Masashi Kaneta, LBNL Masashi Kaneta for the STAR collaboration Lawrence Berkeley National Lab. First...
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Transcript of Masashi Kaneta, LBNL Masashi Kaneta for the STAR collaboration Lawrence Berkeley National Lab. First...
Masashi Kaneta, LBNL
Masashi Kanetafor the STAR collaboration
Lawrence Berkeley National Lab.
First results from STAR experiment at RHIC- Soft hadron physics -
Masashi Kaneta, LBNL
Focus onHadrons
Measured : h, ±, K±, K0s, K*0, K*0, p, p, d, 3He, 3He,
t,In future : 0 +’, , J/ and more
Freeze-out conditions of low momentum hadrons by
Spectra/Ratios• Thermal/Chemical Freeze-out
Particle correlations• Size parameters, Phase space density
Event anisotropy• v2
Masashi Kaneta, LBNL
Spectra
Momentum distributionsInformation of thermal (kinetic) freeze-out
The inverse slope parameter of mT distribution reflects temperature and radial flow
Masashi Kaneta, LBNL
Only stat. errors are shown
p
K-
central collisions
6%11-1
8%
26-3
4%
45-5
8%
58-8
5%
Identified particle spectra
p
K-
central collisions
6%11-1
8%
26-3
4%
45-5
8%
58-8
5%
Only stat. errors are shown
Masashi Kaneta, LBNL
Thermal(Kinetic) freeze-out
Thermal freeze-out at RHICTemperature is similar at SPSLarger radial flow than at SPS
STAR (sNN=130 GeV)
c
T fo
60.0
MeV95
Hydrodynamical model: E. Schnedermann et al.PRC48(1993)2462
mT-mass [GeV/c2]
mass [GeV/c2]
Inve
rse
slop
e pa
ram
eter
[G
eV/c
2 ]
Masashi Kaneta, LBNL
Ratios
pT dependence anti-particle/particleTest slope for particle and anti-particle
Anti-baryon/baryon ratioStopping or transparent?
Particle ratios from hadronsChemical freeze-out parameters
Masashi Kaneta, LBNL
p/p ratio
Minimum bias dataNo or weak pT dependence
Submitted to PRLSystematic errors<10%
Masashi Kaneta, LBNL
/ ratio
No significant pT dependence in the ratio
The mean ratio = 0.72±0.04
From 200 K Central trigger Au+Au Events (top ~15% multiplicity.)
Systematic errors are under evaluation
|y|<0.5
r
atio
Masashi Kaneta, LBNL
Multiplicity dependence of ratios
Not baryon free at mid-rapidity
An effect of anti-baryon absorption in central collisions?
(nch/nmax)
/ Preliminary
Preliminary
P e r i p h e r a l C e n t r a l
p/p submitted to PRL pT 0.6-0.8 GeV/c |y|<0.3
Only statistic errors are shown Systematic errors p/p : 10%
and : under evaluation
ratio
Masashi Kaneta, LBNL
Chemical freeze-out
Baryonic Potential B [MeV]
Chem
ical Tem
pera
ture
Tch
[M
eV
]
0
200
250
150
100
50
0 200 400 600 800 1000 1200
AGS
SIS
LEP/
SppS
SPS
quarks-gluons
hadrons
RHIC
Experimental ratio
Mod
el p
redi
ctio
n of
rat
io
48±12B
Masashi Kaneta, LBNL
HBT
Pion HBTCentralityTransverse momentumThe HBT excitation function
Phase space densityEvent-by-Event HBTK0
s K0s,
pp, pp correlationsNon-identical particles
Many topics in STAR measurement
The HBT excitation function Focus in this talk
Masashi Kaneta, LBNL
The HBT excitation function
Compilation 3D -HBT parameters as a function of s
• ~10% Central Au+Au(Pb+Pb) events• y ~ 0 • kT 0.17 GeV/c
STAR PreliminaryNo significant jump
from SPS to RHICWe need energy scan between both energy
Masashi Kaneta, LBNL
Event anisotropy
In momentum spaceAnisotropy measured as second harmonic parameter v2
v2 will be scale to initial shape parameter ,
if the source has a hydrodynamical expansion
x
y
p
patan2cos2 v
Momentum space
Almond shape overlap region in coordinate space
y2 x2 y2 x2
Masashi Kaneta, LBNL
Charged particle v2 versus Multiplicity
PRL 86, (2001) 402
|| < 1.3
0.1 < pT < 2.0
Boxes show “initial spatial anisotropy” scaled by 0.19-0.25
nch = primary tracks in || < 0.75
Masashi Kaneta, LBNL
Comparison with a hydrodynamical model
Hydrodynamical calculations: Huovinen, Kolb and Heinz
Masashi Kaneta, LBNL
Charged particle anisotropy 0<pT<4.5 GeV/c
Minimum bias data
Only statistical errors
Systematic error 10% - 20% for pt = 2 – 4.5 GeV/c
Masashi Kaneta, LBNL
Summary
Net-baryon 0 at mid-rapidityAnti-baryon/baryon ratios are toward 1, but still <1
Chemical Freeze-outTch : same or higher than at SPS
B : smaller than at SPS
HBT parametersSimilar to SPS
Large anisotropic flowFrom mid-central to central data,Hydrodynamical model can describe v2 at low pT (<2GeV/c)
Thermal Freeze-outTfo : similar to SPS/AGSLarge radial flow
We need energy scan between SPS and RHIC!
Masashi Kaneta, LBNL
Future plansTOF
PID up to 2GeV/c of pT
SVTIncreasing momentum resolutionMore strangeness baryons
EMCElectron measurement
Full fieldsHigher pT measurementIncreasing momentum resolution
With high statistics
Physics of0, and resonances