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Y. Sumino (Tohoku Univ.)

Effects of Toponium Resonances in Higgs Boson Searches. Y. Sumino (Tohoku Univ.). Collab . S.Kawabata , Y.Kiyo , Y.Shimizu , H.Yokoya. ☆ Plan of Talk. Overview (incl. upshot) bkg for : 1-jet + mode bkg for : 2-jets + mode Summary.

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Y. Sumino (Tohoku Univ.)

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  1. Effects of Toponium Resonances in Higgs Boson Searches Y. Sumino(Tohoku Univ.) Collab. S.Kawabata, Y.Kiyo, Y.Shimizu, H.Yokoya

  2. ☆ Plan of Talk • Overview (incl. upshot) • bkg for: 1-jet + mode • bkg for: 2-jets + mode • Summary

  3. Typical event after all cuts for Higgs searches ( mode) GeV 1 tagged jet or 1 tagged + 1 untagged jets QCD (quasi-)resonances ( ISR: another tagged jet) Upshot of this talk: Contributions ofevents NLO (up-to-date) analysis 0-jet mode negligible Bkg for ATLAS collab., arXiv:1106.2748[hep-ex] 1-jet mode significant Good approx. Bkg for Up-to-date(?) analysis 2-jet mode significant Asai et al., EPJC32S2(2004)19 Likely not good approx. (large enhancement)

  4. Our analysis is based on MC simulations MadEvent MC@NLO Toponium@LHC(by Yokoya) LO NLO LO+LO bound-state eff. PYTHIA, Herwig PGS • Reservations: • Fast detector simulator • Unsophisticated jet reconstruction • No b-tag • No from • No real data to calibrate

  5. Toponium Production Hagiwara, Sumino, Yokoya Kiyo, Kuhn, Moch, Steinhauser, Uwer Tevatron Toponium@LHC LO MC@NLO Toponium@LHC LO MC@NLO LHC(TeV) Sumino, Yokoya MC events (parton level)

  6. : (1-jet + mode) Before cut After cut Threshold region becomes comparatively more important by the cuts.

  7. We find Cut efficiency below threshold Average cut eff. above threshold ~ factor 7 • Main enhancements in • Jet veto constitute single jet • cut low mass • Lepton cutsspin 0 resonance Below threshold Cross section below threshold ~ 1%Total cross section Hence, (cross section)(cut efficiency) below threshold is estimated to be about 7% of that of above threshold region. • Prediction of MC@NLO above threshold: Any Problem? • Slightly underestimates cross section. • Does not produce color-singlet . • At most 7% underestimate. Combining, at most +14% correction to the prediction by MC@NLO.

  8. : (2-jets + mode) jet1 Number of events after cuts is about 4-5 times larger by MC@NLO than by LO (MadEvent+PYTHIA). jet2 TeV, • Main reasons for enhancements: • Production cross section of is larger at NLO than LO, especially close to threshold. • 2-jets (FB) tagging efficiency increases by hard ISR. • Efficiency of jet inv. mass cut () increases by hard ISR.

  9. Similarly to fusion case, we estimate bound-state effects, using Toponium@LHC. Correction to the prediction by MC@NLO is estimated to be at most +5%. MC@NLO prediction is a good approx. Below threshold In our estimate, Asai et al. prediction of bkg is close to LO prediction. • Asai etal. • Produces upto 2-jets by matching: Cross section compared to LO. • Unpolarized decay: Lepton cuts efficiency compared to LO. • No Coulomb enhancement: Cross section compared to MC@NLO. • Use of PYTHIA: Jet cuts efficiencies compared to MC@NLO. Threshold (bound-state) physics We conjecture that bkgincreases significantly from Asaietal’s estimate. As a result, Higgs discovery potential via VBF may be degraded considerably.

  10. Jet1(harder) A new cut to suppressbkg Jet2 Jet1 Jet2(harder) Cut efficiency: sig~0.8, bkg~0.5 : Angle between -system and the tagged-jet with higher energy. sig : Energy asymmetry of tagged 2-jets. : Inv. mass of -system and the tagged-jet with lower energy.

  11. Summary Contributions ofevents 0-jet mode negligible (1) Bkg for NLO (up-to-date) analysis Good approx. 1-jet mode significant Bound-state corr. to NLO predictions not large. (2) Bkg for Bound-state corr. to LO predictions are large. 2-jet mode significant Previous analysis NLO analysis Likely not good approx. NLO analysis urged. Good approx. A new cut to suppressbkg is proposed.

  12. LHC(TeV)

  13. bkg Asaietal cuts for VBF mode Comparison of different event generators

  14. Typical event after all cuts for Higgs searches ( mode) GeV 1 tagged jet or 1 tagged + 1 untagged jets QCD (quasi-)resonances ( ISR: another tagged jet) Upshot of this talk: Contributions ofevents NLO (up-to-date) analysis 0-jet mode negligible Bkg for ATLAS collab., arXiv:1106.2748[hep-ex] 1-jet mode significant Good approx. Bkg for Up-to-date(?) analysis 2-jet mode significant Asai et al., EPJC32S2(2004)19 Likely not good approx. (large enhancement)

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