Y. Sumino (Tohoku Univ.) Collab. S.Kawabata, Y.Kiyo, Y.Shimizu, H.Yokoya Effects of Toponium...
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Transcript of Y. Sumino (Tohoku Univ.) Collab. S.Kawabata, Y.Kiyo, Y.Shimizu, H.Yokoya Effects of Toponium...
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
¿¿
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:
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.
¿
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.
: (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.
¿
Threshold(bound-state)
physics
A new cut to suppress bkg¿
Jet2
Jet1(harder)
𝑊𝑊
𝐻𝑙𝜈𝑙𝜈
𝑞
𝑞¿
Jet2(harder)
Jet1𝑏𝑏¿𝑙𝜈𝑙𝜈𝑔
𝑔𝑔
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 ′
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
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: