identified hadron production at low to mid p t (~5.0gev/c) in au+au and cu+cu collisions maya...

Identified Hadron Production at low to mid pT (~5.0GeV/c)

in Au+Au and Cu+Cu Collisions

Maya SHIMOMURA

University of Tsukuba

2007 年 2 月 10,11 日　 heavy ion café 松本合宿

Contents

• Introduction – Baryon Anomaly at RHIC

• Recent results – Spectra measurements– p/pi ratio for various systems– proton RAA

– (models)

• Summary

Introduction

Baryon Anomaly (Baryon Enhancement ) at RHIC

dη/dpσdT

dη/dpNd)(pR

TNN2

AA

TAA2

TAA

PHENIX: PRL 91, 172301 (2003), PRC 69, 034909 (2004), PRC 74, 024904 (2006)

•RCP (or RAA)• Pions: pT> ２ GeV/c の領域に強い suppression がみられる (jet quenching effect)• Protons: pT =2-5 GeV/c の領域で Rcp= ～ 1 になっている

pp

AAbinaryAAAA Yield

NYieldR

/

Anomalous Composition

• Rcp

– メソンとバリオンで違う曲線を描いている

メソンが、他のメソンと同じ振る舞いをすることから、 mass の違いによるものではないといえる

• p/ and p/ ratios– ｐ T=2~5GeV/c では p/ が p/ に比べ

て大きい– Centrality による違いがはっきりみえる– d+Au, p+p, Au+Au の peripheral は、同じ

振る舞いをする。

results

Many spectra measurements are done.

Phenix preliminary

More and more …

Au+Au/Cu+Cu/p+p, 22.5/62.4/200 GeV, pi(±,0) and (anti-)proton.

Compilation of p/ ratios (central)

Cu+Cu 22.5 GeV, p/ ratio in central agree with p+p.Many protons, mostly from participant nucleons.

* No weak decay feed-down correction applied.


Cu+Cu 62.4 GeV, p/ ratio larger than those in p+p and Cu+Cu 22.5 GeV.



Cu+Cu 200 GeV, similar to those in Cu+Cu 62.4 GeV.



Au+Au 62 GeV, p/- is unchanged, p/+ getting larger.


Au+Au collision の結果を加えると・・・


Au+Au 200 GeV, p/- is enhanced, p/+ is similar to p/-


Compilation of p/ ratios (peripheral)

Conversing to the same line for both p/- and p/+


Centrality dep. of p/ in Au+Au 200 GeV

p/ in Au+Au 200 GeV p/ in Au+Au 200 GeV

- p/ (pbar/) ratios seem to turn over at intermediate pT, and be close to the value of fragmentation at higher pT.- Clear peak in central events than that in peripheral.- Indicating a transition from soft to hard at intermediate pT.

- Baryon enhancement observed in Cu+Cu at 200 GeV.

- pT dependence in Cu+Cu is similar to that in Au+Au.

Centrality dep. of p/ in Cu+Cu 200 GeV

Phenix preliminaryPhenix preliminary

p/ in Cu+Cu 200 GeV p/ in Cu+Cu 200 GeV

Centrality dep. of p/ in Cu+Cu 22.5 GeV

• More protons transported to mid rap. instead of production for Cu+Cu 22GeV. • Almost no centrality dependence in p/.• p/- ratios are ~0.3-0.4 at pT = 2 GeV/c, which is close to the value in p+p.


• p/+ ratios are reduced, compared to those in Cu+Cu 22 GeV. p/- ratio in central collisions reaches R=~0.6 at pT = 2 GeV/c.• Centrality dependence is also seen.

Centrality dep. of p/ in Cu+Cu 62.4 GeV* No weak decay feed-down correction applied.

sNN dep. of p/- and p/+ ratio (central)

• Increasing as a function 　 of s.

p-bar/- と p/+ では、逆の傾向をしめしている。

• decreasing as a function of s.

p/ vs. Npart1/3

Phenixpreliminary

Cu+Cu 200 GeV vs. Au+Au 200 GeV

NOTE: No weak decay feed-down correction applied.

TOF (<3 GeV/c)ACC (>3 GeV/c)

0.6 - 1.5 GeV/c1.0 - 2.0 GeV/c2.0 - 3.0 GeV/c3.0 - 4.0 GeV/c4.0 - 5.0 GeV/c

pT

pT

Phenix preliminary

- Centrality dependence in Cu+Cu looks similar to that in Au+Au (Npart scaling at same sqrt(sNN)!). - Even though overlap region has a different geometrical shape.- Slight difference in the magnitude seen.

