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R. Munoz-Tapia

Publications and source records attributed to R. Munoz-Tapia.

44 records · Page 3Linked to original sources
arXiv1998

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.

hep-th↗
arXiv1998

Limits on the mass of the lightest Higgs in supersymmetric models

In supersymmetric models extended with a gauge singlet the mass of the lightest Higgs boson has contributions proportional to the adimensional coupling $λ$. In minimal scenarios, the requirement that this coupling remains perturbative up to the unification scale constrains $λ$ to be smaller than $\approx 0.7$. We study the maximum value of $λ$ consistent with a perturbative unification of the gauge couplings in models containing nonstandard fields at intermediate scales. These fields appear in scenarios with gauge mediation of supersymmetry breaking. We find that the presence of extra fields can raise the maximum value of $λ$ up to a 19%, increasing the limits on the mass of the lightest Higgs from 135 GeV to 155 GeV.

hep-ph↗
arXiv1997

Gluino signals in 4jet events and vertex tagging at LEP1

Heavy flavour tagging provides a broad range of possibilities in testing QCD features at LEP. We present here a study of 4jets events at LEP I where the so-called light gluinos could be directly produced. We show that microvertex techniques offer a unique chance to exploit simple kinematical distributions in order to optimise the signal coming from gluino production with respect to the background of ordinary QCD events. Our results indicate that experimental analyses along the lines suggested here can exclude or reveal the presence of a gluino for masses up to 10 GeV and lifetimes below 10$^{-9}$ sec. We also point out that a large fraction of gluino events could decay in configurations carrying large missing energy, so to escape the usual selection criteria of 4jet samples. In our study, mass effects of quarks and gluinos have been taken into account exactly. Our results are independent from both the jet algorithm and its resolution parameter.}

hep-ph↗
arXiv1997

Supergravity corrections to $(g-2)_l$ 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.

hep-ph↗
arXiv1996

Light, long-lived and secluded: can gluinos be driven out from LEP1 data ?

We briefly report about a possible settlement of the still ongoing dispute concerning the existence of SUSY signals in 4jet events at LEP1. We base our arguments on a simple selection strategy exploiting secondary vertex tagging and kinematical constraints, which could allow one to access or exclude gluino events for a broad range of masses and lifetimes.

hep-ph↗
arXiv1996

Heavy flavour tagging and QCD tests in four-jet events at LEP1

We present a theoretical review of the possibilities offered by heavy flavour tagging in testing QCD features in 4-jet events at LEP1. Attention is focused mainly on the properties of the angular variables which are used in the experimental analyses to measure the colour factors of the strong interactions. We also comment on a possible settlement of the ongoing controversy about the existence in LEP1 data of SUSY events involving light gluinos. Integrated and differential rates of interest to phenomenological analyses are given and various tagging procedures are discussed.

hep-ph↗
arXiv1992

A Cutoff Procedure and Counterterms for Differential Renormalization

Explicit divergences and counterterms do not appear in the differential renormalization method, but they are concealed in the neglected surface terms in the formal partial integration procedure used. A systematic real space cutoff procedure for massless $ϕ^4$ theory is therefore studied in order to test the method and its compatibility with unitarity. Through 3-loop order, it is found that cutoff bare amplitudes are equal to the renormalized amplitudes previously obtained using the formal procedure plus singular terms which can be consistently cancelled by adding conventional counterterms to the Lagrangian. Renormalization group functions $β(g)$ and $γ(g)$ obtained in the cutoff theory also agree with previous results.

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