Kyoto Univ JSPS RIKEN PHENIX n PHENIX heavy

Kyoto Univ. / JSPS / RIKEN PHENIXにおける重クォーク生成測定 n 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 n PHENIXで測定される電子の生成源 photonic electron non-photonic electron n 光子転換 n n Dalitz 崩壊 n heavy meson 崩壊 ( 欲しい signal ) Kaon 崩壊 n vector meson 崩壊 n 直接光子生成 small, but significant at high p. T 2010/9/11 　 JPS fall meeting 3

Kyoto Univ. / JSPS / RIKEN 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 n 光子転換 n Dalitz 崩壊 n background HBD により除去 直接光子生成 small, but significant at high p. T photonic ~95% non-photonic electron n heavy meson 崩壊 ( 欲しい signal ) Kaon 崩壊 background vector meson 崩壊 ~ a few% of non-photonic electrons negligible 　 2010/9/11 JPS fall meeting 4

Kyoto Univ. / JSPS / RIKEN Hadron Blind Detector (HBD) n Hadron Blind Detector – Cs. I蒸着のGEMによるgas Cherenkov 検出器 n n hadron 除去( hadron 除去能力 > 10 ) – 27 mm pad size n – 1つの電子通過に対して 約 20 個の photoelectron を放出 CF 4 gas HV n γ e- Primary ionization 2010/9/11 photonic electron ( pair electrons ) Mesh Cs. I layer Triple GEM Readout Pads hadron : 平均約 1 photoelectron non-photonic electron ( single electron ) 50 cm HBD Cherenkov blob 直径 ~ 36 mm – non-photonicとphotonicでクラスターの電 荷量が異なる n JPS fall meeting 電荷量によって区別することが可能 5

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

Kyoto Univ. / JSPS / RIKEN Electron Cut n electron cut – – – – n abs(bbc_z) < 20 cm quality==31|51|63 n 0>=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 n n 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 < 135 Me. V non-photonic electron eff. ~ 80% reject single e cluster 2010/9/11 eff. ~ 30% JPS fall meeting merged cluster 8

Kyoto Univ. / JSPS / RIKEN HBD charge distribution (East) #{bin content}/ #{all entry} North South Sect 0 Sect 3 low stat. very low stat. not stable gain Sect 1 very low stat. Sect 4 very low stat. Sect 2 Sect 5 Red: merged cluster Blue: separated cluster n Not including HBD efficiency – Integral(0, inf) = 1 9

Kyoto Univ. / JSPS / RIKEN HBD charge distribution (West) North South Sect 6 Sect 9 strange shape low stat. Sect 7 Sect 10 low stat. Sect 8 low stat. Sect 11 Red: merged cluster Blue: separated cluster 10

HBD charge distribution for Hadrons (fake hits) Kyoto Univ. / JSPS / RIKEN HBD charge distribution of “hadron cut” + “hbd association cut” tracks requiring following cuts n – hadron cut n n n n n – n n n abs(bbc_z) < 20 cm quality == 63 mom > 0. 5 && mom < 3. 0 n 0 <= 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) threshold in offline code hbd association cut n n #{hadron cut && hbd associ cut}/ #{hadron cut} abs(hbdsdphi) < 3. 5 abs(hbdsdz) < 3. 5 hbdsize >= 2 HBD charge [p. e. ] normalized with the number of tracks satisfying hadron cut hadron efficiency < 10% 11

Kyoto Univ. / JSPS / RIKEN 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 n HBD cut HBD association efficiency w/ HBD size cut n – abs(hbdsdphi) < 3. 5 – abs(hbdsdz) < 3. 5 – hbdsize >= 2 今使用しているcut – abs(hbdsdphi) < 3. 5 – abs(hbdsdz) < 3. 5 n efficiency ~ 193/213 = 91% HBD cut n efficiency ~ 162/213 = 76%

