Parity violating Compton amplitude in unified theories

The leading contribution of O(αG_F) to the parity violating piece of the electron Compton amplitude is calculated in the Weinberg Salam unified theory and is shown to vanish. The reason for this is the nonexistence of parity violating charge and electric dipole moment. In the computation, a problem with the usual gauge fixing terms in the Weinberg model was encountered and resolved; the gauge fixing terms made it impossible to satisfy the electromagnetic Ward identity off mass-shell. The resolution of this problem has led to changed Feynman rules resulting in fewer graphs and gauge dependent vertices. Further features are a renormalization of the parity violating infinities, and a discussion of how the γ₅-algebra and n-dimensional regularization can coexist peacefully.     

An analysis of parity violating nuclear effects at low energy

We present an analysis of parity violating nuclear effects at low energy which attempts to circumvent the uncertainties due to the weak and strong nucleon-nucleon interactions at short distances. Extending Danilov's parametrization of the parity violating nucleon-nucleon scattering amplitude, we introduce six parameters: one for the long range contribution due to the pion exchange and five for the shorter range contributions. This choice gives an accurate representation of parity violating effects in the nucleon-nucleon system up to a lab energy of 75 MeV. For calculations in nuclei, we derive an effective two-body potential in terms of the parameters. The analysis of presently measured effects shows that they are consistent, and, in particular, that the circular polarization of photons in n + p → d + γ is not incompatible with the other measurements. It does not imply a dominant isotensor component.     

Explicit R-parity breaking in supersymmetric models

Supersymmetric models generally invoke R parity to ensure that baryon and lepton numbers are symmetries of the renormalizable operators of the low-energy effective theory. The phenomenology of lepton-number violation is analyzed in low-energy models in which R parity is explicitly broken by superrenormalizable operators. Constraints on lepton-number violating parameters are found to be mild. The photino is able to decay, avoiding a stringent cosmological lower bound on its mass. Alternatives to R parity are considered in the context of an SU(5) grand unified model coupled to N=1 supergravity. One possibility, θ parity, leads to new mechanisms for baryon- number violation in addition to lepton-number violation.     

Parity violating effects in Σ→Λγ and Σ→Λe t>+ e − decays

Parity violating effects in Σ→Λγ are calculated in non relativistic quark model usingW, Z and gluon exchanges. These effects are found to give dominant contribution to the parity violating effects in Σ→Λe ⁺⁺ e ^? decay as compared to the neutral current effects.     

Parity Violating Electron Scattering in the Relativistic Eikonal Approximation

The parity violating electron scattering is investigated in the relativistic Eikonal approximation. The parity violating asymmetry parameters for many isotopes are calculated. In calculations the proton and neutron densities are obtained from the relativistic mean-field theory. We take Ni isotopes as examples to analyse the behaviour of the parity violating asymmetry parameters. The results show that the parity violating asymmetry parameter is sensitive to the difference between the proton and neutron densities. The amplitude of the parity violating asymmetry parameter increases with the distance between the minima of proton and neutron form factors. Our results are useful for future parity violating electron scattering experiments. By comparing our results with experimental data one can test the validity of the relativistic mean-field theory in calculating the neutron densities of nuclei.     

Nuclear spin dependent atomic parity violation,nuclear anapole moments and the hadronic axial neutral current

