Search results for "theoretical physics"
showing 10 items of 751 documents
Gauge- and renormalization-group-invariant formulation of the Higgs-boson resonance
1997
A gauge- and renormalization-group- invariant approach implemented by the pinch technique is formulated for resonant transitions involving the Higgs boson. The lineshape of the Higgs boson is shown to consist of two distinct and physically meaningful contributions: a process-independent resonant part and a process-dependent non-resonant background, which are separately gauge independent, invariant under the renormalization group, satisfy naive, tree-level Ward identities, and respect the optical and equivalence theorem individually. The former process-independent quantity serves as the natural extension of the concept of the effective charge to the case of the Higgs scalar, and constitutes …
Elimination of unitarily nonequivalent vacua in supersymmetric grand unified theories by gravity
1983
Abstract In globally supersymmetric grand unified theories, there may be unitarily nonequivalent vacua which are not present in ordinary theories, reflecting the invariance of the Higgs potential under the complex extension of the gauge group. We show that such vacua are eliminated in the presence of N = 1 supergravity coupling, if local supersymmetry is broken and the costomological constant vanishes.
Masses, mixings, Yukawa couplings and their symmetries
1993
We present a method to find the number of real and imaginary observable parameters coming from the Yukawa sector in an arbitrary gauge theory. The method leads naturally to a classification of Yukawa couplings according to their symmetries and suggests a new parametrization of masses and mixings that is useful to study the behaviour of Yukawa couplings under the renormalization group. We apply it to some examples based on the Standard Model with Yukawa couplings obeying various chiral symmetries. We also show how our method of parameter counting can be used in some models with an enlarged leptonic sector.
NONCOMMUTATIVE GEOMETRY AND GRADED ALGEBRAS IN ELECTROWEAK INTERACTIONS
1992
The Standard Model of Electroweak Interactions can be described by a generalized Yang-Mills field incorporating both the usual gauge bosons and the Higgs fields. The graded derivative by means of which the Yang-Mills field strength is constructed involves both a differential acting on space-time and a differential acting on an associative graded algebra of matrices. The square of the curvature for the corresponding covariant derivative yields the bosonic Lagrangian of the Standard Model. We show how to recover the whole fermionic part of the Standard Model in this framework. Quarks and leptons fit naturally into the smallest typical and nontypical irreducible representations of the graded …
Running soft parameters in SUSY models with multiple U(1) gauge factors
2012
Abstract We generalize the two-loop renormalization group equations for the parameters of the softly broken SUSY gauge theories given in the literature to the most general case when the gauge group contains more than a single Abelian gauge factor. The complete method is illustrated at two-loop within a specific example and compared to some of the previously proposed partial treatments.
A holographic approach to low-energy weak interactions of hadrons
2011
We apply the double-trace formalism to incorporate nonleptonic weak interactions of hadrons into holographic models of the strong interactions. We focus our attention upon $\Delta S=1$ nonleptonic kaon decays. By working with a Yang-Mills--Chern-Simons 5-dimensional action, we explicitly show how, at low energies, one recovers the $\Delta S=1$ weak chiral Lagrangian for both the anomalous and nonanomalous sectors. We provide definite predictions for the low energy coefficients in terms of the AdS metric and argue that the double-trace formalism is a 5-dimensional avatar of the Weak Deformation Model introduced long ago by Ecker et al. As a significant phenomenological application, we reasse…
On the evaluation of sunset-type Feynman diagrams
1999
We introduce an efficient configuration space technique which allows one to compute a class of Feynman diagrams which generalize the scalar sunset topology to any number of massive internal lines. General tensor vertex structures and modifications of the propagators due to particle emission with vanishing momenta can be included with only a little change of the basic technique described for the scalar case. We discuss applications to the computation of $n$-body phase space in $D$-dimensional space-time. Substantial simplifications occur for odd space-time dimensions where the final results can be expressed in closed form through rational functions. We present explicit analytical formulas fo…
The self-couplings of vector bosons: does LEP-1 obviate LEP-2?
1992
Abstract Theories beyond the standard model (“meta-theories”) are severely constrained by the current body of data and must necessarily respect the standard gauge symmetry. We analyze the constraints on two generic types of meta-theory, in which fundamental scalar do or do not exist. The novel low-energy effects can be comprehensively described by grafting onto the standard lagrangian new operators that - in the sense of a Taylor expansion - form a complete set. Completeness calls for consideration of previously discarded operators, and for a thorough exploitation of the equations of motion. We illustrate the current strictures by focusing on the allowed range of departures from the most cr…
Electromagnetism in nonleptonic weak interactions
2000
16 páginas, 1 figura.-- PACS: 11.30.Rd; 13.25.Es; 13.40.Ks.-- arXiv:hep-ph/0006172v2
On the classification of accidental symmetries of the two Higgs doublet model potential
2011
Recently, it has been shown [arXiv:1106.3482] that the two-Higgs-doublet-model potential may exhibit a maximum of 13 distinct accidental symmetries. Such a classification is based on a six-dimensional bilinear scalar field formalism realizing the SO(1,5) symmetry group. This note presents the transformation relations for each of the 13 symmetries in the original scalar field space and their one-to-one correspondence to the space of scalar bilinears, thereby providing firm support for the completeness of the classification.