Parity violation in atoms within left-right symmetric gauge models

Predictions for parity violation in atoms within left-right symmetric theories based on the gauge groups SU(2)_L × SU(2)_R × U(1) and SU(2)_L × SU(2)_L × SU(2)_R × U(1)_L × U(1)_R are presented.     

Parity violation in left-right symmetric gauge models

The parity violating effective interaction in models based on the SU(2)_L × SU(2)_R × U(1) gauge group is shown to have the same structure, at zero momentum transfer, as in the Weinberg-Salam model, apart from a constant scale factor.     

Parity violation in SLAC experiment and left-right symmetric gauge models

It is shown that the left-right symmetric gauge models based on the group $\text{G}$ = SU(2)_L × SU(2)_R × U(1)_L × U(1)_R can accommodate quite naturally the results of the recent SLAC experiment concerning parity violation in neutral currents. The possibility of finding a light neutral gauge boson in the PETRA-PEP energy range remains particularly interesting.     

Parity violation correlations in light muonic atoms

The 2S-1S transition in light muonic atoms is very sensitive to parity violation correlations induced via neutral currents. Observables depending on these transitions such as the photon polarization and the angular correlation between the emitted radiation and the atom polarization are a clear signal of weak neutral currents in atoms. We find the relation between the lepton and quark couplings and these observables emphasizing the effect of the nuclear spin. The results expected in muonic, atoms μ-⁴He and μ-³He are given.     

A gauge model without parity violation in heavy atoms

We address the question: “are weak right-handed non-singlet representations of quarks and leptons necessary?” An extension of the Weinberg-Salam model to SU(2) ? U(1) ? U(1) is found to adequately describe all existing weak interaction data including the lack of parity violation in atomic physics experiments. These data tightly constrain the additional parameters introduced by adding the second weak hypercharge. Although such a model may seem regressive when considered from the standpoint of “simple” unification schemes, we feel that it is aesthetics rather than experiment which leads to non-trivial right-handed multiplet structure. In contrast to most other models, ours predicts a substantial parity-violation effect in atomic experiments on hydrogen. We note that the second weak boson in our model is not constrained to be heavy by existing data and thus might already by accessable in pp → μ⁺μ^?X or possibly in the next generation of colliding beam facilities through e⁺e^? → μ⁺μ^?.     

Trimuons in SU(3) gauge models

We discuss models of weak interactions which can account for the recently observed μ^?μ^?μ⁺ events in v_μ reactions by allowing for the production of a new heavy neutral lepton and a new quark. One model is based on an SU(3) × U(1) gauge theory in shich the left-handed leptons are classified in anti-triplets. The second model catagorizes the leptons in an octet in accord with the more restrictive SU(3) weak gauge theory.     

Fixed twist dynamics of SO(3) gauge theory

We perform a thorough study of 3+1-dimensional SO(3) LGT for fixed-twist background. We concentrate in particular on the physically significant trivial and 1-twist sectors. Introducing a ℤ₂ monopole chemical potential the 1st order bulk transition is moved down in the strong coupling region and weakened to 2nd order in the 4-dimensional Ising model universality class. In this extended phase diagram we gain access to a confined phase in every fixed-twist sector of the theory. The Pisa disorder operator is employed together with the Polyakov loop to study the confinement–deconfinement transition in each sector. Due to the specific properties of both operators, most results can be used to gain insight in the ergodic theory, where all twist sectors should be summed upon. An explicit mapping of each fixed-twist theory to effective positive plaquette models with fixed-twisted boundary conditions is applied to better establish their properties in the different phases.     

Parity violation observed in the beta decay of magnetically trapped 82Rb atoms

Laser cooling and atomic trapping techniques have been employed to confine polarized 82Rb atoms ( T1/2 = 75 s) in a magnetic time-orbiting-potential (TOP) trap. We have observed the parity-violating correlation between the emitted positron momentum and the parent nuclear spin as a continuous function of angle and positron energy for this pure Gamow-Teller (GT) transition. These proof-of-principle measurements demonstrate the utility of exploring fundamental symmetries in a TOP trap and the steps required to improve sensitivity in the search for physics beyond the standard model.     