Left-right asymmetries in atomic transitions, depending upon the nuclear spin, could be a source of information on the neutral hadronic axial current. We show that the relevant electroweak parameter can be extracted from experiment by measuring hyperfine component ratios which do not involve the knowledge of the atomic wave function. In the standard electroweak model, the parity violating electron-nucleus interaction associated with the hadronic axial neutral current is accidently suppressed and, as a consequence, dominated by the electron interaction with the nuclear anapole moment, which describes the effect of the parity violating nuclear forces on the nucleus electromagnetic current. One of our objectives was to identify the various physical mechanisms which determine the size of the nuclear anapole moments. As an important step, we have established a simple relation between the anapole moment and the nuclear spin magnetization. From this relation it follows that the computation of the anapole moment can be reduced to that of one-body operators. The basic tool is a unitary transformationW which eliminates the one-body parity violating potential from the nuclear hamiltonian. It generalizes, to more realistic situations, a procedure used by F.C. Michel in the case of constant nuclear density. The fact that the transformationW does not commute with the residual spin-dependent nucleon-nucleon interaction can be accounted for — within some approximation — by a renormalization of the effective coupling constants which appear in the one-body reduction of the two-body parity violating nucleon-nucleon interaction induced by meson exchange. A particular attention was paid to nuclear correlation effects. They are treated semi-empirically in the independent pair approximation. The nuclear anapole moments of⁸⁵Rb,¹³³Cs, and²⁰⁹Bi have been evaluated for three sets of parity violating meson-nucleon coupling constants, taking into account configuration mixing effects in a semi-empirical way. We suggest a possible strategy to disentangle the axial neutral current from the anapole moment contribution. It requires experiments, accurate to few tenths of a percent, performed on several heavy nuclei. The results should be collected in a two-dimensional plot involving a suitably chosen set of variables (X, Y). In an ideal situation — small theoretical uncertainties —the points corresponding to various nuclei should fall on a straight line which crosses the lineX=0 at a point the ordinate of which is the sought for axial coupling constant.     

Weak radiative hyperon decays in the pole model

We compute the parity conserving and parity violating amplitudes of the weak radiative hyperon decays in a pole model which includes negative parity intermediate states. The matrix elements are determined from experimentally known quantities and also evaluated in a nonrelativistic quark model. We find good numerical agreement with the data for the decay Σ⁺→P+γ and obtain predictions for the other decays where experimental information has been scarce up to now.     

WW collisions from polarized electron or proton beams,polarized luminosities and applications

A complete formulation of Vector boson-Vector boson processes ine ⁺ e ^?,pp andep collisions is done including Parity violation and beam polarization effects. Single vector boson (W ^±,Z, ψ) distributions inside leptons, quarks and proton as well as luminosity factors and polarization asymmetry factors are established for all (parity conserving and parity violating) helicity combinations. First applications are given for single particle (Higgs,Z′) production, for vector boson-vector boson scattering and for heavy fermion pair production.     

Radiative decays as a test for right-handed currents

It is shown that the purity violating amplitude for the decays Σ⁺ → pγ and Ξ^? → Σ^?γ vanish in the SU(3) symmetry limit if the charged weak currents possess a U spin symmetry for strangeness changing processes. This applies to Cabibbo currents and their SU (4) generalization. Assuming an asymptotically free model for the strong interactions this result applies to all models with only left-handed charged currents. Observation of a large parity violating amplitude would indicate right-handed charged weak currents. Tests involving other radiative decays are also considered.     

Trapped radioactive isotopes for fundamental symmetry investigations

Discrete symmetries tested in high precision atomic physics experiments provide guidance to model building beyond the Standard Model (SM). Here experimental opportunities arise for searches for permanent electric dipole moments (EDMs) and measurements of atomic parity violation (APV). Heavy atoms are favorable for such experiments since symmetry violating effects in atoms increase faster than the third power of the nuclear charge Z. Of special interest are isotopes of the heavy alkaline earth element radium (Z=88) since they offer large enhancement factors for EDMs and provide a new experimental road towards high precision measurements of atomic parity violation. These opportunities are exploited at the TRIμP facility at KVI, Groningen.     

Projection of Wilson coefficients from deep inelastic leptoproduction data

We show in detail how the techniques of Nachtmann can be applied to the operator product expansion of two-vector (or vector minus axial vector) current in order to extract Wilson coefficients from the deep inelastic leptoproduction data. Included are new results for the G₁ and G₂ (spin dependent) and W₃ (parity violating) structure functions.     