HBD efficiency with J/phi events (select good region) Kyoto Univ. / JSPS / RIKEN 14. 0 cm good region HBD association efficiency w/o HBD size cut n HBD cut 18. 0 cm 26. 5 cm HBD association efficiency w/ HBD size cut n efficiency ~ 100% within error HBD cut – abs(hbdsdphi) < 3. 5 – abs(hbdsdz) < 3. 5 – hbdsize >= 2 – abs(hbdsdphi) < 3. 5 – abs(hbdsdz) < 3. 5 n 22. 9 cm good region n efficiency ~ 66/77 = 86%

Kyoto Univ. / JSPS / RIKEN データからの single e cluster 成分と merged cluster 成分の分離 HBD cluster charge distribution for electron tracks n single e peak 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 merged peak – pt が高くなるにつれて、nonphotonic 成分の占める割合が 大きくなっているのがわかる。 fitting result fitting with the reference charge distributions 8 north) 0. 75 < for pt <electron 1. 00 Ge. V/c HBD(sect charge distribution tracks sect 8 north 0. 75<pt<1. 00 Ge. V/c n 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 2010/9/11 JPS fall meeting 14

Kyoto Univ. / JSPS / RIKEN pt distribution of each component (East) North South Sect 0 Sect 3 Sect 1 Sect 4 Sect 2 Sect 5 NDF = 94 2010/9/11 JPS fall meeting 15

Kyoto Univ. / JSPS / RIKEN pt distribution of each component (West) North South Sect 6 Sect 9 Sect 7 Sect 10 Sect 8 Sect 11 Red: merged cluster Blue: separated cluster NDF = 94 16

Kyoto Univ. / JSPS / RIKEN single e cluster と merged cluster の pt spectra single e cluster and merged cluster spectra n n 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 n electron の分布の 2つの異なる成 分の分離に成功 – pt=1 Ge. V/cで　ΔNsingle/Nsingle~ 0. 3%の誤 差 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 2010/9/11 JPS fall meeting cross section result of run 2005 17

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

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 nonphotonic election and photonic election – calculate the cluster distance distribution for non-photonic elections and photonic electrons – fit these distributions to cluster distribution of Run 9 electron event, detected and determine the fraction e+ e π D single cluster produced by non-photonic electron eanother cluster should be found around the detected track single cluster produced 19 by photonic electron

Kyoto Univ. / JSPS / RIKEN non-photonic and photonic electron spectra reference r distribution form Dalitz events correlation other clusters r distribution + fitting 0. 75 < pt < 1. 00 Ge. V/c Red: separated clusters Blue: merged clusters r [cm] no correlation ~ same distribution as non-photonic electron clusters (no correlation) r [cm] Black : electron data (0. 75 < pt < 1. 00 Ge. V/c) Blue: merged cluster component Red: separated cluster component Violet: Blue + Red 20

Kyoto Univ. / JSPS / RIKEN difficulties in reference distribution reference r distribution form Dalitz events n 0. 75 < pt < 1. 00 Ge. V/c not same as real distribution – large angle decay of pi 0 is out of Central Arm acceptance n distance [cm] n low statistics PISA simulation is required – PISA analysis is on going 2010/9/11 JPS fall meeting 21

Kyoto Univ. / JSPS / RIKEN Roadmap to ALL n HBD simulation (hopefully finish by Nov. ) – on going … – confirm HBD response for electrons – calculate the distance distribution n n extract non-photonic electron spectrum determine cross section spectrum (hopefully finish by Dec. or mid. Jan. ) – acc. x eff. calculation – compare with old data n 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 非対称度の理論曲線 と予想統計誤差 fitting result (sect 8 north) 0. 75 < pt < 1. 00 Ge. V/c ε = S/(S+N) ~10 -3 ~10 -2 ~10 -3 accept region 2010/9/11 efficiency turn on curve assumption PB = 57%, PY = 57% eff(non-photonic) = 80% eff(photonic) = 30% eff(fake hit) = 40% JPS fall meeting 23