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Energy and Centrality Dependence of Mid-Rapidity Charged Particle Multiplicity Measured with

DNP02. Energy and Centrality Dependence of Mid-Rapidity Charged Particle Multiplicity Measured with. Aneta Iordanova University of Illinois at Chicago. Collaboration. ARGONNE NATIONAL LABORATORY Birger Back, Alan Wuosmaa

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Energy and Centrality Dependence of Mid-Rapidity Charged Particle Multiplicity Measured with

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  1. DNP02 Energy and Centrality Dependence of Mid-Rapidity Charged Particle Multiplicity Measured with Aneta Iordanova University of Illinois at Chicago

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

  3. DNP02 Aneta Iordanova • 4p Multiplicity Array • Octagon, Vertex and Ring Counters • Mid-rapidity Spectrometer • TOF wall for high momentum PID • Triggering • Scintillator Paddle Counters • Zero Degree Calorimeter (ZDC) • Čerenkov Counters

  4. Vertex Detector DNP02 Aneta Iordanova • 8192 silicon channels • Outer Layer: 2 × 2048 channels, 0.47mm × 24.1mm • Inner Layer: 2 × 2048 channels, 0.47mm × 12.0mm Y 1 channel X Top f Beam pipe Z, h Inner Layer Bottom Outer Layer 50.4mm 62.1mm • Used for • reconstruction of collision location (“vertex”) • multiplicitymeasurement

  5. Outer Layer Inner Layer DNP02 Aneta Iordanova Tracklet Two-hit combinations from Outer and Inner Vertex (Top or Bottom), pointing to the reconstructed vertex. hit hit Top Vertex Reconstructed Vertex

  6. dh < 0.1 DNP02 Aneta Iordanova Tracklet Reconstruction First Pass • |df| = |fSearch–fSeed| < 0.3 • |dh| =|hSearch–hSeed| < 0.1 • smallestdh combination. fSearch ,hSearch Extrapolate fSeed ,hSeed hit Search Layer hit Seed Layer Top Vertex Reconstructed Vertex Second Pass • Tracklets with a common hit • in the “Search Layer” • smallest |dh| combination.

  7. Multiplicity Determination using Vertex detector Combinatorial Background Efficiency Correction Factor DNP02 Aneta Iordanova

  8. DNP02 Aneta Iordanova Outer Layer Top Inner Layer f Nominal vertex position Inner Layer Bottom Outer Layer Efficiency Correction Factor (a) (from Monte Carlo) • a depends on: • Azimuthal acceptance of detector • Z vertex position • Multiplicity in detector (hits) a~ 0.4 (Z=0cm) to 0.25 (Z=10cm)

  9. DNP02 Aneta Iordanova Efficiency Correction Factor for three different Zvertex positions 19.6 GeV a

  10. DNP02 Aneta Iordanova Combinatorial Background Tracklets (b) Tracklets from hits by rotating Inner layers 1800 about the beam pipe. f Beam pipe Z, h Nbackground_tracklets= b Nreconstructed_tracklets T R U E

  11. Data Monte Carlo DNP02 Aneta Iordanova Background Tracklets for 80 to 100 Hits in Outer Vertex Layer 19.6 GeV Counts Counts dh dh b = 0.76

  12. 200GeV 130GeV 19.6GeV PRELIMINARY DNP02 Aneta Iordanova Scaled charged-particle multiplicity as a function of Npart for Au+Au collisions |h|<1

  13. 200GeV 130GeV 19.6GeV PRELIMINARY DNP02 Aneta Iordanova Scaled charged-particle multiplicity as a function of Npart for Au+Au collisions (Two component fit) |h|<1

  14. DNP02 Aneta Iordanova Scaled charged-particle multiplicity as a function of Npart for Au+Au collisions (Normalized by the corresponding pp value for each energy) |h|<1 200GeV 130GeV 19.6GeV PRELIMINARY Errors from Au+Au only

  15. 200GeV 130GeV 19.6GeV PRELIMINARY DNP02 Aneta Iordanova Scaled charged-particle multiplicity as a function of Npart for Au+Au collisions (KLN saturation model) |h|<1

  16. DNP02 Aneta Iordanova Comparison of central charged-particle multiplicity for different energies. PRELIMINARY PHOBOS 19.6 GeV

  17. DNP02 Aneta Iordanova Conclusion • Phobos has measured charged-particle multiplicity dependence on centrality and energy in Au-Au collisions at √sNN of 200,130 and 19.6GeV. • The mid-rapidity scaled charged-particle multiplicity shows evidence for deviation from Npart scaling over the studied centrality range. • The mid-rapidity scaled charged-particle multiplicity dependence on energy follows the logarithmic rise.

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