Identified Charged Hadron Production at High pT- in 䌥㼖NN = 200 GeV Au+Au Collisions at RHIC-PHENIX -Masahiro Konno(Univ. of Tsukuba)
for the PHENIX Collaboration

1
M.Konno (Univ. of Tsukuba)

Hot Quarks 2006

Outline- Physics motivation- PHENIX detector- Data analysis- Results- Collision system dependence- Comparison with models- Summary

2
M.Konno (Univ. of Tsukuba)

Hot Quarks 2006

Physics motivation
R AA =

Nuclear Modification Factor RAA

Yield AA/"N binary # AA
Yield ppnucl-ex/0603010

Au+Au 200 GeV!

High-pT suppression due toparton energy loss in the medium(jet quenching).

The suppression patterns dependon particle type. Protons are enhanced,
while pions and kaons are suppressed.
3M.Konno (Univ. of Tsukuba)

Hot Quarks 2006

Physics motivation
Baryon Enhancement
PRL 91, 172301 (2003)

d+Au similar to peripheral
Au+Au but much smaller thancentral Au+Au- p/π ratio ~1 for central Au+Au at intermediate pT (2-4 GeV/c).
- Larger than expected from fragmentation (measured in pp, e+e-).
- Baryon / Meson difference at intermediate pT.
(on RAA (nuclear modification factor) , v2 (elliptic flow) etc.)

4M.Konno (Univ. of Tsukuba)

Hot Quarks 2006

Physics motivation
What is the origin of (anti-)protonenhancement at intermediate pT?
Possible sources (medium effect) :- Strong radial flow
- Recombination- Baryon junction

Transverse momentum spectra andparticle ratios provide the most basic tool
to investigate the mechanisms of hadronproduction.
To distinguish the different production
mechanism for protons and pionsat intermediate and higher pT.
M.Konno (Univ. of Tsukuba)

Hot Quarks 20065

PHENIX detector

EMCal- Central Arm Detectors(magnetic spectrometer)- Event Characterization detectors

TOFAerogel Cherenkov Counter
Hadron Identification at High pT- n = 1.0113.
- Full installation in 2004.
- Proton separation from 䃖㻒㻮
up to 8 GeV/c.

Drift Chamber(momentum meas.)
Tracking detectors(PC1,PC2,PC3)

6
M.Konno (Univ. of Tsukuba)

Hot Quarks 2006

Data analysis- Data set: Au+Au 200 GeV (taken in Run4, 2003-2004)- High statistics (440M events used)- Charged Hadron PID:
- TOF
- Aerogel (for PID extension toward high pT, Run4-)- MC Simulations:- Acceptance, efficiency (occupancy) corrections- No feed-down correction
BG Subtraction

3~4 GeV/c

S/N~12

4~5 GeV/c

S/N~5Using residual bendingin φ direction.
Backgrounds:- random association- electrons from photon conversion- decayed products

5~6 GeV/c

S/N~2

6~7 GeV/c

S/N~1

track matching residual (a.u.) 7
M.Konno (Univ. of Tsukuba)

Hot Quarks 2006

Results

8M.Konno (Univ. of Tsukuba)

Hot Quarks 2006

pT spectraof (anti-)proton

Identified
with ACC

pT reach extendedfor (anti-)protons
with fine centrality bins.
9
M.Konno (Univ. of Tsukuba)

Hot Quarks 2006

pT spectraof (anti-)proton

Identified
with TOF
Precise measurement
at high pT thanks tohigh statistics.
10
M.Konno (Univ. of Tsukuba)

Hot Quarks 2006

pbar/p vs. pT

Peripheral

CentralNo significant
centrality or pT dependence(up to 6 GeV/c).
11
M.Konno (Univ. of Tsukuba)

Hot Quarks 2006

p/π vs. pT
p/πACCp/π* No feed-down correction.

- p/π (pbar/π) ratios seem to turn over at intermediate pT,
and close to the value of fragmentation at higher pT.
- Indicating transition from soft to hard at intermediate pT.
12
M.Konno (Univ. of Tsukuba)

Hot Quarks 2006

p/π vs. pT (centrality dep.)

