Possible manifestation of the 2p pionium in particle physics processes

TL;DR

This paper proposes specific particle physics processes where the excited 2p pionium could be observed, analyzing existing data which hints at its possible presence but lacks definitive proof.

Contribution

It introduces new experimental processes to detect 2p pionium and analyzes existing data for potential evidence of this exotic atom.

Findings

Some experimental data suggest the presence of 2p pionium.

Current data do not provide conclusive proof.

Potential detection methods are identified.

Abstract

We suggest a few particle physics processes in which excited 2p pionium $\mathrm{A}^\prime_{2\pi}$ may be observed. They include the $e^+e^-\to\pi^+\pi^-$ annihilation, the $V^0\to\pi^0\ell^+\ell^-$ and $K^\pm\to\pi^\pm\ell^+\ell^-$ ($\ell=e,\mu$) decays, and the photoproduction of two neutral pions from nucleons. We analyze available experimental data and find that they, in some cases, indicate the presence of 2p pionium, but do not provide definite proof.