masashi kaneta, lbnl masashi kaneta for the star collaboration first results from star experiment at...
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![Page 1: Masashi Kaneta, LBNL Masashi Kaneta for the STAR collaboration First results from STAR experiment at RHIC Lawrence Berkeley National Lab](https://reader038.vdocuments.site/reader038/viewer/2022110211/56649ef45503460f94c070b5/html5/thumbnails/1.jpg)
Masashi Kaneta, LBNL
Masashi Kanetafor the STAR collaboration
First results from STAR experiment at RHIC
Lawrence Berkeley National Lab.
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Masashi Kaneta, LBNL
The STAR collaboration
~ 400 collaborators 34 institutions 7 countries
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Masashi Kaneta, LBNL
STAR InstitutionsU.S. Labs:
Argonne, Berkeley, and
Brookhaven National Labs
U.S. Universities:
Arkansas, UC Berkeley,
UC Davis, UCLA,
Carnegie Mellon, Creighton,
Indiana, Johns Hopkins,
Kent State, MIT, MSU,
CCNY, Ohio State,
Penn State, Purdue, Rice,
UT Austin, Washington,
Wayne State, Yale
Brazil :
Universidade de Sao Paol
England:
University of Birmingham
France:
Institut de Recherches Subatomiques Strasbourg, SUBATECH – Nantes
Germany:
Max Planck Institute – Munich, University of Frankfurt
Poland:
Warsaw University Warsaw University of Technology
Russia:
MEPHI – Moscow, LPP/LHE JINR – Dubna, IHEP – Protvino
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Masashi Kaneta, LBNL
STAR DetectorYear1 Ready for next run Next year(2002) or later
ZDC
Silicon Vertex Tracker
Central Trigger Barrel
FTPCs
Barrel EMC (install over next 4 years)
Vertex Position Detectors
Endcap EMC (half in 2003)
Magnet
Coils
TPC Endcap & MWPC
ZDC
RICH
yr.1 SVT ladder
+ TOF patch
Silicon Strip Detector
Time Projection Chamber
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Masashi Kaneta, LBNL
Au+Au, sNN=130 GeV
Central EventFrom real-time Level 3 display.
~2000 tracks in 200msec
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Masashi Kaneta, LBNL
Particle identification
K
p
e
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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
Low pT spectra
h, , K, p Thermal freeze-out
High pT spectra
hhard process
Particle ratios, yield (dN/dy, dN/d)p/p, , , K/K, K/, p/, K*0/h
Stopping Chemical freeze-out
d/p Coalescence
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Masashi Kaneta, LBNL
h- multiplicity
6% systematic error shown on 3 points only
Preliminary
5% Central
ZD
C p
ulse
hei
ght
CTB pulse height
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Masashi Kaneta, LBNL
h- centrality dependence
5%
10%
20%
30%
40%
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Masashi Kaneta, LBNL
h- centrality dependence (cont.)
15% Increase in <pT> from 80% sample to top 5% central
NA49UA1
STAR, Preliminary
STAR, Preliminary
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Masashi Kaneta, LBNL
h- pT distribution
STAR Preliminary
Statistical errors negligibleErrors on points: systematic error on STAR dataGray bars: cumulative error including UA1 scalingHard: Binary collisions TAA = 26 ± 2 mb-1
Soft: Wounded nucleon
STAR Preliminary
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Masashi Kaneta, LBNL
Particle Identification
dE/dxe, , K, p
Kink, V0, Mixed eventKaon to muon decay, etc.Resonances
Kd
e
p
“kinks”:
K +
Vo
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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
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Masashi Kaneta, LBNL
K+K-
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Masashi Kaneta, LBNL
Identified particle spectra
Inverse slope:56540(sta.)50(sys.) MeV
Inverse slope:19015(sta.)20(sys.) MeV
-
K-p
Inverse slope:30015(sta.)30(sys.) MeV
central collisions
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Masashi Kaneta, LBNL
Inverse slope vs. centrality
K- (kink)
P e r i p h e r a l C e n t r a l
STAR Preliminary Indicate increased radial flow in central collisions at RHIC
Event fraction [%]
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Masashi Kaneta, LBNL
Kink K
Kaon from muon decay
K
Inverse slope:2675(sta.)10(sys.) MeV
Inverse slope:2725(sta.)10(sys.) MeV
K-K+
|y|<0.5Event fraction = top 7%
STAR Preliminary STAR Preliminary
|y|<0.5Event fraction = top 7%
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Masashi Kaneta, LBNL
“Kink” Rapidity Distribution
Mid-y K+ dN/dy = 35 ±3(stat.)±5(sys.)
