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

7733

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

?? fb

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