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Recent Results from PHOBOS

Recent Results from PHOBOS. 19 th Winter Workshop on Nuclear Dynamics February 2003. Edmundo García - UIC for the PHOBOS Collaboration. Collaboration (Jan 2002). Birger Back , Mark Baker, Maarten Ballintijn, Donald Barton, Russell Betts, Abigail Bickley ,

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Recent Results from PHOBOS

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  1. Recent Results from PHOBOS 19th Winter Workshop on Nuclear Dynamics February 2003 Edmundo García - UIC for the PHOBOS Collaboration

  2. Collaboration (Jan 2002) Birger Back, Mark Baker, Maarten Ballintijn, Donald Barton, Russell Betts, Abigail Bickley, Richard Bindel, Andrzej Budzanowski, Wit Busza (Spokesperson), Alan Carroll, Patrick Decowski, Edmundo García, Nigel George, Kristjan Gulbrandsen, Stephen Gushue, Clive Halliwell, Joshua Hamblen, George Heintzelman, Conor Henderson, David Hofman, Richard Hollis, Roman Hołyński, Burt Holzman, Aneta Iordanova,Erik Johnson,Jay Kane, Judith Katzy, Nazim Khan, Wojtek Kucewicz, Piotr Kulinich, Chia Ming Kuo,Jang Woo Lee, Willis Lin, Steven Manly, Don McLeod, Jerzy Michałowski, Alice Mignerey, Gerrit van Nieuwenhuizen, Rachid Nouicer, Andrzej Olszewski, Robert Pak, Inkyu Park, Heinz Pernegger, Corey Reed, Louis Remsberg, Michael Reuter, Christof Roland, Gunther Roland, Leslie Rosenberg, Joe Sagerer, Pradeep Sarin, Pawel Sawicki, Wojtek Skulski, Stephen Steadman, Peter Steinberg, George Stephans, Marek Stodulski, Andrei Sukhanov, Jaw-Luen Tang,Ray Teng, Marguerite Belt Tonjes, Adam Trzupek, Carla Vale, Gábor Veres, Robin Verdier, Bernard Wadsworth, Frank Wolfs, Barbara Wosiek, Krzysztof Woźniak, Alan Wuosmaa, Bolek Wysłouch ARGONNE NATIONAL LABORATORY BROOKHAVEN NATIONAL LABORATORY INSTITUTE OF NUCLEAR PHYSICS, KRAKOW MASSACHUSETTS INSTITUTE OF TECHNOLOGY NATIONAL CENTRAL UNIVERSITY, TAIWAN UNIVERSITY OF ILLINOIS AT CHICAGO UNIVERSITY OF MARYLAND UNIVERSITY OF ROCHESTER E. García - UIC

  3. Phobos apparatus (2001) • 137,000 Silicon Readout Channels • 1,300 Scintillator Readout Channels E. García - UIC

  4. Trigger Dt x z CN ZDC N Au Au ZDC P CP PN PP Event Selection (average number of participants <Npart>) E. García - UIC

  5. Multiplicity Measurement Energy Spectrum (DE) in Si pads 1 hit Data MC 2 hits f h h Acceptance (Single Event) E. García - UIC

  6. dN/dEta PHOBOS: nucl-ex/0210015 Oct 2002 - PRL (submitted) Typical systematic errors 200 GeV 19.6 GeV* 130 GeV dNch/dh centrality h Centrality: 0 - 6% 6 - 15 % 15 - 25% 25 – 35% 35 – 45% 45 – 55% *For 19.6 GeV - instead of Paddle Counters – Eoct = SDE(path length corrected energy deposited in octagon) for | h |< 3.2 was used to determine centrality (Npart). E. García - UIC

  7. Limiting Fragmentation PHOBOS Au + Au 0 – 6 % central UA5, Z.Phys.C33, 1 (1986) dN/dh¢ selected systematic errors 35 – 40 % central E. García - UIC

