Parity Violation In Weak Interactions Research Articles

Generation of primordial magnetic fields by α-effect driven by collective neutrino-plasma interaction

We suggest a new mechanism for generation of large-scale magnetic fields in the hot plasma of early universe which is based on the parity violation in weak interactions. The mechanism can result in a self-excitation of an (almost) uniform cosmological magnetic field.

Parity violating asymmetry in $\vec{\gamma} + d \rightarrow n + p$ at low energy

We calculate the parity-violating asymmetry in the $\vec{\gamma} + d \rightarrow n + p$ process where the deuteron is disintegrated by circular photons. The photon energy is considered up to 10 MeV above threshold, where the lowest electromagnetic transition modes M1 and E1 dominate. We employ the Argonne v18 potential for the strong interaction and the DDH potential for the parity-violating weak interaction of the two-nucleon systems. The asymmetry is about 2.5 × 10–8 at threshold, and decreases rapidly to have magnitude of order 10–9 or less for photon energies larger than 3 MeV. The exchange of vector mesons dominates the asymmetry, while the pion contribution is negligible. PACS: 24.80.+y Nuclear tests of fundamental interactions and symmetries

Large-scale magnetic field generation by alpha effect driven by collective neutrino-plasma interaction.

We suggest a new mechanism for the generation of a large-scale magnetic field in the hot plasma of the early Universe which is based on parity violation in weak interactions and depends neither on the helicity of matter turbulence resulting in the standard alpha effect nor on general rotation. The mechanism can result in a self-excitation of an (almost) uniform cosmological magnetic field.

Indications towards a stereoselectivity of the salt-induced peptide formation reaction

Different reaction yields for l- and d-alanine in the salt-induced peptide formation (SIPF) reaction, differences in the circular dichroism spectra and the complex formation constants of the involved chlorocuprate complexes point at a stereoselective differentiation between the two stereoisomers in the SIPF reaction and give a possible explanation towards the origin of homochirality in the process of the origin of life. An explanation of the observed effects can for the time being only be based on assumptions but could possibly be related to the inherent chirality of the Cu II ion as a central atom of the [CuCl(gly)(glyH 2)(H 2O) 2] + complex due to parity violation in weak interactions and to amplification of chirality related to the structural properties of the complex.

Molecular chirality and the fundamental symmetries of physics: influence of parity violation on rovibrational frequencies and thermodynamic properties.

We introduce the topic of fundamental symmetries of physics in relation to molecular chirality by a brief review of the development and current status of the theory of parity violation in chiral molecules. We then discuss in some detail CHBrClF (bromochlorofluoromethane) as a test case, to which the work of André Collet has contributed importantly. For this molecule and its isotopomers, we report here the first detailed theoretical calculations of the influence of parity violation on statistical thermodynamic properties. High-quality ab initio calculations (RPA, random phase approximation, and CASSCF, complete-active-space self-consistent-field) were performed to determine the small energy difference between R- and S-enantiomers of H and D isotopomers of bromochlorofluoromethane (CHBrClF, CDBrClF), and fluorooxirane ((1)H(3)C(2)OF) introduced by the parity-violating weak interaction. Together with vibrational and rotational frequency shifts caused by parity violation, these were used to determine the statistical thermodynamic quantities from the corresponding partition functions within the separable harmonic and in part also anharmonic adiabatic approximation. Temperature-dependent equilibrium constants for the stereomutation were calculated and are discussed in relation to biochemical homochirality.

Application of relativistic theories and quantum electrodynamics to chemical problems

The BERTHA program embodies a new formulation of relativistic molecular structure theory within the framework of relativistic quantum electrodynamics (QED). This leads to a simple and transparent formulation of Dirac–Hartree–Fock–Breit (DHFB) self-consistent field equations along with algorithms for molecular properties, electron correlation, and higher order QED effects. The DHFB equations are solved by a direct method based on a relativistic generalization of the McMurchie–Davidson algorithm for molecular integrals that economizes memory requirements and is not significantly more expensive computationally than comparable nonrelativistic calculations. Some noteworthy features of this approach include the ease with which relativistic point-group symmetry can be analyzed and the ease of calculation of electromagnetic properties, for example, g factors, nuclear hyperfine interactions, nuclear magnetic resonance (NMR) shielding parameters and molecular effects of parity-violating weak interactions. The “negative energy” states, which are often regarded as a dangerous nuisance in other treatments of relativistic effects, make a vital contribution. As well as outlining the main ideas underlying our development, this study presents results for small molecules, some of which involve heavy elements. © 2000 John Wiley & Sons, Inc. Int J Quant Chem 80: 283–297, 2000

