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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

Effects of Toponium Resonances

in Higgs Boson Searches

Y. Sumino(Tohoku Univ.)

Collab. S.Kawabata, Y.Kiyo, Y.Shimizu, H.Yokoya

plan of talk
☆ Plan of Talk
  • Overview (incl. upshot)
  • bkg for: 1-jet + mode
  • bkg for: 2-jets + mode
  • Summary
slide3

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)

slide4

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
slide5

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)

slide6

: (1-jet + mode)

Before cut

After cut

Threshold region becomes comparatively more important by the cuts.

slide7

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.

slide8

: (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.
slide9

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.

slide10

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.

summary
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.

slide13

bkg

Asaietal cuts for VBF mode

Comparison of different event generators

slide17

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)