Exchange current contributions to parity violating electric transitions revisited

A detailed analysis of possible exchange current contributions to parity violating E1 transitions in nuclear processes is presented and applied to the circular polarization P_γ in thermal n-p photocapture. In agreement with previous claims it is found that significant contributions are not expected.     

Long-range parity violating interaction in muonic atoms

Long-range parity violating forces are induced in muonic atoms by virtual γ?Z⁰ conversion between the muon and the nucleus. They are of order G_Fα with range (2m_e)^?1. The relevant diagrams in unified electroweak interactions are calculated and the effects of the corresponding potential on parity admixtures in muonic levels are studied. It is proved that they are negligible for n = 3 orbits, but they have overwhelmed the conventional short-range contribution for n = 5.     

Relativistic invariant approach to the parity violation in np→dγ capture

It is shown that the consistent relativistic invariant approach to the parity violation in np→dγ capture of thermal neutrons leads to results which differ essentially from those of the nonrelativistic approach. In particular the isospin selection rule established earlier for the photon circular polarization is charged due to the contribution of “relativistic” parity violating components of the deuteron and np-scattering wave function.     

Cabibbo angle,CP violation and quark masses

By adding suitable discrete flavor symmetries to SU(2)_L ? SU(2)_R ? U(1) left-right symmetric gauge models of weak and electromagnetic interactions, we are able to express all the mixing angles between the quark flavors (u, d, s,c) in terms of the quark masses. This enables us to compute the Cabibbo angle and the CP violating phases using plausible values for the quark masses. The CP violating K ar 2π decay amplitude η_+? (and η₀₀ in the model is then given purely in terms of the parity violating parameter of the model (m_WL⁺/m_WR⁺)².     

Parity violating two-pion-exchange nucleon-nucleon potential

The isovector part of the parity violating two-pion-exchange NN potential is constructed from the field theoretic amplitude. The parity violating NN coupling is described by the phenomenological Lagrangian $\text{g}{}_{\mathrm{<mtext>W</mtext>}}\text{ψ}\text{(τ × φ)}{}_3\text{ψ}$, with g_W = 3.2 × 10^?8. The effect of p-wave ππ correlations is taken into account.     

Elliptic index and superstring effective actions

Certain N = 1 supersymmetric string one-loop effective actions can be obtained directly from the path integral. As the computation is essentially the same as the one leading to the index of the Dirac-Ramond operator, they are determined by the gauge and gravitational anomaly structure of the theory. Specifically, we calculate the four-point effective action in ten dimensions, the corrections to the kinetic terms in d = 6 (including auxiliary fields) and the Fayet-Iliopoulos D-term in d = 4. We also compute the β-function of four-dimensional N = 2 theories from the elliptic genus in d = 6. Furthermore, we derive supersymmetry Ward type identities in terms of Kac-Moody characters, relating parity conserving with parity violating amplitudes.     

A relativistic potential model

Using parity violating nucleon wave function effects we make predictions for spin asymmetries inpp and \(\bar p\) p scattering at moderate and high energies     

Parity violating neutral currents in a left-right symmetric gauge model

We consider parity violating effects in the neutral sector of a left-right symmetric SU(2)_L × SU(2)_R × U(1) gauge model of weak and electromagnetic interaction. With four quarks and four leptons, the parity violating optical rotation in atoms is estimated to be about an order of magnitude smaller (and of opposite sign) compared to the Salam-Weinberg (SW) model prediction. However, with new quarks and leptons this effect can be arranged to be even smaller. Weak-electromagnetic interference effects are quantitatively different from those found in the SW model. A unified gauge theory which embeds the left-right symmetric gauge model is briefly discussed.     

Effective supersymmetric theory and muon anomalous magnetic moment with R parity violation

The effective supersymmetric theory (ESUSY) with R parity conservation cannot give a large anomalous magnetic moment of μ. It is pointed out that the flavor conservation and a large (g−2)_μ within the experimental limits are achievable in the ESUSY with R parity violating couplings involving the third generation superparticles.