129 research outputs found
pi pi scattering, pion form factors and chiral perturbation theory
I discuss recent progress in our understanding of the pi pi scattering
amplitude at low energy thanks to the combined use of chiral perturbation
theory and dispersion relations. I also comment on the criticism raised by
Pelaez and Yndurain on this work.Comment: 10 pages, 5 figures. Invited talk at the "Quark Confinement and the
Hadron Spectrum" VI Conference, Villasimius, Sardinia, Italy, 21-25 September
200
Theoretical progress on pi pi scattering lengths and phases
pi pi scattering at low energy is sensitive to the structure of the QCD
vacuum. I review the calculations of the pi pi scattering lengths and phases,
and group them in three cathegories: 1. those based on very general theoretical
constraints (like dispersion relations and crossing symmetry) and
phenomenology, 2. those which in addition make explicit use of chiral symmetry,
3. the first-principle ones, done with lattice QCD. I then compare these to the
experimental results. Thanks to recent progress in all these and in the
experimental determination of the scattering lengths we are improving
substantially our knowledge of the QCD vacuum.Comment: 11 pages, talk given at the KAON International Conference, May 21-25
2007 Laboratori Nazionali di Frascati dell'INFN, Rome, Ital
Pion loops in quenched Quantum Chromodynamics
We calculate the divergences of the generating functional of quenched Chiral
Perturbation Theory to one loop for a generic number of flavours. The flavour
number dependence of our result enlightens the mechanism of quark loop
cancellation in the quenched effective theory for any Green function or S
matrix element. We also apply our results to scattering and evaluate
the coefficient of the chiral log in the S-wave scattering lengths for the
quenched case.Comment: Latex, 10 pages, 1 figur
An introduction to CHPT
These lectures provide an elementary introduction to Chiral Perturbation
Theory, focused on the sector of pseudoscalar meson interactions. Basic
concepts and technical methods of this approach are discussed on general
grounds and with the help of a few specific examples.Comment: 45 pages, Latex. Lectures given at at the 2000 LNF Spring School,
Frascati, Italy, 15-20 May 200
A New Dispersive Analysis of eta --> 3 pi
We present a new dispersive analysis of the isospin breaking decay eta --> 3
pi. The resulting representation of the decay amplitude allows us to determine
the quark mass double ratio Q and we find as a preliminary result Q = 22.3 +/-
0.4. Finally, we discuss a number of improvements that we intend to implement
in the future.Comment: 9 pages, 4 figures, to be published in the proceedings of 6th
International Workshop on Chiral Dynamics, CD09, July 6-10, 2009, Bern,
Switzerlan
Theory of pi pi scattering
I describe the current status of the theory of pi pi scattering, reviewing in
particular recent work on the numerical solution of Roy equations and on the
matching between these and the chiral representation. I discuss numerical
results on the scattering lengths and other threshold parameters.Comment: Latex 12 pages, Invited plenary talk at Chiral Dynamics 2000, 17-22
July, Jefferson La
Theoretical Aspects of the Pion-Pion Interaction
We give a brief review of the theoretical description of low energy pion-pion
scattering by the combined use of Chiral Perturbation Theory and Roy equations,
an update of the Regge parametrization of cross sections at high
energies, and a short discussion of the scalar radius of the pion.Comment: 4 pages, talk presented by I. Caprini at the International Conference
on QCD and Hadronic Physics, June 16-20 2005, Beijin
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