Application of relativistic theories and quantum electrodynamics to chemical problems

The BERTHA program embodies a new formulation of relativistic molecular structure theory within the framework of relativistic quantum electrodynamics (QED). This leads to a simple and transparent formulation of Dirac–Hartree–Fock–Breit (DHFB) self-consistent field equations along with algorithms for molecular properties, electron correlation, and higher order QED effects. The DHFB equations are solved by a direct method based on a relativistic generalization of the McMurchie–Davidson algorithm for molecular integrals that economizes memory requirements and is not significantly more expensive computationally than comparable nonrelativistic calculations. Some noteworthy features of this approach include the ease with which relativistic point-group symmetry can be analyzed and the ease of calculation of electromagnetic properties, for example, g factors, nuclear hyperfine interactions, nuclear magnetic resonance (NMR) shielding parameters and molecular effects of parity-violating weak interactions. The “negative energy” states, which are often regarded as a dangerous nuisance in other treatments of relativistic effects, make a vital contribution. As well as outlining the main ideas underlying our development, this study presents results for small molecules, some of which involve heavy elements. © 2000 John Wiley & Sons, Inc. Int J Quant Chem 80: 283–297, 2000

Fully relativisticab initiocalculations of the energies of chiral molecules including parity-violating weak interactions

Fully relativistic<i>ab initio</i>calculations of the energies of chiral molecules including parity-violating weak interactions

Parity Violation in Neutrino Transport and the Origin of Pulsar Kicks

In proto-neutron stars with strong magnetic fields, the neutrino-nucleon scattering/absorption cross sections depend on the direction of neutrino momentum with respect to the magnetic field axis, a manifestation of parity violation in weak interactions. We study the deleptonization and thermal cooling (via neutrino emission) of proto-neutron stars in the presence of such asymmetric neutrino opacities. Significant asymmetry in neutrino emission is obtained because of multiple neutrino-nucleon scatterings. For an ordered magnetic field threading the neutron star interior, the fractional asymmetry in neutrino emission is about 0.006(B/1014 G), corresponding to a pulsar kick velocity of about 200(B/1014 G) km s−1 for a total radiated neutrino energy of 3×1053 ergs.

Differential interaction of chiral β-particles with enantiomers

VESTER1 and Ulbricht2 invoked the parity-violating weak interaction as the cause of biological homochirality. They postulated that a stereoselective synthesis or decay of chiral molecules could be induced by the left circularly polarized bremsstrahlung; this small effect would then be amplified to full homochirality3–5. Despite much effort during the past thirty years, experimental results have been inconclusive and contradictory6–12. The aim of the study described here was more modest; we did not want to demonstrate differential synthesis or the decay of enantiomers bombarded by β-particles. Rather, using pulse-height spectroscopy, we examined the Cerenkov radiation emitted as β-particles pass through liquid chiral enantiomers. Our results show that helical electrons do distinguish between molecules of opposite chirality, and complement results reported in earlier publications in which differential decay6,13, positron annihilation14,15, scattering16,17 or other interactions18–20 were observed.

The enantio-preferential stabilization of D-ribose from parity violation

Ab initio calculations show that a biologically important sugar, D-ribose, is energetically stabilized relative to its unnatural Lenantiomer by the parity-violating weak interactions. This preferential stabilization may account for the exclusive adoption of Dribose rather than its L-enantiomer in the RNA of terrestrial organisms.

Non-mesonic decay modes of hypernuclei

The present status of theoretical descriptions of non-mesonic ( ΛN → NN) decay modes of hypernuclei is reviewed. One model, which evaluates a strangeness-changing, parity-violating weak interaction “potential” in nuclear matter, is examined in detail to exemplify the physics which can be learned and the problems which must be confronted. The importance of measuring the different isospin decay channels and separating the parity-conserving and parity-violating modes is stressed. Finally, this model is briefly compared and contrasted with other existing calculations.

Preferential stabilization of the D-sugar series by the parity-violating weak interactions

Hydrated D-glyceraldehyde is stabilized relative to its corresponding L-enantiomer by the parity-violating weak interactions.

Parity-violating energy differences between chiral conformations of tetrahydrofuran, a model system for sugars

The C2-endo conformations of tetrahydrofuran are stabilized relative to their C3-endo enantiomers by the parity-violating weak interactions.

