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Trigger and Vertexing Efficiency for 200 GeV pp Interactions in PHOBOS (dN/d η )

This paper discusses the hit counting, hit merging, correction factors, vertexing efficiency, and trigger efficiency for 200 GeV pp interactions in the PHOBOS experiment. The status of data collaboration as of October 2003 is also presented.

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Trigger and Vertexing Efficiency for 200 GeV pp Interactions in PHOBOS (dN/d η )

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  1. Trigger and Vertexing Efficiency for 200 GeV pp Interactions in PHOBOS (dN/dη) Joseph Sagerer University of Illinois at Chicago for the Collaboration DNP 2003: Tucson, AZ November 1, 2003 • Hit Counting dN/dη • Hit Merging • Correction Factors • Vertexing Correction • Vertexing Efficiency • Trigger Efficiency • Status of Data

  2. Collaboration (October 2003) Birger Back,Mark Baker, Maarten Ballintijn, Donald Barton, Russell Betts, Abigail Bickley, Richard Bindel, Wit Busza (Spokesperson), Alan Carroll, Zhengwei Chai, Patrick Decowski, Edmundo Garcia, Tomasz Gburek, Nigel George, Kristjan Gulbrandsen, Stephen Gushue, Clive Halliwell, Joshua Hamblen, Adam Harrington, Conor Henderson, David Hofman, Richard Hollis, Roman Hołyński, Burt Holzman, Aneta Iordanova, Erik Johnson, Jay Kane, Nazim Khan, Piotr Kulinich, Chia Ming Kuo, Willis Lin, Steven Manly, Alice Mignerey, Gerrit van Nieuwenhuizen, Rachid Nouicer, Andrzej Olszewski, Robert Pak, Inkyu Park, Heinz Pernegger, Corey Reed, Michael Ricci, Christof Roland, Gunther Roland, Joe Sagerer, Iouri Sedykh, Wojtek Skulski, Chadd Smith, Peter Steinberg, George Stephans, Andrei Sukhanov, Marguerite Belt Tonjes, Adam Trzupek, Carla Vale, Siarhei Vaurynovich, Robin Verdier, Gábor Veres, Edward Wenger, Frank Wolfs, Barbara Wosiek, Krzysztof Woźniak, Alan Wuosmaa, Bolek Wysłouch, Jinlong Zhang 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

  3. f -5.4 -3 0 +3 +5.4 h Hardware: Octagon Detector (Silicon Pads) Z Unrolled Octagon Paddle Triggers Rings Rings

  4. Hit Counting dN/dη STEP 1)Hit Merging: Adjacent silicon pixels with energy above threshold are summed into merged hits and counted vs η. Events are binned by z-vertex position and merged octagon hits RAW HITS MERGED HITS STEP 2)Correction Factors: Correction factors are applied to each bin f(η,z,Octagon Mult) dN/dη vs Mult and Z STEP 3)Efficiency Corrections: Bins are combined based on trigger&vertex efficiencies per bin Min-Bias dN/dη

  5. A high angle hit passes through multiple pixels STEP 1) Hit Merging For η ≠ 0 we have the possibility of a hit striking multiple pixels. Thus a merging algorithm is applied that sums adjacent pixels above threshold. dE of Octagon hits in data before, after merging Unmerged hits Merged hits

  6. STEP 2) Correction factors Monte-Carlo Simulation of PHOBOS 200GeV pp • Red-MC primary tracks dN/dη • Blue-Simulated Octagon Merged hits includes all analysis bias • Blk-correction factor f(η) 200GeV pp MC from HiJing (Pythia) ABS(MCVTX)<20cm

  7. STEP 2) Correction factors Correction Factor Break Down f(η,z,Octagon Mult) = CAcceptance*CVertexing*CMerging*CSecondaries • PHOBOS pp Vertexing: • Different algorithm from AuAu • Has an Efficiency that is highly dependant on Octagon Mult (remember we need this to sum bins in STEP 3) • f can be created directly from MC • We study the C’s to better understand the overall corrections due to MC

  8. Octagon Multiplicity bin:10-20 Z step of 20cm STEP 2) Correction factors (-80,-60) (-60,-40) CVertex is the correction of the hit distribution due to the inaccuracy of the Vertex (-40,-20) (-20,0) Red-MC Hits; η based on MC Vertex Blue-MC Hits; η based on Analysis (OctdE) Vertex (0,20) (20,40) (40,60) (60,80)

  9. STEP 3) Efficiency Corrections Vertexing Efficiency Blk-all MC Vertex Blue-MC Vertices with good analysis vertex Trigger + Vertex Event Acceptance (MC) Octagon Merged Hits

  10. STEP 3) Efficiency Corrections Trigger Hardware Efficiency Trigger Event Acceptance (MC) Octagon Merged Hits

  11. Current State of Data: After STEP 1) Merged Octagon Hits Raw Data Hit distribution for z <±20, summed over all octagon mult. No Corrections applied.

  12. Summary • MC Studies of correction factors for 200GeV pp with PHOBOS have been done • Data is in good shape after hit merging • All is set to produce a min-bias dN/dη for |η|<3 with the rings extending this to |η|<5.4 • Final results for QM

  13. Single Diffractive Events Paddle Single-Arm Trigger • For single Arm trigger • Overall SDE ~25% input to MC • Contamination is low for High Mult (~10%) • Most is lowest Mult bin (~50%) • We have the option to recreate the UA5 cut on SDE using two arm trigger condition or the PHOBOS Silicon Paddle Two-Arm Trigger RESERVE SLIDE JUST IN CASE

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