1 / 17

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.

feoras
Download Presentation

Y. Sumino (Tohoku Univ.)

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  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)

More Related