Constraining differential renormalization in abelian gauge theories

We present a procedure of differential renormalization at the one loop level which avoids introducing unnecessary renormalization constants and automatically preserves abelian gauge invariance. The amplitudes are expressed in terms of a basis of singular functions. The local terms appearing in the renormalization of these functions are determined by requiring consistency with the propagator equation. Previous results in abelian theories, with and without supersymmetry, are discussed in this context.Comment: 13 pages, LaTeX. Some equations corrected and a reference added. Complete ps paper also available at http://www-ftae.ugr.es/papiros.html or ftp://ftae3.ugr.es/pub/rmt/ugft73.p

Fermion Virtual Effects in e+e−−>W+W−e^+ e^- -> W^+ W^- Cross Section

We analyse the contribution of new heavy virtual fermions to the $e^+e^- \rightarrow W^+W^-$ cross section. We find that there exists a relevant interplay between trilinear and bilinear oblique corrections. The result strongly depends on the chiral or vector--like nature of the new fermions. As for the chiral case we consider sequential fermions: one obtains substantial deviation from the Standard model prediction, making the effect possibly detectable at $\sqrt{s}=500$ or $1000$ GeV linear colliders. As an example for the vector--like case we take a SUSY extension with heavy charginos and neutralinos: due to cancellation, the final effect turns out to be negligible.Comment: uuencoded, gz-compressed, tar-ed file. 8 pages, 4 EPS figures, uses EPSFIG.ST

Supersymmetric Sum Rules In Minimal Superstring Unification

The Minimal superstring unification, assuming orbifold compactification, provides interesting and rather detailed implications on physics at low energy. The interesting feature of this model is that the masses of the spectrum are related since all of them are functions of only two parameters: the goldstino angle theta and the gravitino mass m_{3/2}. This fact will help us in studying the modification of the supersymmetric magnetic moments sum rules which are very sensitive to the supersymmetry breaking. We write these rules in case of exact supersymmetry in a form close to the supersymmetric mass relations, namely $\sum_J (-1)^{(2J)} (2 J) A_J=0$, where A_J is the anomalous magnetic moment of the spin J particle. We show that the anomalous magnetic moments of the W-boson and the gauginos can be written as functions of theta and m_{3/2}. Then we obtain a modified version of the supersymmetric magnetic moment sum rule in the context of the minimal superstring unification.Comment: Latex, 18 pages, 4 figure

SUSY Magnetic Moments Sum Rules and Supersymmetry Breaking

It was recently shown that unbroken N=1 Susy relates, in a model independent way, the magnetic transitions between states of different spin within a given charged massive supermultiplet. We verify explicitly these sum rules for a vector multiplet in the case of massless and massive fermions. The purpose of this analysis is to provide the ground for the broken susy case. We study the modifications of these results when an explicit soft Susy breaking realized through a universal mass for all scalars is present. As a by-product we provide a computation of the $g-2$ of the $W$ boson in the standard model which corrects previous evaluations in the literature.Comment: 16+5 pages, Latex,(feynman.tex to print the figures), DFPD 94/TH/2

Supergravity corrections to (g−2)l(g-2)_l in differential renormalization

The method of differential renormalization is extended to the calculation of the one-loop graviton and gravitino corrections to $(g-2)_l$ in unbroken supergravity. Rewriting the singular contributions of all the diagrams in terms of only one singular function, U(1) gauge invariance and supersymmetry are preserved. We compare this calculation with previous ones which made use of momentum space regularization (renormalization) methods.Comment: 23 pages, LaTeX, 4 PostScript figures embedded with epsf ver. 1.13. Complete ps paper and figures available also at ftp://ftae3.ugr.es/pub/rmt/ugft71.p

Role of beam polarization in the determination of WWγWW\gamma and WWZWWZ couplings from e+e−→W+W−e^+e^-\to W^+W^-

We evaluate the constraints on anomalous trilinear gauge-boson couplings that can be obtained from the study of electron-positron annihilation into $W$ pairs at a facility with either the electron beam longitudinally polarized or both electron and positron beams transversely polarized. The energy ranges considered in the analysis are the ones relevant to the next-linear collider and to LEP~200. We discuss the possibilities of a model independent analysis of the general $CP$ conserving anomalous effective Lagrangian, as well as its restriction to some specific models with reduced number of independent couplings. The combination of observables with initial and final state polarizations allows to separately constrain the different couplings and to improve the corresponding numerical bounds.Comment: 24 pages, LaTeX, 9 figures (available on request from the authors

Techniques for one-loop calculations in constrained differential renormalization

We describe in detail the constrained procedure of differential renormalization and develop the techniques required for one-loop calculations. As an illustration we renormalize Scalar QED and show that the two-, three- and four-point Ward identities are automatically satisfied.Comment: LaTex, 29 pages with 4 Postscript figure