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.     

Self-energy correction to the wave function in the effect of parity violation for the amplitude of the 6s–7s transition in the 133Cs atom

The quantum electrodynamic self-energy correction to the wave function in the effect of parity violation for the amplitude of the 6s–7s transition in the ¹³³Cs atom is calculated in explicit form without using the nonrelativistic approximation for the self-energy operator. The result obtained refines some previous estimates and indicates that the correction to the parity violation may be comparable with the corresponding correction to the vacuum polarization. The necessity of taking complete relativistic account of all the quantum electrodynamic corrections in calculations of the electroweak charge Q _W in atomic systems is shown.     

QED corrections to the electromagnetic Abraham force

We develop a QED approach to find the contribution of the quantum vacuum to the electromagnetic Abraham force. Semi-classical theories predict diverging contributions from the quantum vacuum. We show that the divergencies disappear by Kramers-Bethe mass-renormalization. The finite remainder is compared to the relativistic corrections to the Abraham force. This work applies an earlier approach [S.?Kawka, B.A. van Tiggelen, Europhys Lett. 89, 11002 (2010)]1, dedicated to the simpler case of a harmonic oscillator, to the Coulomb interaction, which is more realistic in a QED context.     

QCD corrections to QED vacuum polarization

We compute QCD corrections to QED calculations for vacuum polarization in background magnetic fields. Formally, the diagram for virtual eē loops is identical to the one for virtual qq̄ loops. However, due to confinement, or to the growth of α_s as p² decreases, a direct calculation of the diagram is not allowed. At large p² we consider the virtual qq̄ diagram, in the intermediate region we discuss the role of the contribution of quark condensates 〈qq̄〉 and at the low-energy limit we consider the π⁰, as well as charged pion π⁺π^- loops. Although these effects seem to be out of the measurement accuracy of photon–photon laboratory experiments, they may be relevant for γ-ray burst propagation. In particular, for emissions from the center of the galaxy (8.5 kpc), we show that mixing between the neutral pseudo-scalar pion π₀ and photons renders a deviation from the power-law spectrum in the TeV range. For scalar quark condensates 〈qq̄〉 and virtual qq̄ loops are relevant only for very high radiation density ∼300 MeV/fm³ and very strong magnetic fields of order ∼10¹4 T. PACS 12.20.Ds; 14.40.-n; 12.38.Aw; 14.65.Bt     

QED radiative corrections to impact factors

We consider radiative corrections to the electron and photon impact factors. The generalized eikonal representation for the e ⁺ e ^? scattering amplitude at high energies and fixed momentum transfers is violated by nonplanar diagrams. An additional contribution to the two-loop approximation appears from the Bethe-Heitler mechanism of fermion pair production with the identity of the fermions in the final state taken into account. The violation of the generalized eikonal representation is also related to the charge parity conservation in QED. A one-loop correction to the photon impact factor for small virtualities of the exchanged photon is obtained using the known results for the cross section of the e ⁺ e ^? production during photon-nuclei interactions.     

QED corrections to the evolution of parton distributions

We study the systematic inclusion of QED corrections in the evolution of parton distributions. corrections modify the evolution equation for parton distributions. They introduce additional parton distributions, like the photon distribution in the nucleon, and lead to additional mixing effects. We discuss the modifications for a realistic model of N_f,up up-type flavours and N_f,down down-type flavours. We have implemented these corrections into a numerical program and we quantify the size of these effects in a toy model. The corrections reach the order of 1%.     

QCD and QED corrections to the longitudinal polarization asymmetry

The interplay between QED and QCD corrections to the longitudinal polarization asymmetry,A _LR, ine ⁺ e ^?, annihilation is studied. It is found that measurements with hadronic final states will be well suited for precision tests of the standard model. QCD corrections to the asymmetry are particularly small on top of theZ ⁰, with the leading terms induced by quark mass effects. The influence of initial state radiation inA _LR is essentially accounted for by a slight shift in beam energy. Initial/final state QED bremsstrahlung interference (QED boxes) is studied in detail and its influence onA _LR is found to be negligibly small, especially close to the top of theZ ⁰ peak. A comment on the importance of helicity nonconservation for polarized beams in the presence of photon emission is also included.     

Isotope shifts and hyperfine structure of the 6s-7p transitions in the cesium isotopes 133, 135, and 137

The 6s-7p transitions in cesium at 459.3 nm (7² P _1/2) and 455.5 nm (7² P _3/2) have been investigated by saturation spectroscopy in vapor cells, using a laser spectrometer with 500 kHz bandwidth in the blue spectral range. Isotope shifts as well as hyperfine splittings were determined for the isotopes 133, 135 and 137.     

Core polarization of the133Cs atom by the 7p electron

The hfs of the 7² P _1/2 state of Cs has been measured by optical double resonance yieldingA(7² P _1/2,¹³³Cs)=94.35 (4) MHz. The core polarization contribution to the hfs and the value 〈r ^?3〉 _j =2.54 · 10⁺²⁴ cm^?3 of the 7p electron of Cs has been calculated from the experimental data and was compared with current theories indicating still an appreciable uncertainty in the atomic wave functions of this one-electron atom.     

QED corrections to DIS cross section with tagged photon

We calculate the QED corrections to the deep inelastic scattering cross section with tagged photon at HERA, taking into account the leading and next-to-leading contributions. Different types of event selection are investigated. Pis’ma Zh. éksp. Teor. Fiz. 66, No. 6, 367–372 (25 September 1997) Published in English in the original Russian journal. Edited by Steve Torstveit.     

QED and relativistic corrections in superheavy elements

In this paper we review the different relativistic and QED contributions to energies, ionic radii, transition probabilities and Landé g-factors in super-heavy elements, with the help of the MultiConfiguration Dirac-Fock method (MCDF). The effects of taking into account the Breit interaction to all orders by including it in the self-consistent field process are demonstrated. State of the art radiative corrections are included in the calculation and discussed. We also study the non-relativistic limit of MCDF calculation and find that the non-relativistic offset can be unexpectedly large.