5,627 research outputs found
Lagrangians for invariant sub-spaces of the squared Pauli-Lubanski vector
We present an alternative formalism to the Rarita-Schwinger framework for the
description of "has-been" higher spins at rest that avoids the Velo-Zwanziger
problem.Comment: 3 pages, Contribution to the X Mexican School on Particles and
Fields, 2002; The calculations by the symbolic program Mathematica have been
performed by us during the time period Sept. 10, 2002-Febr. 05, 2003 at the
computer heritage.reduaz,mx, courtesy D.V.Ahluwali
Rare top quark decays in extended models
Flavor changing neutral currents (FCNC) decays t to H + c, t to Z + c, and H
to t + bar{c} are discussed in the context of Alternative Left-Right symmetric
Models (ALRM) with extra isosinglet heavy fermions where FCNC decays may take
place at tree-level and are only suppressed by the mixing between ordinary top
and charm quarks, which is poorly constraint by current experimental values.
The non-manifest case is also briefly discussed.Comment: Contributed talk given at the 10th Mexican Workhop on Particles and
Fields, Morelia, Michoacan, Mexico, 7-12 Nov 200
One-Loop Electroweak Corrections to the Muon Anomalous Magnetic Moment Using the Pinch Technique
The definition of the physical properties of particles in perturbative gauge
theories must satisfy gauge invariance as a requisite. The Pinch Technique
provides a framework to define the electromagnetic form factors and the
electromagnetic static properties of fundamental particles in a consistent and
gauge-invariant form. We apply a simple prescription derived in this formalism
to check the calculation of the gauge-invariant one-loop bosonic electroweak
corrections to the muon anomalous magnetic moment.Comment: 6 pages and 1 eps figur
Anapole moment of the lightest neutralino in the cMSSM
We study the anapole moment of the lightest neutralino in the constrained
Minimal Supersymmetric Standard Model (cMSSM). The electromagnetic anapole is
the only allowed electromagnetic form factor for Majorana fermions, such as the
neutralino. Since the neutralino is the LSP in many versions of the MSSM and
therefore a candidate for dark matter, its characterization through its
electromagnetic properties is important both for particle physics and for
cosmology. We perform a scan in the parameter space of the cMSSM and find that
the anapole moment is different from zero albeit very small (
GeV). Combined with experimental constraints like the Higgs mass and the
DM relic density, the allowed region of parameter space lies within the reach
of future direct DM searches. Thus, the anapole moment could be used as a
complementary constraint when studying the parameter space of the cMSSM and
other similar models.Comment: 22 pages, 13 figures. arXiv admin note: substantial text overlap with
arXiv:1206.505
On the charge radius of the neutrino
Using the pinch technique we construct at one-loop order a neutrino charge
radius, which is finite, depends neither on the gauge-fixing parameter nor on
the gauge-fixing scheme employed, and is process-independent. This definition
stems solely from an effective proper photon-neutrino one-loop vertex, with no
reference to box or self-energy contributions. The role of the box in this
construction is critically examined. In particular it is shown that the
exclusion of the effective WW box from the definition of the neutrino charge
radius is not a matter of convention but is in fact dynamically realized when
the target-fermions are right-handedly polarized. In this way we obtain a
unique decomposition of effective self-energies, vertices, and boxes, which
separately respect electroweak gauge invariance. We elaborate on the tree-level
origin of the mechanism which enforces at one-loop level massive cancellations
among the longitudinal momenta appearing in the Feynman diagrams, and in
particular those associated with the non-abelian character of the theory.
Various issues related to the known connection between the pinch technique and
the Background Field Method are further clarified. Explicit closed expressions
for the neutrino charge radius are reported.Comment: 26 pages, plain Latex, 7 Figures in a separate ps fil
Charge and Magnetic Moment of the Neutrino in the Background Field Method and in the Linear R_xi^L Gauge
We present a computation of the charge and the magnetic moment of the
neutrino in the recently developed electro-weak Background Field Method and in
the linear gauge. First, we deduce a formal Ward-Takahashi identity
which implies the immediate cancellation of the neutrino electric charge. This
Ward-Takahashi identity is as simple as that for QED. The computation of the
(proper and improper) one loop vertex diagrams contributing to the neutrino
electric charge is also presented in an arbitrary gauge, checking in this way
the Ward-Takahashi identity previously obtained. Finally, the calculation of
the magnetic moment of the neutrino, in the minimal extension of the Standard
Model with massive Dirac neutrinos, is presented, showing its gauge parameter
and gauge structure independence explicitly.Comment: Latex, 19 pages, 9 PS and 10 EPS figures. One reference added.
Appendix B modified and Appendices C-E eliminated. To be published in Eur.
Phys. J.
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