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02/13/2009

Azimuthal Anisotropy Measurement of Neutral Pion and Direct Photon in  s NN = 200 GeV Au+Au Collisions at RHIC-PHENIX. (RHIC-PHENIX √ ｓ ＮＮ = 200 GeV 　金・金衝突実験における 中性パイ中間子及び直接光子の方位角異方性の測定 ). 博士論文　本審査・公開発表. Kentaro MIKI Univ. of Tsukuba mail to: kentaro@rcf2.rhic.bnl.gov. 02/13/2009.

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02/13/2009

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  1. Azimuthal Anisotropy Measurement of Neutral Pion and Direct Photon in sNN = 200 GeV Au+Au Collisions at RHIC-PHENIX (RHIC-PHENIX √ｓＮＮ= 200 GeV　金・金衝突実験における中性パイ中間子及び直接光子の方位角異方性の測定) 博士論文　本審査・公開発表 Kentaro MIKI Univ. of Tsukuba mail to: kentaro@rcf2.rhic.bnl.gov 02/13/2009

  2. 0. Outlook 1. Introduction / Physics Motivation -- Quark Gluon Plasma -- Azimuthal Anisotropy -- Photon Emission at Heavy-Ion Collisions 2. Experiment -- RHIC - PHENIX 3. Data Reduction / Analysis -- Event Parameters -- Analysis for Inclusive Photon, 0, and Direct Photon 4. Results / Discussions -- Photon and Hadrons -- High-pT Direct Photon -- Low-pT Direct Photon -- Secondary Contribution of High-pT Direct Photon Yield 5. Conclusion Kentaro Miki

  3. 1-1. Quark Gluon Plasma How to study primordial state of matter? Quark Gluon Plasma -> QGP formed under extreme temperature and energy density. -> The quark and the gluon move freely in a finite volume. Hadron phase QGP phase by Jeffery Mitchell PHENIX web page Tc ~ 170 MeV c ~ 1.2 GeV/fm3 Critical temperature and energy density by Lattice QCD Kentaro Miki

  4. 1-2. Heavy-Ion Collision Experiment Heavy-Ion Collision Experiment -> Relativistic heavy ion collisions provide a unique occasion to achieve the critical temperature for QGP on the earth. BNL Investigations have been taking place both at BNL and CERN CERN Kentaro Miki

  5. 1-3. Space Time Evolution Freeze-out Hadronic scatterings t Hadron gas Hadronization Expansion & Cooling Mixed phase QGP Thermalization pre-equilibrium Hard scattering Initial collision RHIC Au+Au 200 GeV Time scale of space-time evolution of a heavy-ion collision is ~10 fm/c. by Jeffery Mitchell PHENIX web page Kentaro Miki

  6. 1-4. Azimuthal Anisotropy Spatial anisotropy of overlap zone by M.Kaneta and A.Dion PHENIX web page pressure gradient mean free path pz Momentum anisotropy Final particle emission in momentum space reflects the initial spatial anisotropy. px > 2nd coefficient (v2) of Fourier expansion  : azimuthal angle of particles  : azimuthal angle of reaction plane Measured identified hadron v2 in low-pT is well described by the hydro-dynamical prediction. Kentaro Miki

  7. 1-5. Electro Magnetic Probes Photons are the powerful probes to study the property of QGP since they do not interact strongly with any other particles and thus can carry out information on the states where they are emitted. t Hadronic decay Hadronization Thermalization Hard + medium Hard scattering Dinesh K. Srivastava Quark Matter 2008 Photons are emitted from all stage of system development. Kentaro Miki

  8. 1-6. Photon Sources Compton Annihilation Photons in Au+Au Prompt Hard Direct Fragmentation jet-fragmentation QGP Thermal jet-Bremsstrahlung Hadron gas Hard + Thermal Bremsstrahlung jet-photon conversion Hadronic decay Photon conversion Kentaro Miki

  9. 1-7. Experimental Result =Spectra= High-pT direct photons are produced in the initial stage. Thermal radiation are emitted in the low-pT region. thermal window -> 1~3 GeV/c prompt photon window -> 6~ GeV/c Blue line: Ncoll scaled p+p cross section High-pT direct photons are well described by NLO-pQCD calculation. Phys. Rev., C69:014903(2004) Kentaro Miki

  10. 1-8. Experimental Result =RAA= High-pT suppression of hadron yield in Au+Au collisions -> energy loss of hard scattered partons passing through the high density matter Non suppression of high-pT direct photon -> they do not interact strongly with any other particles -> high-pT photons are produced by initial parton collisions Nuclear Modification Factor The yield ratio of Au+Au and p+p normalized by the number of binary nucleon collisions. Kentaro Miki

