相关论文: In-Medium Effective Axial-Vector Coupling Constant
We extend a recent three-loop calculation of nuclear matter in chiral perturbation theory by including the effects from two-pion exchange with single and double virtual $\Delta(1232)$-isobar excitation. Regularization dependent short-range…
In the modern description of nuclear forces based on chiral effective field theory, four-nucleon operators with unknown coupling constants appear. These couplings can be fixed by a fit to the low partial waves of neutron-proton scattering.…
We present a precision measurement of the axial-vector coupling constant $g_A$ in the decay of polarized free neutrons. For the first time, a pulsed cold neutron beam was used for this purpose. By this method, leading sources of systematic…
The existing experimental evidence on the vector and axial-vector coupling constants, $G_V$ and $G_A$, for neutron $\beta$-decay exhibits two prominent problems: (i) the unitarity for the first row of the CKM matrix seems violated; (ii) one…
In-medium chiral perturbation theory is used to calculate the density dependence of the quark condensate $<\bar qq>$. The corrections beyond the linear density approximation are obtained by differentiating the interaction contributions to…
We consider two methods to find the effective parameters of the pion traversing a nuclear medium. One is the first order chiral perturbation theoretic evaluation of the pion pole contribution to the two-point function of the axial-vector…
The behavior of nonperturbative parts of the isovector-vector and isovector and isosinglet axial-vector correlators at Euclidean momenta is studied in the framework of a covariant chiral quark model with nonlocal quark-quark interactions.…
We derive density-dependent corrections to the in-medium nucleon-nucleon interaction from the leading-order chiral three-nucleon force. To this order there are six distinct one-loop diagrams contributing to the in-medium nucleon-nucleon…
We derive a novel chiral power counting scheme for in-medium chiral perturbation theory with explicit nucleonic and pionic degrees of freedom coupled to external sources. It allows for a systematic expansion taking into account local as…
Due to the internal structure of the nucleon, we should expect, in general, that the effective meson nucleon parameters may change in nuclear medium. We study such changes by using a chiral confining model of the nucleon. We use…
The quark-meson coupling model for nuclear matter, which describes nuclear matter as non-overlapping MIT bags bound by the self-consistent exchange of scalar and vector mesons, is modified by introducing medium modification of the bag…
The axial vector coupling constants of the $\beta$ decay processes of neutron and hyperon are calculated in SU(3) chiral colour dielectric model (CCDM). Using these axial coupling constants of neutron and hyperon, in CCDM we calculate the…
We optimize $\Delta$-full nuclear interactions from chiral effective field theory. The low-energy constants of the contact potentials are constrained by two-body scattering phase shifts, and by properties of bound-state of $A=2$ to $4$…
We study the modification of the nucleon axial form factor in nuclear matter. The internal quark substructure of the nucleon is self-consistently described by the quark meson coupling model. We find that the axial form factor of the bound…
A precise measurement of the neutron decay $\beta$-asymmetry $A_0$ has been carried out using polarized ultracold neutrons (UCN) from the pulsed spallation UCN source at the Los Alamos Neutron Science Center (LANSCE). Combining data…
Our extraction of the pion-nucleon coupling constant from \pi p elastic scattering data is outlined. A partial wave analysis (T_{\pi} < 2100 MeV) is performed simultaneously with a fixed-t dispersion relation analysis (T_{\pi} < 800 MeV).…
We present a calculation of the leading two-loop corrections to the axial-vector coupling constant $g_A$ in two covariant versions of two-flavor baryon chiral perturbation theory. Taking the low-energy constants from a combined analysis of…
We study the modification of the nucleon nucleon interaction in a nuclear medium in the scalar isoscalar channel, mediated by the exchange of two correlated ($\sigma$ channel) or uncorrelated pions. For this purpose we use a standard…
Recent heavy ion experiments indicate modifications of the $\rho-$meson mass in medium. In the CERES experiments $\rho-$mesons are produced at $\sim$ normal nuclear matter density, where hadrons are more appropriate constituents than…
We study radiative corrections to low-energy charged-current processes involving nucleons, such as neutron beta decay and (anti)neutrino-nucleon scattering within a top-down effective-field-theory approach. We first match the Standard Model…