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High pt particle spectra and High pt particle spectra and correlations of strange particlescorrelations of strange particles

in pp, dA, and AA in STARin pp, dA, and AA in STAR

Rene BellwiedWayne State University

(for M.Heinz, J.Adams, C. Mironov, J.Bielcikova, L.Gaillard, Y.Guo, J.Rumbell, B. Bezhverkhny, R.Witt)

STAR Analysis MeetingPurdue UniversityMay 16th-17th, 2005

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Talk structureTalk structureFragmentation in pp

Correlations in pp, dA, AA–Trigger species dependence–Trigger pt dependence–System size dependence

Summary

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Fragmentation in ppFragmentation in ppWork by Work by

M.Heinz, J. Adams, R. Witt, C. MironovM.Heinz, J. Adams, R. Witt, C. Mironov

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pp at RHICpp at RHICNLO breaks down for heavy masses ?NLO breaks down for heavy masses ?

p+p->0 + X

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NLO variation (W.Vogelsang et al.)NLO variation (W.Vogelsang et al.)

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PYTHIA studies (M.Heinz)PYTHIA studies (M.Heinz)

PYTHIA 6.221 + kT = 4 GeV/c + K=3= broadening orNLO correctionsvery high

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How strong are the NLO corrections ?How strong are the NLO corrections ?

K.Eskola et al.(NPA 713 (2003):Large NLO corrections notunreasonable atRHIC energies.

STAR

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A newer version of PYTHIAA newer version of PYTHIA

v.6.37 includes more initial state multiple scattering

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Mark’s results (model studies)Mark’s results (model studies)

EPOS (K.Werner): initial state and final state parton cascades (parton ladders), which populate predominantly low pt part of the spectrum. Does well for ALL particle species in pp and dA for STAR, PHENIX and BRAHMS.

Spectrum not dominated by fragmentation.

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New NLO calculation based on STAR data New NLO calculation based on STAR data (AKK, hep-ph/0502188)(AKK, hep-ph/0502188)

K0s (V0 vs NLO)

apparent Einc dependence of separated quark contributions. As of now only tested on light mesons, but also evidence for strange baryons

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AKK quark separated fragmentation functionAKK quark separated fragmentation function

Conditional probability of valence and non-valence quarks contributing to the FF as a function of fractional momentum z (=x). Needs to be

multiplied with partonic production cross section to determine absolute contribution

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Octet baryon fragmentationOctet baryon fragmentationBourrely & Soffer (hep-ph/0305070)Bourrely & Soffer (hep-ph/0305070)

Strong heavy quarkcontribution to parton fragmentation into octet baryons at low fractional momentum in pp !!

Quark separation infragmentation models is important. FFs are not universal.

Depend on Q, Einc,and flavorzz

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Correlations in pp, dA, AACorrelations in pp, dA, AAWork by Work by

Y. Guo, J. Bielcikova, C. Mironov,Y. Guo, J. Bielcikova, C. Mironov,J.Rumbell, L. Gaillard, B. BezhverkhnyJ.Rumbell, L. Gaillard, B. Bezhverkhny

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Λ+h correlations in AuAu and pp

1.5 GeV/c < p1.5 GeV/c < pT,trigT,trig,p,pT,assoT,asso<3.0 GeV/c<3.0 GeV/c

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The associated particle yield is smallThe associated particle yield is small

A few percent compared to the uncorrelated background.

Using the proper fit function becomes very important

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Uncorrelated Background, , ,

, , , ,

,,

1

2

t trigger high t trigger

t trigger low t associated low

p p

trigger cht trigger

trigger t trigger tp p

dN dNB dp

N dp dp

Fitting Method

))*cos(.)cos(()*

)(exp(*)( ,,cos

2021

21 222

1

21 flow

assoflowtriggervvCbgaF

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No dependence on centrality or particle speciesNo dependence on centrality or particle species

Physics results in AACentrality dependence: same and back side yield.

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PHENIX measurementPHENIX measurement

Our data are in agreement with PHENIX

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Are there differences in associated same side yield as a function of trigger species and pt ?

