Search results for "Chiral Perturbation Theory"
showing 10 items of 294 documents
η(′)→π+π−γ(*) in large- Nc chiral perturbation theory
2021
We present a calculation of the decays ${\ensuremath{\eta}}^{{(}^{\ensuremath{'}})}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\gamma}}^{(*)}$ at the one-loop level up to and including next-to-next-to-leading order (NNLO) in large-${N}_{c}$ chiral perturbation theory. The numerical evaluation of the results is performed successively at LO, NLO, and NNLO, fitting the relevant low-energy constants to the available experimental data. We discuss the widths and decay spectra of ${\ensuremath{\eta}}^{{(}^{\ensuremath{'}})}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}\ensuremath{\gamma}$ as well as ${\ensuremath{…
Two-photon decays and transition form factors of π0 , η , and η′ in large- Nc chiral perturbation theory
2020
We present a calculation of $P\ensuremath{\rightarrow}{\ensuremath{\gamma}}^{(*)}{\ensuremath{\gamma}}^{(*)}$ processes, where $P={\ensuremath{\pi}}^{0},\ensuremath{\eta},{\ensuremath{\eta}}^{\ensuremath{'}}$, at the one-loop level up to and including next-to-next-to-leading order (NNLO) in large-${N}_{c}$ chiral perturbation theory. The results are numerically evaluated successively at LO, NLO, and NNLO. The appearing low-energy constants are determined through fits to the available experimental data. We investigate the decay widths to real photons, the single-virtual transition form factors, and the widths of $P\ensuremath{\rightarrow}\ensuremath{\gamma}{l}^{+}{l}^{\ensuremath{-}}$, where…
Proton polarizabilities: status, relevance, prospects
2013
This is a brief review of the status of understanding the proton polarizabilities in chiral perturbation theory and of their relevance to the `proton charge radius puzzle'.
Erratum to: Experimental tests of Chiral Perturbation Theory
2003
Erratum to: In-medium chiral perturbation theory
2003
Three-nucleon forces and the three-nucleon systems
1993
The basic principles and philosophy which have guided the area of few-nucleon physics are motivated and discussed. Recent advances have made it possible to solve accurately the Schrodinger (or Faddeev) equation for many of the configurations of the few-nucleon systems, A brief review is given of some of the results of these calculations, which also Indicate that one-pion exchange plays roughly the same role in binding these systems that it plays in electromagnetic meson-exchange currents. Finally, a qualitative discussion of chiral perturbation theory is presented, which highlights the role that chiral symmetry plays in the nuclear force. Three-body forces from different areas of physics ar…
Axial, induced pseudoscalar, and pion-nucleon form factors in manifestly Lorentz-invariant chiral perturbation theory
2006
We calculate the nucleon form factors G_A and G_P of the isovector axial-vector current and the pion-nucleon form factor G_piN in manifestly Lorentz-invariant baryon chiral perturbation theory up to and including order O(p^4). In addition to the standard treatment including the nucleon and pions, we also consider the axial-vector meson a_1 as an explicit degree of freedom. This is achieved by using the reformulated infrared renormalization scheme. We find that the inclusion of the axial-vector meson effectively results in one additional low-energy coupling constant that we determine by a fit to the data for G_A. The inclusion of the axial-vector meson results in an improved description of t…
Form factors for semileptonic B -> pi and D -> pi decays from the Omnes representation
2000
We use the Omnes representation to obtain the q-squared dependence of the form factors f+ and f0 for semileptonic H -> pi decays from the elastic pi H -> pi H scattering amplitudes, where H denotes a B or D meson. The scattering amplitudes used satisfy elastic unitarity and are calculated from two-particle irreducible amplitudes obtained using tree-level heavy meson chiral perturbation theory (HMChPT). The q-squared dependences for the form factors agree with lattice QCD results when the HMChPT coupling constant, g, takes values smaller than 0.32, and confirm the milder dependence of f0 on q-squared found in sumrule calculations.
Vector meson exchange in radiative kaon decays and chiral perturbation theory
1990
7 páginas, 4 figuras,1 tabla.