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Higgs + 1jet Signatures

Higgs + 1jet Signatures. Yaquan Fang, Bruce Mellado, William Quayle and Sau Lan Wu University of Wisconsin-Madison TEV4LHC Workshop, BNL Higgs Session 02/04/05. Outline. Introduction Combined H+0jet and H+1jet Analysis New discovery channel: H+1jet

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Higgs + 1jet Signatures

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  1. Higgs + 1jet Signatures Yaquan Fang, Bruce Mellado, William Quayle and Sau Lan Wu University of Wisconsin-Madison TEV4LHC Workshop, BNL Higgs Session 02/04/05

  2. Outline • Introduction • Combined H+0jet and H+1jet Analysis • New discovery channel: H+1jet • New discovery channel: H WW(*)+1jet • Calibrating Forward jets • Outlook

  3. ATLAS Eur.Phys.J. C32S2 (2004) 19-54 • Most recent combination includes inclusive and H+2j (VBF) analyses • Inclusion of H+2j (VBF) analyses have significantly enhanced sensitivity to SM Higgs • Important role at low masses of H+2jets (VBF) • Need to add H+1j channels TDR+VBF

  4. Combined H+0jet and H+1jet Analysis

  5. Motivation • Analysis of H+1jet was proposed by S.Abdullin et al. (Phys. Lett. B431: 410, 1998) • Applied in ATLAS by V.Zmushko • ATL-PHYS-1999-014 and ATL-PHYS-2002-020 • Recent re-analysis by Wisconsin • An important question was not addressed: • Is H+1jet, an alternative or a default analysis? • Can the inclusive and H+1jet analysis coexist? Search for  resonances are most optimal when H+0j and H+jets are combined

  6. Optimization of Combined Analysis Pre-selection Pick event if PT1>40 GeV and PT2>25 GeV • Four variables in the signal significance optimization • PT1 ,PT2 ,PTJ and MJ +1j Analysis Pick event if pass cuts on PT1,PT2,PTJ and MJ +0j Analysis Pick rest of the events

  7. H+0j H+0j H+0j H+0j H+1j H+1j H+1j H+1j Optimization Fixed Fixed Effective cross-sections in 2 window

  8. Optimization (cont) H+1j H+0j MC Statistics correspond to ~50 fb-1

  9. Purely inclusive analysis

  10. Overview and Plans for Combined  Analysis • Most optimal way of searching Higgs with  is to combine H+0j and H+1j analysis • Enhances significance by at least 30% • Enhancement will grow because of a number of factors, which will be addressed with full simulation • Resolution  improves with Higgs PT • Photon efficiency improves with PT (ID relaxation for large PT) • Well defined vertex with in j final state • j Analysis has more kinematic variables to use in multivariate analysis

  11. H +1 jet B.Mellado, W.Quayle and Sau Lan Wu (hep-ph/0406095) Accepted by referee in PL

  12. H()+1jet at the LHC • Tag one semi-central jet, require PTH>100 and MHJ>700 GeV and a loose central jet veto (“top killer”) • Allow significant contribution from ggh Higgs Decay Products PTH>100 GeV Tag jet  Not Tagged MHJ Tag jet  Loose Central Jet Veto (“top killer”) Quasi-central Tagging Jet

  13. LO effective cross-sections (MH=120 GeV) Signal Significance for 30 fb-1 (MH=120 GeV 10% systematic error on background)

  14. Jet Jet Overlap With H+2jets (VBF) • D.Zeppenfeld, D.Rainwater, et al. proposed to search for a Low Mass Higgs in association with two jets Tagging Jets   Central Jet Veto Higgs Decay Products

  15. Overlap With H+2jets (VBF) Fraction of signal events in H+1j analysis that pass H+2j analysis after successive cuts • With conservative K factors the overlap is 24% • Higher order corrections on ggh are large • Under investigation in collaboration with SHERPA authors H+1j and H+2j (VBF) analyses should run in parallel, adding significant power to H->

  16. Count on 10% systematic error Critical to know shape of M forZ

  17. Control Sample 3 Signal Region Control Sample 1 Control Sample 2 Z  Loose cuts on Jets Z  Tight cuts on Jets Z ee, Tight cuts on Jets Z ee, Loose cuts on Jets From my talk at Higgs session of TEV4LHC 17/09/04 • Two independent ways of extracting Z shape Determine shape and normalization of Z  background MC extrap. is validated 85<Mll <95 GeV Replace Zee, by Z MC extrap. Mll <75 GeV MHJ

  18. Control Sample 2 Signal Region Z  Loose cuts on MHJ Z  Tight cut on MHJ Shape of M in Z(Method I) • All cuts are kept the same except for the invariant mass of the Higgs candidate and the tagging jet • Assume electrons, muons, jets and missing ET have been calibrated with Zee, • Jet activity in MC is validated with Zee, • Go from Box 1 to Box 3 • Use MC to obtain M shape in signal-like region MC extrap.

  19. Shape of M in Z(Method I) • Shape of M stable with MJ • Changes in spectrum can be corrected with MC • Need to verify this statement with full simulation

  20. Control Sample 3 Signal Region Z ee, Tight cuts on MHJ Z  Tight cuts on MHJ Replace Zee, by Z Shape of M in Z(Method II) • Use data with Zee, and apply same cuts on jets as in the signal-like region. • Remove the two electrons/muons (both calorimeter and tracking) and replace them with ’s, which have the same momenta • Needs to be tested with full simulation at ATLAS

  21. Normalization ofZ using Zee, • Zee, offers about 35 times more statistics w.r.t to Zll • Ratio of efficiencies depends weakly with MHJ and can be easily determined with MC after validation with data

  22. HWW(*) +1 jet B.Mellado, W.Quayle and Sau Lan Wu to be submitted to journal

  23. Use basic property that leading jet associated with Higgs is tends to be more forward than in QCD backgrounds  of leading jet

  24. Control samples in data well defined • W.Quayle will elaborate on this point during next workshop at CERN Mll ll

  25. Preliminary results for combined H WW(*) analysis • Three non-overlapping analysis defined • Background subtraction using data HWW(*) +2jet HWW(*) with jet veto HWW(*) +1jet

  26. Calibrating Forward Jets

  27. Rate of leading jet in Zee, after c.j.v. • Z ee, in association with jets gives a large statistics sample for the calibration of jets and missing ET

  28. Used SHERPA to generate Zee in association with at least one jet. Use PT balance between Zee and leading jet to calibrate forward jets • The addition of extra legs to model sub-leading jets changes the position of the peak by less than 2% • Gives upper bound on theoretical errors

  29. Outlook and Plans • Combined H+0j and H+1j enhances signal significance by at least 30% • Inclusion of new channel, H+1j, enhances further the power of H channels • Pursue combined analysis of Hll+1j, Hll+2j and Hlh+1j, Hlh+2j • Assessed new discovery channel: HWW(*)+1j • Combination of HWW(*) with 0j, 1j and 2j, as three non-overlapping analyses enhances tremendously sensitivity to Higgs Re-evaluate the ATLAS significance with combined H+0,1,2j analyses with full simulation

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