Kyoto Univ. JSPS RIKEN 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 1

Kyoto Univ. / JSPS / RIKEN 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 グルーオン偏極度の測定に適 したチャンネルである 2010/9/112 JPS fall meeting

Kyoto Univ. / JSPS / RIKEN PHENIX における重クォーク生成測定 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 2010/9/11 JPS fall meeting 3 photonic electron 光子転換 Dalitz 崩壊 直接光子生成 small, but significant at high p T non-photonic electron ( 欲しい signal )

Kyoto Univ. / JSPS / RIKEN simulation result of e yield heavy meson 測定におけるバックグラウンド 2010/9/11 JPS fall meeting 4 photonic electron 光子転換 Dalitz 崩壊 直接光子生成 small, but significant at high p T non-photonic electron dominant background background ~ a few% of non-photonic electrons ~ a few% of non-photonic electrons photonic ~95% negligiblenegligible HBD により除去 ( 欲しい signal )

Kyoto Univ. / JSPS / RIKEN Hadron Blind Detector (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 2010/9/11 JPS fall meeting 5 HBD CF 4 gas non-photonic electron ( single electron ) photonic electron ( pair electrons ) Mesh CsI layer Triple GEM Readout Pads e-e- Primary ionization γ HV 50cm

Kyoto Univ. / JSPS / RIKEN HBD Event Display add blob (cluster) information private clustering algorithm 6 HBD charge [p.e.] seed pad seed pad seed pad Clustering Algorithm make a cluster with seed pads add neighbor pads to the cluster cluster charge is the sum of pad charges seed pad: pad with large charge (> 3p.e.) Dead Not Stable SNSN

Kyoto Univ. / JSPS / RIKEN 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) 2010/9/11 JPS fall meeting 7

Kyoto Univ. / JSPS / RIKEN HBD non-photonic & photonic 識別能力 2010/9/11 JPS fall meeting 8 non-photonic electron photonic electron single e cluster merged cluster reject eff. ~ 80% eff. ~ 30% 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

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

Kyoto Univ. / JSPS / RIKEN HBD charge distribution (West) 10 NorthSouthNorthSouth Sect6 Sect7 Sect8 Sect9 Sect10 Sect11 strange shape Red: merged cluster Blue: separated cluster low stat.

Kyoto Univ. / JSPS / RIKEN HBD charge distribution for Hadrons (fake hits) normalized with the number of tracks satisfying hadron cut hadron efficiency < 10% 11 HBD charge distribution of “hadron cut” + “hbd association cut” tracks HBD charge [p.e.] threshold in offline code 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 #{hadron cut && hbd associ cut}/ #{hadron cut}

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

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

Kyoto Univ. / JSPS / RIKEN HBD charge distribution for electron tracks sect8 north 0.75<pt<1.00GeV/c データからの single e cluster 成分と merged cluster 成分の分離 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 N e single and N e merge 2010/9/11 JPS fall meeting 14 HBD cluster charge distribution for electron tracks single e peak merged peak fitting with the reference charge distributions fitting result (sect 8 north) 0.75 < pt < 1.00 GeV/c 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。

Kyoto Univ. / JSPS / RIKEN pt distribution of each component (East) 2010/9/11 JPS fall meeting 15 NorthSouthNorthSouth Sect0 Sect1 Sect2 Sect3 Sect4 Sect5 NDF = 94

Kyoto Univ. / JSPS / RIKEN pt distribution of each component (West) 16 NorthSouthNorthSouth Sect6 Sect7 Sect8 Red: merged cluster Blue: separated cluster Sect9 Sect10 Sect11 NDF = 94

Kyoto Univ. / JSPS / RIKEN single e cluster と merged cluster の pt spectra 2010/9/11 JPS fall meeting 17 cross section result of run2005 heavy quark  e photonic e sources pt に対する振る舞いは正しく一致 fitting 結果、 N e single と N e merge 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  electron の分布の 2 つの異なる 成分の分離に成功 –pt=1GeV/c で ΔN single /N single ~ 0.3% の 誤差 single e cluster and merged cluster spectra fitting により求めた N e single 、 N e merge 、 N fake

Kyoto Univ. / JSPS / RIKEN non-photonic electron non-photonic electron と photonic electron の抽出 ~ next step ~ 2010/9/11 JPS fall meeting 18 HBD single e cluster HBD merged cluster a) b) c) a) b) c) photonic electron (separated event ) 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 electron candidates in detected tracks electron candidates in detected tracks 欲しい signal

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 19 D e detected π e+ e- another cluster should be found around the detected track single cluster produced by non-photonic electron single cluster produced by photonic electron

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

Kyoto Univ. / JSPS / RIKEN difficulties in reference distribution 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 2010/9/11 JPS fall meeting 21 reference r distribution form Dalitz events 0.75 < pt < 1.00 GeV/c distance [cm]

Kyoto Univ. / JSPS / RIKEN 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 2010/9/11 JPS fall meeting 22

Kyoto Univ. / JSPS / RIKEN expected error bar of ALL 2010/9/11 JPS fall meeting 23 fitting result (sect 8 north) 0.75 < pt < 1.00 GeV/c ~10 -3 ~10 -2 ε = S/(S+N) accept region efficiency turn on curve assumption PB = 57%, PY = 57% eff(non-photonic) = 80% eff(photonic) = 30% eff(fake hit) = 40% 非対称度の理論曲線 と予想統計誤差

Kyoto Univ. / JSPS / RIKEN 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 2010/9/11 JPS fall meeting 24

Kyoto Univ. / JSPS / RIKEN electrons in each HBD sector 2010/9/11 JPS fall meeting 25 HBD sector EastWest Black: all e Blue: e- Red: e+