RAA vs. pT

RAA YieldAA/Nbinary AA

Yieldpp

- Proton, antiproton are enhanced at 1.5 - 4 GeV/c for all centralities. (enhancement > suppression)- Suppression is seen for pions, kaons.


Phenix preliminary

RAA vs. pT

RAA YieldAA/Nbinary AA

Yieldpp

- Proton, antiproton are enhanced at 1.5 - 4 GeV/c for all centralities. (enhancement > suppression)- Suppression is seen for pions, kaons.


Phenix preliminary

NOTE: Systematic errors (~10%)for overall normalization not shown.

- Similar Npart dependence for Au+Au / Cu+Cu. (Npart scaling of RAA)- Cronin effect in peripheral

0 RAA, Central Events,Different √s

WA98, EPJ C 23, 225 (2002)

[ new reference compiled by D.d'Enterria nucl-ex/0403055]

PHENIX, PRL 88 022301 (2002)

• No Suppression at 17 GeV (Au+Au) and 22 GeV (Cu+Cu)at medium pT

• Need more study for 17~62.4~ GeV data

π0 Au+Au π0 Cu+Cu

RAA

Error notations:- Error bars: statistical error for HI spectra- Boxes:

1) sys. error for p+p reference.2) sys. error for HI spectra.

- Lines: Ncoll error (1.)

•Moderate suppression for Au+Au 62.4 GeV, larger than one for Cu+Cu 62/22 GeV (pT > 2.0 GeV/c).•π± is similar to π0

Au+Au 200 GeV

- Spectra for heavier particles has a convex shape due to radial flow.- Using Blast-wave fitting, try to estimate p/ ratio as a function of pT.

(hydro p)/(hydro ) (hydro p)/(real )


Central Peripheral

ｐ T が２ GeV/c 以上の領域は、 hydrodynamics だけでは、 proton enhancement を説明できない。　→ recombination や fragmentation の寄与

- Radial flow (ex. blast-wave fit) -

Quark Recombination model (+Fragmentation)

• Example:– Fragmentation: Dq→h(z)

• produces a 6 GeV/c from a 10 GeV/c quark

– Recombination:• produces a 6 GeV/c

from two 3 GeV/c quarks• produces a 6 GeV/c proton

from three 2 GeV/c quarks

Fries, et al, nucl-th/0301087Greco, Ko, Levai, nucl-th/0301093

• Mid pT 領域では、衝突で生成されたquark が　 coalesce してハドロンを生成しているモデル

fragmentation

recombination

p/Phenix preliminary

summary

Proton enhancement is observed in Au+Au/Cu+Cu collisions at 200/62 GeV.

p/ ratios:1. Only antiprotons in Cu+Cu 22.5 GeV system is different from others:

No centrality dependence in p/ ratio at the intermediate pT.Central 0-10% p/ ratio agrees with the value in p+p collisions

2. Indicating a transition from soft to hard production at intermediate pT.3. Npart scaling (dET/dy scaling) over different collision systems.4. Recombination + radial flow would explain the pT, Npart dependencie

s.

Data indicates that an onset of baryon anomaly at RHIC is in between 22 GeV and 62 GeV.

Spectra @High pT

Introduction

<Possible explanation>

•Cronin effect in nuclear. (Initial)

•Gluon interaction in hot dense matter. (final)

The suppression at high pT is due to the final state interaction.

<Question>

Dependence on the System size ?

Dependence on the particles species ?

*PRL 91 072303 (2003)

*No suppression in d+Au collision while Au+Au has factor 3 suppression at high pT.

*Direct photon is not suppressed.

PRL94(2005)232301

Comparison between Au+Au and d+Au collision with high energy.

Many measurements are done for high pT.

Back up

～検出器・解析手法～

PID charged pT spectra analysis in PHENIX

• Detectors: • Drift Chamber, PC1, BBC and

TOF for PID charged analysis.• Centrality:

• Subdivided minimum bias triggered events, based on BBC charge (62 GeV), or the number of PC1 hit (22 GeV).

• Corrections: • Geometrical acceptance, in

flight decay. • NOTE: No weak decay feed-

down correction applied for all plots in this presentation.

Charged particle identification by TOF

Charge x Momentum (GeV/c)

1/ Cu+Cu @ 22.5 GeV

PHENIX detector

Aerogel Cherenkov (PID)

EM Calorimeter (PID)TOF (PID)

Drift Chamber (momentum meas.)

