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RIKEN PHENIX ミーティング D 論用研究　進捗報告 単 電子生成の二重スピン非対称度測定

RIKEN PHENIX ミーティング D 論用研究　進捗報告 単 電子生成の二重スピン非対称度測定. 中村　克朗　（京都大学） 2010 / 10/ 15. 核子内グルーオン偏極度と重クォーク生成の二重スピン非対称度. 核子内グルーオン偏極度 spin puzzle なぜ重クォーク生成か ? g g  Q Q -bar の hard scattering process が主な生成過程となる  より直接的な ΔG の測定が可能となる ΔG の絶対値に感度の高い測定となる グルーオン偏極度の測定に適したチャンネルである.

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RIKEN PHENIX ミーティング D 論用研究　進捗報告 単 電子生成の二重スピン非対称度測定

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  1. RIKEN PHENIX ミーティングD論用研究　進捗報告単電子生成の二重スピン非対称度測定 中村　克朗　（京都大学） 2010 / 10/ 15

  2. 核子内グルーオン偏極度と重クォーク生成の二重スピン非対称度核子内グルーオン偏極度と重クォーク生成の二重スピン非対称度 • 核子内グルーオン偏極度 • spin puzzle • なぜ重クォーク生成か? • g g Q Q-bar のhard scattering process が主な生成過程となる • より直接的な ΔG の測定が可能となる • ΔGの絶対値に感度の高い測定となる • グルーオン偏極度の測定に適したチャンネルである JPS fall meeting

  3. PHENIXにおける重クォーク生成測定 • photonic electron • non-photonic electron • 光子転換 • Dalitz 崩壊 • 直接光子生成 • small, but significant at high pT • heavy meson 崩壊 • Kaon崩壊 • vector meson 崩壊 ( 欲しい signal ) • PHENIXにおける重クォーク生成の測定 • heavy meson 崩壊からの単電子を測定 • PHENIXで測定される電子の生成源 JPS fall meeting

  4. heavy meson測定におけるバックグラウンド simulation result of e yield • photonic electron dominant background background • 光子転換 • Dalitz 崩壊 • 直接光子生成 • small, but significant at high pT photonic ~95% HBD により除去 • non-photonic electron • heavy meson 崩壊 • Kaon崩壊 • vector meson 崩壊 ( 欲しい signal ) background ~ a few% of non-photonic electrons negligible JPS fall meeting

  5. Mesh Primary ionization γ HV e- CsI layer Triple GEM Readout Pads Hadron Blind Detector(HBD) CF4 gas photonic electron ( pair electrons ) non-photonic electron ( single electron ) 50cm HBD • Hadron Blind Detector • CsI蒸着のGEMによるgas Cherenkov 検出器 • hadron除去( ) • hadron除去能力 > 10 • 27mm pad size • Cherenkov blob直径 ~ 36mm • 1つの電子通過に対して約 20 個のphotoelectron を放出 • hadron : 平均約 1 photoelectron •  non-photonicとphotonicでクラスターの電荷量が異なる • 電荷量によって区別することが可能 JPS fall meeting

  6. HBD Event Display HBD charge [p.e.] Clustering Algorithm Not Stable seed pad seed pad seed pad electron track seed pad: pad with large charge (> 3p.e.) Dead Dead • make a cluster with seed pads • add neighbor pads to the cluster • cluster charge is the sum of pad charges N S S N add blob (cluster) information private clustering algorithm

  7. Electron Cut • electron cut • abs(bbc_z) < 20cm • quality==31|51|63 • n0>=2 • e/p cut • ecore>0, mom>0 • abs(emcsdphi_e)<4, abs(emcsdz_e)<4 • prob>0.01 • hbd association cut • abs(hbdsdphi) < 3.5 • abs(hbdsdz) < 3.5 • hbd_cluster_size >=2 : (reject fake hit) JPS fall meeting

  8. HBDnon-photonic & photonic 識別能力 photonic electron non-photonic electron eff. ~ 80% reject eff. ~ 30% single e cluster merged cluster JPS fall meeting • non-photonic electron と photonic electron は HBD のクラスター電荷量により区別される • non-photonic electrons と photonic electrons に対するクラスター電荷量分布は Dalitz 領域の electron pair を用いて測定可能 • Dalitz 領域：　pair mass < 135MeV

  9. HBD charge distribution (East) North South North South #{bin content}/ #{all entry} Sect0 Sect3 low stat. very low stat. not stable gain Sect1 Sect4 very low stat. very low stat. Sect2 Sect5 Red: merged cluster Blue: separated cluster • Not including HBD efficiency • Integral(0,inf) = 1

  10. HBD charge distribution (West) North South North South Sect6 Sect9 strange shape low stat. Sect7 Sect10 low stat. low stat. Sect8 Sect11 Red: merged cluster Blue: separated cluster

  11. HBD charge distribution for Hadrons(fake hits) HBD charge distribution of “hadron cut” + “hbd association cut” tracks #{hadron cut && hbdassoci cut}/ #{hadron cut} • requiring following cuts • hadron cut • abs(bbc_z) < 20cm • quality == 63 • mom > 0.5 && mom < 3.0 • n0 <= 0 • ecore > 0 • e/p <0.4 • abs(emcsdphi_e)<4, abs(emcsdz_e)<4 • prob < 0.01 • hbdsect >= 0 && hbdsect < 12 • (tracks passing HBD acceptance) • hbd association cut • abs(hbdsdphi) < 3.5 • abs(hbdsdz) < 3.5 • hbdsize >= 2 threshold in offline code HBD charge [p.e.] normalized with the number of tracks satisfying hadroncut hadron efficiency < 10%

