charged and neutral kaon correlations in au-au collisions at sqrt(s_nn) = 200 gev using the...
DESCRIPTION
Measurable! F.T. of pion source 1 m r1r1 r2r2 p1p1 p2p2 source (x) x1x1 x2x2 5 fm 1-particle probability (x,p) = U * U 2-particle probability HBT : Probing source geometryTRANSCRIPT
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Charged and Neutral Kaon correlations in Au-Au Collisions at sqrt(s_NN) = 200 GeV using the
solenoidal tracker at RHIC (STAR)
Selemon Bekele
The Ohio State University
for the STAR Collaboration
SQM2003 March 12-17, 2003
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Outline
Motivation Charged Kaons
cuts 1D correlations 3D correlations
Neutral Kaons cuts C2 The f0(980) problem
Summary Outlook
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2
21
2121 )q(~1
)p(P)p(P)p,p(P)p,p(C C
(Qin
v)
Qinv (GeV/c)
1
2
0.05 0.10
Width ~ 1/R
Measurable! F.T. of pion source
222111 p)xri(22
p)xri(11 )p,xU()p,x U(
eeT1 m
r1
r2
p1
p2
source(x)
x1
x2
{2
1
}e)p,x(Ue)p,x(U 212121 p)xr(i21
p)xr(i12
5 fm
12 ppq 1-particle probability
(x,p) = U*U
)xx(iq2
*21
*1T
*T
21e1UUUU
2-particle probability
HBT : Probing source geometry
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Motivation Physics
-Kaon HBT has been suggested as a promising probe of QGP
-Kaon HBT reveals information about strangeness dynamics
M. Gyulassy, Phys. Lett B 286 (1992) 211
-Kaons are less affected by decay of long lived resonances
Technical
-No distortions due to Coulomb interaction
-K0s K0
s HBT extends particle correlation systematics to higher pt allowing studies
of Mt scaling, collective flow effects etc.
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K0s K0
s HBT extends particle correlation systematics to higher pt
WA97
F. Antinori et al. Nucl. Phys. A661 (1999) 130c
No conclusive measurements so far
protons
kaons
pions
electrons
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Charged Kaon Cuts
Main Cutscentral events -0.5 < y < 0.5
for 1D correlations
0.25 GeV < kT < 0.45 GeV
for 3D correlations
0.15 GeV < kT < 0.35 GeV 0.35 GeV < kT < 0.45 GeV
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1)(1)(1)()(
qGqKNqBqA
coul
))(1()()(
)( qGNqKqB
qA
coul
Standard fit
ondistributipair event" mixed")(ondistributipair real"")(
constantion normalizat
)1coul(K Correction Coulomb undiluted"")(formGaussian
,2
)(
qBqAN
qcoulK
ji jqiqijReqG
Bowler/Synukov/CERES
where
Fitting the correlation functions
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STAR Preliminary
Fits to 1D correlation functions
What coulomb radius is used for the correction does not seem to make much difference .
Lambda = 0.333 +- 0.04Rinv = 3.72 +- 0.1 fm
K-K-
K-K-K-K-
STAR Prelim
inary
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Out Side
Long
(qOut, qLong < 45 MeV)(qSide, qLong < 45 MeV)
(qSide, qOut < 45 MeV)
Projections of 3D fits using the standard procedure
Lambda = 0.5096 +- 0.0168Ro = 2.942 +- 0.0685 fmRs = 2.97 +- 0.0668fmRl = 3.29 +- 0.764 fm
))(1()()(
)( qGNqKqB
qA
coul
K- K-
K- K-
K- K-
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Lambda = 0.2871 +- 0.025Ro = 3.62 +- 0.145 fmRs = 3.21 +- 0.134 fmRl = 3.92 +- 0.154 fm
Lambda is small for the Bowler correction !
Out Side
Long
(qSide, qLong < 45 MeV)
(qSide, qOut < 45 MeV)
(qOut, qLong < 45 MeV)
Projections of 3D fits using the Bowler/Synukov procedure
No corrections for purity and momentum resolution
1)(1)(1)()(
qGqKNqBqA
coul
K- K-
K- K-
K- K-
STAR Prelim
inary
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K0s Reconstruction
Vo
dca between daughters
dca of daughters to primary vertex
dca of V0 to primary vertex
decay length
DCA – distance of closest approach
V0 Cuts
central events 0.1 < pt < 3.5 -1.5 < y < 1.5
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K0sK0
s Correlation Function
C2
STAR Prelim
inary
Gives the values
Lambda = 0.506 0.133 Rinv = 5.765 0.691
)exp(1),( 22qRqPC
Fitting to a gaussian
K0s mass peak (Not Background subtracted)
X 10
M (GeV/C2)
Number of K0s
Mean ~ 3.79 / Event
Num
ber o
f eve
nts K0
s multiplicity
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1) 2)
3)Signal Lorentzian
Background 1 ) a + b x 2 ) a + b xc
3 ) a/x + b/(1 + x)
Needs more study
Signal + BackgroundSignal
Background
Signal to Noise studies
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pions K-
Ro
Rs
Rl
Hydro Mt scaling seems to be obeyed for the charged pions and Kaons.
STAR Prelim
inary
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Mt Scaling violated?
Rinv for the neutral Kaons seems to indicate that Mt scaling is not obeyed as for the charged pions and Kaons.
pions K- K0
s
Mt (Gev/c)
R STAR Prelim
inary
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What is the effect of the f0(980)?
Mass of f0(980) = 980 +- 10 MeV
width = 40 - 100 MeV.
=> lifetime ranges between 1.97 fm/c and 4.93 fm/c
Dominant decay mode is pions
Branching ratio to kaons is unknown
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Only those f0s which fall in the shaded region can decay to K0s, since the mass of a K0s is 0.498 GeV
, 1
4)2(
1 22)/(
2
3 iiTEi mpEe
dppni
Ratio of f0(980) to K0s as a function of temperature
f0s are selected from a Briet-wigner mass distribution
M = 0.996
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Correlation function for a pure K0 sample
The effect of the f0 particleassuming the worst case scenario where its decay products are only kaons
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Results from a gaussian fit
The radius changes by a small amount while the lambda seems to be affected most.
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1D and 3D correlations of Charged Kaons preliminary results
Not yet corrected for purity and momentum resolution
1D K0sK0
s correlations preliminary results
Not corrected for purity and momentum resolution The f0(980) effect seems to be small
Summary
Lambda = 0.2871 +- 0.025Ro = 3.62 +- 0145 fmRs = 3.21 +- 0.134 fmRl = 3.92 +- 0.154 fm
Lambda is small for the Bowler procedure!
Lambda = 0.506 0.133 Rinv = 5.765 0.691
Lambda = 0.333 +- 0.04Rinv = 3.72 +- 0.1 fm
K-K-
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Charged Kaon correlations
we need to do more systematic studies purity estimate/correction momentum resolution
with more statistics Multiplicity dependence
Neutral Kaon correlations
we need to do purity estimate/correction momentum resolution
Outlook
Hopefully new results by next Analysis Meeting