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 ) 40 GeV 20 GeV Pt distribution of tau jet (M H =125GeV) Low Pt Tau jet identification and reconstruction are very important to increase statistics. Our Pt threshold of tau jet is 40GeV But many signals are in the lower Pt region. Invariant mass distribution of VBF H  tautau (M H =120GeV) with fast simulationBG Signal But as we can see the statistics of the signal is limited.  We have developed tau identification optimized low Pt region VBF H  tau tau is promising channel for Higgs discovery

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 track3tracks 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) reconstruction identification We also required isolation there is no more Pt>2GeV track in  R<0.4. Tau 1prong Tau 3prong QCD Jet

eta phi PreSamplerEM1EM2EM3 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   Seed Cell Tile Sampling 0 LArHEC Sampling If Seed Cell is not on LArEM  Cell-based narrowness

Narrowness distribution after 1prong/3prong selection Narrowness Signal QCD(35-70GeV) QCD(17-35GeV) 1prong3prong We can enhance the signal against the BG by setting narrowness threshold. For example 0.7/0.6(1prong/3prong)

 Efficiency & Rejection prong3prong We plotted efficiency/rejection as the function of visible Tau Pt. Visible tau Pt [GeV] Tagging Efficiency 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) 1.0 EMEt/TrkPt 1.0 EMEt/TrkPt ~ 1 && HDET/TrkPt ~ 0 を veto Cut の optimize をする。

 muon veto EMEt/TrkPt HDEt/TrkPt 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 phi eta phi eta phi

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。  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)

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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 *  (5)  <  l,  <  (6) |cos  lh | < 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  <  < 

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 signal So 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 0.42fb Signal…

Introduction(2) … ATLAS  ATLAS 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 HD LAr HEC LAr FCal Muon System