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Register a new userHadronic Higgs Production with Heavy Quarks at the Tevatron and the LHC
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We review the status of the QCD corrected cross sections and kinematic distributions for the production of a Higgs boson in association with top quark or bottom quark pairs at the Fermilab Tevatron and at the LHC. Results for b-bbar-H production are presented in the Minimal Supersymmetric Model, where the rates can be greatly enhanced relative to the Standard Model rates. We place particular emphasis on theoretical uncertainties due to renormalization and factorization scale dependence and on the uncertainties coming from the Parton Distribution Functions.
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The present paper is based on the assumption that heavy quarks bound states exist in the Standard Model (SM). Considering New Bound States (NBS) of top-anti-top quarks (named T-balls) we have shown that: 1) there exists the scalar 1S--bound state of $6t+6bar t$; 2) the forces which bind the top-quarks are very strong and almost completely compensate the mass of the twelve top-anti-top-quarks in the scalar NBS; 3) such strong forces are produced by the Higgs-top-quarks interaction with a large value of the top-quark Yukawa coupling constant $g_tsimeq 1$. Theory also predicts the existence of the NBS $6t + 5bar t$, which is a color triplet and a fermion similar to the $t$-quark of the fourth generation. We have also considered the b-quark-replaced NBS, estimated the masses of the lightest fermionic NBS: $M_{NBS}gtrsim 300$ GeV, and discussed the larger masses of T-balls. We have developed a theory of the scalar T-balls condensate and predicted the existence of three SM phases. Searching for heavy quark bound states at the Tevatron and LHC is discussed. We have constructed the possible form-factors of T-balls, and estimated the charge multiplicity coming from the T-balls decays.
We consider the transverse-momentum (q_T) distribution of Standard Model Higgs bosons produced by gluon fusion in hadron collisions. At small q_T (q_T<<m_H, m_H being the mass of the Higgs boson), we resum the logarithmically-enhanced contributions due to multiple soft-gluon emission to all order in QCD perturbation theory. At intermediate and large values of q_T (q_T <~m_H), we consistently combine resummation with the known fixed-order results. We use the most advanced perturbative information that is available at present: next-to-next-to-leading logarithmic resummation combined with the next-to-leading fixed-order calculation. We extend previous results including exactly all the perturbative terms up to order alphas^4 in our computation and, after integration over q_T, we recover the known next-to-next-to-leading order result for the total cross section. We present numerical results at the Tevatron and the LHC, together with an estimate of the corresponding uncertainties. Our calculation is implemented in an updated version of the numerical code HqT.
We update the theoretical predictions for direct Y(nS) hadroproduction in the framework of NRQCD. We show that the next-to-leading order corrections in alpha_s to the color-singlet transition significantly raise the differential cross section at high pT and substantially affect the polarization of the Upsilon. Motivated by the remaining gap between the NLO yield and the cross section measurements at the Tevatron, we evaluate the leading part of the alpha_s^5 contributions, namely those coming from Y(nS) associated with three light partons. The differential color-singlet cross section at alpha_s^5 is in substantial agreement with the data, so that there is no evidence for the need of color-octet contributions. Furthermore, we find that the polarization of the Y(nS) is longitudinal. We also present our predictions for Y(nS) production at the LHC.
Inclusive bottomonium hadroproduction at the Tevatron is firstly examined in a Monte Carlo framework with the colour-octet mechanism implemented in the event generation. We extract some NRQCD colour-octet matrix elements relevant for $Upsilon(1S)$ hadroproduction. Remarkably we find a quite small contribution (compatible with zero) from feeddown of $chi_{bJ}$ states produced through the colour-octet mechanism: $Upsilon(1S)$ indirect production via $chi_{bJ}$ decays should be mainly ascribed to the colour-singlet model. Finally we extrapolate to LHC energies to predict prompt $Upsilon(1S)$ production rates.
We present results for the SM and MSSM Higgs-boson production cross sections at the Tevatron and the LHC. The SM cross sections are a compilation of the state-of-the-art theoretical predictions. The MSSM cross sections are obtained from the SM ones by means of an effective coupling approximation, as implemented in FeynHiggs. Numerical results have been obtained in four benchmark scenarios for two values of tan beta, tan beta = 5, 40.
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