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Directed flow of identified particles from Au+Au Collisions at RHIC

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

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Directed flow of identified particles from Au+Au Collisions at RHIC

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  1. Directed flow of identified particles from Au+Au Collisions at RHIC Jiayun Chen Institute of Particle Physics, Central China Normal Uni. Brookhaven National Lab.

  2. Outline • Motivation • Data sample, Proton selections, & V0reconstruction • Event plane reconstruction • V1 result • Discussion and Summary Berkeley School 05.24.07.

  3. <px> or directed flow rapidity pt Motivation Directed flow (v1) Anisotropic flow Elliptic flow (v2) Higher harmonics Berkeley School 05.24.07.

  4. flow antiflow Motivation Anti-flow/3rd flow component, with QGP  v1 flat at middle rapidity. Directed flow (v1) and phase transition 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) Berkeley School 05.24.07.

  5. Motivation RQMD v2.4 Positive space-momentum correlation, no QGP necessary  v1 wiggle. Directed flow (v1) and baryon stopping R.Snellings, H.Sorge, S.Voloshin, F.Wang, N. Xu, PRL (84) 2803(2000) Berkeley School 05.24.07.

  6. Motivation (GeV) • freeze-out of multi-strange 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) Berkeley School 05.24.07.

  7. Common cut: |Primary Vertex| < 30cm No. Dedx Points > 10 No. fit Points > 20 No. fit Points/No. Max [0.52,1.05] Global DCA < 1.0cm nSigma [-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 Proton & Antiproton Selection STAR Preliminary Berkeley School 05.24.07.

  8. 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 V0sreconstruction 1.11<mass<1.12 0.48<mass<0.51 1.11<mass<1.12 Berkeley School 05.24.07.

  9. Event Planereconstruction 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. Flattening Event Plane FTPC Event Plane distribution Step 1: Apply weight which can be determined with the inverse of the bin content in the raw  distribution. Step 2: Make corrections to the event plane angle itself, & flatten the event plane distribution. The corrected event plane angle is ZDCSMD Event Plane distribution E877 Collaboration, J. Bareeette et al, Phys.Rev.Lett.70,2996(1993) Berkeley School 05.24.07.

  11. Combined Event Plane • After the flatness of YFTPC & YZDCSMD Full EP. The final event plane used is defined by the sum of Where • or weight is from resolution Berkeley School 05.24.07.

  12. Resolution of FTPC,ZDCSMD,{FTPC,ZDCSMD}(62GeV Au+Au) STAR Preliminary The event plane resolution is enhanced by combining EP of FTPC & ZDC-SMD with proper weight. Berkeley School 05.24.07.

  13. Proton & Antiproton v1vs. Rapidity(62GeV) STAR Preliminary STAR Preliminary 30%-60% 30%-60% with combined RP • 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 • Proton v1 is less than 1%, • Antiproton v1 is less than 2%. Berkeley School 05.24.07.

  14. Proton & Antiproton v1vs. Rapidity(200GeV) 30%-60% STAR Preliminary with combined RP • 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 Berkeley School 05.24.07.

  15. Ks v1vs. Rapidity(62GeV) STAR Preliminary v1=ay dv1/dy =-3.2±1.7 Berkeley School 05.24.07.

  16. L & Lv1vs. Rapidity STAR Preliminary STAR Preliminary Work in progress. Berkeley School 05.24.07.

  17. Summary • The event plane resolution is enhanced by combining 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 studydirected flow of K0S & L, L. • Looking forward to analyzing run VII’s data (~60M MB events). Berkeley School 05.24.07.

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