  11. 1-9. Direct Photon v2 The sign of v2 depending on the production processes of photons. jet-fragmentation jet-Bremsstrahlung jet-photon conversion Kentaro Miki

  12. Y X 1-10. Physics Motivation The sign of v2 depending on the production processes of photons. v2 is a powerful tool to explore the source of direct photons. λ >> R Measurement of direct photon v2 and 0v2 experimentally. -- What is the dominant source in high-pT? confirming the dominant source with RAA results. -- Low-pT direct photon represent the thermal radiation picture? -- Can we discuss about secondary contribution in the direct photon yield? Kentaro Miki

  13. 1-11. My Activities and Contributions BNL 2006.05.15 - 2006.07.13 2007.05.07 - 2007.07.07 2007.10.01 - 2007.12.22 2008.01.08 - 2008.01.27 (TOF-E calibration for Run4, Run5, Run6) (Centrality calibration for Run7) (TOF-E, Agel setup for Run7, Run8) JPS 2006.09.21 [0v2 in Run4] 2007.03.27 [direct photon v2 in Run7] International Conference 2006.01 RHIC-AGS meeting (poster) 2006.11 QM2006 in Shanghai (poster) 2006.11 Workshop in Xi’an (oral) 2008.02 QM2008 in India (invited oral) Analysis Results 2007.03 Preliminary for direct photon v2 in Run4 2008.01 Preliminary for 0v2 in Run7 Junior Research Associate working as JRA at RIKEN since Apr 2007 Riken accelerator progress report in 2007 Kentaro Miki

  14. 2-1. RHIC Accelerators Tandem Van de Graaff Linear Accelerator Booster Synchrotron Alternating Gradient Synchrotron Relativistic Heavy Ion Collider Experiments PHENIX, STAR, BRAHMS, PHOBOS Luminosity 2x1026 cm-2s-2 for Au 2x1032 cm-2s-2 for proton Kentaro Miki

  15. 2-2. PHENIX Detectors Reaction Plane Detector 1.0 < || < 2.8 16 sectors in each side Beam-Beam counter event trigger, centrality reaction plane determination lead glass (PbGl) ・energy resolution 0.76  5.95 %/ E1/2 [GeV] lead scintillator (PbSc) ・energy resolution 2.1  8.1 %/ E1/2 [GeV] Kentaro Miki

  16. 3-1. Event Parameters Centrality spectator Npart= number of interacting nucleons Ncoll= number of binary nucleon-nucleon collisions participant spectator Reaction plane <Calibration> <Reaction Plane Resolution> Kentaro Miki

  17. Inclusive photon Direct  hadron decay 3-2. Analysis Process Excess ratio 0   ’ Analysis process - Inclusive photon - 0 - Hadron decay photon - Direct photon PRL, 94, 232301 (2005) Kentaro Miki

  18. 3-3. Inclusive Photon (Raw) Spectra Data Set : Au+Au 200 GeV PHENIX Year-7 (~4.0G events) Event selection : minimum bias trigger (BBCNS > 2 ∩ ZDCNS > 1) BBC vertex < 30 cm Cluster cut : Ecore > 0.2 GeV Bad tower rejection Shower shape profile (2 < 3.0) Charged particle rejection Correction for invariant yield - Geometrical acceptance - Photon conversion - Energy scale - Remaining hadron Kentaro Miki

  19. 3-4. Inclusive Photon v2 Fourier expansion function Kentaro Miki

  20. 3-5. Invariant Mass Distribution of 2 Same cut with inclusive photon analysis. Combinatrial back ground is estimated by event mix distribution. Invariant mass distribution of 2 dN / d distribution of 0 Kentaro Miki

  21. 3-6. Systematical Uncertainty 0 Inclusive Photon Kentaro Miki

  22. 3-7. Hadron Decay Photon by Monte-Carlo above 3GeV, 0 77.6 %  19.0 %  3.7 %  0.5 % ’ 2.0 % Red points are experimental data of 0 (PPG080). Simulation result of 0 is normalized by data. Other hadrons are normalized by 0 and their decay ratio. Cocktailed the decay photons v2 referring to contamination ratio. Kentaro Miki

  23. 3-8. Direct photon v2 Excess ratio (R) Centrality 00 -92 % Direct photon v2 Centrality 00 -92 % Kentaro Miki

  24. 4. Results 0 and charged hadrons (1) Experimental results -- v2 of 0 and inclusive photon (2) Consistency check -- with charged hadrons in low-pT and high-pT Direct Photon (1) Experimental results -- v2 of direct photon Kentaro Miki

  25. 4-1. Results of 0 and inclusive photon - Measured 0 and inclusive photon v2 at 10% and 20% steps in centrality. - Extended up to 16.0 GeV/c Kentaro Miki

