Possible tuning of TGC digitization with collision data

TGC digitizationの改良について
織田
TGC-Jミーティング
2010年6月11日(金)
ATL-COM-PHYS-2010-283 ( as of 31st May )
“Performance of the ATLAS Muon Identification
in Minimum Bias p-p Collision Data at √s = 7 TeV “
p5, Fig4 :
6月1日
Muon Combined Performance
ミーティングでの結束氏のスライド
Data have fewer hits that are associated with a reconstructed muon than MC.
Possible reasons that cause this disagreement are:
- Hit efficiency differences between MC and Data.
- Dead chambers/channels and Masked channels are not taken into account in the MC.
- Cross talk is not taken into account in the MC.
1/10
TGC hit efficiency (1/2)
2008年秋
Wire supports (7mm width) and
• Cosmic data (filled symbol) have lower
efficiency than cosmic MC (open symbol). button supports (7mm diameter)
locate inside TGC.
• Difference is partially understood.
• Active area efficiency
– Test bench data : e~99%
– MC : e=100%
• Inefficiency around supports
• Path length/energy loss dependence
2/10
TGC hit efficiency (2/2)
Wire support
Button support
Unit is mm.
support
Fire Fire Not
fire
gas
Fire
Fire
• Neighboring areas of wire/button supports within 1mm are effectively
inefficient (e=0).
– Beam test : NIM A 367 (1995) 398
• If a charged particle passes through sensitive detector (gas volume), it makes a
hit in MC.
• Energy loss and path length are NOT checked.
• Inefficiency of neighboring region of support within “1mm” is NOT taken into
account.
• Efficiency in MC is always higher than reality.
• How we can improve TGC digitization?
3/10
Three possible solutions
1. Tuning (lowering) of the active area efficiency in digitization
– m_efficiencyOfWireGangs and m_efficiencyOfStrips of
TGC_DigitizationTool are now 100%.
 This is easy and fast.
 However, we cannot describe the position dependence and chambertype dependence of the inefficiency around supports with these two
overall parameters.
• There are 13 TGC chamber types.
2. Digitization using energy loss
– Need to add the energy loss variable in TGCSimHit.
– Emulate the discriminator with a threshold.
 The position dependence and chamber-type dependence of the
inefficiency will be well described (hopefully).
 We can easily implement and test this solution.
 Backward compatibility of TGCSimHit and digitization can be an issue.
3. Modification of detector description 試さない
– Split gas volume into sensitive volume and insensitive volume (around
supports).
 Position and chamber-type dependent inefficiency will be described
well.
 We also need to tune the active area efficiency.
 Not easy to test this solution.
4/10
解決案1 : Tuning (lowering) of the
active area efficiency in digitization
6月1日
Muon Combined Performance
ミーティングでの結束氏のスライド
Pt 15GeV ( STACO )
End cap
Forward
PT>4GeV
|eta| > 1
Red 100%
Green 98%
Blue 96%
Red – Green ~2.2%
Red – Blue ~4.1%
Changing the hit efficiency from 100% to 96%,
the mean of the number of TGC hits becomes somewhat fewer.
 Close to the distribution of data
5/10
解決案2 : Digitization using energy loss
• Geant simulationの出力であるTGCSimHitに
– energyDeposit [MeV] : G4double G4Step::GetTotalEnergyDeposit()
– stepLength [mm] : G4double G4Step::GetStepLength()
を追加。
– MuonSpectrometer/MuonSimEvent
• POOLファイルに記録する部分を更新。
– MuonSpectrometer/MuonCnv/MuonEventTPCnv
– MuonSpectrometer/MuonCnv/MuonEventAthenaPool
• TGCSimHitに値を詰めるところで、energyDepositと
stepLengthも詰めるように変更。
– MuonSpectrometer/MuonG4/MuonG4SD
• リリース15.6.10でコンパイルはできた。
6/10
•
•
•
•
pT=15GeV
etaが-3から+3までフラット
phiが-piから+piまでフラット
Positive muon 5000発、negative muon 5000発
左図の拡大図
d-ray?
2.8 mm以上の飛跡を持つ
ものが多い。
7/10
平均のエネルギー損失は1.4keV
左の拡大図 0.01keV未満の場合がある。
全体の1.2%
dE<0.01keVの場合(青)は飛跡が短い。
かすっただけのトラック
dE=0.2keVで切ればe=100%-3.3%=96.7%
8/10
dE<0.01keVの割合
サポート周り1mmの割合に
ほぼ等しくなるはず。
その割合はDaniel’s Table
に載っています。
まだ統計が少ない。
|h|
M4 E1はEIチェンバー。
他は1%くらいなのに19%と5%。
どこかにバグがあるはず。
9/10
今後試さないといけないこと
• MuonSpectrometer/MuonDigitization/TGC_Digitizationを
energyDepositを使うように実装すること。
– 簡単に実装可能。
– Backward compatibilityも問題ない。
• いくつかのpTでsingle muon MCをたくさん作る。
• 「サポート周り1mmの割合」を良く記述するかを確認する。
• 実データで検出効率を評価し、それに合わせて閾値を決める。
• もしくは、number of TGC eta/phi hitsの分布が合うように閾値を
決める。
• しかし、どういうMCを作れば良いのだろう?
• MinBias MCが良いが、個人的にたくさんのイベント x 何通りか
の閾値の組み合わせを作るのは大変。
• Single muon MCだと、pT分布、inflight decayの寄与が気になる。
10/10

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