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arXiv 0705.1330hep-ph
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束缚态辐射衰变的软能区

The soft-energy region in the radiative decay of bound states

Pedro D. Ruiz-Femenia

摘要:

在相空间中研究了正电子偶素衰变为三个光子的过程,其中一个光子的能量相当于e+e-系统的相对三动量(w ~ m α)。NRQED计算表明,在这种情况下,主要的贡献来自距离~ 1/(mw)^(1/2),这允许处理库仑相互作用微扰。从完全QED的1-圈衰变谱的小光子能量展开产生与有效理论相同的结果。通过对单圈QED振幅的阈值展开,我们证实了首项来自于q^0 ~ q^2/m ~ w的圈动量区域。这对应于一个新的非相对论性环动量区域,它必须考虑到通过软光子发射衰变的非相对论性粒子-反粒子系统的描述。

英文摘要:

The orthopositronium decay to three photons is studied in the phase-space region where one of the photons has an energy comparable to the relative three-momentum of the e+e- system (w ~ m alpha). The NRQED computation in this regime shows that the dominant contribution arises from distances ~ 1/(mw)^(1/2), which allows to treat the Coulomb interaction perturbatively. The small-photon energy expansion of the 1-loop decay spectrum from full QED yields the same result as the effective theory. By doing the threshold expansion of the 1-loop QED amplitude we confirm that the leading term arises from a loop-momentum region where q^0 ~ q^2/m ~ w. This corresponds to a new non-relativistic loop-momentum region, which has to be taken into account for the description of a non-relativistic particle-antiparticle system that decays through soft photon emission.

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