Rapidity and kT dependence of HBT correlations in Au+Au

collisions at 200 GeVBurt Holzman

Brookhaven National Laboratoryfor

the PHOBOS Collaboration:

Birger Back, Mark Baker, Maarten Ballintijn, Donald Barton, Russell Betts, Abigail Bickley, Richard Bindel, Wit Busza (Spokesperson), Alan Carroll, Zhengwei Chai, Patrick Decowski, Edmundo García, 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

Burt Holzman (BNL) 2QM2004

PHOBOS Schematic200 GeV Au+Au dataset after HBT cuts:

1 million events7 million pairs

Burt Holzman (BNL) 3QM2004

PHOBOS Spectrometer

• Reversible 2T field• Two symmetric arms• Fine pixel granularity

gives small two- particle inefficiency region (25x50 mrad)

• p/p < 1.5%• Pairs with small q

also have small separation at detector: small detectors are good for HBT!

Burt Holzman (BNL) 4QM2004

HBT @ RHIC: Challenge for Theory

Newer models include opacity but still don’t fit data, i.e. Hirano & Tsuda [NPA 715, 815 (2002)]

• I will not be solving the HBT puzzle; but I will dump more pieces into the mix!

PHOBOS 200 prelim. -- [NPA 715, 611 (2002)]

STAR 130 [PRL 87, 082301 (2001)]PHENIX 130 [PRL 88, 192302 (2002)]

Theory: Soff, Bass, Dumitru [PRL 86, 3981 (2001)]

• Huge (15 fm) source doesn’t exist at RHIC

• Ro/Rs ~ 1

PHOBOS Preliminary

Burt Holzman (BNL) 5QM2004

Some HBT definitions

• kT: pair transverse momentum

• Bertsch-Pratt (BP) parameterization

• Yano-Koonin-Podgoretsky (YKP) parameterization22222222 )()(1)( longYKtimetimetimeYKlonglongperpperp QvQRQvQRQReQC

2222222 21)( OLLOSSLLOO RQQRQRQRQeQC

Source velocity included in correlation function

)pp(2

1k 21T

Burt Holzman (BNL) 6QM2004

Rout (fm) Rside (fm) Rlong (fm) Rol (fm)

MC .48.02

3.2 .14

18.0 .9 5.8 .2 1.2 .4

Recon .43.02

3.1 .15

16.1 .9 5.8 .3 1.5 .3

MC studies

• First principles HBT generator [Kadija & Seyboth, PLB 287, 63, (1992)] - we can do 15 fm!

• That was our first naive attempt -- let’s try something else

Burt Holzman (BNL) 7QM2004

Rout (fm) Rside (fm) Rlong (fm) Rol (fm)

MC .5 4.0 4.0 4.0 2.0

Recon .52 .02

4.1 .13

4.2 .4 4.2 .2 1.6 .7

MC studies

• HIJING (weight “actual” pairs), simulate detector with GEANT, real reconstruction

• We can reproducecorrelation functions quite well

Burt Holzman (BNL) 8QM2004

2

Plane3

2

Coulomb3

Coul)r(ψ)rS(r d

)r(ψ)rS(r dR)(q,K

PHOBOS Coulomb Correction

Usual plotGamowλ = 1 Rinv = 5 fmλ = 0.5 Rinv = 5 fmλ = 0.1 Rinv = 5 fm

Co

ulo

mb

Co

rrec

tio

n

Qinv (GeV/c)

PHOBOS Coulomb Correction: Used from Day 1

22

22

Rq

CoulRq

PHOCoul

λe1

R)(q,)Keλ(1λ1λ)R,(q,K

~

Rout

Rside

Rlong

Rol

0.57 .05 4.7 .3 fm4.3 .4 fm 5.1 .3 fm1.2 1.9 fm2

PHOBOSCoulCorr

Ceres02CoulCorr

2

PHOBOS data corrected with

0.57 0.04 4.8 0.3 fm4.4 0.4 fm5.0 0.3 fm1.6 1.8 fm2

Burt Holzman (BNL) 9QM2004

Coulomb Correction II

1)exp(1)(1)(

)( 2 jiijcoul qqRqKNqB

qA

Bowler(‘91)/Sinyukov(‘98)/CERES(‘02)/STAR(‘03)/PHENIX(‘03)

)exp(1)exp(1

1)exp(1)(1

)(

)( 22

2

jiijjiij

jiijcoul qqRqqR

qqRqKN

qB

qA

),(~

qKcoul

PHOBOS(‘02)

)exp(1

1)exp(1)(1),(

~22

22

invinv

invinvcoulPHOcoul QR

QRqKNqK

Burt Holzman (BNL) 10QM2004

Particle Identification

K-

p

Contamination from K, pp, pK < 10%Contamination from KK, pp < 1%

Burt Holzman (BNL) 11QM2004

Bertsch-Pratt vs. kTAu+Au -- 0-15% central

Burt Holzman (BNL) 12QM2004

Bertsch-Pratt vs. kT: RHIC data

PHOBOS 200 GeV prelim.STAR QM2002 [NPA 715, 623 (2002)]PHENIX PRL (sub.) [nucl-ex/0401003]

Au+Au -- centralPHOBOS Preliminary PHOBOS Preliminary

PHOBOS Preliminary PHOBOS Preliminary

Burt Holzman (BNL) 13QM2004

Bertsch-Pratt vs. Y

Within errors, no BP Y-dependence in our acceptance

PHOBOS Preliminary PHOBOS Preliminary PHOBOS Preliminary

Burt Holzman (BNL) 14QM2004

Why YYKP ?

YYKP

Y

YYKP

Y

Exploding source in zstrong p-z correlations

Y scales with YYKP

Slowly expanding source in zweak p-z correlations

Y slowly varies

z z

Burt Holzman (BNL) 15QM2004

Yano-Koonin-Podgoretsky vs. Y

• Pair rapidity scales with source rapidity

Fit in LCMS framePHOBOS Preliminary0-15 % Central

Fit in Lab frame

PHOBOS Preliminary0-15% Central

All results presented in lab frame

Burt Holzman (BNL) 16QM2004

Comparison to NA49

• SPS (sNN = 17.2 GeV) RHIC (sNN = 200 GeV) both exhibit similar scaling behavior

Fit in LCMS frame

NA49: .1 < kT < .2 GeV/c

PHOBOS: .1 < kT < 1.4 GeV/c

?

PHOBOS PreliminaryNA49 [EPJ c2, 661 (1998)]

Burt Holzman (BNL) 17QM2004

Conclusions & Outlook

• More pieces added to the puzzle– PHOBOS nicely complements the current

RHIC HBT dataset in kT and Y

• Rout, Rside, Rlong: consistent with weak or no rapidity dependence from .4 < Y < 1.3

• Pair rapidity scales with source rapidity

• High statistics from current RHIC run will decrease errors and increase kT reach

• See C. Ming Kuo’s poster at 5 pm