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Register a new userProduction of (super)heavy quarkonia and new Higgs physics at hadron colliders
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Based on the two Higgs doublet model, we study the effect of Higgs-boson exchange on the (super)heavy quarkonium bar QQ, which induces a strong attractive force between a (super)heavy quark Q and an antiquark bar Q. An interesting application is the decay of (super)heavy quarkonia bar QQ into a Higgs boson associated with gauge bosons. The criterion for making the bar QQ bound state is studied. We also show that non-perturbative effects due to gluonic field fluctuations are rather small in such a heavy quark sector. Possible enhancement for productions and decays of bar QQ bound states made from the fourth generation quark Q is discussed for bar p p (at the Tevatron) and pp (at the LHC) collisions.
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We study Higgs boson pair production processes at future hadron and lepton colliders including the photon collision option in several new physics models; i.e., the two-Higgs-doublet model, the scalar leptoquark model, the sequential fourth generation fermion model and the vector-like quark model. Cross sections for these processes can deviate significantly from the standard model predictions due to the one-loop correction to the triple Higgs boson coupling constant. For the one-loop induced processes such as $gg to hh$ and $gammagammato hh$, where $h$ is the (lightest) Higgs boson and $g$ and $gamma$ respectively represent a gluon and a photon, the cross sections can also be affected by new physics particles via additional one-loop diagrams. In the two-Higgs-doublet model and scalar leptoquark models, cross sections of $e^+e^-to hhZ$ and $gammagammato hh$ can be enhanced due to the non-decoupling effect in the one-loop corrections to the triple Higgs boson coupling constant. In the sequential fourth generation fermion model, the cross section for $ggto hh$ becomes very large because of the loop effect of the fermions. In the vector-like quark model, effects are small because the theory has decoupling property. Measurements of the Higgs boson pair production processes can be useful to explore new physics through the determination of the Higgs potential.
This talk presents a review of recent results for quarkonium production at the LHC from ATLAS, CMS, LHCb, and ALICE. Production cross sections for $J/psi$, $psi(2S)$, and $Upsilon(mS)$, and production ratios for $chi_{c,bJ}$ are found to be in good agreement with predictions from non-relativistic QCD. In contrast, spin-alignment (polarization) measurements seem to disagree with all theoretical predictions. Some other production channels useful for investigating quarkonium hadroproduction mechanisms are also considered.
I report on a calculation of the inclusive Higgs boson production cross section at hadron colliders at next-to-next-to-leading order in QCD. The result is computed as an expansion about the threshold region. By continuing the expansion to very high order, we map the result onto basis functions and obtain the result in closed analytic form.
We study the pair production of neutral Higgs bosons through gluon fusion at hadron colliders in the framework of the Minimal Supersymmetric Standard Model. We present analytical expressions for the relevant amplitudes, including both quark and squark loop contributions, and allowing for mixing between the superpartners of left- and right-handed quarks. Squark loop contributions can increase the cross section for the production of two CP-even Higgs bosons by more than two orders of magnitude, if the relevant trilinear soft breaking parameter is large and the mass of the lighter squark eigenstate is not too far above its current lower bound. In the region of large $tan beta$, neutral Higgs boson pair production might even be observable in the $4 b$ final state during the next run of the Tevatron collider.
We study heavy physics effects on the Higgs production in $gamma gamma $ fusion using the effective Lagrangian approach. We find that the effects coming from new physics may enhance the standard model predictions for the number of events expected in the final states $bar bb$, $WW$, and $ZZ$ up to one order of magnitude, whereas the corresponding number of events for the final state $bar tt$ may be enhanced up to two orders of magnitude.
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