11,827 research outputs found
Hadronic light-by-light scattering contribution to the muon g-2
We briefly review the current status of the hadronic light-by-light
scattering correction to the muon g-2. Then we present our semi-analytical
evaluation of the pion-pole contribution, using a description of the
pion-photon-photon form factor based on large-N_C and short-distance properties
of QCD. We also sketch an effective field theory approach to hadronic
light-by-light scattering. In view of several still unsolved problems, our
conservative estimate for the full hadronic light-by-light scattering
contribution is a_{mu}(LbyL;had) = + 8 (4) x 10^{-10}.Comment: 4 pages including 2 figures, Latex, uses espcrc2.sty; Talk presented
at the 9th International High-Energy Physics Conference in Quantum
Chromodynamics (QCD 2002), Montpellier, France, 2-9 July 200
On some properties of the fourth-rank hadronic vacuum polarization tensor and the anomalous magnetic moment of the muon
Some short-distance properties of the fourth-rank hadronic vacuum
polarization tensor are re-examined.Their consequences are critically discussed
in the context of the hadronic light-by-light scattering contribution to the
anomalous magnetic moment of the muon.Comment: Latex2e, 19 page
Chiral perturbation theory confronted with experiment
The general framework and the present status of the low energy theory of the
standard model are briefly reviewed. Recent applications to a few topic of
interest for the determinations of Vud and of Vus are discussedComment: Talk given at the DAPHNE 2004 Workshop, Frascati, June 7 - 11, 2004;
9 pages, uses frascatiphys.st
Minimal Hadronic Ansatz to Large-Nc QCD and Hadronic tau Decay
I report on some recent work done in collaboration with Santi Peris and Boris
Phily (hep-ph/0007338) where, using the Aleph data on vector and axial-vector
spectral functions, we test simple duality properties of QCD in the large-Nc
limit which emerge in the approximation of a {\it minimal hadronic ansatz} of a
spectrum of narrow states. These duality properties relate the short- and
long-distance behaviours of specific correlation functions, which are order
parameters of spontaneous chiral symmetry breaking, in a way that we find well
supported by the data.Comment: 7 pages with 3 figures. Latex file. Contribution to the
Euroconference QCD00, Montpellier, Franc
Unfactorizing Polychromatic Penguins
Firstly, I report on a recent work --carried out with T. Hambye and E. de
Rafael-- on how to use the large-Nc expansion to calculate unfactorized
contributions from the strong penguin operators, and their impact on
observables such as epsilon'/epsilon and the Delta I = 1/2 rule. Secondly,
based on work done with M. Golterman, I explain how this calculation allows one
to predict some rather dramatic consequences for quenched QCD. This may help
explain the present discrepancy between lattice and experimental results for
epsilon'/epsilon. The emphasis of this article is put on the explanation of the
method of calculation used, which is fully analytic. This allows one to build
some intuition and understand the role played by the different hadronic scales
in determining the size of the different contributions.Comment: 6 pages, 1 figure. Invited talk delivered at the "X Int. Conference
on Quantum Chromodynamics", Montpellier, France, July 200
A new start for local composite operators
We present a formalism for local composite operators. The corresponding
effective potential is unique, multiplicatively renormalizable, it is the sum
of 1PI diagrams and can be interpreted as an energy-density. First we apply
this method to theory where we check renormalizability up to
three loops and secondly to the Coleman-Weinberg model where the gauge
independence of the effective potential for the local composite operator
is explicitely checked up to two loops.Comment: 20 page
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