Tau identification for VBF H tautau

TauID Algorithm に関する研究
Motivation
Tau identification
To do for improvement
conclusion
中村浩二
Motivation (TauIDの改良)
VBF Htau tau is promising
channel for Higgs discovery
But as we can see the statistics
of the signal is limited.
Pt distribution of tau jet (MH=125GeV)
40 GeV
20 GeV
Invariant mass distribution of
VBF Htautau (MH=120GeV) with
fast simulation
BG
Signal
Our Pt threshold of tau jet is
40GeV
But many signals are in the
lower Pt region.
Low Pt Tau jet identification and reconstruction are
very important to increase statistics.
 We have developed tau identification optimized low Pt region
Tau identification
 Tau candidates are selected
based on track (finding Isolate
1 track or 3 tracks)
 We also use cells information .
Find Pt >5 GeV tracks
only 1 track
Tau
1prong
Tau
3prong
QCD
Jet
We also required isolation
there is no more Pt>2GeV
track in DR<0.4.
3tracks in DR<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 6s of Noise near the track)
reconstruction
identification
“Narrowness” cut is applied for identification
( I will talk in later slides)
 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、DhxDf=0.025x0.025と、
segment が細かい。
phi
PreSampler
EM1
EM2
EM3
0.4
0.4
eta We
use cell based narrowness definition
not DR.
 Cell-based narrowness
LArEM Sampling 2
Tile Sampling 0
LArHEC Sampling 0
0.025
f
0.025
0.1
If Seed Cell is
not on LArEM
33
7 7
0.1
h
EMEt33
Narrowness
EMEt77
Seed Cell
Narrowness
HDEt1x1
HDEt3x3
Narrowness distribution after 1prong/3prong
selection
We can enhance the signal against the BG by setting
narrowness threshold. For example 0.7/0.6(1prong/3prong)
1prong
3prong
Signal
QCD(17-35GeV)
QCD(35-70GeV)
Narrowness
Narrowness
Efficiency & Rejection
We plotted efficiency/rejection as
For di-jet sample
the function of visible Tau Pt.
(20GeV-140GeV)
Tagging Efficiency
1pr…0.7 3pr…0.6
1prong 3prong
0.7 0.6
Total
gluon jet
quark jet
1/R
10
50
Visible tau Pt [GeV]
Jet Pt [GeV]
50%のefficiency が得られる。Rejectionに関しては、
改善の可能性がある。
To do…
Track invariant mass for 3prong
Mp±=139.6 [MeV] を仮定して、3本の
track の invariant mass を求める。
Signal
Di-Jet
Track invariant mass for 3prong [GeV]
Electron veto
Gen Matching Tau
purely tau
Inclusive Tau
Inclusive Tau
Electron peak !
Signal MC all tau candidate
(tau, electoron,muon,VBFjets)
Gen Matching Tau
1.0 EMEt/TrkPt
Pt(Pi+-)<Pt(Pi0)
1.0
EMEt/TrkPt ~ 1 &&
HDET/TrkPt ~ 0 を veto
Cut のoptimize をする。
EMEt/TrkPt
muon veto
Gen Matching Tau
Muonは、tau jet Et cut
でveto される
Inclusive Tau
muon
EMEt~HDEt~0
EMEt/TrkPt
Electron
HDEt=0 EMEt~1
QCD Event Topology のcheck
Di-Jet event Pt>2GeV tracks
phi
phi
Pt>2GeV track event display
▼ # of Tracks distribution
Rec Track (iPad)
~10% becomes
1pr/3pr candidate
Mean :6.3
# of Tracks in 1 Jet
eta
phi
phi
eta
phi
eta
eta
phi
eta
eta
Conclusion
VBF 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。
To do (Plan)
3prong のtrack invariant mass cut
Lepton veto
QCD event topology の再チェック
p0 p+- invariant mass
すべての cut valuable のoptimization
などなど
Back Up
Signal selection
(1) electron Pt>25GeV,muon Pt>20GeV
(2) Tau jet with Pt>40GeV DR >0.7(from lepton)
(3) Forward Jet : At least 2 Jet , Pt>20GeV(Leading 40GeV)
(4) Forward Jet : h1*h2<0,|h1-h2|>4.4
(5) h1+0.7< hl,t <h2-0.7
(6) |cosflh| < 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 h1+0.7< h <h2-0.7
Background
Signal…
 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
o WWjj
: WWjj -> tau tau jj -> cross section is small
o ttbar
-> l tau jj
last talk of this session
: WWbb ->tau tau jj
Fake of W->lepton(tau) is also suppress with W transverse Mass cut
 Z->tt background
o Z+njets : Zjj -> tau(l)tau(h)jj
Final state is the same as the signal
So we can only use “central jet veto” for suppress the BG
Introduction(2) … ATLAS
ATLAS検出器
LAr HEC
Tile HD
LAr FCal
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
LAr EM
Muon System
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

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