188 research outputs found
On the position of a heavy Higgs pole
Higher loop calculations in the Higgs sector of the standard model at the
Higgs mass scale have shown that perturbation theory diverges very badly at
about 1 TeV in the on-shell renormalization scheme. The prediction of the
position of the Higgs pole in the complex s-plane becomes unreliable. We show
that in the pole renormalization scheme this appears to have much better
convergence properties, while showing good agreement with the on-shell scheme
over the validity range of the latter. This suggests that the pole scheme
should be preferable for phenomenological studies of heavy Higgs bosons. We
discuss whether this behaviour can be the result of a certain relation between
the on-shell mass and the pole mass at the nonperturbative level.Comment: replaced by the published version, 12 pages LaTex, 3 eps figures
include
Loops and legs beyond perturbation theory
Within the non-perturbative 1/N expansion, we discuss numerical methods for
calculating multi-loop Feynman graph needed to derive physical scattering
amplitudes. We apply higher order 1/N methods to the scalar sector of the
standard model, and show the existence of a mass saturation effect. The mass
saturation has direct implications for future searches at the LHC and at
possible muon colliders.Comment: Talk presented at the Loops and Legs in Quantum Field Theory 2000
meetin
Nonperturbative three-point functions of the O(N) sigma model in the 1/N expansion at NLO
We present a calculation of the three-point functions of the O(N)-symmetric
sigma model. The calculation is done nonperturbatively by means of a
higher-order 1/N expansion combined with a tachyonic regularization which we
proposed in previous publications. We use the results for calculating the
standard model process ff -> H -> WW nonperturbatively in the quartic coupling
of the scalar sector
Reduction and evaluation of two-loop graphs with arbitrary masses
We describe a general analytic-numerical reduction scheme for evaluating any
2-loop diagrams with general kinematics and general renormalizable
interactions, whereby ten special functions form a complete set after tensor
reduction. We discuss the symmetrical analytic structure of these special
functions in their integral representation, which allows for optimized
numerical integration. The process Z -> bb is used for illustration, for which
we evaluate all the 3-point, non-factorizable g^2*alpha_s mixed electroweak-QCD
graphs, which depend on the top quark mass. The isolation of infrared
singularities is detailed, and numerical results are given for all two-loop
three-point graphs involved in this process
Mass and Width of a Heavy Higgs Boson
The gauge dependence of the Higgs-boson mass and width in the on-shell scheme
of renormalization is studied in the heavy-Higgs-boson approximation. The
corresponding expansions in the pole scheme are analyzed adopting three
frequently employed parametrizations. The convergence properties and other
theoretical features of the on-shell and pole expansions, as well as their
relative merits, are discussed.Comment: 8 pages (Latex), 1 figure (Postscript
Analytic evaluation of two-loop renormalization constants of enhanced electroweak strength in the Higgs sector of the Standard Model
We calculate renormalization constants Z_H, Z_w, the Higgs and W-boson mass
and tadpole counterterms in the on-mass-shell renormalization scheme to two
loops in the heavy-Higgs-boson limit m_H >> M_W. Explicit analytic formulae are
presented for the two-loop integrals with masses, which are not known in the
literature. As an application, the analytic expression for the two-loop leading
correction to the fermionic Higgs boson width is obtained.Comment: 8 pages, 3 Postscript figures, uses epsfig.st
Muon colliders and the non-perturbative dynamics of the Higgs boson
A muon collider operating in the TeV energy range can be an ideal s-channel
Higgs boson factory. This is especially true for a heavy Higgs boson. The
non-perturbative dynamical aspects of such a Higgs boson were recently
investigated with large N expansion methods at next to leading order, and
reveal the existence of a mass saturation effect. Even at strong coupling, the
Higgs resonance remains always below 1 TeV. However, if the coupling is strong
enough, the resonance becomes impossible to be detected.Comment: Contributed to the International Conference on Physics Potential and
Development of mumu Colliders, December 15-17, 1999, San Francisco, C
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