ACC* No feed-down correction.

p/πp/πPeripheral

Central- p/π ratios look to have a peak at intermediate pT (2-4 GeV/c).
- Clear peak in central events than that in peripheral.
M.Konno (Univ. of Tsukuba)

Hot Quarks 200613

p/π vs. pT (centrality dep.)p/πACCp/π* No feed-down correction.
* p+p data (nucl-ex/0603010)- Centrality dependence seen in the magnitude.
- p/π ratio in peripheral lies slightly above the p+p ratio.
14
M.Konno (Univ. of Tsukuba)

Hot Quarks 2006

Proton RCP

TOF

Yield Central/"N binary # Central
R CP =
Yield Peripheral/"N binary # Peripheral!

- Proton RCP shows unity above 2 GeV/c.
- Peak structure at 2~3 GeV/c.
15
M.Konno (Univ. of Tsukuba)

Hot Quarks 2006

Proton RCP

TOF- Proton RCP seems to show decreasing above 3 GeV/c.
- Expected to merge to pion RCP at higher pT.
- Need more statistics to look at high-pT points.
16
M.Konno (Univ. of Tsukuba)

Hot Quarks 2006

Collision system dep.

17
M.Konno (Univ. of Tsukuba)

Hot Quarks 2006

p/π ratio in 62 GeV Au+Au

62 GeV Au+Au- Rapidly increasing with pT for 62 GeV.
- Weaker centrality dependences (62GeV) than those of 200 GeV.
- Significant difference for p and pbar at 62 GeV.
(Indicating more baryon transport and less p-pbar pair production at 62 GeV
than 200 GeV.)
18
M.Konno (Univ. of Tsukuba)

Hot Quarks 2006p/π ratio in Cu+Cu / Au+Au

200 GeV Cu+Cu

Central Au+Au

Central Cu+Cu* No feed-down correction.

- Observed a large p,pbar contribution at intermediate pT,
as seen in 200 GeV data.
- Npart dependences on particle ratios have similar trend
as in Au+Au (Npart scaling).
19
M.Konno (Univ. of Tsukuba)

Hot Quarks 2006

Comparison with models

20
M.Konno (Univ. of Tsukuba)

Hot Quarks 2006

Comparison with models
PRC 69, 034908 (2004)

PRC 68, 044902 (2003)

PRC 67, 034902 (2003)

p/π

PRL 90, 202302 (2003)- Only look through several models (recombination, hydro+jet, …).
- Novel mechanism of hadron production at intermediate pT. 21
M.Konno (Univ. of Tsukuba)

Hot Quarks 2006

Recombination

At intermediate pT, recombinationof partons may be a more efficientmechanism of hadron production
than fragmentation.

Fries, R et al PRC 68 (2003) 044902
Greco, V et al PRL 90 (2003) 202302
Hwa, R et al PRC 70(2004) 024905
22

M.Konno (Univ. of Tsukuba)

Hot Quarks 2006

Scaling of elliptic flow
PHENIX Preliminary(mT - m0)
Example of partonic degrees of freedom
23
M.Konno (Univ. of Tsukuba)

Hot Quarks 2006

Summary- pT reach of PID (especially for p, pbar) extended with:- High statistics 200 GeV Au+Au data
- New PID detector (Aerogel)- Results:- pbar/p ratio No centrality or pT dependence- p/π ratio Indicating transition from soft to hard at intermediate pT- RCP (Anti-)proton RCP shows decreasing above 3 GeV/c- Collision system dependence:- Similar turnover curve on p/π in 62 GeV Au+Au- Npart scaling on particle ratios (Cu+Cu / Au+Au)- Comparison with models:- Recombination models seem to be matchedto the experimental data.

Next- Improve data analysis, reduce sys. errors for PID at high pT- Analyze Run5 p+p (abundant) data to make RAA at higher pT- MRPC-TOF (σTOF~100ps) to be installed for PID upgrade
24

M.Konno (Univ. of Tsukuba)

Hot Quarks 2006