Related papers: Pionic Hydrogen at PSI
We construct an effective non-relativistic quantum field theory that describes bound states of pi+ pi- pairs and their hadronic decays. We then derive a general expression for the lifetime of the ground state at next-to-leading order in…
We calculate the leading isospin conserving few-nucleon contributions to pion scattering on $^2$H, $^3$He, and $^4$He. We demonstrate that the strong contributions to the pion-nucleus scattering lengths can be controlled theoretically to an…
We demonstrate the first step of a complete program, which consists in establishing an x-ray energy standard scale with the use of few-body atoms, in the few keV range. Light pionic and muonic atoms as well as one and two-electron ions from…
We calculate the complete $T$ matrices with decuplet contributions for pion-nucleon scattering to order $\mathcal{O}(\epsilon^3)$ in heavy baryon SU(3) chiral perturbation theory. The baryon mass in the chiral limit $M_0$ and the low-energy…
A review of photo-pion experiments on the nucleon in the near threshold region is presented. Comparisons of the results are made with the predictions of the low energy theorems of QCD calculated using chiral perturbation theory (ChPT) which…
A new tool which combines chiral perturbation theory and unitarity in coupled channels is applied with success to the study of the meson-meson interaction, extending the theoretical predictions up to sqrt{s} = 1.2 GeV, hence improving…
Deep inelastic neutron scattering experiments using indirect time-of-flight spectrometers have reported a smaller cross section for the hydrogen atom than expected from conventional scattering theory. Typically, at large momentum transfers,…
The pi+pi+ s-wave scattering phase-shift is determined below the inelastic threshold using Lattice QCD. Calculations were performed at a pion mass of m_pi~390 MeV with an anisotropic n_f=2+1 clover fermion discretization in four lattice…
For the first time, elastic pion-nucleon scattering is analyzed in the framework of chiral perturbation theory up to fourth order with explicit $\Delta$ degrees of freedom. The analysis is performed within the heavy-baryon expansion as well…
There is an important connection between the low energy theorems of QCD and the energy dependence of the Delta resonance in pi-N scattering, as well as the closely related gamma^{*} N -> pi N reaction. The resonance shape is due not only to…
The next-to-leading order chiral pion-nucleon Lagrangian contains seven finite low-energy constants. Two can be fixed from the nucleon anomalous magnetic moments and another one from the quark mass contribution to the neutron-proton mass…
Elastic deuteron Compton scattering and the quartet S wave of nd scattering are investigated in the effective field theory of nuclear physics with perturbative pions. Convergence and aggreement with experiment are good.
The pi+pi- atom decays -in the ground state - predominantly into two neutral pions. We present a general expression for the corresponding decay width in the framework of QCD (including photons). It contains all terms at leading and…
The pseudoscalar particles pions, kaons and the $\eta$-particle are considerably lighter than the other hadrons such as protons or neutrons. Their lightness was understood as a consequence of approximate chiral symmetry breaking. This led…
Chiral dynamics is a pretty mature field. Nonetheless, there are many exciting new developments. In this opening talk, I consider S-wave, isospin-zero pion-pion scattering and the calculation of the width of the lightest baryon resonances…
The static electric polarizability of the neutron is evaluated using domain-wall valence quarks on a MILC asqtad sea quark ensemble corresponding to a pion mass of m_pi = 357 MeV. Both connected as well as disconnected contributions are…
We compare the dependences on the number of colors of the leading pion pion scattering amplitudes using the single index quark field and two index quark fields. These are seen to have different relationships to the scattering amplitudes…
We study pion--nucleon scattering with a chiral lagrangian of pions, nucleons, and $\Delta$-isobars to order $Q^3$, where $Q$ is a generic small momentum. We compare the results from heavy baryon chiral perturbation theory with those from…
The S-matrix approach is used to calculate charged as well as neutral pion production reactions from NN scattering, with the same set of underlying processes and interactions. The chiral perturbation theory piN scattering amplitude is used.…
Low-energy theorems (LETs) for effective-range parameters in nucleon-nucleon scattering encode properties of the long-range part of the nuclear force. We compute LETs for S-wave neutron-proton scattering using chiral effective field theory…