Bergen, Norway 10University of Bucharest, Romania 11University of Kansas, Lawrence,USA 12 University of Oslo Norway Ericeira Jens Jørgen Gaardhøje, Niels Bohr Institute

  31. At lower energy the opposite is seen :High pt enhancement CERN- SPS (snn=17 GeV) High p_t enhancement seen when compared to p+p scaled by N_binary. Cronin effect: quark mult scattering Ericeira Jens Jørgen Gaardhøje, Niels Bohr Institute

  32. p+p reference at 62.4 GeV: a problem Ericeira Jens Jørgen Gaardhøje, Niels Bohr Institute

  33. Transverse spin asymmetry for pions using polarized p+p collisions AN = (s+ - s-) / (s+ + s-) D.L.Adams (E704) Phys.Lett B264,462(1991); Phys.ReV D53, 4747 (1996). FNAL704 STAR PRL 92,06230(2004) Ericeira Jens Jørgen Gaardhøje, Niels Bohr Institute

  34. First results at high XF • AN = ε /P P=0.40 - 0.45 • ε = (N+ /L+ - N-/L-) / (N+ /L+ + N-/L-) • = (N+ - L*N-) / (N+ + L*N-) with L = L+ / L- BRAHMS preliminary π+ • < ε >~ +0.022 • AN = +0.05 +- 0.005 +- [0.015] 0.17 < xF < 0.32 <ε >~ -0.035 • AN = -0.08 +- 0.005 +- [0.015] 0.17 < xF < 0.32 Ericeira Jens Jørgen Gaardhøje, Niels Bohr Institute

  35. BRAHMS whitepaperon RHIC discoveries Conclusion: … There is no doubt that the experiments at RHIC have revealed a plethora of new phenomena that for the most part have come as a surprise. In this sense it is clear that the matter that is created at RHIC differs from anything that has been seen before. What name to give it must await our deeper understanding of this matter. Nucl-ex/0410020, subm. Nucl. Phys. A Ericeira Jens Jørgen Gaardhøje, Niels Bohr Institute

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