Tau ID Algorithm Motivation Tau identification To do

Tau. ID Algorithm に関する研究 Motivation Tau identification To do for improvement conclusion 中村浩二

Motivation (Tau. IDの改良) VBF H 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=125 Ge. V) 40 Ge. V 20 Ge. V Invariant mass distribution of VBF H tautau (MH=120 Ge. V) with fast simulation BG Signal Our Pt threshold of tau jet is 40 Ge. V 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 ² Tau candidates are selected based on track (finding Isolate 1 track or 3 tracks) ² We also use cells information. Find Pt >5 Ge. V tracks only 1 track Tau 1 prong Tau 3 prong QCD Jet We also required isolation there is no more Pt>2 Ge. V track in DR<0. 4. 3 tracks in DR<0. 1 (Find two more Pt>2 Ge. V tracks) Find a seed cell associated with this track, and make Cluster (The seed is defined as a cell with larger than 6 s of Noise near the track) reconstruction identification “Narrowness” cut is applied for identification ( I will talk in later slides)

Ø 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、 Dhx. Df=0. 025 x 0. 025と、segment が細かい。 phi Pre. Sampler EM 1 EM 2 EM 3 0. 4 eta We use cell based narrowness definition not DR.

Ø Cell-based narrowness LAr. EM Sampling 2 Tile Sampling 0 LAr. HEC Sampling 0 0. 025 f 0. 025 0. 1 If Seed Cell is not on LAr. EM 0. 1 h Seed Cell

Narrowness distribution after 1 prong/3 prong selection We can enhance the signal against the BG by setting narrowness threshold. For example 0. 7/0. 6(1 prong/3 prong) 1 prong 3 prong Signal QCD(17 -35 Ge. V) QCD(35 -70 Ge. V) Narrowness

ØEfficiency & Rejection We plotted efficiency/rejection as For di-jet sample the function of visible Tau Pt. (20 Ge. V-140 Ge. V) Tagging Efficiency 1 pr… 0. 7 3 pr… 0. 6 1 prong 3 prong 0. 7 0. 6 Total gluon jet quark jet 1/R 10 50 Visible tau Pt [Ge. V] Jet Pt [Ge. V] 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… ØTrack invariant mass for 3 prong Mp±=139. 6 [Me. V] を仮定して、3本の track の invariant mass を求める。 Signal Di-Jet Track invariant mass for 3 prong [Ge. V]

ØElectron veto Gen Matching Tau purely tau Inclusive Tau Electron peak ! Signal MC all tau candidate (tau, electoron, muon, VBFjets) Gen Matching Tau 1. 0 EMEt/Trk. Pt Pt(Pi+-)<Pt(Pi 0) 1. 0 EMEt/Trk. Pt ~ 1 && HDET/Trk. Pt ~ 0 を veto Cut のoptimize をする。 EMEt/Trk. Pt

Ømuon veto Gen Matching Tau Muonは、tau jet Et cut でveto される HDEt/Trk. Pt Inclusive Tau muon EMEt~HDEt~0 EMEt/Trk. Pt Electron HDEt=0 EMEt~1

ØQCD Event Topology のcheck Di-Jet event Pt>2 Ge. V tracks phi Pt>2 Ge. V track event display ▼ # of Tracks distribution Rec Track (i. Pad) ~10% becomes 1 pr/3 pr candidate Mean : 6. 3 # of Tracks in 1 Jet eta phi eta eta

Conclusion ²VBF 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tau. IDのアルゴリズムを開発中である。 ²Efficiency 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。 ²QCD 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) ² 3 prong のtrack invariant mass cut ²Lepton veto ²QCD event topology の再チェック ²p 0 p+- invariant mass ²すべての cut valuable のoptimization などなど

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Signal selection (1) electron Pt>25 Ge. V, muon Pt>20 Ge. V (2) Tau jet with Pt>40 Ge. V DR >0. 7(from lepton) (3) Forward Jet : At least 2 Jet , Pt>20 Ge. V(Leading 40 Ge. V) (4) Forward Jet : h 1*h 2<0, |h 1 -h 2|>4. 4 (5) h 1+0. 7< hl, t <h 2 -0. 7 (6) |cosflh| < 0. 9 for missing Et (7) Transverse mass between lepton and missing energy less than 30 Ge. V (8) Missing Et > 30 Ge. V (9) Invariant mass of the tagged forward jets larger than 700 Ge. V (10)Central Jet Veto : There is no Pt>20 Ge. V jet in h 1+0. 7< h <h 2 -0. 7

Background Signal… b f 2 0. 4 Ø Major QCD background o W+3 jets : Wjjj -> ltaujj -> depend on mainly Tau. ID b f 7. 2 0 o bbjj : bbjj -> l tau jj bbjj -> l j tau j o jjjj o WWjj o ttbar : jjjj -> l tau jj last talk of this session b f ? ? : WWjj -> tau jj -> cross section is small fb b 0 f 4 0. 0 : WWbb ->tau jj 0. 0 Fake of W->lepton(tau) is also suppress with W transverse Mass cut Ø Z->tt background fb 9 o Z+njets : Zjj -> tau(l)tau(h)jj 0. 1 Final state is the same as the signal So we can only use “central jet veto” for suppress the BG