Multi-strange Baryon Correlations in p+p and d+Au Collisions at √ s NN = 200 GeV

Multi-strange Baryon Multi-strange Baryon CorrelationsCorrelations in in p+pp+p andand

d+Au d+Au Collisions atCollisions at √√ssNNNN = 200 GeV = 200 GeV

Betty BezverkhnyBetty Bezverkhny

Yale UniversityYale University

For the Collaboration

Hot Quarks ’04, Taos, New Mexico

Betty BezverkhnyBetty Bezverkhny HotQuarks 2004 HotQuarks 2004 22

Why Study Identified Correlations?Why Study Identified Correlations?

trigger

Adler et al., PRL90:082302 (2003), STAR

Previously published:Ncharged correlations in p+p

STAR measured jet suppression, collective flow, RAA suppression. Did it measure a QGP?

A detailed study needed to understand the medium created at RHIC

• Difference in particle-antiparticle production mechanisms?

• Difference with respect to strange-quark content?

• What fraction of ’s are made in jets? A predominant mechanism in p+p and d+Au? Which pT range?

• Base line for a Au+Au study?


Data Sets Available: • Au+Au Y01 130 GeV • Au+Au Y02 200 GeV• p+p Y02 200 GeV • d+Au Y03 200 GeV• p+p Y03 200GeV

high pT trigger

• Au+Au Y04 200 GeV• Au+Au Y04 62 GeV

•Detectors used in the study: TPC & CTB

•14M minBias p+p Y02 events available

•20M d+Au Y03 events available

Solenoidal Tracker At RHIC:

50 institutions from 14 countries – 500+ collaborators!

The STAR The STAR ExperimentExperiment


p+p

Procedure: 1. Apply loose cuts to find and

Anti-’s with ppTT >2 >2 GeV/c in a

given event

2. Find primary tracks with ppTT>1.5>1.5 GeV/c in the same

event3. Make sure tracks are not

decay products4. Calculate and plot it

What we’re up What we’re up against in p+p:against in p+p:

• Mean multiplicity of a p+p event: 5.5

• Raw ’s and A-’s per event: 3x10-4

•d+Au: higher multipl., better statistics…

y

High pHigh pTT

tracktrack

x

daughtersa p-/+ and a +/-

bachelor, a ±


mu

ltip

lici

ty

pT (GeV/c)

STAR Preliminary

p+p @ 200 GeV

The mean pT appears to increase with multiplicity for for ’s and K0S

(See Mark Heinz’ talk today at 10:45).

Are ’s made in higher mult. events? Does it mean ’s are made in jets?

Understanding the data

p+p : Mean pp+p : Mean pT T as a function of Multiplicityas a function of Multiplicity

STAR Preliminaryp+p @ 200 GeV

Mean ppMinBias event multiplicity: 5.55.5 primary tracks/event

Further

study

needed


Pythia numbers:Pythia numbers: • 3.2 x 107 events• 4.2 x 105 (1.3% events) w/a -

• 1921 -’s w/pT>2 GeV/c (0.0016% events)

• 515 events with at least 1 track w/pT >1.5 GeV and a w/pT>2GeV/c

• 705 correlations (1.37 Corr/-);• |y| < 0.75

3.2x107 PYTHIA events

p+p -

PYTHIA -

PYTHIA Spectrum is softer:

At high pT: significantly fewer ’s

data dN/dy: 0.00181 data <pT>: 0.97 GeV/c

p+pp+p: PYTHIA Simulation: PYTHIA Simulation


•Used both and Anti- for the study

•Used nHits cut to remove same-side split-track correlations, charged tracks are CTB-matched to remove pile-up

•13M events, ~770/13M = 0.0052% events with a high pT or

• Not every one of 972 candidate events had a valid primary track

STAR PreliminarySTAR Preliminary

p+pp+p: Real Data Correlations (data: Y02 ppMinBias): Real Data Correlations (data: Y02 ppMinBias)

Correlation Candidates: 972972

Correlated: 232232 in 295 correlations (1.3 correlation per candidate)

Uncorrelated: 740740


pT distribution:

at higher pT statistics start looking similar, however not enough to see a signal. Need to go farther down in pT to gain stats

40M events in Y05 40M events in Y05 run?run?

Matched or Anti-

UnMatched or Anti-



p+p = 200 GeV Y02

p+p = 200 GeV Y02

pT

pT

NNs

NNs

p+p: What’s Being Correlated?p+p: What’s Being Correlated?


No hope in p+p.

d+Au?

972 trigger particles


On to d+Au…On to d+Au… dAu Challenges : dAu Challenges :

• underlying event shape, • lots more background

dAu Advantages: dAu Advantages: • Lots more statistics• background is manageable • no thermalized medium expected, thus still a

base line Omegas (not yet!..) ?Omegas (not yet!..) ? AllAll trigger trigger ppTT are above 2 GeV/c, all are above 2 GeV/c, all associatedassociated ppT T

are above 1.5 GeV/care above 1.5 GeV/c


• 11.6M dAu Minimum Bias events considered (more data coming)

• 6.2M passed all event cuts (triggerID and Z vtx <50 cm)

• 2477 events with a or candidate with pT > 2 GeV

d+Au Minimum Bias Y03d+Au Minimum Bias Y03

0 t

rack

s co

rre

late

d:

10

85

ev

1 t

rack

co

rre

late

d:

77

2 e

v

2+ tracks: 510 ev


d+Au Correlationsd+Au Correlations

Height of the same-side peak is comparable to p+p Height of the same-side peak is comparable to p+p -h-h±± same- same-side peak height: ~0.4 (side peak height: ~0.4 () vs. ~0.3 () vs. ~0.3 () () (See talk byYing Guo on

Saturday))

•1392 events with at least 1 correlation

•2399 trigger particles

•2358 Correlations

•1.5 Corr/ !


Conclusions and OutlookConclusions and Outlook Good NewsGood News: There’s hope in : There’s hope in d+Aud+Au!! In In p+p p+p about 25% of observed about 25% of observed ’s above 2GeV seem to be ’s above 2GeV seem to be

correlatedcorrelated Might get much more data in Y05… Might get much more data in Y05… Not-so-good NewsNot-so-good News: Currently not enough data for a thorough p+p : Currently not enough data for a thorough p+p

study.study.Lots more to do!Lots more to do! Need better PYTHIA. Tuning?Need better PYTHIA. Tuning? Need a thorough Need a thorough d+Aud+Au study: study:

• Add all available statistics• Process the high pT-triggered dataset• Measure and subtract the underlying soft physics correlations

(momentum conservation) Need models: how many Need models: how many ’s come from ’s come from resonances? How many resonances? How many

should we expect from hard scattering? should we expect from hard scattering? March on to March on to Au+AuAu+Au……


The end. Thank you, thank you, thank you.The end. Thank you, thank you, thank you.


d+Au Correlationsd+Au Correlations: 2 Gaussians fit (2/ndf : 1.031/3)

Height of the same-side peak is comparable to p+p Height of the same-side peak is comparable to p+p -h-h±± same- same-side peak height: ~0.4 (side peak height: ~0.4 () vs. ~0.3 () vs. ~0.3 () () (See talk byYing Guo on

Saturday))

•1392 events with at least 1 correlation

•2399 trigger particles

•2358 Correlations

•1.5 Corr/ !


Documents

Multi-strange Baryon Correlations in p+p and d+Au Collisions at √ s NN = 200 GeV