Parity-nonconserving Amplitude Research Articles

QED Theory of Transition Probabilities and Line Profiles in Highly Charged Ions

A rigorous QED theory of the spectral line profiles is applied to transition probabilities in few-electron highly charged ions. Interelectron interaction corrections are included as well as radiative corrections. Parity nonconserving (PNC) amplitudes with effective weak interactions between the electrons and nucleus are also considered. QED and interelectron interaction corrections to the PNC amplitudes are derived.

Erratum: Vacuum-Polarization Corrections to the Parity-Nonconserving6s-7sTransition Amplitude inC133s[Phys. Rev. Lett. 87, 233001 (2001)

The dominant one-loop radiative corrections to atomic wave functions, those associated with vacuum polarization in the nuclear Coulomb field, are evaluated for the 6s-7s parity-nonconserving (PNC) transition amplitude in 133Cs. These corrections increase the size of the PNC amplitude by 0.4% and, correspondingly, increase the difference between the experimental value of the weak charge Q_W(133Cs) and the value predicted by the standard model.

Correlated many-body treatment of the Breit interaction with application to cesium atomic properties and parity violation

Corrections from the Breit interaction to basic properties of atomic ${}^{133}\mathrm{Cs}$ are determined in the framework of third-order relativistic many-body perturbation theory. The corrections to energies, hyperfine-structure constants, off-diagonal hyperfine $6S\ensuremath{-}7S$ amplitude, and electric-dipole matrix elements are tabulated. It is demonstrated that the Breit corrections to correlations are comparable to the Breit corrections at the Hartree-Fock level. Modification of the parity-nonconserving (PNC) $6S\ensuremath{-}7S$ amplitude due to Breit interaction is also evaluated; the resulting weak charge of ${}^{133}\mathrm{Cs}$ shows no significant deviation from the prediction of the standard model of elementary particles. The neutron skin correction to the PNC amplitude is also estimated to be -0.2% with an error bound of 30% based on the analysis of recent experiments with antiprotonic atoms. The present work supplements publication [A. Derevianko, Phys. Rev. Lett. 85, 1618 (2000)] with a discussion of the formalism and provides additional numerical results and updated discussion of parity violation.

Calculation of the nuclear spin-dependent parity-nonconserving amplitude for the(7s,F=4)→(7s,F=5)transition inFr

Many-body calculation of nuclear spin-dependent parity-nonconserving amplitude for (7s,F=4) --> (7s,F=5) transition between hyperfine sublevels of the ground state of $^{211}$Fr is carried out. The final result is <7s,F=5 ||d_PNC|| 7s,F=4> = -0.49 10^{-10} i kappa a.u., where kappa is the dimensionless coupling constant. This is approximately an order of magnitude larger than similar amplitude in Cs. The dominant contribution to kappa is associated with the anapole moment of the nucleus.

High-accuracy calculation of 6s --> 7s parity-nonconserving amplitude in Cs.

We calculated the parity-nonconserving (PNC) 6s-->7s amplitude in Cs. In the Dirac-Coulomb approximation our result is in good agreement with other calculations. Breit corrections to the PNC amplitude and to the Stark-induced amplitude beta are found to be -0.4% and -1%, respectively. The weak charge of 133Cs is Q(W) = -72.5+/-0.7 in agreement with the standard model.

High-precision calculation of the parity-nonconserving amplitude in francium

A high-precision calculation of the $7s\ensuremath{-}8s$ parity-nonconserving (PNC) transition amplitude in francium, based on a relativistic all-order method, is presented. Our values for the PNC amplitudes in ${}^{223}\mathrm{Fr}$ and ${}^{210}\mathrm{Fr}$ are ${E}_{\mathrm{PNC}}=15.41(17)$ and $14.02(15),$ respectively, in units ${10}^{\ensuremath{-}11}i|e|{a}_{0}(\ensuremath{-}{Q}_{W}/N),$ where ${Q}_{W}$ is the weak charge and N is the neutron number. Spin-dependent contributions to the PNC amplitude are calculated for Fr isotopes with nucleon numbers $A=207,$ 209, 211, and 213. To assess the accuracy of our calculations, we apply the present all-order method to the $6s\ensuremath{-}7s$ PNC amplitude in cesium and obtain a result in close agreement with previous high-precision calculations.

Correlation effects in the parity-nonconserving 6s-->7s transition in cesium.