Left-right symmetric gauge theory and its prediction for parity violation in atoms

We have evaluated radiatively induced parity violating effects in atoms in a manifestly left-right symmetric SU(2)_L x SU(2)_R x U(1) gauge theory that forbids them at the tree level. Our results indicate possible large enhancements due to the contribution of the physical Higgs scalars.     

Defect melting as an SO(3) lattice gauge theory

We show that defect melting is closely related to SO(3) lattice gauge theory. The phase transition of this system corresponds to a Lindemann melting parameter L≈50γ where γ≈2 is a parameter characterizing the unharmonic content in the elastic forces. This is in rough agreement with experiment. The equivalence may help in visualizing the crucial rule of defects in quark confinement.     

Parity violation in pion-proton scattering

Parity-violating pion-proton scattering is strongly dominated by so-called penguin operators. These operators are due to the presence of the neutral current, and their strength is further enhanced by the QCD renormalization effects. Without such contributions the elastic asymmetry (A_l) would be an order of magnitude smaller (up to 150 MeV of the pion laboratory kinetic energy). Possible contributions from the resonance poles (?-meson, ($\text{1}\text{2}{}^{\mathrm{+}}\text{)}{}^1\text{-}\text{reson}$) have been also included. Thus pion scattering on the polarized proton can test the commonly-used effective QCD renormalized weak hamiltonian.     

Parity violation in electron scattering

By comparing the cross sections for left- and right-handed electrons scattered from various unpolarized nuclear targets, the small parity-violating asymmetry can be measured. These asymmetry data probe a wide variety of important topics, including searches for new fundamental interactions and important features of nuclear structure that cannot be studied with other probes. A special feature of these experiments is that the results are interpreted with remarkably few theoretical uncertainties, which justifies pushing the experiments to the highest possible precision. To measure the small asymmetries accurately, a number of novel experimental techniques have been developed.     

Parity violation in two-nucleon systems

Nuclear few-body systems become attractive avenues for the study of low-energy parity violation because experiments start to meet the precision requirements and theoretical calculations can be performed reliably. In this talk, an attempt of parametrizing low-energy parity-violating observables by the Danilov parameters will be introduced. Analyses of two-nucleon observables, based on the modern phenomenological potentials or the one of effective field theory, will be discussed.     

Parity violation in electron scattering

Approximations based on the 2PI effective action are used to investigate the process of equilibration in ϕ⁴ theory in 3+1 dimensions, both in the symmetric and broken phase. A special emphasis is put on the study of the kinetic and chemical equilibration.     

Baryogenesis via B−L violation in SO(10) unified models

We discuss the problem of baryon number generation in the framework of a class of SO(10) grand unified models with an intermediate mass scale. In these theories the neutrino mass spectrum allows for the τ neutrino to be a good candidate for the hot component of the dark matter and, at the same time, an implementation of the MSW mechanism is possible. We show that an adequate matter-antimatter asymmetry is achievable through the interplay of B−L violating decays of scalar bosons into massive right-handed neutrinos with the anomalous B+L violating processes mediated by sphalerons.     

Parity violation in polarised electron deuteron scattering

Preliminary calculations show that the parity violating asymmetry in polarised electron deuteron elastic scattering can be as large as observed in the SLAC experiment even in the intermediate energy region. We propose that experiments should be done to search for these asymmetries.     

Symmetry breaking and asymptotic freedom in colour SU(3) gauge models

A class of quark models based on the colour gauge group SU(3) is shown to be asymptotically free despite the conplete breakdown of local symmetry to guarantee infrared stability. The symmetry breakdown is achieved by the presence of elementary scalar fields either through the Higgs mechanism or dynamically as first proposed by Coleman and Weinberg. Asymptotic freedom is preserved by imposing eigenvalue conditions on the coupling constants as first proposed by Chang. New quark species must be present, but below their production threshold, colour can still be a global symmetry which is approximate under SU(3), but exact under SU(2). Among the many implications of this class of models is the possibility of producing isolated quarks and gluons of non-zero mass without altering the short-distance behaviour of the superstrong interaction which binds them.