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Same side yield for different trigger particle speciesSame side yield for different trigger particle species

Indication of different trigger pT dependence for different trigger particle species..

Systematic Errors: Uncorrelated background --

8~10% Flow – 2.1~2.6% Fitting method – 3% misidentified V0s < 1% trigger bias <1.5%

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ppTT(trigger) dependence in d+Au:(trigger) dependence in d+Au:

is there a difference between is there a difference between ΛΛ and and ΛΛ ? ?

Within statistical errors the yield/trigger does not depend on type of trigger particle

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Jana’s study (new AA production,Jana’s study (new AA production,statistics comparable)statistics comparable)

Old New No more difference between particle & anti-particle

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Jana’s study (the very latest)Jana’s study (the very latest)

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What do we learn from system size ?What do we learn from system size ?

Large AA/pp ratio

Same side correlations in AA appear to have larger amplitude and width.

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Large AA/pp ratio for different trigger particle species

•Approaches unity at higher pT and in peripheral collisions•Apparent description possible through correlated recombination

Rudy Hwa. et al Rudy Hwa. et al

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R. Hwa et al. R. Hwa et al. predictions based on recombination of predictions based on recombination of

thermal and shower partonsthermal and shower partons

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Alternate (?) explanation: Additional Alternate (?) explanation: Additional long range long range correlations correlations in AA (D. Magestro et al.)in AA (D. Magestro et al.)

In Au+Au, jetlike correlation sits on top of an additional, ~flat correlation in : cannot differentiate between the two correlations : additional

correlation

gets grouped into

subtracted

background

d+Au, 40-100%

Au+Au, 0-5%

STAR preliminary

3 < pT(trig) < 6 GeV2 < pT(assoc) < pT(trig)

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: system size dependence at 200 GeV: system size dependence at 200 GeV

STAR preliminary

Au+Au: peak broadens, height drops with centrality3 < pT(trig) < 6 GeV

2 < pT(assoc) < pT(trig)|| < 0.5

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: p: pTT(trig) dependence of width(trig) dependence of width

Broadening in Au+Au compared to p+p, d+Au– Difference grows with decreasing pT(trig)

– All systems are consistent for largest pT(trig) bin [6<pT<12 GeV]

– Systematic error not assigned (fit range, projection window)

STAR preliminary

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: p: pTT(trig) dependence of correlated yield(trig) dependence of correlated yield

Gaussian areas consistent within errors for all pT(trig)– Yield growth with pT(trig): more assoc. particles for higher-pT parton

– Correlation yield preserved despite broadening of correlation

widths from previous slideSTAR preliminary

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R. Hwa et al. R. Hwa et al. predictions based on recombination of predictions based on recombination of

thermal and thermal partonsthermal and thermal partons

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Leon Gaillard’s study (pid Leon Gaillard’s study (pid correlations) correlations)

Needs more statistics What to do with the ridge ?

charged-charged Lambda-charged

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John Rumbell’s study:John Rumbell’s study:Associated same side yieldAssociated same side yield

in pp, dA, AA in pp, dA, AA

1.0<Pt(assoc)<2.0

2.0<Pt(trigger)<4.0

Circle = Ying AA 200GeV

X’s = Jana dA 200GeV

Stars = John pp 200 GeV

charged-charged K0-charged

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Very different trigger particle species (and multiplicities) give very similar associated

particle yields

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Same side associated particle pt spectraSame side associated particle pt spectra

In agreement with thermal distribution ?? large AA/pp ratio.No significant difference between distribution different trigger particle species.

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SummarySummary Significant NLO contributions in strange particle

production in pp. Differences in fragmentation due to non-valence quark contributions ?

Associated particle yield not leading particle species dependent in our pt range. Distributions surprisingly similar in multiplicity and kinematics.

Large difference in associated particle multiplicity from pp to dA to AA. Can not be explained by fragmentation. Either recombination (thermal-shower) or long range correlation contribution, which could also be from recombination (thermal-thermal)