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T: Teilchenphysik

T 207: Höhere Ordnungen

T 207.4: Vortrag

Freitag, 4. März 2005, 14:45–15:00, TU H2037

The Orthopositronium Decay Spectrum in NRQED — •Pedro Ruiz-Femenia — Max-Planck-Institut fur Physik

The behaviour of the orthopositronium decay amplitude to three photons in the low energy end of the spectrum can be obtained from the corresponding non-radiative amplitude by virtue of gauge invariance, a result commonly known as Low’s theorem. As recently noticed, the Ore-Powell’s classical calculation of this decay amplitude fails to fulfill Low’s theorem requirements. I shall discusss the implications of Low’s theorem applied to this decay considering the interplay between the soft photon limit and the energy scales present in the e⁺e⁻ system. For energetic photons, the spectrum agrees with the Ore-Powell result, but deviates from it when the photon energy is comparable to the positronium binding energy. In this region it is found that bound states effects are essential to reach agreement with Low’s theorem and the decay spectrum can be computed in the framework of the non-relativistic effective theory of QED. The positronium structure function obtained resums the leading Coulomb interaction between the intermediate e⁺e⁻ pair to all orders.