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

Abstract

The observed alteration of the S-wave ${\pi }^0{\pi }^0$ mass spectrum in the reaction ${\pi }^{-}p\to {\pi }^0{\pi }^{0}n$ 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 ${\pi }^{-}p\to {\pi }^0{\pi }^{0}n$ 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.

Comments: 20 pages (RevTex), 5 figures (PS), minor typos corrected (in particular in Fig. 4), replaced to match the version accepted in Phys. Rev. D