riken phenix ミーティング d 論用研究　進捗報告単...

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

2010/9/11 2JPS fall meeting

LG 21

21

gg

ggadxdxA gg

LLLL

21~


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

eKD

eKD

e

e

0

0

photonic electron 光子転換 Dalitz 崩壊直接光子生成 small, but significant at high pT

non-photonic electron heavy meson 崩壊 Kaon 崩壊 vector meson 崩壊　

material)(in )(0 ee

ee )(0

D

0K e

e

cc

eKK ee : 03

eeJ ,,,,

XeD ( 欲しい signal )


simulation result of e yield

heavy meson 測定におけるバックグラウンド


photonic electron 光子転換 Dalitz 崩壊直接光子生成 small, but significant at high pT

non-photonic electron heavy meson 崩壊 Kaon 崩壊 vector meson 崩壊　

material)(in )(0 ee

ee )(0

eKK ee : 03

eeJ ,,,,

XeD

dominant backgroundbackground

background~ a few% ofnon-photonic electrons

photonic~95%

negligible

HBD により除去

( 欲しい signal )


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


HBD

CF4 gas

D

e

non-photonic electron( single electron )

ee

photonic electron( pair electrons )

Mesh

CsI layer

Triple GEM

Readout Pads

e-

PrimaryionizationγHV

e

0 ~ field 0 ~ masspair

B

50cm

GeV/c 4p


HBD Event Display

add blob (cluster) information private clustering algorithm

6

HBD charge [p.e.]

electron track

seedpad

seedpad

seedpad

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 Dead

NotStable

SN S N


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)



HBD non-photonic & photonic 識別能力


D

e

non-photonic electron

ee

photonic electron


Bsingle e clustermerged cluster

, MeV/c135regionrich Dalitz

mass

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


HBD charge distribution (East)

Not including HBD efficiency– Integral(0,inf) = 1

9

North South North South

Sect0

Sect1

Sect2

Sect3

Sect4

Sect5very low stat. very low stat.

very low stat. not stablegain

Red: merged clusterBlue: separated cluster

low stat.

#{bin content}/#{all entry}


HBD charge distribution (West)

10


Sect6

Sect7

Sect8

Sect9

Sect10

Sect11

strange shape


low stat.

low stat. low stat.


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}


HBD association efficiencyw/o HBD size cut

HBD association efficiencyw/ 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


HBD association efficiencyw/o HBD size cut

HBD association efficiencyw/ 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%

goodregion

goodregion

26.5cm

22.9cm

18.0cm

14.0cm


HBD charge distribution for electron tracks

sect8 north0.75<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 Ne

single and Nemerge


HBD cluster charge distribution for electron trackssingle e

peakmerged

peak

electronsingleN

electronmergeN

fitting with the reference charge distributionsfitting 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。


pt distribution of each component (East)



Sect0

Sect1

Sect2

Sect3

Sect4

Sect5

NDF = 94


pt distribution of each component (West)

16


Sect6

Sect7

Sect8


Sect9

Sect10

Sect11

NDF = 94


single e cluster と merged cluster の pt spectra


cross sectionresult of run2005

heavy quark ephotonic e sources

pt に対する振る舞いは正しく一致

fitting 結果、 Nesingle と Ne

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– pt=1GeV/c で　 ΔNsingle/Nsingle~ 0.3% の誤差

single e cluster and merged cluster spectra

fitting により求めた Nesingle 、 Ne

merge 、 Nfake


D

e


non-photonic electron と photonic electron の抽出~ next step ~



photonic electron (single e cluster on HBD)

photonic electron (merged cluster on HBD)

HBD single e clusterHBD merged cluster

a)

b)

c)

a)

b)

c)

0

ee

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

ee

photonic electron


B

electron candidatesin 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 shouldbe found around the detected track

single cluster producedby non-photonic electron

single cluster producedby photonic electron


non-photonic and photonic electron spectra

20

reference r distributionform Dalitz events

Black : electron data (0.75 < pt < 1.00 GeV/c)Blue: merged cluster componentRed: separated cluster componentViolet: Blue + Red

r [cm]

r [cm]

other clusters r distribution + fitting

Red: separated clustersBlue: merged clusters

0.75 < pt < 1.00 GeV/c

no correlation

correlation

~ same distribution as non-photonic electron clusters(no correlation)


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


reference r distributionform Dalitz events

0.75 < pt < 1.00 GeV/c

distance [cm]


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



expected error bar of ALL


fitting result(sect 8 north) 0.75 < pt < 1.00 GeV/c

dataLL

signalLL

dataLL

dataLL

dataLL

dataLL

signalLL

dataLL

backgroundLL

dataLL

signalLL

AA

AA

AAA

A

ArrA

rA

1

)()(1)(

111

1

2

2

4

22

22

~10-3

~10-3

~10-2

ε = S/(S+N)

accept region

efficiency turn on curve

assumptionPB = 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


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


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