  8. PHOBOS Au + Au 19.6 GeV 200 GeV dN/dh’/<Npart>/2> systematic errors not shown h’ h’ systematic errors on error bars E. García - UIC

  9. (dN/dyT ) e+e- scales like AA near midrapidity Similarity of AA and e+e- at mid rapidity PHOBOS: nucl-ex/0301017 Jan 2003 - PRL (submitted) E. García - UIC

  10. Comparison <NCh> vs. Energy <Nch>/ <Npart>/2> E. García - UIC

  11. Total charged multiplicity scaling with Npart Open symbols are UA5 data at 200 GeV and results from an interpolation at lower energies The dotted lines show the values From the e+e- fit Shaded band is uncertainty on extrapolation procedure Errors include contributions from overall Nch and Npart scaling E. García - UIC

  12. p K d p Particle Spectra E. García - UIC

  13. PHOBOS: nucl-ex/0301017, PRL 87(102301)2001, Particle Ratios 12% most central Au+Au ratio < p ->/< p+> <K->/<K+> <p->/<p+> 200 GeV: 0.2 < y < 0.8 K,p 0.35 < y < 1.5 p systematic errors in bars E. García - UIC - mb = 45  5 at 130 GeV to mb = 27  2 at 200 GeV (Tch 160 – 170 MeV)

  14. Transverse Momentum and Centrality dependence of particle ratios PHOBOS 200 Au+Au 10% most central Preliminary Preliminary Errors bars are systematic uncertainties E. García - UIC

  15. Current systematic errors ~20%() ~40%(K) ~50%(p) p ± 200GeV Au+Au PHOBOS ± K (2ppT)-1 d2N/dydpT ± p y=-0.1 to 0.4, 15% most central pT (GeV/c) (Ullrich QM2002) Particle Spectra – low pT nucl-ex/0210037 July 2003 Centralities: Brahms 10 % Phenix 5 % Star 5% Phobos 15% E. García - UIC

  16. Particle Spectra – high pT PHOBOS: nucl-ex/0210006 Oct 2002 Particle rapidities between 0.2 and 1.4 assuming pion mass to calculate y E. García - UIC

  17. Yield/<Npart/2>/p+p fit Particle spectra notes pT (GeV/c) Multiplicity yield per participant pair divided by a fit to the invariant cross-section for proton proton collisions (200 GeV UA1) E. García - UIC

  18. pT (GeV/c) Yield/<Npart/2>/peripheral fit Multiplicity yield per participant pair divided by a fit to the most peripheral bin E. García - UIC

  19. Particle Spectra Npart Evolution of the charged hadron yield in Au + Au scaled by <Npart>/2, normalized to the most peripheral bin as function of Npart, for selected pT bins E. García - UIC

  20. Multiplicity • Energy independence of dN/dh’over a large range of h’ - Limiting Fragmentation. dN/dh’ is not independent of centrality at high h’ • The fragmentation region becomes a dominant feature of the pseudo-rapidity distributions at high energy • At high energies the Au+Au multiplicity per participant pair scales in similarly to e+e- data. • Total charged multiplicity in high-energy Au+Au scales approximately with number of wounded nucleons (Npart).Total particle production in Au+Au per participant pair is the same as total particle production in e+e- at the same sqrt(s). • Particle Ratios • For anti-protons/protons the data indicates a rapidly decrease of the net-baryon density near mid-rapidity • Ratios, within the errors, are independent of pT and Npart. E. García - UIC

  21. Spectra (low pT) • No enhancement of low pT yields • pbar + p extrapolate to PHENIX data at higher pT. Flattening of spectra due to collective radial expansion. • Particle Spectra (high pT) • Found significant changes in the transverse momentum spectra between ppbar and peripheral AuAu • Comparing peripheral to central AuAu collisions, the yields scale with the number of participant nucleons • To Come: • pp Data with PHOBOS at 200 GeV • pp and dA data with PHOBOS at 200 GeV with enhanced trigger capabilities and forward proton calorimeter E. García - UIC

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