Parity-violating energy differences of chiral minerals and the origin of biomolecular homochirality

The biochemistry of terrestrial organisms is based on chiral (handed) molecules, with one of the two possible series of enantiomers (mirror-image isomers) being predominant. Specifically, terrestrial biochemistry is homochirally supported by L-α-amino acids and D-sugars to the almost complete exclusion of the enantiomeric D-α-amino acids and L-sugars. This particular homochiral selection may be a result of very small differences between the electronic energies of enantiomeric prebiotic molecules due to the parity-violating weak interactions. The energy differences are, however, so small for simple chiral molecules, that the propagation of homochirality would require a dissymmetry amplification mechanism involving both large quantities of reactants and a long reaction time. An alternative theory, presented here, considering the effects of the parity-violating weak interactions in crystalline enantio-selective prebiotic catalysts, such as the clay silicates, may require considerably less amplification.

The effects of parity violation of molecular structure

Through the action of the parity-violating weak interactions, a chiral molecule and its enantiomer are expected to have equilibrium structures which slightly deviate from an exact mirror-image relationship. It is found that such deviations, and the resulting small differences in the electromagnetic interactions within enantiomeric molecules, are insufficient to perturb significantly or counteract the inherent parity-violating energy differences between enantiomers.

Cancellation of equilibrium parity-violating currents

It has recently been shown that in a rotating equilibrium system there exist neutrino and antineutrino currents parallel to the rotation axis. This suggests that particles other than neutrinos can also develop equilibrium currents if parity-violating weak interactions are taken into account. This possibility is examined using quantum field theory at finite temperature, density, and angular velocity. Regularization and renormalization of such a theory are discussed. The result obtained is negative. It is found that in the model considered the equilibrium current vanishes in the lowest order of perturbation theory. This is a surprising result, since the existence of a nonzero current is not forbidden by the symmetries of the Lagrangian. The question naturally arising from this result is whether a nonzero current appears in higher orders of perturbation theory or in different models or there is some deep physical reason which makes the equilibrium current equal to zero for all particles except neutrinos.

Neutrino pairing as the origin of parity violation in a chiral flavor theory of weak interactions

In this paper we study the space-time and internal-symmetry aspects of weak interactions together with their interplay. We propose that the weak interaction be obtained by gauging the strong-interaction chiral flavor group and consider explicitly the group $\mathrm{SU}{(4)}_{L}\ifmmode\times\else\texttimes\fi{}\mathrm{SU}{(4)}_{R}\ifmmode\times\else\texttimes\fi{}\mathrm{U}(1)$ as a candidate unified gauge theory of weak and electromagnetic interactions. In the symmetry limit the theory is both parity conserving and flavor conserving. The neutrinos in the theory are four-component spinors. We introduce a new dynamical mechanism for obtaining parity violation in weak interactions, namely neutrino pairing, in which we allow pairs of right-handed neutrinos to condense into the vacuum. The group theory associated with this pairing produces maximal parity violation in both the lepton and quark charged-current sectors of the weak interaction and also the conventional Weinberg mixing pattern in the neutral-current sector, while keeping the observed left-handed electron and muon neutrinos massless. In the right-handed sector of the theory, however, the pairing causes the right-handed electron and muon neutrinos to combine into one massive fourcomponent spinor. The unusual phenomenology associated with this new observable massive neutral lepton is studied in detail. Using other representations of the gauge group we also break flavor spontaneously to provide a group-theoretical origin for the Cabibbo angle. Through our approach we can incorporate current algebra and the Gell-Mann-Oakes-Renner Hamiltonian phenomenology into weak-interaction theory. We discuss briefly the implications of our work for constructing grand-unified theories of the strong, electromagnetic, and weak interactions.

Parity-violating effects of weak interactions in molecules

Effects of neutral-current parity-violating weak interactions in molecules are investigated. Asymmetries in the spectra of optically active mirror systems are estimated. The activity induced by weak interactions in rotational and vibrational transitions of nonactive molecules is computed.

Atomic spectroscopy search for a parity-violating weak interaction between electrons and nuclei

Theoretical analysis is made of the effect expected from a hypothetical weak interaction between electrons and nuclei due to neutral currents. A simple estimate is obtained of the magnitude of the parity-violating effects in heavy atoms and this estimate shows that such effects may be detected by modern spectroscopic methods. The effects which may appear for different types of weak interaction associated with neutral currents are considered. The results are given of detailed calculations for thallium, lead, and bismuth, which are the elements of the greatest experimental interest from the point of view of the expected effects.