system size dependence of strange particle correlations in cu+cu and au+au collisions at s nn = 200...

System size System size dependence of strange dependence of strange particle correlations in particle correlations in

Cu+Cu and Au+Au Cu+Cu and Au+Au collisions at collisions at ssNNNN

= 200 GeV at RHIC= 200 GeV at RHIC

Christine Nattrass (Yale University)Christine Nattrass (Yale University)STAR CollaborationSTAR Collaboration

SQM 2007, LevoSQM 2007, Levočča, Slovakiaa, Slovakia

Christine Nattrass, Yale University SQM 2007 Levoča, Slovakia

STAR 2

Outline

MotivationAnalysis techniqueResultsConclusions


STAR 3

Intermediate pT baryon/meson enhancement

Large enhancement of baryon/meson ratio in central collisions relative to p+p

in both Au+Au and Cu+Cu

reaches maximum at pT ~ 2-3 GeV/cnot unmodified jet fragmentation

Baryon/meson splitting of Rcp

strange and non-strange particles show similar suppression

nucl-ex/0608017

nucl-ex/0608017

A. Timmins, SQM 2007

A. Timmins, QM 2006


STAR 4

Motivation – particle identification in jets

Particle/antiparticle differences

Quark vs gluon jetsMeson/baryon differences

Coalescence/ recombination mechanisms

Consistent with particle ratiosTestable with identified particle correlations?

PartonParton

PartoPartonn

HadronsHadrons

HadronsHadronsKK00

SS,,

KK00SS,,


STAR 5

Strange particle identification

Full azimuthal acceptanceReconstruction of decay vertices possible~95% purity in Cu+Cu high pT

Vo

STAR

Preliminary

Arb

itra

ry s

cale

STAR Preliminary

Arb

itra

ry s

cale

KK00SS

STAR

Preliminary

Arb

itra

ry s

cale

2.0 GeV<p2.0 GeV<pTT<2.5 GeV, 0-<2.5 GeV, 0-

10%10%

ΞΞ++

STAR Preliminary

Arb

itra

ry s

cale

Mass (GeV/c)

STAR Preliminary

ΞΞ--

Arb

itra

ry s

cale

Mass (GeV/c)

2.0 GeV<p2.0 GeV<pTT<2.5 GeV, 0-10%<2.5 GeV, 0-10%

6


STAR 6

Motivation - Long-range pseudorapidity correlations

Long-range pseudorapidity () correlations observed by STAR in Au+Au at intermediate pT

Near side jet peak sits on plateau (Ridge)

Significant contribution to the near-side yield in central Au+Au

Look for particle and system size dependencies which might reveal information about production mechanism

nucl-ex/0701074

h-h


STAR 7

ΔΦ-Δη Correlation

s -Method

Ridge previously observed to be flat in To determine relative contributions, find yields for near-side, take projections in

-0.75<<0.75 Jet + Ridge0.75<||<1.75 RidgeJet = (Jet+Ridge) – Ridge*.75/1.75Ridge = yield from -1.75<<1.75 – jet yield

Flow contributions to jet cancel

v2 roughly flat with

3<pt,trigger<4 GeV

pt,assoc.>2 GeV

Ridge

Jet+ Ridge

Ridge

Au+Au 0-10% STAR preliminary

h+h

nucl-ex/0701074


STAR 8

The Ridge in Cu+CuIs there a Ridge in Cu+Cu?

projection flat at large Small and large regions match on away sideSmall yield above background in large regionJet yield in consistent with Jet in subtracting (Jet+Ridge)-Ridge

1/N

trig d

2N

/d

d

3.0 GeV<p3.0 GeV<pTTtrigtrig<6.0 GeV, 1.5 <6.0 GeV, 1.5

GeV<pGeV<pTTassocassoc<p<p

TTtrigtrig

h-h, 0-20% Cu+Cu h-h, 0-20% Cu+Cu ssNNNN = 200 GeV = 200 GeV

STAR Preliminary

1/N

trig d

N/d

0

~.13~.13

-1<-1<<1<1STAR STAR PreliminaryPreliminary



TTtrigtrig


STAR Preliminary

Jet + Jet + RidgeRidge

RidgeRidge

RidgeRidge

1/N

trig d

N/d

STAR STAR PreliminaryPreliminary

Jet+RidgeJet+Ridge--.75<.75<<.75<.75

RidgeRidge.75<|.75<||<1.75|<1.75scaled by .75scaled by .75

~.20~.20

Different Different flow flow background background parametersparameters



TTtrigtrig


1/N

trig d

N/d

~.19~.19

(Jet+Ridge)(Jet+Ridge) - - Ridge*.75Ridge*.75

9


STAR 9

Determination of yields and

errorsBackground:

B(1+2 v2trig v2

assoc cos(2ΔΦ))

