system size and energy dependence of strangeness production

[email protected] Matter 2005

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System Size and Energy Dependence System Size and Energy Dependence of Strangeness Productionof Strangeness Production

Sevil SalurSevil Salur

Yale University

for the STAR Collaboration


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pT spectra and kinetic freeze-out of particles . Investigation of strange particle yields and ratios.

Study of resonances (thermal vs chemical freeze-outs )

Comparison of RHIC and SPS yields Strangeness enhancement

(Energy dependence & source type) RAA comparison with RCP and RdAu

Investigation of strangeness ordering. Is there a scaling in Au+Au production for the strange

quarks? N Participants vs N Binary ?

Outline


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200 GeV Au+Au

ssssss200 GeV Au+Au

udss200 GeV Au+Au

dssss200 GeV Au+Au

The Corrected Strange ParticleSpectra

200 GeV p+p 200 GeV p+p

200 GeV d+Au

200 GeV d+Au 200 GeV d+Au

62 GeV Au+Au 62 GeV Au+Au 62 GeV Au+Au

*(1520) (ud*(1520) (udss))**(uu(uuss))

QM Posters:

R. Bellwied,

M.Lamont,

C.Markert,

M.Munhoz&J.Takahashi,

J.Speltz

Y-4 Au+Au and Y-5 Cu+Cu is in Y-4 Au+Au and Y-5 Cu+Cu is in progress !progress !


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• ,K, p <T> at 200 GeV > 62 GeV Tkin at 200 GeV =62 GeV

• <T> at 200 GeV = 62 GeV Tkin at 200 GeV >62 GeV

Tkinetic vs Transverse velocity (<T>)

Tkinetic from a Blast-Wave is not same as the Temperature from a Hydro Model.

QM Poster: J.Speltz

• Temperature Tkinetic is higher for baryons with higher strange quark content for Blast-wave fits.

• Spectral shapes are different.

Most Central Collisions

0.13

T=100 MeV

T=132 MeV


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STAR Preliminary

QM Poster: M.Munhoz&J.Takahashi

• s-Baryon production is ~constant at mid-rapidity.

STAR Preliminary

Strange Baryon Production and Collision Energy…

s-Baryon production equals s-Baryon at RHIC Energies!

s-Baryon rises smoothly at mid-rapidity.

• s-Baryon Resonance follow the same trend.

Au+Au

Pb+Pb

STAR Preliminary


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/ ratios are approximately independent of the system

size at RHIC energies.

Strange ParticleRatios vs System Size

independent of system size at 200 GeV and equal to p+p values at lower energies.

QM Poster: C Markert, D. Mishra

Re-scattering and regeneration is needed ! t > 0, constant for different centralities!Regeneration σ(K*) > σ(*)


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and yields in AuAurelative to pp

rises.

System Size Dependence at 200 GeV

Correlation volume not well modelled by Npart

Is the scaling more important than normalization ?

Canonical suppression increases with increasing

strangeness

and arenot flat

Redlich et al.


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s-Quarks Have Different Scaling!

Scaling according to quark content?

u, d – scale with Npart

– already observed.

s – scale with Nbin

– appears better for strange particles.

K0s – 1/2*Npart + 1/2*Nbin

p – Npart

– 2/3*Npart + 1/3*Nbin

– 1/3*Npart + 2/3*Nbin

– Nbin

– Nbin

Npart

Does strangeness “see” a significant NBin contribution?

Normalized to central data

QM Poster: H. Caines

is puzzling!


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Nuclear Modification Factor Rcp

0-5%

40-60%Y-4 K0

s

√sNN=200 GeV

Baryons and mesons are different !

QM Poster: M.Lamont

62 GeV Rcp shows less suppression.

√sNN=62 GeV 0-5%

40-60%

Baryon and meson suppression sets in at different pT .


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Phys. Rev. Lett. 92 (2004) 052302 Au+Au √sNN=200 GeV

Au+Au √sNN=62 GeV

STAR Preliminary

Baryon and meson suppression sets in at

same quark pT .

0-5%

40-60%

√sNN=200 GeV

Nuclear Modification Factor Rcp

Coalescence vs Fragmentation?

0-5%

40-60%

Baryon and meson suppression sets in at

different pT .

Y-4 K0s

√sNN=200 GeV


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s-quark

Ordering with strangeness content!

Mesons (h+ + h-, K0s , ) follow

similar trends.

Strange baryons don’t show suppression.

Rcp Raa for strange baryons. Canonical suppression in p+p …?

s-quarks scaled with NBin

u&d-quarks scaled with Npart

scaled with N Part

STA

R

Pre

limin

ary

Au+Au

p+p

0-5%

√sNN=200 GeV

s-quarks scaled with NBin

u&d-quarks scaled with Npart

scaled with N Bin

STA

R

Pre

limin

ary

Au+Au

p+p

0-5%

√sNN=200 GeV

RAA of Strange Particles

STAR Preliminary

Au+Au

p+p

0-5%

√sNN=200 GeV

STA

R

Pre

limin

ary

Particles with strange quarks scale differently than non-

strange!


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Does entropy drive the strangeness yield?

SPS and RHIC data follows same curves…

Is there a universal scaling?

Enhancements are the same or even bigger at RHIC than at SPS !

Instead of Npart dNch/dη

Correlated to the entropy of the system!


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Summary and Conclusions

Transverse velocity T increases with collision energy.

TFO > TFOfrom Blast-wave but TFO = TFOfrom Hydro

s-Baryon production equals that of s-Baryon at RHIC energies.Baryon transport is ~ independent of system size at RHIC energies.

Rescattering and regeneration are required to model resonance production. Cross-sections and lifetimes vary (K* vs *). t > 0 between chemical and thermal freezeout for all centralities.

RAA different than RCP - canonical suppression is being investigated in RAA and RdAu .

Coalescence can explain the meson baryon difference at 62 GeV collisions too.

Particles with s-quarks appear to scale differently than non-s quarks. Maybe s-quarks “see“ a different correlation volume than light quarks?

Yields scale with dNch/d for SPS and RHIC

(universal scaling?)


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• 19 D. Mishra Measurement of++ and K∗ production in d+Au collisions at √sNN = 200 GeV

• 33 G. Van Buren The Ratio at RHIC • 60 R. Bellwied Strange particle production mechanisms in pp collisions at RHIC • 61 B. Bezverkhny Initial studies of two particle azimuthal correlations using baryons

in collisions at RHIC• 67 L. Gaillard Identified two-hadron correlations at STAR using , and K0

s with charged hadrons in AuAu at √sNN = 200 GeV

• 131 H. Caines The effects of varying the correlation volume on strangeness • 146 M. A. Lamont High momentum strange baryon anomalies in heavy ion collisions at

RHIC • 151 C. Markert The influence of medium properties on the resonance production in

RHIC collision• 152 C. M. Mironov STAR measurements of strange hadron R AuAu and R dAu

• 155 M. G. Munhoz Measurements of K0s and production in collisions at

√sNN = 62 GeV Au+Au • 163 F. Simon Forward production and nuclear stopping power in d+Au

collisions at RHIC • 164 J. Speltz Energy dependence systematics of strange and multi-strange

particle production • 167 A. Tang Strangelet search at RHIC

Strange Poster Presentations:


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• EXTRAS…


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Nuclear Modification Factor RdAu

QM Poster: C. Mironov

Resonances follow a similar trend !

Cronin Effect might explain R dAu above 1

Less so for mesons than baryons !

d+Au

p+p

√sNN=200 GeV

system size and energy dependence of strangeness production

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