Transcript Results from the Relativistic Heavy Ion Collider (Part II)

Soft-hadron Physics at RHIC
Results from the Relativistic Heavy Ion Collider (Part II)
First joint Meeting of the Nuclear Physics Divisions of APS and JPS
Maui, Hawaii, 2001 Oct. 19
/ Masashi Kaneta
LBNL
[email protected]
http://www.rhic.bnl.gov/~kaneta/
Masashi Kaneta, First joint Meeting of the Nuclear Physics Divisions of APS and JPS
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3 Years ago, in JPS meeting
• Summary of SPS results by M.K.
Masashi Kaneta, First joint Meeting of the Nuclear Physics Divisions of APS and JPS
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Outline
• Introduction
• Particle ratios / yield
• Identified single particle spectra
• Event anisotropy
• Particle correlation (HBT)
• Summary
• Open issues
Masashi Kaneta, First joint Meeting of the Nuclear Physics Divisions of APS and JPS
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• Goal
 Study bulk
properties of matter
under extremely
high energy and
particle density
 Information of
observable come
from Parton / hadron
level
Thermal
freeze-out
time
Introduction
Chemical
freeze-out
elastic
interaction
hadron
parton
inelastic
interaction
space
• Focus of this talk
 Low pT and mid-rapidity data
Masashi Kaneta, First joint Meeting of the Nuclear Physics Divisions of APS and JPS
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Particle ratios/yield
• Anti-baryon/baryon ratio and
net-proton
 Stopping or transparent?
• Particle ratios from hadrons
 Chemical freeze-out parameters
Masashi Kaneta, First joint Meeting of the Nuclear Physics Divisions of APS and JPS
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Anti-Baryon/Baryon ratio
• B/B <1
Not baryon free
statistical error only
STAR PRL86 (2001) 4778
L/L ratio
N
ch
• Less centrality
dependence
/N
max
130 GeV RHIC : STAR / PHENIX /
PHOBOS / BRAHMS
from this meeting
17.4 GeV SPS : NA44, WA97
statistical error only
dNh / d
Masashi Kaneta, First joint Meeting of the Nuclear Physics Divisions of APS and JPS
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Net-proton
Measured in STAR acceptance
Extrapolated yields
BRAHMS preliminary
• Inclusive net-proton
• Net-proton
increases with
centrality
STAR data
: from this meeting
BRAHMS data : Quark Matter 2001
Masashi Kaneta, First joint Meeting of the Nuclear Physics Divisions of APS and JPS
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Chemical freeze-out model
Hadron resonance ideal gas
Refs. J.Rafelski PLB(1991)333
J.Sollfrank et al. PRC59(1999)1637
Particle density
of each particle
Qi
si
gi
mi
: 1 for u and d, -1 for u and d
: 1 for s, -1 for s
: spin-isospin freedom
: particle mass
Tch
mq
ms
gs
: Chemical freeze-out temperature
: light-quark chemical potential
: strangeness chemical potential
: strangeness saturation factor
All resonances and unstable particles are decayed
Comparable particle ratios to experimental data
Masashi Kaneta, First joint Meeting of the Nuclear Physics Divisions of APS and JPS
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Chemical fit result
Ratio (chemical fit)
Central
BRAHMS
PHENIX
PHOBOS
STAR
K+/h
p/p
K*0/h
K0s/h
Chemical freeze-out
parameters
Tch = 179±4 MeV
mB
= 51±4 MeV
ms
= -0.8±2.0 MeV
gs
= 0.99 ±0.03
c2/dof = 1.5
X/h
X+/h
Ratio (data)
Model:
M.Kaneta, Thermal Fest (BNL, Jul 2001),
N.Xu and M.Kaneta, nucl-ex/0104021
Masashi Kaneta, First joint Meeting of the Nuclear Physics Divisions of APS and JPS
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Chemical freeze-out
Lattice QCD predictions
central collisions
• Beam energy
dependence
RHIC
130GeV
 Temperature increases
 Baryon chemical
potential decreases
SPS
• At RHIC
Baryon Chemical Potential mB [GeV]
 Being close to phase
boundary
 Fully strangeness
equilibration (gs~1)
Neutron
star
parton-hadron phase boundary
<E>/<N>~1GeV, J.Cleymans and
K.Redlich, PRC60 (1999) 054908
Masashi Kaneta, First joint Meeting of the Nuclear Physics Divisions of APS and JPS
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Identified single particle spectra
• Transverse momentum distributions
 Boltzmann-like distribution
 Information of thermal (kinetic) freeze-out
• Temperature
• Radial flow
 The pressure gradient generates collective motion
s
u (t, r, z  0)  (cosh  , er sinh  , 0)
  tanh1 r
 r   s f ( x, p)
Masashi Kaneta, First joint Meeting of the Nuclear Physics Divisions of APS and JPS
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mT distribution at RHIC
p
0.8
0.6
L
0.6
0.5
0.4
0.4
0.6
centrality
p
p
X+, X
0.4 < pT < 3.6
K-
K+
dE/dx
K0s
0.2 < pT < 2.4
STAR Preliminary
f
K-
K+
Central events
(top 14%)
K*0
kink method
Statistical error only
MT-M0 (GeV/c2)
Masashi Kaneta, First joint Meeting of the Nuclear Physics Divisions of APS and JPS
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Slope parameter vs. centrality and mass
from Quark Matter 2001
p
p
K
K
p
from J. Burward-Hoy’s talk
in Thermal fest (BNL, Jul 2001)
p
from H.Long’s talk
this meeting
• Inverse slope parameter
 Increasing
• with centrality
• with particle mass
Masashi Kaneta, First joint Meeting of the Nuclear Physics Divisions of APS and JPS
L
L
K 0s
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Radial flow and temperature
Tth = 120+50-25 [MeV]
<r>= 0.52+0.12-0.08 [c]
PHENIX Preliminary
from J. Burward-Hoy’s talk
in Thermal fest (2001 Jul.)
solid : used for fit
K-
p-
c2 /dof = 30.4/35
Tth ~ 104  21 [MeV]
< r > ~ 0.5  0.1 [c]
p
L
fit by M.Kaneta
to STAR Preliminary data
• Spectra are describe by Tth and < r >
• Also, hydrodynamical model can
reproduce the data
The model is from E.Schenedermann et al. PRC48 (1993) 2462
based on Blast wave model
Masashi Kaneta, First joint Meeting of the Nuclear Physics Divisions of APS and JPS
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Tth and <r> systematic
 saturates around AGS
energy
 increased at RHIC?
• Tth
PHENIX
STAR
Tth [GeV]
<r> [c]
• <  r>
 saturates around AGS
energy
 behavior in (1-10 GeV)
predicted by Stocker et al.
in 1981 and Hagedorn
• Need 200GeV data
and lower energy data
Masashi Kaneta, First joint Meeting of the Nuclear Physics Divisions of APS and JPS
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Event anisotropy
• The pressure gradient generates
collective motion (aka flow)
 Central collisions
z
• radial flow
 Peripheral collisions
• radial flow and
anisotropic flow
y
x
Almond shape
overlap region in
coordinate space
y 2  x 2 
 2
y + x 2 
Momentum space
v2  cos2f
f  atan
Masashi Kaneta, First joint Meeting of the Nuclear Physics Divisions of APS and JPS
py
px
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v2 vs. centrality at RHIC
Charged hadron mid-rapidity: | |<1.0
Hydrodynamic limit
STAR: PRL86 (2001) 402
PHOBOS preliminary
• Central region
follows
Hydrodynamical
model at RHIC
(PHOBOS : Normalized Paddle Signal)
Masashi Kaneta, First joint Meeting of the Nuclear Physics Divisions of APS and JPS
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v2 of identified particle
• Blast wave mode and hydrodynamical model can
describe data in low pT (~2GeV/c)
• Mass dependence
Event anisotropy v2
Event anisotropy v2
 Typical hydrodynamic behavior
STAR PRL87 (2001)182301
p
K
p
Hydrodynamical model results
L
STAR preliminary
0.2
from J. Fu’s talk
this meeting
0.1
STAR Preliminary
from this meeting
0
dashed
solid
Tth [MeV]
135  20
100  24
<br> [c]
0.52  0.02
0.54  0.03
pT [GeV/c]
0
1
2
3
pT [GeV/c]
Masashi Kaneta, First joint Meeting of the Nuclear Physics Divisions of APS and JPS
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Energy dependence of v2
• Elliptical flow v2 increases with collision energy
min-bias
charged hadron
Data
RQMD(v2.4)
Masashi Kaneta, First joint Meeting of the Nuclear Physics Divisions of APS and JPS
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Particle correlation (HBT)
• Probe of the space
time extent of heavy
ion collisions
• Radius parameters
 space-time geometry
of the emitting source
 dynamical information
(e.g. collective flow)

