相关论文: Pion-delta sigma-term
We have previously calculated the pion-nucleon $\Sigma_{\pi N}$ term in the chiral mixing approach with $u,d$ flavors only, and found the lower bound $\Sigma_{\pi N} \geq \left(1 + \frac{16}{3} \sin^2 \theta \right){3 \over 2}…
Pion photoproduction off the nucleon close to threshold is studied in covariant baryon chiral perturbation theory at O($p^3$) in the extended-on-mass-shell scheme, with the explicit inclusion of the $\Delta(1232)$ resonance using the…
We investigate the possibility to determine the value of the pion-nucleon sigma term $\sigma_{\pi N}$ precisely by the experimental observables of the deeply bound pionic atoms. We discuss the sensitivity of the observables to $\sigma_{\pi…
We report a new analysis of lattice simulation results for octet baryon masses in 2+1-flavor QCD, with an emphasis on a precise determination of the strangeness nucleon sigma term. A controlled chiral extrapolation of a recent PACS-CS…
The scalar isoscalar form factor of the nucleon is calculated in the limit of a large number of colours in the framework of the chiral quark-soliton model. The calculation is based on an approximation justified by arguments from the…
Pion electro- and photoproduction off the nucleon close to threshold is studied in covariant baryon chiral perturbation theory at O($p^3$) in the extended-on-mass-shell scheme, with the explicit inclusion of the $\Delta(1232)$ resonance.…
The pion-nucleon amplitude is considered in the vicinity of the elastic scattering threshold within a relativistic dynamical model dressing the pi N N and pi N Delta vertices self-consistently with an infinite number of meson loops. The…
The chiral nonlinear ($\sigma,\pi,\omega$) mean-field model is an extension of the conserving nonlinear (nonchiral) $\sigma$-$\omega$ hadronic mean-field model which is thermodynamically consistent, relativistic and Lorentz-covariant…
A new result for the pion nucleon Sigma term from a George Washington University/TRIUMF group analysis of pion nucleon data is presented. The value Sigma=79$\pm$7 MeV was obtained, compared to the canonical value 64$\pm$8 MeV found by Koch.…
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,…
We investigate the pion-mass dependence of the nucleon mass within the covariant SU(2) baryon chiral perturbation theory up to order p4 with and without explicit Delta(1232) degrees of freedom. We fit lattice QCD data from several…
The pion-mass dependence of the nucleon mass within the covariant SU(2) baryon chiral perturbation theory both without and with explicit Delta(1232) degrees of freedom up to order p^4 is investigated. By fitting to lattice QCD data in 2 and…
The chiral soliton model including pi, rho, omega mesons is extended for the case when the scalar - isoscalar sigma meson has an anomalous dimension - d. The form factor of the sigma - nucleon interaction calculated and to be found not…
We develop an extension of chiral perturbation theory to the $\Delta$(1232)-resonance energy region and apply it to investigate the pion electroproduction off the nucleon ($e^- N \to e^- N\pi$). We present a complete calculation of this…
The composite operator formalism is applied to QCD at finite temperature to calculate the masses of scalar and pseudoscalar mesons. In particular the ratio of the sigma mass to the pion mass is an interesting measure of the degree of chiral…
We present a theoretical study of the radiative pion photoproduction on the nucleon ($\gamma N \to \pi N \gamma'$) in the $\De$-resonance region, with the aim to determine the magnetic dipole moment (MDM) of the $\Delta^+(1232)$. The study…
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,…
We calculate the one--loop contributions of order $M_\pi^4$ to the difference $\Delta_R$ between the on--shell pion--nucleon scattering amplitude $\bar{D}^+(0,2M_\pi^2)$ at the Cheng--Dashen point $\nu =0$, $t=2M_\pi^2$ and the scalar form…
We calculate the chiral and thermal susceptibilities for two confining Dyson-Schwinger equation models of QCD with two light flavours, a quantitative analysis of which yields the critical exponents, beta and delta, that characterise the…
Sum of the time component of $\Sigma$ term and the induced pseudo scalar term in axial current is shown to be the t-channel pion pole in Born terms for pion electroproduction near threshold. We also show that this $\Sigma$ term represents…