Two-Pion Correlations withTwo-Pion Correlations with @ RHIC @ RHICChia-Ming, KuoChia-Ming, KuoNational Central University, TaiwanNational Central University, Taiwanfor PHOBOS Collaborationfor PHOBOS Collaboration

CollaborationCollaboration

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

MotivationMotivationPrediction : First order phase transition leads to a prolonged hadronization time Expectation : Large HBT radii

“ “ The HBT Puzzle “The HBT Puzzle “

STARPHENIX

PHENIX and STAR results show that Rout/Rside ~ 1 at 130 GeV

X (out)

Y (side)

22

22

~)~(

yR

txR

side

xout

2222 )( sideout RRif x-t correlation is absent & x ～ y

DNP, APS 2003 Fall Meeting / Chia-Ming, Kuo

Detector @ 2001Detector @ 2001

137000 Silicon Pad Channels

1m

Spectrometer

Octagon

Vertex

Ring CountersPaddle Trigger Counter

Cerenkov Counter

12 meters of Beryllium beampipeZDC

ZDC

DNP, APS 2003 Fall Meeting / Chia-Ming, Kuo

Spectrometer & TrackingSpectrometer & Tracking

Reversible 2T magnetic field

Two symmetric spectrometer arms

Tracking within 10 cm of interaction point – providing a small two-particle inefficiency (~ 25x50 mrad in θ and ψ space)

Phi acceptance of 3% each arm

Ghost tracks ~ 0.3%

p/p is better than 1.5% for p<0.7GeV

DNP, APS 2003 Fall Meeting / Chia-Ming, Kuo

PID & Spec. AcceptancePID & Spec. Acceptance

--

DNP, APS 2003 Fall Meeting / Chia-Ming, Kuo

Coulomb CorrectionCoulomb Correction

Gamowλ = 1 Rinv = 5 fmλ = 1 Rinv = 10 fm

Gamowλ = 1 Rinv = 5 fmλ = 0.5 Rinv = 5 fmλ = 0.1 Rinv = 5 fm

Cou

lom

b C

orre

ctio

n

Cou

lom

b C

orre

ctio

n

Qinv (GeV/c) Qinv (GeV/c)

Full-Wave Coulomb Correction “Partial” Coulomb Correction

“E866” Approximate Coulomb Correction

)λe(1R)(Q,)Feλ(1λ1λ)R,(Q,F 22

22

RQFull

RQ

Part

2

Plane3

2Coulomb

3

Full)r(ψ)rS(r d

)r(ψ)rS(r dR)(Q,F

DNP, APS 2003 Fall Meeting / Chia-Ming, Kuo

(PRC 66, 54906 (2002))

Data SampleData Sample

PHOBOS 200 GeV preliminary

Cut off the area that two-particle acceptance < 95 % Apply “Partial” Coulomb (λ≠1) correction to mixed pairs

DNP, APS 2003 Fall Meeting / Chia-Ming, Kuo

HBT ResultsHBT Results

2222222 21 OLLOSSLLOO RQQRQRQRQeC

- - 0.540.02 5.80.2

5.10.4 6.80.3

Rout Rside Rlong

++ 0.570.03 4.90.4 7.30.3

5.80.2

R2out-long

4.91.74.51.9

Phobos preliminary

200 GeV Au-Au0.15<kT<0.35

0.2<y<1.5

Systematic error on radii of 1 fm, on of 0.06

15 % most central events

DNP, APS 2003 Fall Meeting / Chia-Ming, Kuo

Scaling with EnergyScaling with Energy-- data

DNP, APS 2003 Fall Meeting / Chia-Ming, Kuo

Preliminary 200 GeV results are agreed between PHOBOS, STAR & PHENIX

● E895○ E866■ NA49▼ NA44

WA98◆▲ STAR● PHOBOS Prelim.

ConclusionsConclusions

Using RHIC 2001 run data (Au+Au @ 200 GeV) to analyze HBT correlations HBT radii are similar to RHIC 130 GeV results The HBT puzzle still goes on ….. More Kt bins will come Systematic studies are underway

DNP, APS 2003 Fall Meeting / Chia-Ming, Kuo

Trigger & Event SelectionTrigger & Event SelectionNegativ

e Paddles

Positive Paddles

Au Aux

zPPPN

Positive ZDC

Negative ZDC

NegativeCerenkov Positive

Cerenkov

• Coincidence between Paddle counters at t = 0 defines a valid collision

• Paddle + ZDC timing reject background

• Trigger sensitive to 97% of inelastic cross section for Au+Au at 200 GeV

Paddle signal (a.u.)ZD

C S

igna

l (a.

u.)

Npart

Nsp

e cta

tor=

2 A-N

par t

Central

Peripheral

200 GeV Data

Analyzing 15% most central events -12 < Vertex Z < 10 cm

Two-Particle AcceptanceTwo-Particle Acceptance

ΔYA = 0 ΔYA = 1

ΔYA = 2 ΔYA = 3

TPA is parameterized by (Δθ,ΔYA)

Cut off two-particleacceptance < 95 %

Rout/Rside @ 200GeV Rout/Rside @ 200GeV

Systematic errors are not shown

● PHOBOS 200 GeV preliminary STAR 200 GeV preliminary★

▲ PHENIX 200 GeV preliminary

DNP, APS 2003 Fall Meeting / Chia-Ming, Kuo