C. H. Hyun

Parity-violating polarization innp→dγwith a pionless effective field theory

We consider the two-nucleon weak interaction with a pionless effective field theory. Dibaryon fields are introduced to ensure fast convergence of the perturbative expansion. Weak interactions are accounted for with the parity-violating dibaryon-nucleon-nucleon vertices, which contain unknown weak coupling constants. We apply the model to the calculation of a parity-violating observable in the radiative neutron capture on a proton at threshold. Result is obtained up to the linear order of the weak dibaryon-nucleon-nucleon coupling constants. We compare our result to the ones obtained from other approaches, and discuss investigation of the weak interaction in few-body systems.

Hadronic parity violation in n p → dγ with effective field theory

Abstract The parity-violating nucleon–nucleon (NN) potential is considered up to next-to-next-to leading order in heavy-baryon chiral perturbation theory. We include one-pion exchange at leading order and the two-pion exchange and two-nucleon contact terms at next-to-next-to-leading order. The effects of intermediate (two-pion exchange) and short-range (two-nucleon contact) terms are probed by calculating the photon asymmetry A γ in n → p → d γ employing Siegerts theorem and an accurate phenomenological potential for the parity-conserving NN interaction. We explore in detail the uncertainties due to the parameters that control the contribution of the short-range interaction. We obtain about 20% uncertainty in the value of A γ up to the next-to-next-to leading order. We discuss the implication of this uncertainty for the determination of the weak pion–nucleon coupling constant and how the uncertainty can be reduced.

Parity-violating nucleon-nucleon interaction from different approaches

Two-pion exchange parity-violating nucleon-nucleon interactions from recent effective field theories and earlier fully covariant approaches are investigated. The potentials are compared with the goal of obtaining better insight into the role of low-energy constants appearing in the effective field theory approach and its convergence in terms of a perturbative series. The results are illustrated by considering the longitudinal asymmetry of polarized protons scattering off protons, p-vector+p{yields}p+p, and the asymmetry of the photon emission in radiative capture of polarized neutrons by protons, n-vector+p{yields}d+{gamma}.

Parity-nonconserving observables in thermal neutron capture on a proton

Abstract.We calculate parity-nonconserving observables in the processes where a neutron is captured on a proton at the threshold energy radiating a photon. Various potential models such as Paris, Bonn and Argonne v18 are used for the strong interactions, and the meson exchange description is employed for the weak interactions between hadrons. The photon polarization Pγ in the unpolarized-neutron capture process and photon asymmetry Aγ in the polarized-neutron capture process are obtained in terms of the weak meson-nucleon coupling constants. Aγ turns out to be basically insensitive to the employed strong interaction models and thus can be uniquely determined in terms of the weak coupling constants, but Pγ depends significantly on the strong interaction models.

Two-pion-exchange parity-violating potential and np → dγ

Abstract.We calculate the parity-violating nucleon-nucleon potential in heavy-baryon chiral perturbation theory up to next-to-next-to-leading order. The one-pion exchange enters in leading order and the next-to-next-to-leading order consists of two-pion-exchange and the two-nucleon contact terms. In order to investigate the effect of the higher-order contributions, we calculate the parity-violating asymmetry in np → dγ at threshold. The one-pion-exchange contribution dominates the physical observable, while the two-pion-exchange contribution is about or less than 10% of the one-pion-exchange one.

Deuteron anapole moment with heavy mesons

Parity-nonconserving two-body currents due to vector meson exchange are considered with the aim to determine the related contributions to the anapole moment. A particular attention is given to the requirement of current conservation which is essential for a reliable estimate of this quantity. An application is made for the deuteron case.

Polarization of the neutron induced from hadronic weak interactions in the photo-disintegration of the deuteron

New observables with which we can study the two-nucleon weak interactions at low energies are considered. In the breakup of the deuteron by photons, polarization of outgoing neutrons can depend on the parity-violating component of two-nucleon interactions. We express the parity-violating polarization in general forms, and perform numerical calculations with a pionless effective field theory. The theory has unknown parity-violating low energy constants, and the results are expressed in linear combination of them. We discuss the results and their implication to the understanding of the hadronic weak interactions.

The anapole moment of the deuteron with the Argonne v18 nucleon–nucleon interaction model

Abstract We calculate the nuclear part of the deuteron anapole moment with the wave functions obtained from the Argonne v 18 nucleon–nucleon interaction model. The anapole moment operators are considered at the leading order. To minimize the uncertainty due to a lack of current conservation, we calculate the matrix element of the anapole moment from the original definition. In virtue of accurate wave functions, we can obtain a more precise value of the deuteron anapole moment which contains less uncertainty than the former works. We obtain a result reduced by more than 25% in the magnitude of the deuteron anapole moment. The reduction of individual nuclear contributions is much more important however, varying from a factor 2 for the spin part to a factor 4 for the convection and associated two-body currents.

Neutron Stars with Bose-Einstein Condensation of Antikaons as MIT Bags

We investigate the properties of an antikaon in medium, regarding it as a MIT bag. We rst construct the MIT bag model for a kaon with and in order to describe the interaction of s-quarks in hyperonic matter in the framework of the modied quark-meson coupling model. The coupling constant g 0B K in the density-dependent bag constant B( ) is treated as a free parameter to reproduce the optical potential of a kaon in a symmetric matter and all other couplings are determined by using SU(6) symmetry and the quark counting rule. With various values of the kaon potential, we calculate the eective mass of a kaon in medium to compare it with that of a point-like kaon. We then calculate the population of octet baryons, leptons and K and the equation of state for neutron star matter. The results show that kaon condensation in hyperonic matter is sensitive to the s-quark interaction and also to the way of treating the kaon. The mass and the radius of a neutron star are obtained by solving the Tolmann-Oppenheimer-Volko equation.

Kaon condensation in neutron star using relativistic mean field models

We use the modified quark-meson coupling and the quantum hadrodynamics models to study the properties of neutron star. Coupling constants of both models are adjusted to reproduce the same saturation properties. The onset of kaon condensation in neutron star matter is studied in detail over a wide range of kaon optical potential values. Once the kaon condensation takes place, the population of kaons increases very rapidly, and kaons become the dominant component, possibly making the neutron star matter a kaonic matter if the kaon optical potential is large.