Abstract:
We investigate parity-violating asymmetries in polarized n p radiative capture, and deuteron electro-disintegration in quasi-elastic kinematics, using the DDH model for the parity-violating nucleon-nucleon interaction. We find dramatic cancellations between the asymmetries induced by the parity-violating interaction and those arising from the associated parity-violating pion-exchange currents. In np capture, the model-dependence of the result is nevertheless quite small because of constraints arising through the Siegert evaluation of the relevant E1 matrix element. In quasi-elastic electron scattering these processes are found to be insignificant comared to the asymmetry produced by the gamma-Z interference on individual nucleons. These two experiments, then, provide clean probes of different aspects of weak-interaction physics associated with parity violation in the np system.

Abstract:
The longitudinal quasielastic parity-violating electron scattering response is explored within the context of a model that builds antisymmetrized RPA-HF correlations on a relativistic Fermi gas basis. The large sensitivity to nuclear dynamics of this observable, found in previous studies where only pionic correlations were included, is shown to survive in the present model where the effects from pion, rho, sigma and omega exchange in a version of the Bonn potential are incorporated. Through an intricate diagrammatic cancellation/filtration mechanism the longitudinal parity-violating response turns out to be close to the one obtained in first-order perturbation theory with the pion alone. Finally, in accord with our previous work, the parity-violating response is seen to display appreciable sensitivity to the electric strangeness content of the nucleon, especially at high momentum transfer.

Abstract:
We present a new contribution of the R-parity violating supersymmetry (SUSY) to neutrinoless double beta decay via the pion exchange between decaying neutrons. The pion coupling to the final state electrons is induced by the R-parity violating SUSY interactions. We have found this pion-exchange mechanism to dominate over the conventional two-nucleon one. The latter corresponds to direct interaction between quarks from two decaying neutrons without any light hadronic mediator like pion. The constraints on the certain R-parity violating SUSY parameters are extracted from the current experimental neutrinoless double beta decay half-life limit. These constraints are significantly stronger than those previously known or expected from the ongoing accelerator experiments.

Abstract:
We have made a needed correction to our earlier paper (nucl-th/9511002), which contains a sign error. With this correction, the weak parity-violating pion-nucleon coupling is about 3 x 10^(-7).

Abstract:
We consider the parity-violating two-pion-exchange potential obtained from the covariant formalism in the past and the state-of-the-art effective field theory approach. We discuss the behavior of the potential in coordinate space and its application to the parity-violating asymmetry in $\vec{n} p \to d \gamma$ at threshold.

Abstract:
We calculate the parity-violating nucleon-nucleon potential in heavy-baryon chiral perturbation theory up to the next-to-next-to-leading order. The one-pion exchange comes in the 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 $\vec{n} p \to d \gamma$ at the threshold. The one-pion dominates the physical observable and the two-pion contribution is about or less than 10% of the one-pion contribution.

Abstract:
We calculate in chiral perturbation theory the parity-violating two-pion exchange nucleon-nucleon potentials at leading one-loop order. At a distance of $r= m_\pi^{-1} \simeq 1.4 $fm they amount to about $\pm 16%$ of the parity-violating $1\pi$-exchange potential. We evaluate also the parity-violating effects arising from $2\pi$-exchange with excitation of virtual $\Delta(1232)$-isobars. These come out to be relatively small in comparison to those from diagrams with only nucleon intermediate states. The reason for this opposite behavior to the parity-conserving case is the blocking of the dominant isoscalar central channel by CP-invariance. Furthermore, we calculate the T-matrix related to the iteration of the parity-violating $1\pi$-exchange with the parity-conserving one. The analytical results presented in this work can be easily implemented into calculations of parity-violating nuclear observables.

Abstract:
In a recent preprint, hep-ph/0012253, Zhu et al. calculated a part of the next-to-leading order corrections to parity-violating pion photoproduction (pol)gamma p-> pi^+ n in heavy-baryon chiral perturbation theory. They claim they have found the contribution as large as the leading-order. If correct, the process will not be a clean way to extract the longest range PV pion-nucleon coupling constant h_{\pi NN}^(1), as was asserted in our previous publications (hep-ph/0011230, nucl-th/0011100). In this comment we show that there is no solid evidence to support Zhu et al.'s claim. Moreover, we show that the subleading parity-violating coupling h_V cannot be extracted from observables at the order of interest based on the formalism of effective field theory.

Abstract:
We use QCD sum rules to obtain the weak parity-violating pion-nucleon coupling constant $f_{\pi NN}$. We find that $f_{\pi NN}\approx 3\times 10^{-8}$, up to an order of magnitude smaller than the ``best estimates" based on quark models. This result follows from the cancellation between perturbative and nonperturbative QCD processes not found in quark models, but explicit in the QCD sum rule method. Our result is consistent with the experimental upper limit found from $^{18}$F parity-violating measurements.

Abstract:
We use QCD sum rules to obtain the weak parity-violating pion-nucleon coupling constant $f_{\pi NN}$. We find that $f_{\pi NN}\approx 2\times 10^{-8}$, about an order of magnitude smaller than the ``best estimates'' based on quark models. This result follows from the cancellation between perturbative and nonperturbative QCD processes not found in quark models, but explicit in the QCD sum rule method. Our result is consistent with the experimental upper limit found from $^{18}$F parity-violating measurements.