Mid-y K- dN/dy = 30±2.5(stat.)±4(sys.)
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Masashi Kaneta, LBNL
mT distribution from Hydro model
Cylindrical source
Flow profile included
u t r z er ( , , ) (cosh , sinh , )= =
β= −tanh 1r ( )β βr s r R= /
R
βs
Ref. : E.Schnedermann et al, PR C48 (1993) 2462
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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
>=<
=
β
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
p/p ratioMinimum bias dataSystematic errors<10% for bothNo or weak pT and rapidity dependence
rapidity
STAR submittedSTAR submitted
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Masashi Kaneta, LBNL
and
~0.84 /event, ~ 0.61/event
V0Mixed event
Higher statistics than V0 method (~10 times/event)
Invariant mass [GeV] Invariant mass [GeV]
Top 15% central event
Minimum Bias (150K event)
0<p<2GeV/c
STAR submitted
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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
ra
tio
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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
+ and -
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Masashi Kaneta, LBNL
Centrality dependence of ratios
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
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Masashi Kaneta, LBNL
Centrality dependence of ratios (cont.)
K+/K ratio seems to be independent of centrality in each measurement
STAR preliminary
dE/dx KinksSTAR preliminarypT < 0.35 GeV/c
# primary trackdN/d
K+/K
rat
io
K+/K
rat
io
P e r i p h e r a l C e n t r a l P e r i p h e r a l C e n t r a l
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Masashi Kaneta, LBNL
K/ and p/ ratios
K-/- , p/-
enhanced by ~2 in central vs. peripheral collisions
p/K ~ constant
In central collisions:
K-/- 15%
p/- 8%
P e r i p h e r a l C e n t r a l
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Masashi Kaneta, LBNL
K*0K++-
Central events (top 14%)
primary tracks: K+-
K* signalmK*0 = 0.8930.003 [GeV]
K*0 = 0.058 0.015 [GeV] (stat. error only)
PDG mK*0 = 0.89610.00026 [GeV] K*0 = 0.05070.0006 [GeV]
Background estimate: 20%
Breit-Wigner
)4/)((2 220 +−
MmA
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Masashi Kaneta, LBNL
K*0K-++
Central events (top 14%)
primary tracks: K-+
K* signalmK*0 = 0.8960.004 [GeV]
K*0 = 0.063 0.011[GeV] (stat. error only)
PDG mK*0 = 0.89610.00026 [GeV] K*0 = 0.05070.0006 [GeV]
Background estimate: 18%
Breit-Wigner
)4/)((2 220 +−
MmA
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Masashi Kaneta, LBNL
K*0
The first measurement of K*0 in heavy ion collisionsK
*0/h
K*0/h
(K*0 +K*0)/2 / h
Centrality h/hmax
K*0/hSTAR preliminary
Only statistical errors are shownSystematic error ~ 25%
|y|<0.50.2<pT<2.0 GeV/c
pp (s=63GeV) : K*0/
e+e (s=91GeV) : K*0/
h : ||<0.5 pT>0.1 GeV/c
P e r i p h e r a l C e n t r a l
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Masashi Kaneta, LBNL
Summary of ratios
Anti-particle/particle ratio is flat as a function of pT
Anti-baryon/baryon ratio is larger than at SPS, but not baryon free at mid-rapidity at RHIC
(stat.) (sys.) (Event fraction)
p/p = 0.60 0.02 0.06 (top6%)
/(M.B. trig.) = 0.70 0.02 (top8%)
/(central trig.) = 0.72 0.04 (top15%)
- = 0.82 0.08 (top15%)
K+/K-(kink) = 1.17 0.07 (top15%)
K+/K-(dE/dx) = 1.14 0.01 0.06 (top6%)
K-/- = 0.15 0.02 (top6%)
p/- = 0.080 0.008 (top6%)
K*0/h- = 0.060 0.006 0.015 (top15%)
K*0h- = 0.058 0.006 0.015 (top15%)
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Masashi Kaneta, LBNL
sq sq +=
Chemical freeze-out model
Comparable particle ratios to experimental data
q: 1 for u and d, -1 for u and d q: lightquark chemical potential
s: 1 for s, -1 for s s: strangeness chemical potential
Particle densityof each particle
Decay all resonances
g : spi-isospin freedom
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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
