first results from star experiment at rhic - soft hadron physics -
DESCRIPTION
First results from STAR experiment at RHIC - Soft hadron physics -. Masashi Kaneta for the STAR collaboration Lawrence Berkeley National Lab. Focus on. Hadrons Measured : h - , p ± , K ± , K 0 s , K *0 , K *0 , p , p , d , 3 He , 3 He , t , L , L , X - , X + , - PowerPoint PPT PresentationTRANSCRIPT
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Masashi Kaneta, LBNL
Masashi Kanetafor the STAR collaboration
Lawrence Berkeley National Lab.
First results from STAR experiment at RHIC- Soft hadron physics -
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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
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Masashi Kaneta, LBNL
Spectra
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Masashi Kaneta, LBNL
Spectra
Momentum distributionsInformation of thermal (kinetic) freeze-out
The inverse slope parameter of mT distribution reflects temperature and radial flow
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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
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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 ]
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Masashi Kaneta, LBNL
Ratios
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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
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Masashi Kaneta, LBNL
p/p ratio
Minimum bias dataNo or weak pT dependence
Submitted to PRLSystematic errors<10%
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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
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Masashi Kaneta, LBNL
K+/K ratiora
tio
pT [GeV/c]
STAR Preliminary
|y|<0.5Event fraction = top 7%
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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
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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
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Masashi Kaneta, LBNL
HBT
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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
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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
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Masashi Kaneta, LBNL
EventAnisotropy
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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
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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
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Masashi Kaneta, LBNL
Charged and p+p, v2(pT) (M.B.)
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Masashi Kaneta, LBNL
Comparison with a hydrodynamical model
Hydrodynamical calculations: Huovinen, Kolb and Heinz
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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
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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!
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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
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Masashi Kaneta, LBNL
Typical e+e pairfrom
e+
e+
e+
e+
e-
e-
e-e-
invariant mass [GeV]
STAR Preliminary
and0
The e+e pair from conversion is measured
Large acceptance pT = 50 MeV/c to ~4 GeV/c, ||<1.8