Anti-particle to Particle Ratios in Cu+Cu Collisions @ RHIC Vasundhara Chetluru University of...

Anti-particle to Particle Ratios in Cu+Cu Collisions @ RHIC

Vasundhara Chetluru

University of Illinois, Chicago

For the collaboration

Division of Nuclear Physics, Nashville

October 27th, 2006

DNP Nashville, Oct 27 2006 2

PHOBOSEXPERIMENT

Vasundhara Chetluru

Burak Alver, Birger Back, Mark Baker, Maarten Ballintijn, Donald Barton, Russell Betts, Richard

Bindel,

Wit Busza (Spokesperson), Vasundhara Chetluru, Edmundo García, Tomasz Gburek, Joshua

Hamblen, Conor Henderson, David Hofman, Richard Hollis, Roman Hołyński, Burt Holzman, Aneta

Iordanova, Chia Ming Kuo, Wei Li, Willis Lin, Constantin Loizides, Steven Manly, Alice Mignerey,

Gerrit van Nieuwenhuizen, Rachid Nouicer, Andrzej Olszewski, Robert Pak, Corey Reed, Christof

Roland, Gunther Roland, Joe Sagerer, Peter Steinberg, George Stephans, Andrei Sukhanov,

Marguerite Belt Tonjes, Adam Trzupek, Sergei Vaurynovich, Robin Verdier, Gábor Veres, Peter

Walters, Edward Wenger, Frank Wolfs, Barbara Wosiek, Krzysztof Woźniak, Bolek Wysłouch

ARGONNE NATIONAL LABORATORY BROOKHAVEN NATIONAL LABORATORYINSTITUTE OF NUCLEAR PHYSICS PAN, KRAKOW MASSACHUSETTS INSTITUTE OF TECHNOLOGY

NATIONAL CENTRAL UNIVERSITY, TAIWAN UNIVERSITY OF ILLINOIS AT CHICAGOUNIVERSITY OF MARYLAND UNIVERSITY OF ROCHESTER

PHOBOS Collaboration

DNP Nashville, Oct 27 2006 3

PHOBOSEXPERIMENT

Vasundhara Chetluru

Outline• Ratios measurement

• PHOBOS detector.

• Particle identification using PHOBOS

• Corrections

• Results & Conclusions

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PHOBOSEXPERIMENT

Vasundhara Chetluru

Identified particle ratios

)(*)(* hhGAhh tedreconstruc

h

h

Particles

lesAntiparticRatioParticle Identified

h-/+ : identified anti-particle/particle count per event

GA : Geometric Acceptance

)(

)(*

)(

)(*

h

h

hGA

hGA

h

h

h

h

tedreconstruc

tedreconstruc

ε : Efficiency , Feed-down, Absorption

DNP Nashville, Oct 27 2006 5

PHOBOSEXPERIMENT

Vasundhara Chetluru

PHOBOS Detector

DNP Nashville, Oct 27 2006 6

PHOBOSEXPERIMENT

Vasundhara Chetluru

Acceptance

Z Z

Backward

Bending

Forward

Bending

90% contour

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PHOBOSEXPERIMENT

Vasundhara Chetluru

Different field settings

near mid-rapidity

Z

near mid-rapidity

Z

)()(21

BB hGAhGA

For a given bending direction

Ratios are measured independently for different bending directions.

B1

B2

DNP Nashville, Oct 27 2006 8

PHOBOSEXPERIMENT

Vasundhara Chetluru

Particle identification

Pions

Kaons

Protons

Deuterons

Electrons

DNP Nashville, Oct 27 2006 9

PHOBOSEXPERIMENT

Vasundhara Chetluru

Detector Acceptance

)(

)(*

)(

)(*

h

h

hGA

hGA

h

h

h

h

tedreconstruc

tedreconstruc

• Decay particles produced from the heavier particles.

• Absorption of the particles by the detector material and production of the particles from the detector.

DNP Nashville, Oct 27 2006 10

PHOBOSEXPERIMENT

Vasundhara Chetluru

Absorption Correction

pT GeV/C

Ab

sorp

tion

co-

effi

cien

t

ProtonsAntiprotons

Absorption correction is particle dependent.

DNP Nashville, Oct 27 2006 11

PHOBOSEXPERIMENT

Vasundhara Chetluru

Particle Ratio Results

DNP Nashville, Oct 27 2006 12

PHOBOSEXPERIMENT

Vasundhara Chetluru

Summary• Proton ratios are constant with in errors as a

function of centrality.

• As the collision energy increases, we observe that the antiproton to proton ratios increases.– Contribution from pair production becomes more

dominant than baryon transport.