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
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.
Berkeley School 05.24.07.2
STARSTAROutline
• Motivation• Data sample, Proton selections,
& V0 reconstruction• Event plane reconstruction• V1 result• Discussion and Summary
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
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
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
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
)
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
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
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
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
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
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
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
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%
Berkeley School 05.24.07.15
STARSTAR
v1=ay dv1/dy =-3.2±1.7
Ks v1 vs. Rapidity(62GeV)
STAR Preliminary
Berkeley School 05.24.07.16
STARSTAR
Work in progress.
& v1 vs. Rapidity
STAR Preliminary STAR Preliminary
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).