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Register a new userHeavy quark pair production in gluon fusion at next-to-next-to-leading ${cal O}(alpha_s^4)$ order: One-loop squared contributions
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We calculate the next-to-next-to-leading order ${cal O}(alpha_s^4)$ one-loop squared corrections to the production of heavy-quark pairs in the gluon-gluon fusion process. Together with the previously derived results on the $q bar{q}$ production channel the results of this paper complete the calculation of the one-loop squared contributions of the next-to-next-to-leading order ${cal O}(alpha_s^4)$ radiative QCD corrections to the hadroproduction of heavy flavors. Our results, with the full mass dependence retained, are presented in a closed and very compact form, in dimensional regularization.
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We calculate the next-to-next-to-leading order ${cal O}(alpha_s^4)$ one-loop squared corrections to the production of heavy quark pairs in quark-antiquark annihilations. These are part of the next-to-next-to-leading order ${cal O}(alpha_s^4)$ radiative QCD corrections to this process. Our results, with the full mass dependence retained, are presented in a closed and very compact form, in the dimensional regularization scheme. We have found very intriguing factorization properties for the finite part of the amplitudes.
We calculate the one-loop squared contributions to the next-to-next-to-leading order ${cal O}(alpha^2alpha_s^2)$ radiative QCD corrections for the production of heavy quark pairs in the collisions of unpolarized on--shell photons. In particular, we present analytical results for the squared matrix elements that correspond to the product of the one--loop amplitudes. All results of the perturbative calculation are given in the dimensional regularization scheme. These results represent the Abelian part of the corresponding gluon--induced next-to-next-to-leading order cross section for heavy quark pair hadroproduction.
The total cross section for Higgs production in bottom-quark annihilation is evaluated at next-to-next-to-leading order (NNLO) in QCD. This is the first time that all terms at order alpha_s^2 are taken into account. We find a greatly reduced scale dependence with respect to lower order results, for both the factorization and the renormalization scales. The behavior of the result is consistent with earlier determinations of the appropriate factorization scale for this process of mu_F ~ M_H/4, and supports the validity of the bottom parton density approach for computing the total inclusive rate. We present precise predictions for the cross section at the Tevatron and the LHC.
I compute the contributions of the one-loop single-real-emission amplitudes, $ggto H g$, $qgto H q$, etc., to inclusive Higgs boson production through next-to-next-to-next-to-leading order (N^3LO) in the strong coupling $alpha_s$. The next-to-leading (NLO) and next-to-next-to-leading order (NNLO) terms are computed in closed form, in terms of $Gamma$-functions and the hypergeometric functions ${}_{2}F_{1}$ and ${}_{3}F_{2}$. I compute the nnlo terms as Laurent expansions in the dimensional regularization parameter through order $(epsilon^{1})$. To obtain the nnlo terms, I perform an extended threshold expansion of the phase space integrals and map the resulting coefficients onto a basis of harmonic polylogarithms.
We present predictions for the total ttbar production cross section sigma_ttbar at the Tevatron and LHC, which include the resummation of soft logarithms and Coulomb singularities through next-to-next-to-leading logarithmic order, and ttbar bound-state contributions. Resummation effects amount to about 8 % of the next-to-leading order result at Tevatron and about 3 % at LHC with 7 TeV centre-of-mass energy. They lead to a significant reduction of the theoretical uncertainty. With m_t=173.3 GeV, we find sigma_ttbar=7.22^{+0.31+0.71}_{-0.47-0.55} pb at Tevatron and sigma_ttbar=162.6^{+7.4+15.4}_{-7.5-14.7} at the LHC, in good agreement with the latest experimental measurements.
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