rapidity dependence of pion elliptic flow hironori ito 1 erik johnson 2 steve sanders 2 brahms...
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Rapidity Dependence of Pion Elliptic Flow
Hironori Ito1
Erik Johnson2
Steve Sanders2
BRAHMS Collaboration
1Brookhaven National Laboratory2University of Kansas
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BRAHMS Collaboration
I.Arsene, I.G. Bearden7, D. Beavis1, S.Bekele11, C. Besliu10, B. Budick6,
H. Bøggild7, C. Chasman1, C. H. Christensen7, P. Christiansen7, R.Clarke10,
R. Debbe1,J. J. Gaardhøje, K. Hagel8, H. Ito1, A. Jipa10, J. I. Jordre10, F. Jundt2, E.B.Johnson11, J.I.Jordre9, C.Jørgensen7, R. Karabowicz3,
E. J. Kim11,
T.M. Larsen7, J. H. Lee1, Y. K.Lee5, S.Lindal12, G. Løvhøjden2, Z. Majka3,
M. Murray11, J. Natowitz8, B.S.Nielsen7, D.Ouerdane7, R.Planeta4, F. Rami2, C.Ristea7, O.Ristea10, D. Röhrich9, B. H. Samset12, S. J. Sanders11, R.A.Sheetz1, P. Staszel3, T.S. Tveter12, F.Videbæk1, R.
Wada8, H.Yang9, Z. Yin9, and I. S. Zgura10
1Brookhaven National Laboratory, USA, 2IReS and Université Louis Pasteur, Strasbourg, France 3Jagiellonian University, Cracow, Poland, 4Institute of Nuclear Physics, Cracow, Poland, 5Johns
Hopkins University, Baltimore, USA, 6New York University, USA, 7Niels Bohr Institute, University of Copenhagen, Denmark, 8Texas A&M University, College Station. USA, 9University of
Bergen, Norway, 10University of Bucharest, Romania, 11University of Kansas, Lawrence,USA,12 University of Oslo
Norway
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BRAHMS Detector Setup
Event planedetectors
PID detectors
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Event Plane Detectors
Flow Ring 2Si Ring 1
Tile Ring 1
Flow Ring 3
●Flow Ring 2 (silicon strips):● 42 segments per 2π● -2 < η < 0.2
●Flow Ring 3 (silicon strips):● 42 segments per 2π● -2 < η < 1.2
●Si Ring 1 (silicon strips):● 6 segments per 2π● -2.4 < η < 0.8
●Tile Ring 1 (scintillator tile):● 6 segments per 2π● -2 < η < -0.8
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Introduction to Flow
φ
Initial spatial anisotropy... ...final momentum anisotropy
...after rescatteringleads to ...
Elliptic Flow: n = 2
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Rapidity Dependence?Current Status
PHOBOS and STAR have measured p
T
integrated v2
over a wide pseudorapidity range.
→pT integrated
v2 has strong
pseudorapidity dependence.
Charged Hadron
STAR also measured charged hadron v
2(p
T) at forward rapidity, and find a large
pT dependence.
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Method
a,b and c are the Scintillator Tile, the Silicon Strip and the Beam-Beam counters
Methods describe by A. M. Poskanzer and S. A. VoloshinPhys. Rev. C58 (1998) 1671
Nth order event plane
Observed v2
Event plane resolution correction
Real v2
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Particle Identification at Midrapidity
Time-of-Flight Identification● Pions: 2.5 GeV/c● Protons: 4 GeV/c● Kaons: 2 GeV/c
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Particle Identification at Forward Rapidity
RICH identification● Pions:28 GeV/c● Protons: 35 GeV/c● Kaons: 28 GeV/c
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Charged HadronErrors are statistical only
10-20% Central
Charged Hadron V2 at Midrapidity
Strong pT
dependence is seen at midrapidity.
10-20% Central
Errors are statistical only
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Pion V2 at Midrapidity
Errors are statistical only
10-20% central events ...pion v2(p
T) is
also consistent with STAR data.
Error is statistical only
10-20% central events
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Find strong pt dependence
PionError is statistical only
η = 3.2
Pion V2 at Forward Rapidity
PionErrors are statistical only
η = 0
PionsError is statistical only
η = 3.2
Pion elliptic flow at forward rapidity is very smilar to that at midrapidity.
10-20%
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η = 1
η = 3.2
η = 0
Rapidity Dependence
Small η dependence found.η = 0
η = 1
η = 3.2
3D Hydro(Hirano)
3D Hydrodynamic calculation also shows a very small pseudorapidity dependence.
Charged hadrons
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Charged hadrons
pT Integrated v
2
Integrated v2 are derived
using the measured spectra and v
2(p
T). (See
a poster by C. Ristea.)
Integrated v2 are also
relatively flat.
<η> <pT> GeV/c
0 0.55 1 0.53 2. h+ 0.506 h- 0.423
η = 0
η = 1
η = 3.2
3D Hydro(Hirano)
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Centrality Dependence
Large centrality dependence is seen for p
T
integrated v2 —
consistant with PHOBOS results.
Centrality dependence at midrapidity
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Conclusion
● v2(p
T) for charged hadrons and pions have been measured at
midrapidity as well as at forward rapidity. ● v
2(p
T) shows small pseudorapidity dependence—consistent with
3D Hydro model.● η dependence of p
T integrated v
2 is strongly sensitive to
measured spectra. ● Strong centrality dependence observed.
Proton and Kaon results are forthcoming.