  12. HBD efficiency with J/phi events using good sector (sect 2,3,4(south), 8,9,10) HBD association efficiency w/o HBD size cut HBD association efficiency w/ HBD size cut HBD cut abs(hbdsdphi) < 3.5 abs(hbdsdz) < 3.5 hbdsize >= 2 efficiency ~ 162/213 = 76% • HBD cut • abs(hbdsdphi) < 3.5 • abs(hbdsdz) < 3.5 • efficiency ~ 193/213 = 91% 今使用しているcut

  13. HBD efficiency with J/phi events(select good region) 14.0cm 22.9cm good region good region HBD association efficiency w/o HBD size cut HBD association efficiency w/ HBD size cut HBD cut abs(hbdsdphi) < 3.5 abs(hbdsdz) < 3.5 hbdsize >= 2 efficiency ~ 66/77 = 86% • HBD cut • abs(hbdsdphi) < 3.5 • abs(hbdsdz) < 3.5 • efficiency ~ 100% within error 18.0cm 26.5cm

  14. データからの single ecluster 成分と merged cluster 成分の分離 HBD cluster charge distribution for electron tracks single e peak merged peak • リファレンスの電荷量分布を fit することにより、single e clusterの数と merged clusterの数を導出する • determine Nesingle and Nemerge • pt ごとに single e cluster の成分と merged clusterの成分の比が異なるのがわかる • pt が高くなるにつれて、non-photonic 成分の占める割合が大きくなっているのがわかる。 fitting result (sect 8 north) 0.75 < pt < 1.00 GeV/c fitting with the reference charge distributions HBD charge distribution for electron tracks sect8 north 0.75<pt<1.00GeV/c JPS fall meeting

  15. pt distribution of each component (East) North South North South Sect0 Sect3 Sect1 Sect4 Sect2 Sect5 NDF = 94 JPS fall meeting

  16. pt distribution of each component (West) North South North South Sect6 Sect9 Sect7 Sect10 Sect8 Sect11 NDF = 94 Red: merged cluster Blue: separated cluster

  17. single e cluster とmerged cluster の pt spectra single e cluster and merged cluster spectra fitting により求めたNesingle、Nemerge、Nfake heavy quark  e photonic e sources pt に対する振る舞いは正しく一致 cross section result of run2005 JPS fall meeting • fitting 結果、NesingleとNemergeを pt に対して plot • 2つの異なる slope を持っていることを確認 • non-photonic electron is dominant in single e cluster event • photonic electron is dominant in merged cluster event •  electron の分布の2つの異なる成分の分離に成功 • pt=1GeV/cで　ΔNsingle/Nsingle~ 0.3%の誤差

  18. non-photonic electronとphotonic electron の抽出~ next step ~ electron candidates in detected tracks 欲しい signal a) c) a) b) non-photonic electron b) photonic electron c) HBD merged cluster HBD single e cluster • single e cluster には若干の photonic electron が混ざっている • これを取り除くことにより non-photonic electron の収量が得られる • HBD の simulation により、この割合を評価することができる photonic electron (separated event ) JPS fall meeting

  19. calculation of the fraction of photonic electron in single electron event • the positions of 2 separate clusters produced by Dalitz electron pair are close each other • Dalitz pair makes correlation in distance between clusters • different cluster distribution around the track between non-photonic election and photonic election • calculate the cluster distance distribution for non-photonic elections and photonic electrons • fit these distributions to cluster distribution of Run9 electron event, and determine the fraction e e+ D e- π detected another cluster should be found around the detected track single cluster produced by non-photonic electron single cluster produced by photonic electron

  20. non-photonic and photonic electron spectra reference r distribution form Dalitz events other clusters r distribution + fitting correlation 0.75 < pt < 1.00 GeV/c r [cm] Red: separated clusters Blue: merged clusters no correlation r [cm] Black : electron data (0.75 < pt < 1.00 GeV/c) Blue: merged cluster component Red: separated cluster component Violet: Blue+Red ~ same distribution as non-photonic electron clusters (no correlation)

  21. difficulties in reference distribution reference r distribution form Dalitz events 0.75 < pt < 1.00 GeV/c distance [cm] • not same as real distribution • large angle decay of pi0 is out of Central Arm acceptance • low statistics •  PISA simulation is required • PISA analysis is on going JPS fall meeting

  22. Roadmap to ALL • HBD simulation (hopefully finish by Nov.) • on going … • confirm HBD response for electrons • calculate the distance distribution • extract non-photonic electron spectrum • determine cross section spectrum (hopefully finish by Dec. or mid. Jan.) • acc. x eff. calculation • compare with old data • calculation of the asymmetry • Preliminary request(in this fiscal year !?) • systematic error estimation JPS fall meeting

  23. expected error bar of ALL 非対称度の理論曲線 と予想統計誤差 ε = S/(S+N) ~10-2 ~10-3 fitting result (sect 8 north) 0.75 < pt < 1.00 GeV/c ~10-3 accept region assumption PB = 57%, PY = 57% eff(non-photonic) = 80% eff(photonic) = 30% eff(fake hit) = 40% JPS fall meeting efficiency turn on curve

  24. Summary 陽子内のグルーオン偏極度に制限をかけるべく、Open Heavy Flavor生成断面積の二重スピン非対称度の解析を行っています。 Open Heavy Flavorからのheavy mesonにはnon-photonic electronを見ることによりアクセスできる。 Run9ではnon-photonic electronを見るためのHBDが稼働 HBDのデータを解析することにより、single electron cluster eventの収量を見積もることに成功 あとはHBD simulationにより、non-photonic electronの収量を得る。 今年度内の非対称度の導出+Preliminary取得を目標にしています JPS fall meeting

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