Transcript p T

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
RAA
v2
(models)
• Summary
Results are mostly talken from T.Chujo, M.Konno’s and
B.Sahlmüller’s QM06 talk.
2
Introduction
Baryon Anomaly (Baryon Enhancement ) at RHIC
PHENIX: PRL 91, 172301 (2003), PRC 69, 034909 (2004),
PRC 74, 024904 (2006)
2
R AA (p T ) 
d N
2
AA
T AA d σ
R AA 
Yield
AA
/  N binary  AA
Yield
pp
/dp T dη
NN
/dp T dη
•RCP (or RAA)
• Pions: pT>２GeV/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
4
Anomalous Composition
•
Rcp
– メソンとバリオンで違う曲線を描いている
 f 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
– ｐT=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。
5
results
Many spectra measurements are done.
More and more …
Phenix preliminary
Au+Au/Cu+Cu/p+p, 22.5/62.4/200 GeV, pi(±,0) and (anti-)proton.
7
Compilation of p/ ratios (central)
* No weak decay feed-down correction applied.
Taken from QM06 T.chujo’s Talk
Cu+Cu 22.5 GeV, p/ ratio in central agree with p+p.
Many protons, mostly from participant nucleons.
8
Compilation of p/ ratios (central)
* No weak decay feed-down correction applied.
Taken from QM06 T.chujo’s Talk
Cu+Cu 62.4 GeV, p/ ratio larger than
those in p+p and Cu+Cu 22.5 GeV.
9
Compilation of p/ ratios (central)
* No weak decay feed-down correction applied.
Taken from QM06 T.chujo’s Talk
Cu+Cu 200 GeV, similar to those in Cu+Cu 62.4 GeV.
10
Au+Au collision の結果を加えると・・・
Compilation of p/ ratios (central)
* No weak decay feed-down correction applied.
Taken from QM06 T.chujo’s Talk
Au+Au 62 GeV, p/- is unchanged, p/+ getting larger.
11
Compilation of p/ ratios (central)
* No weak decay feed-down correction applied.
Taken from QM06 T.chujo’s Talk
Au+Au 200 GeV, p/- is enhanced, p/+ is similar to p/12
Compilation of p/ ratios (peripheral)
* No weak decay feed-down correction applied.
Taken from QM06 T.chujo’s Talk
Conversing to the same line for both p/- and p/+
13
Centrality dep. of p/ in Au+Au 200 GeV
Taken from QM06 M.Konno’s Talk
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.
14
Centrality dep. of p/ in Cu+Cu 200 GeV
Taken from QM06 M.Konno’s Talk
p/ in Cu+Cu 200 GeV
Phenix preliminary
p/ in Cu+Cu 200 GeV
Phenix preliminary
- Baryon enhancement observed in Cu+Cu at 200 GeV.
- pT dependence in Cu+Cu is similar to that in Au+Au.
15
Centrality dep. of p/ in Cu+Cu 22.5 GeV
Taken from QM06 T.chujo’s Talk
* No weak decay feed-down correction applied.
• 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.
16
Centrality dep. of p/ in Cu+Cu 62.4 GeV
Taken from QM06 T.chujo’s Talk
* No weak decay feed-down correction applied.
• 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.
17
sNN dep. of p/- and p/+ ratio (central)
Taken from QM06 T.chujo’s Talk
• decreasing as a function of s.
• Increasing as a function of s.
p-bar/- と p/+では、逆の傾向をしめしている。
p-bar/- は、２２GeVと６４GeVの間で大きく変化
18
p/ vs. Npart1/3
Taken from QM06 M.Konno’s Talk
Cu+Cu 200 GeV vs. Au+Au 200 GeV
0.6
3.0
4.0
1.0 - 5.0
2.0
1.5
4.0
2.0 GeV/c
3.0
Phenix
preliminary
Phenix preliminary
pT
- 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.
NOTE: No weak decay
- Slight difference in the magnitude seen.
feed-down correction
applied.
pT
19
RAA vs. pT
R AA 
Yield
AA
/ N binary  AA
Yield
pp
Phenix preliminary
Taken from QM06 M.Konno’s Talk

- Proton, antiproton are enhanced at 1.5 - 4 GeV/c
for all centralities. (enhancement > suppression)
- Suppression is seen for pions, kaons.
NOTE: No weak decay feed-down correction applied.
20
 RAA, Central Events,Different √s
0
π0
Au+Au
WA98, EPJ C 23, 225 (2002)
π0 Cu+Cu
Taken from QM06 B.Sahlmüller’s Talk
[ 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
21
• Need more study for 17~62.4~ GeV data
RAA Comparison
Taken from QM06 T.Chujo’s Talk
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
22
RAA vs. pT
R AA 
Yield
AA
/ N binary  AA
Yield
pp
Phenix preliminary
Taken from QM06 M.Konno’s Talk

- Similar Npart dependence
for Au+Au / Cu+Cu.
(Npart scaling of RAA)
- Cronin effect in peripheral
NOTE: Systematic errors (~10%)
for overall normalization not shown.
- Proton, antiproton are enhanced at 1.5 - 4 GeV/c
for all centralities. (enhancement > suppression)
- Suppression is seen for pions, kaons.
NOTE: No weak decay feed-down correction applied.
23
v2 results
v2 Au+Au/Cu+Cu 62.4 and 200GeV comparison
Au+Au
Cu+Cu
それぞれのセントラリティで62.4GeVと200GeVの結果はよく一致している。
25
Comparison of 62.4 and 200GeV at AuAu and CuCu (1)
黒 AuAu 200GeV
赤 AuAu 62.4GeV
緑 CuCu 200GeV
青 CuCu 62.4GeV
1.0-2.0 GeV/c
0.2-1.0 GeV/c
v2 は、Npart では、スケールしていない。
26
Comparison of 62.4 and 200GeV at AuAu and CuCu (2)
黒 AuAu 200GeV
赤 AuAu 62.4GeV
緑 CuCu 200GeV
青 CuCu 62.4GeV
2.0-4.0 GeV/c
1.0-2.0 GeV/c
0.2-1.0 GeV/c
反応関与部の楕円率
eccentrici ty =
y
2
- x
2
y
2
+ x
2
v2 は、Eccentricity でスケールしている。
（最も中心衝突が外れているのは、Eccentricityの取り方で変わる可能性あり.。）
CuCu 62.4GeVの結果は他の結果と同じ傾きでスケールしない。→System 依存あり。27
Taken from QM06 M.Konno’s Talk
- Radial flow (ex. blast-wave fit) -
- 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.
NOTE: No weak decay feed-down correction applied.
(hydro p)/(hydro )
Central
Au+Au 200 GeV
(hydro p)/(real )
Peripheral
ｐTが２GeV/c以上の領域は、 hydrodynamics だけでは、proton enhancement を28
説明できない。 →recombination や fragmentation の寄与
Quark Recombination model (+Fragmentation)
• 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
•
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
p/
recombination
Phenix preliminary
fragmentation
Taken from QM06 M.Konno’s Talk
Fries, et al, nucl-th/0301087
Greco, Ko, Levai, nucl-th/0301093
29
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
dependencies.
Data indicates that an onset of baryon anomaly at RHIC is
in between 22 GeV and 62 GeV.
30