Search results for "Chiral Perturbation Theory"
showing 10 items of 294 documents
The role of the $\Delta(1232)$-resonance in covariant baryon chiral perturbation theory
2013
We stress, on theoretical and phenomenological grounds, the importance of the $\Delta(1232)$-resonance in a chiral effective field theory approach applied to the study of $\pi N$ scattering. We show how its inclusion as a dynamical degree of freedom allow us to obtain reliably valuable information from $\pi N$ scattering data.
Pion photo- and electro-production and the chiral MAID interface
2016
We discuss the extended on-mass-shell scheme for manifestly Lorentz-invariant baryon chiral perturbation theory. We present a calculation of pion photo- and electroproduction up to and including order q 4 . The low-energy constants have been fixed by fitting experimental data in all available reaction channels. Our results can be accessed via a web interface, the so-called chiral MAID (http://www.kph.uni-mainz.de/MAID/chiralmaid/). We explain how our program works and how it can be used for further analysis.
Including theΔ(1232)resonance in baryon chiral perturbation theory
2005
Baryon chiral perturbation theory with explicit $\ensuremath{\Delta}(1232)$ degrees of freedom is considered. The most general interactions of pions, nucleons, and \ensuremath{\Delta} consistent with all underlying symmetries as well as with the constraint structure of higher-spin fields are constructed. By use of the extended on-mass-shell renormalization scheme, a manifestly Lorentz-invariant effective-field theory with a systematic power counting is obtained. As applications, we discuss the mass of the nucleon, the pion-nucleon \ensuremath{\sigma} term, and the pole of the \ensuremath{\Delta} propagator.
Chiral expansion of the nucleon mass to order q^6
2006
We present the results of a complete two-loop calculation at order q^6 of the nucleon mass in manifestly Lorentz-invariant chiral perturbation theory. The renormalization is performed using the reformulated infrared renormalization, which allows for the treatment of two-loop integrals while preserving all relevant symmetries, in particular chiral symmetry.
The role of resonances in chiral perturbation theory
1989
32 páginas, 2 figuras, 5 tablas.-- BUTP-88-18 ; CERN-TH-5185-88 ; CPT-2158 ; UWTHPH-1988-29.
In-medium pi-pi Correlation Induced by Partial Restoration of Chiral Symmetry
2000
We show that both the linear and the non-linear chiral models give an enhancement of the pi-pi cross section near the 2pi threshold in the scalar-iso-scalar (I=J=0) channel in nuclear matter. The reduction of the chiral condensate, i.e., the partial chiral restoration in nuclear matter, is responsible for the enhancement in both cases. We extract an effective 4pi-nucleon vertex which is responsible for the enhancement but has not been considered in the non-liear models for in-medium pi-pi interaction. Relation of this vertex and a next-to-leading order terms in the heavy-baryon chiral lagrangian, L_piN^(2), is also discussed.
Chiral dynamics in the γ→p→pπ0 reaction
2015
Abstract We investigate the neutral pion photoproduction on the proton near threshold in covariant chiral perturbation theory with the explicit inclusion of Δ degrees of freedom. This channel is specially sensitive to chiral dynamics and the advent of very precise data from the Mainz microtron has shown the limits of the convergence of the chiral series for both the heavy baryon and the covariant approaches. We show that the inclusion of the Δ resonance substantially improves the convergence leading to a good agreement with data for a wider range of energies.
Non-Leptonic Kaon Decays and the Chiral Anomaly
1994
32 páginas, 3 figuras, 4 tablas.-- El PDF es el artículo publicado en el CERN en Junio de 1993.
Anomalous non-leptonic kaon decays
1992
8 páginas, 1 figura.
Pion photo- and electroproduction in relativistic baryon chiral perturbation theory and the chiral MAID interface
2013
We present a calculation of pion photo- and electroproduction in manifestly Lorentz-invariant baryon chiral perturbation theory up to and including order ${q}^{4}$. We fix the low-energy constants by fitting experimental data in all available reaction channels. Our results can be accessed via a Web interface, the so-called chiral MAID. We explain how our program works and how it can be used for further analysis.