riken phenix ミーティング d 論用研究 進捗報告 単...
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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. 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. - PowerPoint PPT PresentationTRANSCRIPT
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~
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
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 )
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 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 )
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
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
Kyoto Univ. / JSPS / RIKEN
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
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
D
e
non-photonic electron
ee
photonic electron
0 ~ field 0 ~ masspair
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
Kyoto Univ. / JSPS / RIKEN
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}
Kyoto Univ. / JSPS / RIKEN
HBD charge distribution (West)
10
North South North South
Sect6
Sect7
Sect8
Sect9
Sect10
Sect11
strange shape
Red: merged clusterBlue: separated cluster
low stat.
low stat. 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 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
Kyoto Univ. / JSPS / RIKEN
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
Kyoto Univ. / JSPS / RIKEN
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
2010/9/11 JPS fall meeting 14
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。
Kyoto Univ. / JSPS / RIKEN
pt distribution of each component (East)
2010/9/11 JPS fall meeting 15
North South North South
Sect0
Sect1
Sect2
Sect3
Sect4
Sect5
NDF = 94
Kyoto Univ. / JSPS / RIKEN
pt distribution of each component (West)
16
North South North South
Sect6
Sect7
Sect8
Red: merged clusterBlue: 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 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
Kyoto Univ. / JSPS / RIKEN
D
e
non-photonic electron
non-photonic electron と photonic electron の抽出~ next step ~
2010/9/11 JPS fall meeting 18
non-photonic electron
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
0 ~ field 0 ~ masspair
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
Kyoto Univ. / JSPS / RIKEN
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)
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 distributionform 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
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
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