Different fit methods for determination of B

Zero Yield At Minimum (ZYAM)1 point, 3 pointsB as Free parameter (used as best guess)

v2 errorv2 measurements in progress

upper bound for v2 measuredv2 10-15% depending on pT, centrality

estimate for lower bound, near 0

Λ,Λ,K0S,Ξ

-,Ξ+ v2 not measured

Assume quark scaling of h v2 in Cu+Cu

fit with ZYAM with 3 points, high v2

fit with ZYAM with 1 point

fit with ZYAM with 3 points, best v2

fit with ZYAM with 3 points, low v2

fit with background as free parameter

reflectedreflected

3.0 GeV<pTtrig<6.0 GeV, 1.5 GeV<pT

assoc<pTtrig

h-h, 0-20% Cu+Cu sNN = 200 GeV

STAR Preliminary

Arb

itra

ry u

nit

s


STAR 10

Near-side Yieldvs Npart

Jet yield flat with Npart within errorsno v2 or background error due to method

Ridge yield very smallflat with Npart within errors

No trigger particle type dependence

Data points at same Npart offset for visibilityJet yields: 10% error added to V0 and h triggers to account for track merging, 15% to triggers


STAR 11

Near-side Yield vs Npart Cu+Cu vs Au+Au

Jet yield comparable in Cu+Cu and Au+AuRidge yield consistent with Npart in Cu+Cu and Au+Au

Data points at same Npart offset for visibility

STAR Preliminary

d+Au, Au+Au from nucl-ex/0701047


STAR 12

Near-side yieldvs pT

trigger

Jet yield rises with pT

trigger in h-hYield roughly constant with centrality

No particle type dependence within error barsCentral Au+Au and 0-60% Cu+Cu jet yields comparable

nucl-ex/0701047


STAR 13

pT-distribution of associated

particlesRidge spectra similar to the bulk

Cu+Cu measurements probably not possible

Jet spectra are slightly harder

Cu+Cu T within error of Au+AuCu+Cu fit only to h-h

nucl-ex/0701047

416 ± 11 (stat.)

406 ± 20 (stat.)

438 ± 4 (stat.)

T(ridge) MeV

445 ± 49 Λ

530 ± 61 K0S

478 ± 8h+/-

T (jet) MeVTrigger particle

445 445 20 MeV 20 MeV

Fit to A exp(-pT/T)

J. Putschke, QM 06


STAR 14

ConclusionsRidge yields

Cu+Cu very smallCu+Cu and Au+Au consistent at the same Npart

No trigger particle type dependence within errors

including non-strange, and singly and doubly strange triggers

Jet yieldsCu+Cu and Au+Au consistent at the same Npart

increases with pT triggerconstant with centralityindependent of system


STAR 15

Future work

SystematicsReduce systematic error from v2

Identified particle v2

Coming soonIdentified associated particles in Cu+Cu

triggersComparisons to Au+Au – See B. Abelev's SQM talk

Away-side yieldsEnergy dependence of Jet and Ridge yields

~1000 ~1000 triggers in triggers in central Cu+Cu with central Cu+Cu with ppTT>2.5 GeV/c!>2.5 GeV/c!~2000 in central Au+Au~2000 in central Au+Au

STAR Preliminary


STAR 16

STAR CollaborationSTAR CollaborationUniversity of Illinois at Chicago - Argonne National Laboratory Institute of High Energy Physics - University of Birmingham Brookhaven National Laboratory - California Institute of Technology - University of California, Berkeley - University of California, Davis - University of California, Los Angeles - Carnegie Mellon University - Creighton University – Nuclear Physics Inst., Academy of Sciences - Laboratory of High Energy Physics - Particle Physics Laboratory - University of Frankfurt - Institute of Physics, Bhubaneswar - Indian Institute of Technology, Mumbai - Indiana University Cyclotron Facility - Institut de Recherches Subatomiques de Strasbourg - University of Jammu - Kent State University - Institute of Modern Physics - Lawrence Berkeley National Laboratory - Massachusetts Institute of Technology - Max-Planck-Institut fuer Physics - Michigan State University - Moscow Engineering Physics Institute - City College of New York - NIKHEF and Utrecht University - Ohio State University - Panjab University - Pennsylvania State University - Institute of High Energy Physics - Purdue University – Pusan National University - University of Rajasthan - Rice University - Instituto de Fisica da Universidade de Sao Paulo - University of Science and Technology of China - Shanghai Institue of Applied Physics - SUBATECH - Texas A&M University - University of Texas, Austin - Tsinghua University - Valparaiso University – Variable Energy Cyclotron Centre, Kolkata - Warsaw University of Technology - University of Washington - Wayne State University - Institute of Particle Physics - Yale University - University of Zagreb

Thank Thank you!you!


STAR 17

Backup slides

18


STAR 18

system size dependence of strange particle correlations in cu+cu and au+au collisions at s nn = 200...

Documents

yale university sqm

au collisions

hchristine nattrass

slovakiachristine nattrass

particle ratiostestable

central au aulook

correlations methodridge

cu cureaches maximum