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arXiv · 1607.05510

On enhanced corrections from quasi-degenerate states to heavy quarkonium observables

Yuichiro Kiyo·Go Mishima·Yukinari Sumino
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Abstract

It is well known that in perturbation theory existence of quasi-degenerate states can rearrange the order counting. For a heavy quarkonium system, naively, enhanced effects ($l$-changing mixing effects) could contribute already to the first-order and third-order corrections to the wave function and the energy level, respectively, in expansion in $α_s$. We present a formulation and note that the corresponding (lowest-order) corrections vanish due to absence of the relevant off-diagonal matrix elements. As a result, in the quarkonium energy level and leptonic decay width, the enhanced effects are expected to appear, respectively, in the fifth- and fourth-order corrections and beyond.

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Yuichiro Kiyo, Go Mishima, Yukinari Sumino. 2016-07-19. On enhanced corrections from quasi-degenerate states to heavy quarkonium observables. https://doi.org/10.1016/j.physletb.2016.08.026

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