1
R
Masashi Kaneta, First joint Meeting of the Nuclear Physics Divisions of APS and JPS
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Radius parameters
pp correlation
pT  170MeV/c
• similar radius with SPS!
• strong spacemomentum correlation?
Kt = pair Pt
Rout
Rside
STAR data : PRL87(2001) 082301
Masashi Kaneta, First joint Meeting of the Nuclear Physics Divisions of APS and JPS
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Radii vs. pT
• Blast wave model describes pT
dependence
 Consistent Tth and r with them
from spectra and v2
Blast wave model :
Mike Lisa, ACS Chicago, 2001
STAR PRL87(2001) 082301
PHENIX Preliminary from this meeting
p+p+
pp
• However
 Hydrodynamical QGP + (uRQMD
or RQMD) can not reproduce Ro<Rs
model:
R=13.5 fm, t=1.5 fm/c
Tth=0.11 GeV, r = 0.5 c
PRL86 (2001) 3981
S. Soff, S.A. Bass and
A. Dumitru
pT [GeV/c]
Masashi Kaneta, First joint Meeting of the Nuclear Physics Divisions of APS and JPS
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Summary (I)
• Many new interesting results from RHIC year 1
• Not yet baryon free (p/p<1)
• Chemical freeze-out
 Tch~180 MeV, mB~50 MeV, ms~0 MeV, gs~1 (central)
• Full strangeness equilibration!
• Close to phase boundary!
• Thermal freeze-out




Consistent results from spectra, HBT, and v2
Tth~100-140MeV, <r>~0.5
Larger flow than one at SPS
Success of hydrodynamical approach
• mT spectra, v2 ,and HBT (but only by blast wave model)
Masashi Kaneta, First joint Meeting of the Nuclear Physics Divisions of APS and JPS
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Summary (II)
• All hadrons are at same thermal freeze-out?
• p, K, p, and L
• Seem to have common Tth and radial flow
• Inverse slope parameters increase with mass
• However…
 Cascade (X) seems to freezeout early
STAR preliminary
PHENIX preliminary
SPS
• Multi strange particle is one of
keys for information of early
stage
Masashi Kaneta, First joint Meeting of the Nuclear Physics Divisions of APS and JPS
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Open issues
• What stage is the origin of strong flow?
 Partonic and/or hadronic level?
• We don’t have a perfect microscopic model
to describe data!
• Thermal/statistical model assumes ideal gas
 The source may not be ideal gas in real world
• How to connect from hadron observable to
parton level?
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