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BRAHMS 18. JUNI 2003 BNL High Pt Colloquium I.G.Bearden, Niels Bohr Institute 1 BRAHMS High P T Measurements with BRAHMS I.G. Bearden, Niels Bohr Institute For The BRAHMS collaboration
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BRAHMS 18. JUNI 2003 BNL High Pt Colloquium I.G.Bearden, Niels Bohr Institute 2 The BRAHMS Collaboration I.G. Bearden 7, D. Beavis 1, C. Besliu 10, Y. Blyakhman 6, J.Brzychczyk 4, B. Budick 6, H. Bøggild 7,C. Chasman 1, C. H. Christensen 7, P. Christiansen 7,J.Cibor 4, R.Debbe 1, J. J. Gaardhøje 7,M. Germinario 7,K. Grotowski 4, K. Hagel 8, O. Hansen 7, H. Ito 11, E. Jacobsen 7, A. Jipa 10, J. I. Jordre 10, F. Jundt 2, C.E.Jørgensen 7, E. J. Kim 5, T. Kozik 3, T.M.Larsen 12, J. H. Lee 1, Y. K.Lee 5, G. Løvhøjden 2, Z. Majka 3, A. Makeev 8, B. McBreen 1, M. Murray 8, J. Natowitz 8, B. Neuman 11,B.S.Nielsen 7, K. Olchanski 1, D. Ouerdane 7, R.Planeta 4, F. Rami 2, D. Roehrich 9, B. H. Samset 12, S. J. Sanders 11, I. S. Sgura 10, R.A.Sheetz 1, Z.Sosin 3, P. Staszel 7, T.S. Tveter 12, F.Videbæk 1, R. Wada 8 and A.Wieloch 3,Z. Yin 9 1 Brookhaven National Laboratory, USA, 2 IReS and Université Louis Pasteur, Strasbourg, France 3 Jagiellonian University, Cracow, Poland, 4 Institute of Nuclear Physics, Cracow, Poland 5 Johns Hopkins University, Baltimore, USA, 6 New York University, USA 7 Niels Bohr Institute, Blegdamsvej 17, University of Copenhagen, Denmark 8 Texas A&M University, College Station. USA, 9 University of Bergen, Norway 10 University of Bucharest, Romania, 11 University of Kansas, Lawrence,USA 12 University of Oslo Norway - 52 people from 12 institutions-
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BRAHMS 18. JUNI 2003 BNL High Pt Colloquium I.G.Bearden, Niels Bohr Institute 3 The BRAHMS Experiment 95° 30° 15° 2.3°
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BRAHMS 18. JUNI 2003 BNL High Pt Colloquium I.G.Bearden, Niels Bohr Institute 4 Au+Au Charged Hadron Spectra =0 ~2
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BRAHMS 18. JUNI 2003 BNL High Pt Colloquium I.G.Bearden, Niels Bohr Institute 5 d+Au Charged Hadron Spectra 200GeV (BRAHMS preliminary) =0
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BRAHMS 18. JUNI 2003 BNL High Pt Colloquium I.G.Bearden, Niels Bohr Institute 6 Nuclear Modification Factor Hard processes (incoherent) scaling with the number of binary collisions N bin. The nuclear modification factor: Glauber calculation N binary Au+Au 0-10%892 10-20%570 20-40%281 40-60%81 dAu MinBias7.3
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BRAHMS 18. JUNI 2003 BNL High Pt Colloquium I.G.Bearden, Niels Bohr Institute 7 How does it look at lower energies? p+A : Modification quantified by: pA =A ( pT ) pp Central Pb+Pb (SPS): High p T enhancement explained by initial state multiple scattering (“Cronin effect”) and (for SPS) transverse flow…
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BRAHMS 18. JUNI 2003 BNL High Pt Colloquium I.G.Bearden, Niels Bohr Institute 8 Reference Spectrum UA1 acceptance | | < 2.5 STAR acceptance | | < 0.5 BRAHMS acceptance: (this analysis) MRS: | | < 0.15 FS: 2.0 < < 2.2 scale UA1 results to BRAHMS acceptance. ( s NN =200 GeV)
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BRAHMS 18. JUNI 2003 BNL High Pt Colloquium I.G.Bearden, Niels Bohr Institute 9 Nuclear Modification =0 Central to “peripheral” (cancellation of systematic errors) BRAHMS preliminary Au+Au at 200GeV Large high p T suppression for central collisions Not seen for “peripheral” collisions BRAHMS preliminary
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BRAHMS 18. JUNI 2003 BNL High Pt Colloquium I.G.Bearden, Niels Bohr Institute 10 Nuclear Modification =2 BRAHMS preliminary Au+Au at 200GeV Central to “peripheral” (cancellation of systematic errors) Qualitatively same behaviour as seen at =0 BRAHMS preliminary
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BRAHMS 18. JUNI 2003 BNL High Pt Colloquium I.G.Bearden, Niels Bohr Institute 11 BRAHMS preliminary Comparison =0 to =2 =0 =2 =0 =2
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BRAHMS 18. JUNI 2003 BNL High Pt Colloquium I.G.Bearden, Niels Bohr Institute 12 d+Au Nuclear Modification =0 High p T enhancement observed in d+Au collisions at s NN =200 GeV. Comparing Au+Au to d+Au strong effect of dense nuclear medium
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BRAHMS 18. JUNI 2003 BNL High Pt Colloquium I.G.Bearden, Niels Bohr Institute 13 Au+Au at s NN =200 GeV, =0: Strong high p T suppression in central collisions Suppression not observed in semi-peripheral collision (40-60%) Strong effect of dense medium! Au+Au at s NN =200 GeV, 2: Similar behaviour as observed at =0 (calls for additional theoretical work) Medium extends to =2! d+Au at s NN =200 GeV, =0: “Cronin” like enhancement Medium not present in d+Au! Summary BRAHMS preliminary Au+Au, 2 Au+Au, =0 d+Au, =0 BRAHMS preliminary
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