The amplitude of the parity-nonconserving (PNC) electric-dipole transition 6s\ensuremath{\rightarrow}7s in cesium is calculated to third order in many-body perturbation theory. Inclusion of the corresponding corrections in calculations of parity-conserving transition amplitudes and atomic hyperfine constants leads to agreement with experiment at a level under 5%. We obtain a value of 0.951${\mathrm{iea}}_{0}$\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}11}$${Q}_{W}$/-N with an estimated error of 5% for the PNC amplitude. A determination of the Weinberg angle is made by combining the present calculation with recent measurements of the PNC amplitude: the result is ${\mathrm{sin}}^{2}$${\mathrm{\ensuremath{\theta}}}_{\mathrm{W}}$=0.229 ${(24)}_{\mathrm{expt}}$ ${(16)}_{\mathrm{theor}}$. Issues involved in improving the accuracy of the calculations of atomic properties of cesium are discussed.

Atomic-beam measurement of parity nonconservation in cesium.

We present a new measurement of parity nonconservation in cesium. In this experiment, a laser excited the 6S\ensuremath{\rightarrow}7S transition in an atomic beam in a region of static electric and magnetic fields. The quantity measured was the component of the transition rate arising from the interference between the parity nonconserving amplitude, ${\mathrm{scrE}}_{\mathrm{PNC}}$, and the Stark amplitude, \ensuremath{\beta}E. Our results are Im${\mathrm{scrE}}_{\mathrm{PNC}/\mathrm{\ensuremath{\beta}}=\mathrm{\ensuremath{-}}1.65\ifmmode\pm\else\textpm\fi{}0.13}$ mV/cm and ${C}_{2p}$=-2\ifmmode\pm\else\textpm\fi{}2, where ${C}_{2p}$ is the proton-axial-vector--electron-vector neutral-current coupling constant. These results are in agreement with previous less precise measurements in cesium and with the predictions of the electroweak standard model. We give a detailed discussion of the experiment with particular emphasis on the treatment and elimination of systematic errors. This experimental technique will allow future measurements of significantly higher precision.

Search for Parity Nonconservation in Atomic Bismuth

In a search for optical rotation near the 8755-\AA{} magnetic-dipole absorption line in atomic Bi, our first results set an upper limit $F&lt;{10}^{\ensuremath{-}6}$ on a parity nonconserving amplitude associated with the line. This limit improves upon earlier parity tests in atoms by three orders of magnitude. Further improvement of at least another order of magnitude appears possible by this method which should then provide an exacting test of parity conservation in the neutral weak-current interaction in atoms.

Pole Model of Nonleptonic Hyperon Decays, and Model of Hadrons and Their Fundamental Weak Interaction

The pole model of nonleptonic hyperon decays proposed by Kawasaki, Imoto and Furui (KIF) and Lee and Swift is reexamined for the purpose of establishing connection between the phenomenology and subnuclear structure of hadrons and their weak interaction. It is assumed that there exist three urbaryons which play an essential role in composing hadrons. Baryons are assumed to be nonrelativistic bound states of such three urbaryons. Two types of hyperon models are considered: One is the quartet-like model (ModelI), and the other is the quark-like model (ModelII). The effective two-body weak Hamiltonian between baryons becomes parity-conserving, and in a simplified limit in which all strong interaction corrections are neglected this Hamiltonian is of the D or F type for ModelI or II, respectively. In general, matrix elements of nonleptonic hyperon decays are written by using effectively five parameters. η (or η′), a member of the parameters, is introduced which is regarded as a measure of departure from the simplified limit. For any value of η (or η′), one can reproduce all the experimental data on nonleptonic hyperon decays including decay probabilities. This is possible only when the F/Dratio (a member of the five parameters) of the strong baryon-pseudoscalar-meson interaction is equal to ~ (0.5 ~ 0.6). Consistency of the values of adjusted parameters with other phenomena is investigated. It is concluded that to regard the weak Jp·Jp+ interaction as the only fundamental interaction responsible for nonleptonic decays is unlikely, where Jp stands for an appropriate urbaryonic or Cabibbo-like current. It seems difficult at present to determine which of the two Models is superior owing especially to the lack of knowledge of the parity-nonconserving amplitude.

Branching Ratios IntoKμ2,Ke3, andKe4in the Partially Conserved Axial-Vector Current

The partially conserved axial-vector current hypothesis (PCAC) [1] has been successfully applied to the parity-nonconserving amplitudes of the nonleptonic hyperon decays [2] and to the nonleptonic K decays [3]. The ΔI = 1/2 rules are proved for all the processes except Σ decays in the approximation of putting the pion four-momenta equal to zero [4]. In addition, the branching ration K3π/K2π is calculated and found to be in good agreement with experiment.