  26. 4-2. Comparison in low pT Universal v2 -> collective flow of quarks v2 of 0 also shows the KET scaling. Kentaro Miki

  27. 4-3. Comparison in high pT High-pTv2 of 0 is consistent with that of non-identified charged hadron. Invariant yield of ±, 0, and proton at RHIC energy [Phys. Rev. C76, 034904] [Ph.D thesis by M. Konno] p/ ratio in Au+Au and p+p collisions The influence of baryon enhancement is also observed in 0v2 result. Kentaro Miki

  28. 4-4. Results of Direct Photon v2 Measured direct photon v2 at sNN = 200 GeV Au+Au collisions in PHENIX Year-7 up to pT = 16 GeV/c. First observation in the world! - systematical error is significantly large in low-pT due to bad S/N. Kentaro Miki

  29. 5. Discussions Motivation -- What is the dominant source in high pT? confirming the dominant source with invariant yield and RAA results. -- Low-pT direct photon represent the thermal radiation picture? -- How to investigate about secondary contribution in the direct photon yield at high pT? Discussions 1. High-pT Direct Photon 2. Low-pT Direct Photon 3. Secondary Contribution of Direct Photon Kentaro Miki

  30. 5-1. Discussion 1 1. High-pT Direct Photon 2. Low-pT Direct Photon 3. Secondary Contribution of Direct Photon High-pT Direct Photon (1) Experimental results of high-pT direct photon have good accuracy. -- due to hadron suppression, and so on… (2) What is the dominant source in high pT? Hard Thermal Hard + Thermal Prompt QGP Bremsstrahlung Fragmentation Hadron gas Photon conversion Kentaro Miki

  31. 5-2. Results of Direct Photon v2 Measured direct photon v2 at sNN = 200 GeV Au+Au collisions in PHENIX Year-7. Direct photon v2 is equal to zero within error bar. Statistical error Systematical error 0-20 % 0.020 ± 0.0066(sta.) ± 0.028(sys.) 20-40 % 0.038 ± 0.0102(sta.) ± 0.055(sys.) Kentaro Miki

  32. 5-3. High-pT Photon Source Invariant yield v2 RAA Invariant yield -> corresponds to NLO-pQCD calculation dominant source of high-pT direct photon is prompt photon. v2 -> equal to zero RAA -> equal to 1 by Klaus Reygers at QM2008 Kentaro Miki

  33. 5-4. Summary 1 Summary of results and discussion 1 Measured v2 of 0 and inclusive photon in sNN = 200 GeV Au+Au collisions at RHIC-PHENIX Year-7. - results is consistent with v2 of charged hadrons - influence of baryon enhancement is also observed in 0v2 result Measured v2 of direct photon in sNN = 200 GeV Au+Au collisions at RHIC-PHENIX Year-7. - extended up to pT = 16 GeV/c - v2 is equal to zero above pT = 6 GeV/c - systematical error is significantly large in low-pT Comparison with invariant yield and RAA - dominant source of high-pT direct photon is prompt photon Kentaro Miki

  34. 6. Discussion 2 1. High-pT Direct Photon 2. Low-pT Direct Photon 3. Secondary Contribution of Direct Photon (1) Low-pT direct photon is presented by PHENIX -- dilepton analysis (2) v2 calculation in low-pT -- by using alternative excess ratio (3) Discussion -- compared with charged hadrons and KET scaled v2 Kentaro Miki

  35. 6-1. Low Mass Dilepton Direct Photon via Dilepton relation between real photon and dilepton production Alternative approach to low-pT direct photon. Any source of high energy photons can also emit virtual photons which convert to low mass lepton pair. m > me gluon compton scattering low mass electron production [nucl-ex/arXiv:0804.4168] Kentaro Miki

  36. 6-2. Excess Ratio Fraction of direct photon escapes a big influence from 0. fit range : 80 < mee < 300 MeV/c2 fc and fdir are normalized to the data for mee < 30 MeV/c2 separately. Dashed curve: modified power-law fit to the p+p data scaled by TAA. Black curve: exponential plus the TAA scaled p+p fit. T=221±23(sta.)±18(sys.) = Hydrodynamical model = Tinit ~ 300 - 600 MeV at t0 ~ 0.6 - 0.15 fm/c [nucl-ex/arXiv:0804.4168] Kentaro Miki

  37. 6-3. Low-pTv2 Fraction of direct photon by using dilepton analysis is big advantage in low-pT due to avoid a big influence from 0. -> v2 of direct photon should be also improved Kentaro Miki

  38. 6-4. Discussion at Low-pT Theoretical prediction curve of low-pT direct photon - prediction curve of low-pT direct photon is reproduced the experimental results at RHIC energy. - v2 curves show the experimental. - v2 of prompt photon is assumed that equal to zero. - value of direct photon v2 is between that of 0 and KET scaled v2. Note: Black curve is estimated by photon fraction in central and v2 in min. bias… Kentaro Miki

