directed flow of identified particles from au+au collisions at rhic
DESCRIPTION
Directed flow of identified particles from Au+Au Collisions at RHIC. Jiayun Chen Institute of Particle Physics, Central China Normal Uni. Brookhaven National Lab. Outline. Motivation Data sample, Proton selections, & V0 reconstruction Event plane reconstruction V 1 result - PowerPoint PPT PresentationTRANSCRIPT
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STARSTAR
Directed flow of identified particles fr
om Au+Au Collisions at RHIC
Jiayun ChenInstitute of Particle Physics, Central China Normal Uni.
Brookhaven National Lab.
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Berkeley School 05.24.07.2
STARSTAROutline
• Motivation• Data sample, Proton selections,
& V0 reconstruction• Event plane reconstruction• V1 result• Discussion and Summary
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Berkeley School 05.24.07.3
STARSTAR
r
pt
Higher harmonics
rapidity
<px> or directed flow
)](cos[
)](cos[212
1
1
2
3
3
rn
nrn
tt
nv
nvdydpp
Nd
pd
NdE
Anisotropic flow
Directed flow (v1)
Elliptic flow (v2)
Motivation
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Berkeley School 05.24.07.4
STARSTARMotivation
flow
antiflow
Brachmann, Soff, Dumitru, et. al. , PRC 61 (2000) 024909.L.P. Csernai, D. Roehrich PLB 458, 454 (1999) M.Bleicher and H.Stocker, PLB 526,309(2002)
Anti-flow/3rd flow component, with QGP v1 flat at middle rapidity.
Directed flow (v1) and phase transition
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Berkeley School 05.24.07.5
STARSTARMotivation
RQMD v2.4
R.Snellings, H.Sorge, S.Voloshin, F.Wang, N. Xu, PRL (84) 2803(2000)
Positive space-momentum correlation, no QGP necessary v1 wiggle.
Directed flow (v1) and baryon stopping
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Berkeley School 05.24.07.6
STARSTAR Motivation• freeze-out of multi-str
ange hadrons- at higher temperature Tfo
- with lower collective velocity T
→ less interaction of strange hadrons with non-strange hadrons
• sensitivity to the early, partonic stage
Nucl. Phys. A757, 102 (2005)
(GeV
)
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Berkeley School 05.24.07.7
STARSTARProton & Antiproton Selection
Common cut:|Primary Vertex| < 30cmNo. Dedx Points > 10No. fit Points > 20No. fit Points/No. Max [0.52,1.05]Global DCA < 1.0cmnSigma [-2.5,2.5]
Proton: 0.4 < pT <1.0 (GeV/c)
Antiproton: 0.15< pT <1.0 (GeV/c)
DataSet:62GeV Au+Au Minimum Bias200GeV Au+Au Minimum Bias
STAR Preliminary
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Berkeley School 05.24.07.8
STARSTARV0s reconstruction• cuts:
– Distance of closest approach(DCA)
between daughters < 0.8cm– DCA of V0 to Primary Vertex (PV) < 0.5cm– Daugter’s DCA to PV > 0.8 cm– decay length > 6.0cm– daughter’s Tpc Hits > 15
0.48<mass<0.51 1.11<mass<1.12 1.11<mass<1.12
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Berkeley School 05.24.07.9
STARSTAREvent Plane reconstruction
the event plane vector and the event plane angle from the nth harmonic of the particle’s azimuthal distribution are defined by the equations:
-- the azimuthal angle of the ith particle in the event plane determination
-- weights
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Berkeley School 05.24.07.10
STARSTAR
Flattening Event Plane
Step 1:Apply weight which can bedetermined with the inverseof the bin content in the raw distribution.Step 2:Make corrections to the eventplane angle itself, & flattenthe event plane distribution. The corrected event planeangle is
E877 Collaboration, J. Bareeette et al, Phys.Rev.Lett.70,2996(1993)
FTPC Event Plane distribution
ZDCSMD Event Plane distribution
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Berkeley School 05.24.07.11
STARSTAR
• After the flatness of FTPC & ZDCSMD Full EP. The final event plane used is defined by the sum of
Where
• or
weight is from resolution
Combined Event Plane
ZDCSMDZDCSMDFTPCFTPC UweightUweight **
FTPCU
ZDCSMDU
combinedUZDCSMDFTPC UU
yyZDCSMDxxZDCSMDZDCSMD
yyFTPCxxFTPCFTPC
eQeQU
eQeQU
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Berkeley School 05.24.07.12
STARSTARResolution of FTPC,ZDCSMD,{FTPC,ZDCS
MD}(62GeV Au+Au)
The event plane resolution is enhanced by combining EP of FTPC & ZDC-SMD with proper weight.
STAR Preliminary
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Berkeley School 05.24.07.13
STARSTARProton & Antiproton v1 vs. Rapidity(62GeV)
Proton 0.4<pT<1.0 (GeV/c) v1=ay dv1/dy = -0.4± 1.1 Antiproton 0.15<pT<1.0 (GeV/c) v1=ay dv1/dy = 1.3± 1.5
30%-60%
with combined RP
STAR Preliminary
• Proton v1 is less than 1%,
• Antiproton v1 is less than 2%.
30%-60%STAR Preliminary
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Berkeley School 05.24.07.14
STARSTARProton & Antiproton v1 vs. Rapidity(200GeV)
Proton 0.4<pT<1.0 (GeV/c) v1=ay dv1/dy = -2.6± 2.9 Antiproton 0.15<pT<1.0 (GeV/c) v1=ay dv1/dy = 3.1± 3.1
with combined RP
STAR Preliminary30%-60%
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Berkeley School 05.24.07.15
STARSTAR
v1=ay dv1/dy =-3.2±1.7
Ks v1 vs. Rapidity(62GeV)
STAR Preliminary
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Berkeley School 05.24.07.16
STARSTAR
Work in progress.
& v1 vs. Rapidity
STAR Preliminary STAR Preliminary
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Berkeley School 05.24.07.17
STARSTARSummary• The event plane resolution is enhanced by c
ombining EP of FTPC & ZDC-SMD with proper weight;
• Au+Au 62.4GeV/c – Proton v1 is less than 1%.– AntiProton v1 is less than 2%.
• Made an attempt to study directed flow of K0S
& , .• Looking forward to analyzing run VII’s data (~
60M MB events).