Weak Parity Research Articles

A quark model calculation of the weak parity violating asymmetry in high-energy proton-nucleon scattering

We perform a quark-model calculation of the parity-violating asymmetry in high-energy polarized proton-unpolarized nucleon scattering. Strong interaction enhancement has been taken into account using both renormalization group techniques and precise one-loop calculations. Essential high-twist (bound state) contributions to the asymmetry have been included. Our results indicate large (∼10 −6) positive values for the parity-violating asymmetry at high energy, in agreement with the experimental results of Lockyer et al.

QCD corrections to the weak hamiltonian and parity violation in N-N reactions

The gluon corrections to the weak ΔS=O hamiltonian are calculated taking into account the intermediate distances x > mc−1. It is shown that these corrections give large negative contributions to the calculated values of the λ-polarization Pγ in np→dγ and the asymmetry parameter App in p→pp, so that Pγth can even change sign and Appth increases in absolute value.

Parity violating observables in low energy nucleon-nucleon scattering

We have calculated the parity violating observables in p-p and n-p scattering using a number of strong nucleon-nucleon potentials for a large class of weak parity violating potentials.

Electron Configuration Mixing and Parity Nonconservation in Atomic Bi

Configuration mixing is investigated in a relativistic theory for states in Bi which dominate the effects of weak parity nonconservation. The corrections to the parity-nonconserving electric dipole and parity-conserving magnetic dipole transition matrix elements between the lowest two states are computed and found to be less than 4%. Such effects do not remove the discrepancy between atomic experiments and the Weinberg-Salam theory.

Gamma polarisation in the n + p → γ + d reaction due to weak parity violating effects

We study the effect of parity violating weak interactions on the polarisation of the photon in the thermal neutron capture np → γd. The effect of various strong potentials is analysed in detail in the non-relativistic calculation. It is shown that, due to the short range of the weak interactions, the high momenta tail of the deuteron wave functions plays an important role. The effects of relativistic corrections are then considered. They are shown to be important for a precise quantitative calculation, but unable to explain the present disagreement between theory and experiment.

Parity mixing in 19F and the weak parity non-conserving nucleon-nucleon interaction

We report calculations of the asymmetry of the 110 keV photon emitted in the decay of the polarized 1 2 − first excited state of 19F. The calculations employ short range correlations obtained by solving the Bethe-Goldstone equation in the A = 20 system, and are carried out for a wide range of weak parity non-conserving potentials suggested in the literature. Because of the large experimental error of the observed asymmetry, many of these potentials give results compatible with the experimental value. A calculation of the parity allowed E1 matrix element suggests that the standard Cabibbo potential gives results which disagree in sign with the observed asymmetry, which has also been the case in other parity non-conserving transitions.

Dispersion theory of parity non-conservation in pion-nucleon scattering at low energies

We examine the possibility for testing the weak parity non-conserving (pnc) interaction in pion-nucleon scattering at low energies. We start out analysis by assuming the existence of a pnc πNN coupling which conserves time reversal invariance and has the isospin selection rule ΔI = 1, and the existence of fixed- t dispersion relations obeyed by the pnc invariant amplitudes. By using the nonrelativistic expansion, we then derive dispersion relations for the partial-wave amplitudes. We calculate parity-odd observables in π −p → π −p and in π −p → π 0n, e.g., the up-down asymmetry α in the total cross section for a polarized target and the longitudinal polarization P of the recoil nucleon. In the conventional Cabibbo model for the weak interaction P and α are found to be of order 10 −7 to 10 −8. We have also examined the t-channel pnc ϱ-exchange process which has the isospin selection rule ΔI = 0, 2 and found it to contribute dominantly to P in the charge-exchange channel π −p → π 0n.

Weak Neutral Currents and Parity Violating Nuclear Interactions

The weak neutral currents almost established in high energy neutrino reactions contribute to the parity violating nuclear interactions. We evaluate the effects of neutral currents to the circular polarization P1 in the 482 keV gamma transition in tantalum 181Ta. Use is made of .two types of neutral currents : One is the V-A neutral current with isovector and iso­ scalar mixing which we proposed recently and the other is the neutral current in the frame­ work of the gauge theory of Weinberg and Salam. In the former case we obtain reasonable magnitudes with the correct sign for P 1 , while in the latter case our calculation leads us to values with the sign opposite to the' experimentally determined sign.

Model of Weak and Electromagnetic Interactions

We present here a model of weak and electromagnetic interactions of leptons and hadrons based on the spontaneously broken gauge symmetry O(3) \ifmmode\times\else\texttimes\fi{} O(2). The advantages of the model are the following: (1) The universality of the $\ensuremath{\beta}$ and $\ensuremath{\mu}$ decays emerges naturally; (2) there appears only positively charged heavy leptons, and no neutral heavy leptons which might affect the muon ($g\ensuremath{-}2$) factor adversely; (3) a neutral current shows up only as a short-range weak parity violation in electromagnetism, and nowhere else.

Strong interactions and the weak parity violating nuclear potential

The one-pion exchange weak, parity non-conserving, potential is calculated, taking into account the effect of strong interactions in the lowest order. The corrections are estimated and compared with the rho-exchange potential.

Weak interactions with scalar intermediate bosons

A theory of weak interactions with scalar bosons is considered. it is pointed out that if the bosons couple to a triplet of scalar and pseudoscalar currents with unequal strength, we get a consistent theory, with weak parity and strangeness violations, and with effective octet structure for the strangeness-changing non-leptonic interaction. Higher-order weak and electromagnetic processes are evaluated under the assumption that the lowest order weak and electromagnetic processes are renormalizable and finite. The calculations for K L 0 → μ + μ −, K + → π + μ + μ − and K 1 0K 2 0 mass difference yield consistent results for a scalar boson mass of about 10 GeV.

The circular polarization of γ rays from 181Ta and the parity violating one pion exchange potential

A value for the weak parity violating n → p + π − amplitude is deduced from the circular polarization of γ transitions in 181Ta by describing the nuclear states in the unified collected model. A large discrepancy with previous calculations is found. From our result, the possibility of a small upper limit for the time reversal violating electromagnetic interaction is discussed.

Possible tests for the violation of parity and time-reversal invariance in nuclei

Consequences of the assumption that time-reversal ( T) invariance is weakly violated together with the weak parity ( P) violation in the nucleus are investigated in connection with the observed K 2 0→2 π decay. The odd- T terms in the nucleon-nucleon effective force are calculated and their contribution to the average nuclear potential are estimated. Various possible electromagnetic nuclear transitions are considered that can be used as tests for the simultaneous violation of T- and P-invariance in the nucleus.

The one pion exchange contribution to the weak parity violating nucleon-nucleon potential

Abstract The one pion exchange contribution to the weak parity violating nucleon-nucleon potential is calculated by relating the weak NNπ vertex to the nonleptonic hyperon decays by the Suzuki-Sugarawa method. It is also shown that the G parity odd part of the weak Hamiltonian cannot contribute to the potential.