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Masashi Kaneta, LBNL
HBT
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Masashi Kaneta, LBNL
Particle correlations (HBT)
Size parametersTransverse and longitudinal direction
Duration time• From Rout and Rside
Phase space density• Combination of radius parameter and yield
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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
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Masashi Kaneta, LBNL
3D analysis
Information:
• source size
• duration time (for transparent sources)
)(
)2()1(
)2,1(
21
222222
1),( LongLongSideSideOutOut RqRqRq
mixedNrealN
pPpP
ppPeppC ++−+=== λ
Pratt-Bertsch Parameterization (measured in the LCMS frame; (p1+ p2)z=0)
βτ 22SideOut RRÄ −=
p1
qOut
p2
qSide
x
y p1+p2
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Masashi Kaneta, LBNL
3 Dimensional - - HBT
Top 12% central events
0.125<pT<0.225 [GeV/c]
|y|<0.5
1D Projections of the 3D Pratt-Bertsch Parameterization
21.012.007.7
16.009.047.5
23.011.086.5
03.001.050.0
±±=±±=±±=±±=
Long
Side
Out
RRR
λ
qSide,qLong<20MeV/c qOut,qLong<20MeV/c
Systematic error result from the pair cuts (merging) and Coulomb correction
C(q
out)
C(q
Sid
e)
qout [GeV/c] qSide [GeV/c]
C(q
Long
)
qLong [GeV/c]
qOut,qSide<20MeV/c
[fm]
[fm]
[fm]
Coulomb corrected with a 5 fm source
No Coulomb correction
(sta.) (sys.)
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Masashi Kaneta, LBNL
Centrality dependence0.125 GeV/c < pT <0.225 GeV/c
tot: 32-72% 12-32% 0-12%
STAR Preliminary• ++, --, parameters similar
• λ`s don’t change with multiplicity• radii increase with multiplicity• roughly similar to AGS/SPS
Comparison with AGS/SPS • parameters roughly same • similar increase in ROut, RSide (geometric effect)
sys.error
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Masashi Kaneta, LBNL
mT dependence12 % most central events
0.125<pT<0.225 [GeV/c]
STAR Preliminary
0.225<pT<0.325 [GeV/c]0.325<pT<0.450 [GeV/c]
• ++, -- HBT parameters similarwith increasing mT
λ increases fewer resonances• radii decrease
position-momentum correlations
Comparison with AGS/SPS• parameters roughly similar to AGS/SPSWith increasing mT
• similar increase in λ• similar decrease of radii• stronger effect in ROut than at
AGS/SPS
2/)( 21TTT ppK +=
STAR
Preliminary
sys.error
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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 anisotropyThe pressure gradient generates collective motion (aka flow)
Central collisions• radial flow
Peripheral collisions
• radial flow and anisotropic flow
Momentum spaceAlmond shape overlap region in coordinate space
ε =⟨y2 −x2⟩⟨y2 +x2⟩
x
z
y
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Masashi Kaneta, LBNL
Charged particle v2 versus centrality
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
Excitation function
WA98
NA49
h-
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Masashi Kaneta, LBNL
Charged and p+p, v2(pT) (M.B.)
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Masashi Kaneta, LBNL
A Hydro view of the world
Hydro calculations: Huovinen, Kolb and Heinz
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Masashi Kaneta, LBNL
Charged particle anisotropy 0<pT<4.5 GeV/c
Only statistical errors
Systematic error 10% - 20% for pt = 2 – 4.5 GeV/c
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Masashi Kaneta, LBNL
Conclusions
Net-baryon 0 at mid-rapidity! Anti-baryon/baryon ratios are toward 1, but still <1
Chemical Freeze-outTch ~ 200 GeV (150-200 MeV @ SPS,90-150 MeV @ AGS)
B ~ 50 MeV (200-270 MeV @ SPS,550-600 MeV @ AGS)
Large anisotropic flowHydro model can describe v2 an low pT (<2GeV/c)
Large v2 early thermalization
Thermal Freeze-outStrong space-momentum correlationsLarge radial flow ~ 0.6c (SPS/AGS <ß>= 0.4-0.5c)Tfo = 95-110 MeV (similar to SPS/AGS)