Trigger and Vertexing Trigger and Vertexing Efficiency for 200 GeV pp Efficiency for 200 GeV pp Interactions in PHOBOS Interactions in PHOBOS

(dN/d(dN/dηη))Joseph SagererJoseph Sagerer

University of Illinois at ChicagoUniversity of Illinois at Chicago

for the Collaborationfor the Collaboration

DNP 2003: Tucson, AZ November 1, DNP 2003: Tucson, AZ November 1, 20032003

•Hit Counting dN/dη

•Hit Merging

•Correction Factors

•Vertexing Correction

•Vertexing Efficiency

•Trigger Efficiency

•Status of Data

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 LABORATORYINSTITUTE OF NUCLEAR PHYSICS, KRAKOW MASSACHUSETTS INSTITUTE OF TECHNOLOGYNATIONAL CENTRAL UNIVERSITY, TAIWAN UNIVERSITY OF ILLINOIS AT CHICAGO

UNIVERSITY OF MARYLAND UNIVERSITY OF ROCHESTER

Hardware:

Z

Paddle Triggers

0 +3-3 +5.4-5.4

Octagon Detector (Silicon Pads)

Unrolled Octagon

Rin

gs

Rings

Hit Counting dN/dη

RAW HITS

STEP 2) Correction Factors: Correction factors are applied to each bin f(η,z,Octagon Mult)

STEP 3) Efficiency Corrections: Bins are combined based on trigger&vertex efficiencies per bin

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 MERGED

HITS

dN/dη vs Mult and Z

Min-Bias dN/dη

dE of Octagon hits in data before, after merging

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.

A high angle hit passes through multiple pixels

Unmerged hits Merged hits

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

STEP 2)Correction factors

Correction Factor Break Down

f(η,z,Octagon Mult)

= CAcceptance*CVertexing*CMerging*CSecondaries

•f can be created directly from MC

•We study the C’s to better understand the overall corrections due to MC

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)

STEP 2)Correction factors

dVertex) (MCdN

dVertex) (AnalysisdN

Hits

Hits

vertexC

Red-MC Hits; η based on MC Vertex

Blue-MC Hits; η based on Analysis (OctdE) Vertex

CVertex is the correction of the hit distribution due to the inaccuracy of the Vertex

STEP 2)Correction factors

Octagon Multiplicity bin:10-20 Z step of 20cm

(-80,-60) (-60,-40)

(-40,-20) (-20,0)

(0,20) (20,40)

(40,60) (60,80)

Vertexing Efficiency

Octagon Merged Hits

Blk-all MC Vertex

Blue-MC Vertices with good analysis vertex

STEP 3)Efficiency Corrections

Trigger + Vertex Event Acceptance (MC)

Trigger Hardware Efficiency

OctMult 0-10 10-20 20-30 30-40 40-50 50-60

EffP 0.797 0.961 0.99 0.998 0.997 0.96EffN 0.75 0.953 0.99 0.999 0.981 0.91

2

2

2

2

2

)1(

)(

)(x

MCyONLY

MCARM

MCARM

DATAyONLY

DATAARM

DATAARM

x EffO

NNN

NNN

Eff

Trigger Event Acceptance (MC)

Octagon Merged Hits

STEP 3)Efficiency Corrections

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.

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

Single Diffractive Events

• 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 Single-Arm Trigger

Paddle Two-Arm Trigger

RESERVE SLIDE JUST IN CASE