Related papers: The pion-nucleon $\sigma$ term from pionic atoms
We extend a recent calculation of the nuclear energy density functional in the framework of chiral perturbation theory by computing the isovector surface and spin-orbit terms: $(\vec \nabla \rho_p- \vec \nabla \rho_n)^2 G_d(\rho)+ (\vec…
We determine the $\Delta(1232)$ resonance parameters using lattice QCD and the L\"uscher method. The resonance occurs in elastic pion-nucleon scattering with $J^P=3/2^+$ in the isospin $I = 3/2$, $P$-wave channel. Our calculation is…
A simple matching procedure is proposed to extract constraints on effective meson theories. In this way, a QCD prediction for the pion decay constant is found, F(pi)=2 m(pi)/pi, i.e. approximately 90MeV. The same procedure also determines…
A historical review of pion-nucleon interactions at low energy is presented, with aims toward an introductory, pedagogic approach focusing on issues germane to current research. These topics include the use of chiral effective field theory,…
Several new theoretical and experimental developments concerning the determination of the nucleon sigma term are presented and discussed. Contribution to the Eighth International Symposium on Meson-Nucleon Physics and the Structure of the…
We present new N_f=2 data for the nucleon generalized form factors, varying volume, lattice spacing and pion mass, down to 150 MeV. We also give an update of our direct calculation of the nucleon sigma term for a range of pion mass values…
We have recently studied in the delta-resonance--nucleon-hole model the dependence of the pion spectral function in hot dense asymmetric nuclear matter on the charge of the pion due to the pion p-wave interaction in nuclear medium. In a…
The weak decay of the kaon to two pions is studied within the NJL Model. Using the standard effective weak Hamiltonian, both the decay amplitude arising from an intermediate state \sigma-meson and the direct decay amplitude are calculated.…
The in-medium chiral condensate is studied with a new approach which has the advantage of no need for extra assumptions on the current mass derivatives of model parameters. It is shown that the pion-nucleon sigma term is 9/2 times the…
We calculate both connected and disconnected contribution to the $\pi$-$N$ $\sigma$-term in quenched lattice QCD with Wilson quark action on a $12^3\times 20$ lattice at $\beta=5.7$. The latter is evaluated with the aid of the variant wall…
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…
Fits of the p^4 covariant SU(2) baryon chiral perturbation theory to lattice QCD nucleon mass data from several collaborations for 2 and 2+1 flavors are presented. We consider contributions from explicit Delta(1232) degrees of freedom,…
The s-wave isoscalar amplitude for pion-pion scattering in a nuclear medium is evaluated using a nonperturbative unitary coupled channels method and the standard chiral Lagrangians. The method has proved successful to describe the pion-pion…
We have measured the energy spectra of pions and protons emitted in the weak decay of 12_Lambda_C, 28_Lambda_Si, and Lambda_Fe hypernuclei produced via the (pi+, K+) reaction. The decay widths of the pi- mesonic decay (Lambda -> p + pi-)…
Background: Until now the knowledge about nucleon resonances with a mass higher than 2 GeV has been scarce. Huge amounts of experimental data of the multipion photoproduction have been accumulated, and more can be expected in the future in…
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…
Changes in the meson-nucleon coupling constant and the vertex form factor in nuclear matter are studied in a modified Skyrme Lagrangian including the sigma-meson field that satisfies the scale invariance. Renormalization of the axial-vector…
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…
It has been argued that the leading scalar-isoscalar WIMP-nucleus interactions receive parametrically enhanced contributions in the context of nuclear effective field theories. These contributions arise from meson-exchange currents (MECs)…
We evaluate the in-medium spectral functions for pions, nucleon and isobar resonances in a self consistent and covariant manner. The calculations are based on a recently developed formulation which leads to predictions in terms of the…