New explanation of the GAMS results on the $f_0(980)$ production in the reaction $\pi^-p\to \pi^0\pi^0n$

TL;DR

This paper offers a new explanation for the GAMS experimental results on the $f_0(980)$ production in $ ext{pi}^- ext{p} o ext{pi}^0 ext{pi}^0 ext{n}$, highlighting the role of the $a_1$ Regge pole exchange mechanism in the reaction.

Contribution

It introduces a novel interpretation of the GAMS results based on the $a_1$ Regge pole contribution, supported by experimental evidence from unpolarized targets.

Findings

Evidence for $a_1$ exchange mechanism in the reaction.

Explanation of the mass spectrum alteration with increasing $-t$.

Comparison with previous explanations and proposed experimental tests.

Abstract

The observed alteration of the S-wave $\pi^0\pi^0$ mass spectrum in the reaction $\pi^-p\to\pi^0\pi^0n$ with increasing $-t$, i.e., the disappearance of a dip and the appearance of a peak in the region of the $f_0(980)$ resonance as $-t$ increases, is explained by the contribution of the $\pi^-p\to f_0(980)n$ reaction amplitude with the quantum numbers of the $a_1$ Regge pole in the $t$ channel. It is very interesting that nontrivial evidence for the $a_1$ exchange mechanism in the reaction $\pi^-p\to \pi^0\pi^0n$ follows for the first time from the experiment on an unpolarized target. The explanation of the GAMS results suggested by us is compared with that reported previously. Two ways of experimentally testing these explanations are pointed out.