charged and neutral kaon correlations in au-au collisions at sqrt(s_nn) = 200 gev using the
DESCRIPTION
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. Outline. Motivation Charged Kaons cuts 1D correlations - PowerPoint PPT PresentationTRANSCRIPT
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
Outline
Motivation Charged Kaons
cuts 1D correlations 3D correlations
Neutral Kaons cuts C2 The f0(980) problem
Summary Outlook
2
21
2121 )q(~1
)p(P)p(P)p,p(P
)p,p(C
C (Q
inv)
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
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.
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
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
1)(1)(1)(
)( qGqKN
qB
qAcoul
))(1()()(
)( qGN
qKqB
qA
coul
Standard fit
ondistributipair event" mixed")(
ondistributipair real"")(
constantion normalizat
)1coul(K Correction Coulomb undiluted"")(
formGaussian ,
2
)(
qB
qA
N
qcoulK
ji jqiqijR
eqG
Bowler/Synukov/CERES
where
Fitting the correlation functions
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 Pre
limin
ary
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()()(
)( qGN
qKqB
qA
coul
K- K-
K- K-
K- K-
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)(
)( qGqKN
qB
qAcoul
K- K-
K- K-
K- K-
STAR Pre
limin
ary
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
K0sK0
s Correlation Function
C2
STAR Pre
limin
ary
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
Nu
mb
er o
f ev
ents
K0s multiplicity
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
pions K-
Ro
Rs
Rl
Hydro Mt scaling seems to be obeyed for the charged pions and Kaons.
STAR Pre
limin
ary
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)
RSTAR P
relim
inary
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
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
dppn
i
Ratio of f0(980) to K0s as a function of temperature
f0s are selected from a Briet-wigner mass distribution
M = 0.996
Correlation function for a pure K0 sample
The effect of the f0 particleassuming the worst case scenario where its decay products are only kaons
Results from a gaussian fit
The radius changes by a small amount while the lambda seems to be affected most.
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-