Tracking detectors (PC1,PC2,PC3)

- Central Arm Detectors (magnetic spectrometer)- Event Characterization detectors- PID (particle identification) is a powerful tool to study hadron production.

p (p) ID up to 7 GeV/c-

p (p) ID up to 4 GeV/c-

Time of Flight (TOF)

Veto for proton ID

π+

K+p

Aerogel Cherenkov (ACC)

Back Up

~ 説明 ~

RAA Normalization

ddpdT

ddpNdpR

TNN

AA

TAA

TAA /

/)(

2

2

<Nbinary>/inelp+p

nucleon-nucleon cross section

1. Compare Au+Au to nucleon-nucleon cross sections2. Compare Au+Au central/peripheral

Nuclear Modification Factor:

If no “effects”: RAA < 1 in regime of soft physics RAA = 1 at high-pT where hard scattering dominates Suppression: RAA < 1 at high-pT

AA

AA

AA

What is the definition of baryon anomaly at RHIC?

• pT region of interest is the intermediate pT (2.0 - 5.0 GeV/c).

p/ (p/) ratios are much larger than the fragmentation expectations (p+p).– Strong centrality dependence in heavy ion data.

• Different nuclear modification factor (RCP or RAA) between pions and (anti)protons.– Pions: suppression.– (anti)protons: no suppression.

probe rest frame

r/ggg

• Color Glass Condensate• Gluon fusion reduces number of

scattering centers in initial state.• Theoretically attractive; limits DG

LAP evolution/restores unitarity

Back up

～結果～

pT spectra in p+p 62.4 GeV• Data from Run-6 (2006) at

RHIC.• Provides an important

baseline for pT spectra in Au+Au and Cu+Cu at sNN = 62.4 GeV.

• Presented the invariant yields here.

• Working on the determination of inelastic cross section and trigger bias in PHENIX experiment for the absolute normalization in pT spectra.


pT spectra (Cu+Cu √sNN = 200 GeV)


Phenix preliminary

- pT reach extended for (anti-)protons with fine centrality bins. <= (1) Aerogel Cherenkov, (2) Enough statistics in Au+Au/Cu+Cu

(Anti-) protons ACC

pT spectra (p+p √s = 200 GeV)

- High statistics 200 GeV p+p data. More than10 times statistics used compared to previous Run3 p+p analysis.- The p+p data provides baseline spectra to heavy ion data, and it is important to quantify in-medium nuclear effects in heavy ion collisions at RHIC.


Phenix preliminary

TOF

Medium II: Thermalization

• Hadron yields and spectra are consistent with thermal emission from a strongly expanding source.

• The observed strangeness production is consistent with complete chemical equilibrium

/K/p measurement in aBroad pt range

Stat. model fit:Tch~ 160MeV, s~1.0Strangeness saturation at RHIC?

stronger radial flow at RHIC?

Exp

ansi

on v

eloc

ity

Tkin ~ 100 MeV<vT/c> ~ 0.5

Chemical freezeout

Thermal freezeout

RHIC

p/ratios in p+p 62.4 GeV

RAA for charged pions (by ISR fit)

Error notations:- Error bars: statistical error for HI spectra- Boxes:

1) sys. error for p+p reference.2) sys. error for HI spectra.

- Lines: Ncoll error (1.)

• Used ISR fit (nucl-ex/0411049, D. d’Enteria) for p+p parameterization.

• Using ISR fit: Moderate suppression for Au+Au 62.4 GeV, larger than one for Cu+Cu 62/22 GeV (pT > 2.0 GeV/c).


RAA for antiprotons (by ISR fit)

• Used ISR data at 63 GeV (Alper. NPB 100, 237) for p+p reference.

• Similar RAA for all three systems.


RAA for protons (by ISR fit)

• Used ISR data at 63 GeV (Alper. NPB 100, 237) for p+p reference.

• Largest RAA for Cu+Cu 22.5 GeV.

• RAA for Au+Au 62.4 GeV is smaller than that in Cu+Cu 62.4 GeV.


p/ vs. pT (Low pT)

At low pT, p/ shows weak and decreasing Npart dependence because inverse slope (from mT exponential fitting) also shows it.


- Radial flow -

(Anti-)protonsTOF

Phenix preliminary Phenix preliminary

Recombination model と結果の比較

Fries, R et al PRC 68 (2003) 044902Greco, V et al PRL 90 (2003) 202302Hwa, R et al PRC 70(2004) 024905 etc.

Hydro + Recombination + Fragmentation で、説明できるか？

？

Au+Au 200GeVSTAR preliminary

identified hadron production at low to mid p t (~5.0gev/c) in au+au and cu+cu collisions maya...

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