Identified Hadron Production in Au Au and Cu Cu Collisions at RHIC-PHENIX

1
Identified Hadron Production in AuAu and CuCu
Collisions at RHIC-PHENIX
Masahiro Konno (Univ. of Tsukuba) for the PHENIX
Collaboration
Contact e-mail konno_at_rcf.rhic.bnl.gov
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 (25 GeV/c).
• The relative contributions and particle-type
• dependence are not yet fully understood.

?p/?-
p/? in pp (vsNN 62.4, 200 GeV)
Outstanding question

• (Anti-)proton enhancement observed/confirmed at
  pT 25 GeV/c
• Larger than expected from jet fragmentation
  (measured in pp, ee-)
• p/? ( ?p/?) ratios turn over at 23 GeV/c , and
  fall towards the ratio in pp 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 vsNN
ltlt Proton and antiproton production gtgt -
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 (lt1 GeV/c)
• How about ambiguity due to velocity profile?
• gt Several velocity profile tested n1 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
Freeze-out temperature
Transverse velocity
Soft Blast-wave fit (thermal radial
flow) Hard pp spectra, Nbin scaling, constant
suppression factor
Ref PRC 68 (2003) 044902 PRL 90 (2003)
202302 PRC 70(2004) 024905
- Consistent description for pions and protons -
Trying to explain soft/hard crossover
Phenix preliminary
Fraction of soft/hard components
pp spectra
- Cross point (SH) 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/?-
Radial flow is one of the explanations of baryon
enhancement. Its significant.
PHENIX detector
(Two-arm magnetic spectrometer, ?lt0.35)
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)
?, pTgt0 GeV/c
?, pTgt4 GeV/c
?, pTgt2 GeV/c
TOF (PID)
Pad Chambers (tracking)
Drift Chamber (momentum meas.)
Black sum Blue soft Red hard
p, pTgt4 GeV/c
p, pTgt0 GeV/c
p, pTgt2 GeV/c
Particle Identification
Aerogel Cherenkov (n1.011) 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 (3.5-4.0 GeV/c)
p

• - Origin of baryon enhancement
• Its 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 Whats the relation of
  hadronic and partonic radial flow?

K
Conclusion
?
Clear proton line up to high pT
INPC, June/2007, Tokyo