Y. Sumino 　 (Tohoku Univ.)

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

Effects of Toponium Resonances

in Higgs Boson Searches

☆ Plan of Talk

Overview (incl. upshot)

bkg for : 1-jet + mode

bkg for: 2-jets + mode

Summary

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( ISR: another tagged jet)

Typical event after all cuts for Higgs searches ( mode)¿

1 tagged jet or 1 tagged + 1 untagged jets

QCD (quasi-)resonances

0-jet mode negligible

1-jet mode significant

Contributions of events ¿Bkg for

NLO (up-to-date) analysis

Good approx.ATLAS collab., arXiv:1106.2748[hep-ex]

Bkg for 2-jet mode significant

Up-to-date(?) analysis

Likely not good approx. (large enhancement)

Asai et al., EPJC32S2(2004)19

𝑔

GeV

Upshot of this talk:

Our analysis is based on MC simulations

MadEventMC@NLO

Toponium@LHC(by Yokoya)

PYTHIA, Herwig

PGS

LONLOLO+LO bound-state eff.

Reservations: • Fast detector simulator• Unsophisticated jet reconstruction• No b-tag• No from • No real data to calibrate

Tevatron

LHC(TeV)

Toponium@LHCLOMC@NLO

Hagiwara, Sumino, YokoyaKiyo, Kuhn, Moch, Steinhauser, Uwer

Sumino, YokoyaMC events (parton level)

Toponium Production

Toponium@LHCLOMC@NLO

: (1-jet + mode)

Before cut

After cut

Threshold region becomes comparatively more important by the cuts.

𝑀 𝑡𝑡

Below threshold

We find

Cut efficiency below thresholdAverage cut eff. above threshold ~ factor 7

Main enhancements in• Jet veto constitute single jet• cut low mass• Lepton cuts spin 0 resonance

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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.

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Prediction of MC@NLO above threshold: Any Problem?• Slightly underestimates cross section.• Does not produce color-singlet .

At most 7% underestimate.

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Combining, at most +14% correction to the prediction by MC@NLO.

: (2-jets + mode)

Number of events after cuts is about 4-5 timeslarger by MC@NLO than by LO (MadEvent+PYTHIA).

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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.

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𝑔TeV,

jet1

jet2

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%.

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.

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Below thresholdMC@NLO prediction is a good approx.

We conjecture that bkg increases significantly from Asai etal’s estimate.As a result, Higgs discovery potential via VBF may be degraded considerably.

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Threshold(bound-state)

physics

A new cut to suppress bkg¿

Jet2

Jet1(harder)

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Jet2(harder)

Jet1𝑏𝑏¿𝑙𝜈𝑙𝜈𝑔

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𝑡𝑡¿

: Angle between -system and the tagged-jet with higher energy.

: Energy asymmetry of tagged 2-jets.

¿ 𝐴(𝐸 ¿¿ 𝑗)∨¿¿c os𝜃𝑙𝑗

¿ 𝐴(𝐸 ¿¿ 𝑗)∨¿¿c os𝜃𝑙𝑗

Cut efficiency: sig~0.8, bkg~0.5¿

: Inv. mass of -system and the tagged-jet with lower energy.

𝑀 𝑙𝑗 ′

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sig

0-jet mode negligible

1-jet mode significant

Contributions of events ¿Bkg for

NLO (up-to-date) analysisGood approx.

Bkg for 2-jet mode significant

Previous analysisLikely not good approx.

NLO analysis urged.

Summary

NLO analysisGood approx.

Bound-state corr. to NLO predictions not large.

Bound-state corr. to LO predictions are large.

(1)

(2)

A new cut to suppress bkg is proposed.¿

LHC(TeV)

Asai etal cuts for VBF mode 𝑙𝑙=𝑒𝜇 bkg¿Comparison of different event generators

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𝑡

𝑏𝑏

𝑊

𝑊

𝑙

𝑙𝜈

𝜈

𝑔

𝑔

𝑡

𝑡

𝑏𝑏

𝑊

𝑊

𝑙

𝑙𝜈

𝜈

¿ ¿

( ISR: another tagged jet)

Typical event after all cuts for Higgs searches ( mode)¿

1 tagged jet or 1 tagged + 1 untagged jets

QCD (quasi-)resonances

0-jet mode negligible

1-jet mode significant

Contributions of events ¿Bkg for

NLO (up-to-date) analysis

Good approx.ATLAS collab., arXiv:1106.2748[hep-ex]

Bkg for 2-jet mode significant

Up-to-date(?) analysis

Likely not good approx. (large enhancement)

Asai et al., EPJC32S2(2004)19

𝑔

GeV

Upshot of this talk: