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arXiv · 1506.08120

Origin of the structures observed in $e^+e^-$ annihilation into multipion states around the $\bar pp$ threshold

Johann Haidenbauer·Christoph Hanhart·Xian-Wei Kang·Ulf-G. Meißner
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Abstract

We analyze the origin of the structures observed in the reactions $e^+e^-\to 3(\pi^+\pi^-)$, $2(\pi^+\pi^-\pi^0)$, $\omega\pi^+\pi^-\pi^0$, and $e^+e^-\to 2(\pi^+\pi^-)\pi^0$ around the antiproton-proton ($\bar pp$) threshold. We calculate the contribution of the two-step process $e^+e^-\to \bar NN \to$ multipions to the total reaction amplitude. The amplitude for $e^+e^-\to \bar NN$ is constrained from near-threshold data on the $e^+e^-\to \bar pp$ cross section and the one for $\bar NN \to$ multipions can be likewise fixed from available experimental information, for all those $5 \pi$ and $6\pi$ states. The resulting amplitude for $e^+e^-\to$ multipions turns out to be large enough to play a role for the considered $e^+e^-$ annihilation channels and, in three of the four reactions, even allows us to reproduce the data quantitatively near the $\bar NN$ threshold. The structures seen in the experiments emerges then as a threshold effect due to the opening of the $\bar NN$ channel.

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Johann Haidenbauer, Christoph Hanhart, Xian-Wei Kang, Ulf-G. Meißner. 2015-06-26. Origin of the structures observed in $e^+e^-$ annihilation into multipion states around the $\bar pp$ threshold. https://doi.org/10.1103/physrevd.92.054032

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