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Elliptic Flow in PHENIX

Elliptic Flow in PHENIX. Hiroshi Masui for the PHENIX collaboration CIPANP 2006, Westin Rio Mar Beach Puerto Rico May 30 – Jun 3, 2006. Why Elliptic Flow ?. Z. Study the properties of matter created at RHIC The probe for early time

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Elliptic Flow in PHENIX

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  1. Elliptic Flow in PHENIX Hiroshi Masui for the PHENIX collaboration CIPANP 2006, Westin Rio Mar Beach Puerto Rico May 30 – Jun 3, 2006

  2. Why Elliptic Flow ? Z • Study the properties of matter created at RHIC • The probe for early time • The dense nuclear overlap is ellipsoid at the beginning of heavy ion collisions • Pressure gradient is largest in the shortest direction of the ellipsoid • Spatial anisotropy  Momentum anisotropy • Signal is self-quenching with time • Elliptic flow (v2) is defined by the 2nd coefficient of Fourier expansion Reaction plane Y X Pz Py Px Hiroshi Masui / University of Tsukuba

  3. Outline partonic hadronic Elliptic Flow, v2 • Bulk, early probe • Charged hadrons give us a base line direct  Elliptic Flow, v2 time D , K, p Partonic degrees of freedom, Thermalization, ..  Meson • Small interaction cross section, long lived life time (~40 fm/c) Penetrating probes • Heavy flavor electrons (charm) • Direct  Hiroshi Masui / University of Tsukuba

  4. Baseline : charged hadrons Charged hadrons, v2 vs pT PHENIX : PRL 91, 182301 (2003) • Large elliptic flow at RHIC • Consistent with hydrodynamics with rapid thermalization,  ~ 1 fm/c • v2 scales initial eccentricity () of reaction zone v2 ~ k   Hiroshi Masui / University of Tsukuba

  5. Hydro scaling M. Issah, A. Taranenko, nucl-ex/0604011 Hydro scaling of v2 K0S,  (STAR) : PRL 92, 052302 (2004)  (STAR) : PRL 95, 122301 (2005) , K, p (PHENIX) : preliminary • Scaling holds up to KET = 1 GeV • Meson/Baryon v2 • Possible hint of partonic degrees of freedom Meson v2 Baryon v2 * KET ~ mT – m0 at y ~ 0 Hiroshi Masui / University of Tsukuba

  6. 1.  meson v2 Hiroshi Masui / University of Tsukuba

  7. Clear  signal •  reconstruction via K+K- decay channel • S/N ~ 0.3 • Centrality 20 – 60 % • S/N is good • Event plane resolution is good • Separation between meson/baryon v2 is good • v2 do not be varied too much. Before subtraction Signal + Background Background After subtraction Hiroshi Masui / University of Tsukuba

  8. “Meson” type flow !  v2 vs pT • Hydro. mass ordering for pT < 2 GeV/c • v2() ~ v2(), v2(K) for pT > 2 GeV/c • Mass Number of constituent quarks • Consistent with the description by quark coalescence, recombination models Hiroshi Masui / University of Tsukuba

  9. Hint of partonic d.o.f Hydro scaling of v2 K0S,  (STAR) : PR 92, 052302 (2004)  (STAR) : PRL 95, 122301 (2005)  (STAR) : preliminary , K, p, 0, d (PHENIX) : preliminary • Hydro + Nquark scaling • Works for a broad range of KET •  meson also follow the scaling • Partonic degrees of freedom WWND 2006, M. Issah Hiroshi Masui / University of Tsukuba

  10. 2. Heavy flavor electron v2 Hiroshi Masui / University of Tsukuba

  11. Clean heavy flavor electron Cocktail subtraction Converter subtraction Signal / Background ratio • Two different techniques show an excess heavy flavor electron signal • Signal/Background > 1 for pT > 1 GeV/c Run4 Run2 Hiroshi Masui / University of Tsukuba

  12. Hint of Charm flow e v2 vs pT V. Greco, C. M. Ko, R. Rapp: PL B 595, 202 (2004) • Data indicate finite v2 of charm quark • Suggest thermalization of c quark as well as light quarks • What is the origin of high pT drop ? Hiroshi Masui / University of Tsukuba

  13. b quark contribution ? e v2 vs pT H. Hees, V. Greco, R. Rapp: PRC 73, 034913 (2006) (1) • D or B meson v2 • decrease, (2) flat at high pT input (2) • High pT drop might be explained by B meson contribution v2 D  e output B  e (1) Simulation B  e (2) SQM 2006, S. Sakai pT (GeV/c) Hiroshi Masui / University of Tsukuba

