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 (for the STAR Collaboration) Institute of Particle Physics, Wuhan, P.R. China Brookhaven National Lab. Outline. Motivation Data sample, Proton selections, & V0 reconstruction - PowerPoint PPT PresentationTRANSCRIPT
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STARSTAR
Directed flow of identified particles from Au+Au Collisions at RHIC
Jiayun Chen(for the STAR Collaboration)
Institute of Particle Physics, Wuhan, P.R. ChinaBrookhaven National Lab.
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STARSTAROutline
• Motivation• Data sample, Proton selections, & V0 reconstruction• Event plane reconstruction• v1 results• Discussion and Summary
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STARSTAR
r
pt
Higher harmonics
rapidity
<px> or directed flow
)](cos[
)](cos[2121
1
2
3
3
rn
nrn
tt
nv
nvdydppNd
pdNdE
Anisotropic flow
Directed flow (v1)
Elliptic flow (v2)
Motivation
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STARSTARMotivation
flowantiflow
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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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 Bias 200GeV Au+Au Minimum Bias STAR Preliminary
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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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STARSTAR
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
Event Plane reconstruction
iiinnn
iiinnn
nwYnQ
nwXnQ
)sin()sin(
)cos()cos(
i
iw
)cos(
)sin(tan1 1
ii
i
ii
i
n nw
nw
n
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STARSTARFlattening Event Plane
E877 Collaboration, J. Bareeette et al, Phys.Rev.Lett.70,2996(1993)
Principle of shifting:Make corrections to the event planeangle itself, & flatten the event planedistribution. The corrected event plane angle is
FTPC Raw Phi distributionPrinciple of weighting:Due to detector acceptance effects, theevent plane distribution isn't isotropic. Tocorrect those effects, more weight is givento the particles that are detected at theplace where the least particle are detected.We are compensating for the “blind spots”of the FTPC.
FTPC weighed Psi distribution
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STARSTAREvent PlaneFTPC Event Plane distribution ZDCSMD Event Plane distribution
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STARSTAR
• After the flattening 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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STARSTARResolution of FTPC,ZDCSMD,{FTPC,ZDCSMD}(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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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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STARSTARResolution of FTPC,ZDCSMD,{FTPC,ZDCSMD}(200GeV Au+Au)
Because the directed flow moves to larger pseudo-rapidity at the higher beam energy, the FTPC is less useful. no obvious improvement for combined event plane at 200GeV.
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STARSTARProton & Antiproton v1 vs. Rapidity(200GeV)
Proton 0.4<pT<1.0 (GeV/c) v1=ay dv1/dy = -1.9± 0.8 Antiproton 0.15<pT<1.0 (GeV/c) v1=ay dv1/dy = -0.6± -1.0
with {ZDC-SMDs} RP
STAR Preliminary30%-60%
• Proton v1 is less than 1%,
• Antiproton v1 is less than 2%.
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STARSTARProton & Antiproton v1 vs. Centrality
• v1(proton & antiproton) at 62GeV have weak centrality dependence.
STAR PreliminarySTAR Preliminary
62GeV combined RP 200GeV ZDC-SMDs RP
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STARSTAR
v1=ay dv1/dy =-3.2±1.7
Ks v1 vs. Rapidity(62GeV)STAR Preliminary
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STARSTAR
Work in progress.
& v1 vs. Rapidity(62GeV)STAR Preliminary STAR Preliminary
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STARSTARSummary• The event plane resolution is enhanced by combini
ng EP of FTPC & ZDC-SMD with proper weight;• Au+Au at 62.4GeV & 200GeV
– Proton v1 is less than 1%.– AntiProton v1 is less than 2%.– Weak centrality dependence at 62GeV.
• Made an attempt to study directed flow of K0S & ,
.• Looking forward to analyzing run VII’s data (~60M
MB events).
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STARSTAR
Backup
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STARSTAR
SMD is 8 horizontal slats & 7 vertical slats located at 1/3 of the depth of the ZDC
• New knowledge of the direction of the impact parameter vector• Minimal, if any, non-flow effects• Worse resolution than from TPC, but that disadvantage is minor
ZDC side view
Transverse plane of
ZDC
STAR ZDC-SMD
Scintillator slats of Shower Max Detector
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STARSTARMotivationRQMD 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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STARSTAR Motivation• freeze-out of multi-stra
nge 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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STARSTAR