  39. 7. Discussion 3 1. High-pT Direct Photon 2. Low-pT Direct Photon 3. Secondary Contribution of Direct Photon (1) Enhancement source of direct photon in Au+Au (2) Npart dependence of photon and hadrons (3) Fraction of high-pT direct photon source (4) v2 of additional photon source Kentaro Miki

  40. 7-1. Enhancement of Photon in Au+Au Direct photon source at p+p collisions nprompt + nfragment Photon yield from fragmentation should be suppressed in Au+Au collisions. No suppression of direct photon is observed in Au+Au. Where is influence of jet-suppression? There is positive finite (and small) value in high-pT direct photon…? We might be able to observe the second contribution in high-pT direct photon…? Kentaro Miki

  41. 7-2. Npart Dependence of Photon and Hadron Extending discussion about secondary contribution in the high-pT direct photon yield. Direct photon source in high-pT - p+p prompt + fragment - Au+Au prompt + fragment + additional The v2 of 0 and direct photon are averaged above pT = 6 GeV/c to obtain less statistical error, and represents as a function of the number of participating nucleons. Kentaro Miki

  42. 7-3. Fraction of Photon Source 1 Direct photon in p+p collisions nprompt + nfragment Direct photon in Au+Au collisions Nprompt + Nfragment + Nadditional assumption : all of high-pT0 are produced by jet-fragmentation Nb : scale factor of number of binary collisions a = nfragment / nprompt bNadd / Nprompt = (1+a)RAAdirect - aRAA0 - 1 Contamination of additional photon source is estimated from a= nfragment / nprompt , RAA of direct photon and RAA of 0. Kentaro Miki

  43. 7-4. Fraction of Photon Source 2 RAA of direct photon and 0 prompt to fragment ratio in p+p RAAfragment ~ 0.24±0.02 a = nfragment / nprompt ~ 0.35/0.65 = 0.54 Y (additional source) ~ 0.5 x Y (prompt photon) Kentaro Miki

  44. 7-5. v2 of Secondary Component v2add ~ 0.045 ± 0.030 - There is additional photon source except prompt and fragment in high-pT. - v2 of additional production source is expected to finite positive value approximately 0.045 + 0.030 in central. Kentaro Miki

  45. 7-6. Summary 2 Summary of discussion 3 and discussion 4 Low-pT Direct Photon - Alternative approach for low-pT direct photon by using internal conversion of virtual photon (described in [nucl-ex/arXiv:0804.4168]). - v2 of direct photon is improved by using excess ratio with higher accuracy. - value of direct photon v2 is between that of 0 and KET scaled v2. Study of Secondary Contribution of high-pT Direct photon - There is additional source at half-ratio to prompt photon. - v2 of additional production source is expected to finite positive value approximately 0.045 + 0.030 in central. Kentaro Miki

  46. 8. Conclusion Measured v2 of inclusive photon, 0 and direct photon at sNN = 200 GeV Au+Au collisions at RHIC-PHENIX Year-7. - expended up to pT = 16 GeV/c - v2 is equal to zero above pT = 6 GeV/c - confirmed the dominant source of high-pT direct photon as prompt photon We performed the extending discussions at low-pT and high-pT direct photon yield and its v2. -low-pTv2 of direct photon is improved by using excess ratio which determined by internal conversion analysis of virtual photon - value of its v2 is finite positive (and small) - there is additional source at half ratio to prompt photon at high pT - v2 of additional production source is expected to finite positive value approximately 0.045 + 0.030 in central collisions Kentaro Miki

  47. Ex Back up Kentaro Miki

  48. 3-1. Clustering Algorithm Isolated Cluster - 10 MeV threshold is applied - cluster formed with neighboring towers Local Maximum Tower - 80 MeV threshold - maximum amplitude in around 3x3 towers - “peak area towers” formed around 5x5 towers Split the Peak Area - divide the tower energy to each peak area by using parameterized shower profile Core Clustering - energy threshold (2% of energy sum in peak area) - Shower shape profile test (2 < 3.0) energy scale calibration by 0 peak position width Kentaro Miki

  49. 3-8. Photons from Hadron Decays Since components other than 0 are not measured directly, the photons from hadrons other than 0 is estimated by using Monte-Carlo. Kentaro Miki

  50. 7-3. Fraction of Photon Source 1 Direct photon source at p+p collisions nprompt + nfragment Additional Photon Source … all of high-pT0 are produced by jet-fragmentation Au+Au Nb : scale factor of number of binary collisions a = nfragment / nprompt b = Nadd / (npromptNb) b = (1+a)RAAdirect - aRAA0 - 1 Kentaro Miki

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