  14. 3. Direct  v2 Hiroshi Masui / University of Tsukuba

  15. Clear Direct  signal PRL 94, 232301 (2005) • Large direct  excess • 0 is suppressed but direct  not • Both results are consistent with pQCD Hiroshi Masui / University of Tsukuba

  16. Possible 3 different scenarios  v2 vs pT PRL 96, 032302 (2006) • Direct  v2 1. Hard scattering • v2 = 0 2. Parton fragmentation • v2 > 0 3. Bremsstrahlung • v2 < 0 • Inclusive  • Consistent with expected  v2 from hadron decays Hiroshi Masui / University of Tsukuba

  17. v2direct = 0 ?  v2 vs pT PRL 96, 032302 (2006) • Direct  v2 • Direct  excess ratio is consistent with v2BG/v2inclusive, suggest v2direct = 0 • Favors prompt photon production for dominant source of direct  Hiroshi Masui / University of Tsukuba

  18. Conclusions • Elliptic Flow is powerful tool to study hot and dense matter at RHIC •  meson  Partonic degrees of freedom • Hydro. mass ordering for pT < 2 GeV/c • For pT > 2 GeV/c, v2() prefer quark composition not mass • Hydro + Nquark scaling works for  meson as well as other hadrons • Heavy flavor electron  Thermalization • Consistent with non-zero charm flow, suggest thermalization of c quark as well as light quarks • Bottom contribution at high pT need to be studied experimentally • Direct   Coming soon … • v2direct = 0, consistent with the scenario of direct  production from initial hard scattering • Year-4 data may enable us to reduce statistical error bars, and extend pT reach, and to measure thermal  v2 Hiroshi Masui / University of Tsukuba

  19. Thank you Hiroshi Masui / University of Tsukuba

  20. Back up Hiroshi Masui / University of Tsukuba

  21. Converter Subtraction method Ne 0.8% 1.1% ? % 1.7% With converter Photonic electron W/o converter Photon Converter (Brass 1.7 % X0) around beam pipe Conversion from beam pipe Dalitz : 0.8 % X0 equivalent Non-photonic electron 0 X0 • Source of background electrons • Photon conversion 0    e+e- • Dalitz decay (0ee,  ee, etc) • Di-electron decays of , ,  • Kaon decays • Conversion of direct photons Hiroshi Masui / University of Tsukuba

  22. Inclusive electron v2 (w., w/o. converter) • Converter subtraction method • Inclusive electron v2 w. and w/o. converter. • Clear difference between them. • Electron v2 with converter include large photonic component. Hiroshi Masui / University of Tsukuba

  23. Inclusive & photonic electron v2 photonic e v2 • Photonic electron v2 • pT < 1 GeV/c  Converter method • pT > 1 GeV/c • Simulation • v2(inclusive) < v2 (photonic)  v2(non-photonic) < v2(photonic) inclusive e v2 (w/o. converter) Hiroshi Masui / University of Tsukuba

  24. Centrality dependence • Non zero heavy flavor electron v2 ! Hiroshi Masui / University of Tsukuba

  25. Run4 inclusive  v2 0 v2 inclusive  pT Hiroshi Masui / University of Tsukuba

  26. Independent on system size Eccentricity scaling • Eccentricity scaling • A wide range of centrality • Independent of system size • Integrated v2 eccentricity • Reduce systematic error from eccentricity calculation • Cancel systematic error by the ratio of v2(pT) / (integrated v2) Hiroshi Masui / University of Tsukuba

  27. Hadron identification • Time-of-flight • || < /4, || < 0.35 • Timing resolution ~ 120 ps • /K separation ~ 2 GeV/c • K/p separation ~ 4 GeV/c • EM Calorimeter • || < /2, || < 0.35 • Timing resolution ~ 400 ps • /K separation ~ 1 GeV/c • K/p separation ~ 2 GeV/c Hiroshi Masui / University of Tsukuba

  28. The PHENIX experiment • Acceptance • Central arm: || < , || < 0.35 • Centrality • Beam-Beam Counter, Zero Degree Calorimeter. • Event plane • BBC • Tracking • Drift chamber, Pad chambers. • Particle identification • Electron • Electro-Magnetic Calorimeter • Hadron • Time-of-Flight, Aerogel Cherenkov Counter, EMCal Hiroshi Masui / University of Tsukuba

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