1. Identified Hadron Production in Au+Au and Cu+Cu Collisions at RHIC-PHENIX
Masahiro Konno (Univ. of Tsukuba) for the PHENIX　Collaboration
Contact
Motivation
Baryon/Meson difference in yield and emission pattern
Hadron production in relativistic heavy ion collisions
Phenix preliminary
Hadronization
Interactions
in the medium
Low-pT (soft)
Thermal emission
Quark recombination
Thermalization
Collective flow
High-pT (hard)
Jet fragmentation
Hard scattering
Jet quenching
p/+
- There are multiple hadronization mechanisms
at intermediate pT (2~5 GeV/c).
The relative contributions and particle-type
dependence are not yet fully understood.
p/-
p/ in p+p (√sNN = 62.4, 200 GeV)
Outstanding question:
(Anti-)proton enhancement observed/confirmed at pT = 2~5 GeV/c
Larger than expected from jet fragmentation (measured in pp, e+e-)
p/ ( p/) ratios turn over at 2~3 GeV/c , and fall towards the ratio in p+p collisions
- Indicating a transition from soft to hard at intermediate pT
- What pT does hydrodynamic contribution exist up to?
- Quark recombination process is really necessary?
- Can we separate hadron radial flow and quark radial flow ?
Focusing on:
- The ratio is controlled by the initial size of the created systems (~Npart)
- Transverse energy density is a connection key between different √sNN
<< Proton and antiproton production >>
- Sensitive to collective flow due to its relatively large mass
- Indicator of baryon number transport at lower energies
(Hadronization)
Blast wave model:
Quark recombination model:
Simple parameterization at low pT (<1 GeV/c)
How about ambiguity due to velocity profile?
=> Several velocity profile tested; n=1 is best case
One of the hadron production mechanisms
Recombination of thermal quarks
Separation of soft/hard components
(extrapolation because
of thermal distribution)
Two component model:
Transverse velocity
Freeze-out temperature
Soft: Blast-wave fit (thermal + radial flow)
Hard: p+p spectra, Nbin scaling, constant suppression factor
Ref:
PRC 68 (2003)
PRL 90 (2003)
PRC 70(2004)
- Consistent description for pions and protons
- Trying to explain soft/hard crossover
Phenix preliminary
Fraction of soft/hard components
p+p spectra
- Cross point (S=H) vs. pT - p
Blue: data
Red: data - Hydro
B.W. line
In a simple recombination picture,
radial flow cannot be distinguished
between hadron and quark phases p
Intermediate pT: Hard pions vs. Soft protons
Separation in v2
Separation in p/
Hard v2 is not zero. It may be
caused by jet quenching.
Phenix preliminary
++ - (0) v2
(BW p)/(BW )
BW v2 +
p/+
Blue: data
Red: data - B.W.
(BW p)/(real ) -
Blue: data v2
Red: estimated hard v2
p+p v2
p/-
Central
Peripheral
Central
Peripheral
Radial flow is one of the explanations
of baryon enhancement. It’s significant.
PHENIX detector
(Two-arm magnetic spectrometer, ||<0.35)
Both soft/hard yields (dN/dy) are not scaled with Npart.
Multiple scattering, energy loss should be considered.
Separation in yield (dN/dy/(Npart/2))
Aerogel Cherenkov (PID)
EM Calorimeter (PID)
, pT>0 GeV/c
, pT>2 GeV/c
, pT>4 GeV/c
TOF
(PID)
Pad Chambers
(tracking)
Drift Chamber
(momentum meas.)
Black: sum
Blue: soft
Red: hard
p, pT>0 GeV/c
p, pT>2 GeV/c
p, pT>4 GeV/c
Particle Identification
Aerogel Cherenkov (n=1.011)
proton ID up to 7 GeV/c
Time of Flight (~120 ps)
proton ID up to 4 GeV/c
Veto for proton ID
m2 distributions
( GeV/c) p
- Origin of baryon enhancement:
It’s transverse radial flow which is pushing particles to higher pT
Contribution of soft component at higher pT
The enhancement and freeze-out properties are controlled by system size
The next question: What’s the relation of hadronic and partonic radial flow? K+
Conclusion +
Clear proton line up to high pT
INPC, June/2007, Tokyo