Post on 09-Jan-2016
description
TauID Algorithm TauID Algorithm に関する研究に関する研究
Motivation
Tau identification
To do for improvement
conclusion
中村浩二
Motivation (TauID の改良 )
40 GeV40 GeV
20 GeV20 GeV
Pt distribution of tau jet (MH=125GeV)
Low Pt Tau jet identification and reconstruction Low Pt Tau jet identification and reconstruction are very important to increase statistics.are very important to increase statistics.
Our Pt threshold of tau jet is 40GeOur Pt threshold of tau jet is 40GeV V But many signals are in the lower But many signals are in the lower Pt region. Pt region.
Invariant mass distribution of VBF Htautau (MH=120GeV) with fast simulation
BGBG
SignalSignal
But as we can see the But as we can see the statistics of the signal is statistics of the signal is limited.limited.
We have developed tau identification optimized low Pt regionWe have developed tau identification optimized low Pt region
VBF HVBF Htau tau is promising chatau tau is promising channel for Higgs discovery nnel for Higgs discovery
Tau identification Tau candidates are selected base
d on track (finding Isolate 1 track or 3 tracks)
We also use cells information .
Find Pt >5 GeV tracks
only 1 track 3tracks in R<0.1(Find two more Pt>2GeV
tracks)
Find a seed cell associated with this track, and make Cluster
(The seed is defined as a cell with larger than 6 of Noise near the track)
“Narrowness” cut is applied for identification
( I will talk in later slides)
reconstructionidentification
We also required isolation there is no more Pt>2GeV track in R<0.4.
Tau 1prong
Tau 3prong QCD
Jet
eta
phi PreSampler EM1 EM2 EM3
0.4
0.4 We use cell based narrowness definition not R.
Energy deposit on EM calorimeter
ATLAS の EM calorimeter は、 presampler と、 3 つの sampling 層からなる。
Sampling 2 が、 main component で、 x=0.025x0.025 と、 segment が細かい。
LArEM Sampling 2
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0.025
0.025
Seed Cell
Tile Sampling 0 LArHEC Sampling 0
0.1
0.1
If Seed Cell is not on LArEM
77
33
EMEtEMEt
Narrowness
3x3
1x1
HDEtHDEt
Narrowness
Cell-based narrowness
Narrowness distribution after 1prong/3prong selection
Narrowness
Narrowness
Signal
QCD(35-70GeV)QCD(17-35GeV)
1prong
3prong
We can enhance the signal against the BG by setting narrowness threshold. For example 0.7/0.6(1prong/3prong)
Efficiency & Rejection
0.7 0.61prong
3prong
We plotted efficiency/rejection as the function of visible Tau Pt.
Visible tau Pt [GeV]
Taggin
g E
ffici
ency
Jet Pt [GeV]
1pr…0.7 3pr…0.6
1/R
50% の efficiency が得られる。 Rejection に関しては、改善の可能性がある。
For di-jet sample(20GeV-
140GeV)
Total
quark jet gluon jet
50
10
To do…Track invariant mass for 3prong
Signal
Di-Jet
Track invariant mass for 3prong [GeV]
M±=139.6 [MeV] を仮定して、 3 本の track の invariant mass を求める。
Electron veto Inclusive Tau
Gen Matching Tau
Electron peak !
Pt(Pi+-)<Pt(Pi0)
Gen Matching Tau purely tau Inclusive Tau Signal MC all tau candidate (tau, electoron,muon,VBFjets)
1.0EMEt/TrkPt
EMEt/TrkPt1.0
EMEt/TrkPt ~ 1 && HDET/TrkPt ~ 0 を veto
Cut の optimize をする。
muon veto
EMEt/TrkPt
HD
Et/T
rkPt
Electron
HDEt=0 EMEt~1
muon
EMEt~HDEt~0
Inclusive Tau
Gen Matching Tau
Muon は、 tau jet Et cut
で veto される
QCD Event Topology のcheck
Rec Track (iPad)
Mean :6.3
# of Tracks in 1 Jet
~10% becomes 1pr/3pr candidate
Di-Jet event Pt>2GeV tracks
▼ # of Tracks distribution
Pt>2GeV track event display
eta
phi
eta
phi
eta
phi
eta
phieta
phi
eta
phi
ConclusionVBF process で生成し、 tau レプトン対に崩壊する Higgs 粒子探索で、統計を増やすため、 low Pt の tau に optimize した、 track base の tauID のアルゴリズムを開発中である。
Efficiency に関しては、 50% 程度出ているが、 Rejectionに関しては、十分な性能が出ていない。
QCD background を suppress するため、 Rejection factor を、現在の 3-5 倍よくする必要がある。 -> Wjjj, jjjj BG から。
3prong の track invariant mass cut
Lepton veto
QCD event topology の再チェック
0 +- invariant mass
すべての cut valuable の optimization などなど
To do (Plan)
Back Up
Signal selection
(1) electron Pt>25GeV,muon Pt>20GeV(2) Tau jet with Pt>40GeV R >0.7(from lepton)(3) Forward Jet : At least 2 Jet , Pt>20GeV(Leading 40GeV)(4) Forward Jet :1*2<0,|1-2|>4.4 (5) 1+0.7< l,<2-0.7(6) |coslh| < 0.9 for missing Et(7) Transverse mass between lepton and missing energy less than 30GeV(8) Missing Et > 30GeV(9) Invariant mass of the tagged forward jets larger than 700GeV(10)Central Jet Veto : There is no Pt>20GeV jet in 1+0.7< <2-0.7
Background Major QCD background
o W+3jets : Wjjj -> ltaujj -> depend on mainly TauID
o bbjj : bbjj -> l tau jj bbjj -> l j tau j
o jjjj : jjjj -> l tau jj
o WWjj : WWjj -> tau tau jj -> cross section is small o ttbar : WWbb ->tau tau jj
Z-> background o Z+njets : Zjj -> tau(l)tau(h)jj
Final state is the same as the signalSo we can only use “central jet veto” for suppress the BG
last talk of this session
Fake of W->lepton(tau) is also suppress with W transverse Mass cut
0.27fb
0.19fb
0.00fb
0.04fb
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0.42fbSignal…
Introduction(2) … ATLASATLAS 検出器
飛跡検出器Pixel シリコンピクセル検出器SCT シリコンマイクロストリップ検出器
TRT 遷移輻射ストローチューブチェンバー
カロリーメータLAr EM 液体アルゴンカロリーメータ (Pb)
Tile HD シンチレータタイルカロリメータ
LAr HEC ハドロンエンドキャップ (Cu)
LAr FCal 超前方カロリーメータ (Pb)
Muon 検出器MDT ドリフトチューブチェンバー
TGC,RPC ,CSC トリガー用チェンバー
LAr EM
Tile HDLAr HEC
LAr FCal
Muon System