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ttHww study in ATLAS

ttHww study in ATLAS. Lianyou SHAN ATLAS group of IHEP, CAS LHC-MiniWS12, Xi’an June 15’ th 2014. Outline. Introduction Recent Higgs analyses in ATLAS ttHww studies Summary. Introduction. To this workshop Honor and pleasure to visit Xi’an An ancient land with legends, thanks !

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ttHww study in ATLAS

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  1. ttHww study in ATLAS Lianyou SHAN ATLAS group of IHEP, CAS LHC-MiniWS12, Xi’an June 15’th 2014

  2. Outline • Introduction • Recent Higgs analyses in ATLAS • ttHww studies • Summary ttHww in Xi'an

  3. Introduction • To this workshop • Honor and pleasure to visit Xi’an • An ancient land with legends, thanks ! • Seeking for overlap/collaborations • Learn more from you theorists • Informal and preliminary • Please pardon for possible ignorance/bias • Please do not cite/spread the plots/numbers yet • Birdview of LHC • ATLAS in brief ttHww in Xi'an

  4. 日内瓦湖 • CMS • LHCb • 机场 • ALICE • ATLAS Birdview of LHC • circum27 Km，100m underground CM energy 8-14TeV ttHww in Xi'an

  5. 25 ns 8cm length & 16*10-4 cm radius Event rate: N = L x (pp)  109 interactions/s Mostly soft (low pT) events Interesting hard (high-pT) events are rare  very powerful detectors needed ttHww in Xi'an

  6. ATLAS in Brief NJU SDU IHEP, USTC ttHww in Xi'an

  7. ATLAS in BRIEF • physics principle known • Quantified with empirical practice • Range is important • Material,geometry, • Readout… • Precision is more crucial • Dead time • ERRORS are always there ttHww in Xi'an

  8. Pile up effiEct • A price trade for high Lumi • Main challenge to 2012 , even Run2 analyses • Obstacle • In electron/muon reconstruction • In γ/jet energy measurement • Finally extra Backgrounds Fortunately the experiences from Run1 are leading us out of the backgrounds ttHww in Xi'an

  9. ATLAS performance • Trigger rate • Particle reconstruction an d Identification • 80% 8000 • 75% • 90% 900 • 60% 30 • 60% 400(8) • Event shape 60% 6 • Tot • Few% systematics from each individual source ttHww in Xi'an

  10. Most moving A new particle is announced in July 4 of 2012, via γγ and ZZ Compatible with the Standard Model Higgs, 2013 Nobel ttHww in Xi'an

  11. Recent Higgs analyses in ATLAS • Subjects • Production strength • Mass combination • Rare decays • Higgs decay to taus • invisible • Reminders/Warning : • Not a full list and tech details are skipped ( doc 600p+ ) • Neither ATLAS result Nor evidence for your paper • Merely for your peekings/feelings ttHww in Xi'an

  12. Production strength via γγ Benefit from new calibration, main systematics are … less dependent on mass In ZZ channel one peeks : ttHww in Xi'an

  13. Higgs mass combining γγ & ZZ ttHww in Xi'an

  14. Rare decay to Zγ ttHww in Xi'an

  15. Decay to taus ttHww in Xi'an

  16. Invisible higgs ttHww in Xi'an

  17. ttHwwstudies • ATLAS Upgrades for Run2 • The Physics and status of ttHww • Simulations for Run2 • Some challenges ttHww in Xi'an

  18. Upgraded ATLAS • Pixel : extracted, repaired and reinserted • TRT leaks fixed • Insertable B Layer(IBL) upgraded • Tilecal and LAr LV power supplies • extracted, inserted, extracted, inserted… • Jet reconstruction, egamma energy • Muon repairing • RPC for trigger • CSC for better momentum • Some others … less sensitive to phys… ttHww in Xi'an

  19. Reminder for Run2 triggers • Single lepton trigger will be pre-scaled • Unless very high ptthreshould • Combined trigger is expected to help • Di-lepton, lepton+jets, lepton+MET … ttHww in Xi'an

  20. The physics in ttHww • The process read : • Or j3j4 /j1j2 can be replaced with 2 leptons • To explore : • 1’st direct measuring of Yukawa Yt • Searching for Massive (extra) Higgs • Detect possible CP Violation ( b term ) ttHww in Xi'an

  21. The physics in ttHww • We chosen better channels • SS2L ( 4.1% ) • 3L ( 2.6% ) or 2L+τ ( 4.1% ) • All are balances • Between x-sec and backgrounds • Please let me know • if you find better channels ttHww in Xi'an

  22. The status of ttHww • CMS : PAS HIG-13-020 • ttHWW signal is not established yet ttHww in Xi'an

  23. 8TeV ttHww in ATLAS • Objects definations |η| < 2.5 pT > 20 in SS2L Leading pT > 15 for 3L HT > 100GeV ttHww in Xi'an

  24. 8TeV ttHww in ATLAS • Reject main backgrounds • Wjets, Zjets suppression • lepton isolation • MET against Zjets • Further WZ suppression • ≥ 2 b-tag • fake is serious ttHww in Xi'an

  25. Preliminary numbers • This is NOT any result ! ttHww in Xi'an

  26. Simulations for Run2 • Siganl enhance over topless backgrounds • For the gluonic PDF • Unfortunately , ,are still heavy • Final particles are boost • survive di-lepton trigger • Survive pileup cleanings • Higher pTthreshould • Better b-tag • Upgraded IBL ttHww in Xi'an

  27. Only a hint An realistic extrapolation from 8 to 14 TeV There are also independent “predictions” ECLA-ATL-PHYS-PUB -2013-014 ArXiv 1307.7280-v2 Please note only 5 times of signal, close to the margin of statistics ttHww in Xi'an

  28. Challenges • Estimate fake from real data • A essential but tedious/hard step • Uncertainty from high jets multiplicity • No sufficiently reliable x-sect for and WZ yet • An independent measurement of ? • Event topology reconstruction • probable pairing the charged lepton and b ? • Probable recovering or merging of neutrinos ? ttHww in Xi'an

  29. kinematical topology reconstruction Could we find an angle or an energy As the signature of Higgs ? • Something like fat jet ? • Any variant of MT ? Something like MT2 ? • Most probable/likely ? Charge lepton assignment ? neutrino recovering ? ttHww in Xi'an

  30. Summary • Higgs properties are investigated in LHC • But the output is still very preliminary • expect more data from Run2 • ttHww seem meaningful • Preparations/progress for experiment • The core parts are identified … • Your contributions/solutions are welcome ! Thanks ! ttHww in Xi'an

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