y. sumino (tohoku univ.)
DESCRIPTION
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. - PowerPoint PPT PresentationTRANSCRIPT
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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𝑡
𝑡𝑏𝑏
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:
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
¿
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).
¿
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.
¿
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.
¿
¿
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)
𝑊𝑊
𝐻𝑙𝜈𝑙𝜈
𝑞𝑞¿
Jet2(harder)
Jet1𝑏𝑏¿𝑙𝜈𝑙𝜈𝑔
𝑔 𝑔𝑡𝑡¿
: 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 ′
𝑡𝑡¿
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
𝑔
𝑔
𝑡
𝑡𝑏𝑏
𝑊
𝑊
𝑙
𝑙𝜈
𝜈
𝑔
𝑔
𝑡
𝑡𝑏𝑏
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: