Related papers: Pion-nucleon sigma term $\sigma_{\pi N}$ and deepl…
We evaluate the contribution of second order terms to the pion-nucleus s-wave optical potential of pionic atoms generated by short range nuclear correlation. The corrections are sizeable because they involve the isoscalar s-wave $\pi N$…
The pion-nucleon coupling constant $g_{\pi N}$ is studied on the basis of the QCD sum rules. Both the Borel sum rules and the finite energy sum rules for $g_{\pi N}$ are used to examine the effects of higher dimensional operators (up to…
The value of $59 \pm 12$ MeV for the pion-nucleon ($\pi N$) $\Sigma$ term, which Stahov, Clement, and Wagner recently extracted from the differential cross sections (DCSs) of the CHAOS Collaboration, does not match well the expectation of…
There has been a discrepancy between values of the pion-nucleon sigma term extracted by two different methods for many years. Analysis of recent high precision pion-nucleon data has widened the gap between the two determinations. It is…
We present a novel analysis of the $\pi N$ scattering amplitude in Lorentz covariant baryon chiral perturbation theory renormalized in the extended-on-mass-shell scheme. This amplitude, valid up to $\mathcal{O}(p^3)$ in the chiral…
Bound states of the pion--nucleus system are investigated in momentum space using a microscopic optical potential with inherent energy dependences and nonlocalities arising from elementary potential models. The wave equation and…
We evaluate the pion-nucleon and the pion-Delta sigma terms by employing the method of quantum chromodynamics (QCD) sum rules. The obtained value of the pion-nucleon sigma term is compatible with the larger values already anticipated by the…
Fermilab E781 plans measurements of gamma-Sigma and $\gamma$-pion interactions using a 600 GeV beam of Sigmas and pions, and a virtual photon target. Pion polarizabilities and radiative transitions will be measured in this experiment. The…
We have studied nuclear quadrupole deformation effects in deeply bound pionic atoms theoretically. We have evaluated the level shifts and widths of the hyperfine components using the first order perturbation theory and compared them with…
We use the framework of effective field theories to discuss the determination of the S-wave \pi N scattering lengths from the recent high-precision measurements of pionic deuterium observables. The theoretical analysis proceeds in several…
We present in this article an optical potential for the $\pi$-nucleus interaction that can be used in various studies involving $\pi$-nucleus channels. Based on earlier treatments of the low energy $\pi$-nucleus optical potential, we have…
We discuss an on-shell approach to pion-nucleon physics that is consistent order by order in a $1/f_{\pi}$ expansion with the chiral reduction formula, crossing, and relativistic unitarity. A number of constraints between the on-shell…
Analysis is performed of calculations of the elastic scattering differential cross sections of pions on the $^{28}$Si, $^{40}$Ca, $^{58}$Ni and $^{208}$Pb nuclei at energies from 130 to 290 MeV basing on the microscopic optical potential…
This presentation reviews recent developments in the understanding of low-energy pion- and kaon-nucleon interactions as they relate to deeply bound pionic atoms and possible antikaon-nuclear bound states. A brief update is given on 1s…
A theoretical analysis of the $(\pi^-,\gamma\gamma)$ reaction in nuclei is made in order to find the viability of this reaction to test modifications of the $\sigma$ meson mass in nuclear matter. The $\pi\pi$ correlation in the…
Predictions of the existence of well-defined deeply bound pionic atom states for heavy nuclei and the eventual observation of such states by the (d,3He) reaction have revived interest in the pion-nucleus interaction at threshold and in its…
We present a high statistics study of the pion and nucleon light and strange quark sigma terms using $N_f=2$ dynamical non-perturbatively improved clover fermions with a range of pion masses down to $m_\pi\sim 150$ MeV and several volumes,…
The main experimental works, where dipole polarizabilities of charged pions have been determined, are considered. Possible reasons for the differences between the experimental data are discussed. In particular, it is shown that the account…
In recent years, a persistent tension between phenomenological and lattice QCD determinations of the pion-nucleon $\sigma$-term $\sigma_{\pi N}$ has developed. In particular, lattice-QCD calculations have matured to the point that…
We summarize results obtained in our studies of the pion-nucleon coupling constant. Several different techniques have been applied to pi-N and NN elastic scattering data, and the existing database for single-pion photoproduction. The most…