91 research outputs found
Light-by-Light Scattering Nonlogarithmic Corrections to Hyperfine Splitting in Muonium
We consider three-loop corrections to hyperfine splitting in muonium
generated by the gauge invariant set of diagrams with virtual light-by-light
scattering block. These diagrams produce both recoil and nonrecoil
contributions to hyperfine splitting. Recoil corrections are enhanced by large
logarithms of the muon-electron mass ratio. Both nonrecoil and logarithmically
enhanced radiative-recoil corrections where calculated some time ago. Here we
calculate nonlogarithmic radiative-recoil corrections generated by the
insertions of the light-by-light scattering block.Comment: Minor corrections, version to be published in Phys. Rev.
Hard Three-Loop Corrections to Hyperfine Splitting in Positronium and Muonium
We consider hard three-loop corrections to hyperfine splitting in muonium and
positronium generated by the diagrams with closed electron loops. There are six
gauge-invariant sets of such diagrams that generate corrections of order
. The contributions of these diagrams are calculated for an
arbitrary electron-muon mass ratio without expansion in the small mass ratio.
We obtain the formulae for contributions to hyperfine splitting that in the
case of small mass ratio describe corrections for muonium and in the case of
equal masses describe corrections for positronium. First few terms of the
expansion of hard corrections in the small mass ratio were earlier calculated
for muonium analytically. We check numerically that the new results coincide
with the sum of the known terms of the expansion in the case of small mass
ratio. In the case of equal masses we obtain hard nonlogarithmic corrections of
order to hyperfine splitting in positronium.Comment: 19 pages, 8 figure
One-Loop Electron Vertex in Yennie Gauge
We derive a compact Yennie gauge representation for the off-shell one-loop
electron-photon vertex, and discuss it properties. This expression is
explicitly infrared finite, and it has proved to be extremely useful in
multiloop calculations in the QED bound state problem.Comment: Revtex, 12 pp., 1 fig., one reference added. Two misprints in
intermediate formulae correcte
One More Hard Three-Loop Correction to Parapositronium Energy Levels
A hard three-loop correction to parapositronium energy levels of order mα7 is calculated. This nonlogarithmic contribution is due to the insertions of one-loop photon propagator in the fermion lines in the diagrams with virtual two-photon annihilation. We obtained ΔE = 0.03297(2)(mα7 / π3) for this energy shift
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