1,720,999 research outputs found
COMPARATIVE-ANALYSIS OF ELECTROWEAK CORRECTIONS TO E++E--]F+FBAR IN ON-SHELL AND MSBAR FRAMEWORKS
No full textA novel analysis of the electroweak radiative corrections to e+ + e- --> f + fBAR, carried out in three different schemes, is presented. The first parametrizes the corrections in terms of G-mu, m(Z) and sin2-theta-W = 1 - m(W)2/m(Z)2 and employs recently proposed renormalized self-energies satisfying simple renormalization conditions. The second is parametrized in terms of m(Z) and the MSBAR couplings e2(m(Z)) and sin2-theta-W(m(Z)). The third introduces an effective gauge-invariant angle sin2-theta-W(eff). Compact formulae to evaluate the differential cross sections, partial widths and asymmetries are given. A numerical comparison is made of various predictions obtained on the basis of the first two schemes as well as on Hollik's formulation
GAUGE-INVARIANT SELF-ENERGIES AND VERTEX PARTS OF THE STANDARD MODEL IN THE PINCH TECHNIQUE FRAMEWORK
No full textThe pinch technique (PT) is applied to obtain one-loop gauge-invariant self-energies, vertex and box diagrams in the electroweak sector of the standard model. Describing the interaction of vector bosons with fermions in terms of current correlation functions, we propose to directly identify the pinch parts with the contributions of equal-time commutators in the relevant Ward identities. We argue that this procedure isolates the parts of vertex and box diagrams that are independent of strong interaction dynamics. The formalism promptly leads us to very simple gauge-invariant transverse self-energies, as well as vertex and box diagrams relevant to four-fermion processes mediated by charged and neutral currents. They automatically possess very desirable theoretical properties. We then apply the PT to e+e----> W+W- and explicitly demonstrate that the propagatorlike pinch parts are absorbed in the same self-energies encountered in the four-fermion case. The PT self-energies and vertex corrections are compared with those obtained in other formulations. A number of applications are discussed, including the possibility of a gauge-invariant on-shell definition of the vector-boson mass
GAUGE DEPENDENCE OF BASIC ELECTROWEAK CORRECTIONS OF THE STANDARD MODEL
No full textThe gauge dependence of some basic one-loop electroweak corrections of the Standard Model (SM) is succinctly described in terms of three functions of the vector boson masses, the gauge parameters and the invariant momentum transfer. We consider self-energies, tadpoles and vertex and box diagrams relevant to four-fermion processes. The analysis of the latter is greatly simplified by using current correlation functions and their associated current algebra. A number of applications are discussed, including the gauge properties of partial amplitudes that have played an interesting role in recent discussions of electroweak physics and the Z0 mass. The hypothetical cancellation of quadratic divergencies in the SM and the corresponding predictions for the Higgs boson mass are briefly reviewed in an appendix
Dependence of the Higgs coupling hMS(M) on mH and the possible onset of new physics
No full textThe simple renormalization framework previously discussed by one of us is extended to treat the Higgs potential of the standard model. As an application, we obtain in a straightforward manner the one-loop correction δ(M) in the natural relation h(M) = √ 1 2 GμmH2[1 + δ(M)], where mH is the physical mass of the Higgs boson, Gμ the accurately known μ decay coupling constant and h(M) the MS quartic Higgs coupling at mass scale M. The correction δ(M) contains contributions proportional to ξ ≡ mH2/mZ2 and ξ-1 and become large for ξ≫1 or ξ≪1. The dependence of h(M) on M and mH is analyzed by combining our one-loop results (which provide initial conditions) and approximate analytic solutions of relevant renormalization group equations. A parameter Mc, which roughly describes the mass scale at which perturbation theory breaks down and the possible onset of new physics, is discussed as a function of mH. © 1986
RELATIONS BETWEEN THE ON-SHELL AND MS FRAMEWORKS AND THE MW-MZ INTERDEPENDENCE
No full textIt is shown that the recently introduced radiative corrections DELTA-r and DELTA-r(w) automatically incorporate the leading higher-order contributions arising from resummation of one-loop fermionic contributions. With slight modifications, they can be made to include all such contributions (not just the leading ones). Simple relations between DELTA-r, DELTA-r(w), DELTA-r, sin2-theta-w and sin2-theta-w(m(z)) are derived. These expressions bridge the MSBAR and on-shell renormalization schemes and are very useful to compute DELTA-r and sin2-theta-w in the case of large m(t). The m(w)-m(z) interdependence is expressed in two equivalent ways: in terms of DELTA-r and in terms of the parameter p = m(w)2/m(z)2cos2-theta-w(m(z)). Applications of the expressions derived in the paper are illustrated numerically
GAUGE-INVARIANT FORMULATION OF THE S, T, AND U PARAMETERS
No full textIt is shown that the bosonic contributions to the S, T, and U parameters, defined in terms of conventional self-energies, are gauge dependent in the standard model (SM). Moreover, T and U are divergent unless a constraint is imposed among the gauge parameters. Implications of this result for renormalization schemes of the SM are discussed. A gauge-invariant formulation of S, T, and U is proposed in the pinch-technique framework. The modified S, T, and U parameters provide a gauge-invariant parametrization of leading electroweak radiative corrections in the SM and some of its extensions
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