Reactions gamma gamma -> pi pi and gamma gamma -> K \bar K: the (IJ^{PC}=00^{++})-wave spectra at E_{gamma gamma}^{(c.m.)} = 300- 1900 MeV

Abstract

We calculate the $00^{++}$-wave two-meson spectra for the reactions $γγ\toπ^0π^0$, $γγ\toπ^+π^-$, $γγ\to K^0\bar K^0$ and $γγ\to K^+ K^-$ on the basis of: (i) the results of the $K$-matrix analysis of the $00^{++}$ amplitudes for the reactions $ππ\to ππ$, $K\bar K$, $ηη$, $ηη'$, $ππππ$, and (ii) recently developed method for calculation of the decay amplitudes $f_0(1^3P_0q\bar q)\to γγ$, $f_0(2^3P_0q\bar q)\to γγ$. The reconstructed $ππ$ and $K\bar K$ spectra can be used as a guide for the extraction of partial widths of scalar/isoscalar resonances $f_0(980)\to γγ$, $f_0(1300)\to γγ$, $f_0(1500)\to γγ$, $f_0(1750)\to γγ$. As follows from our calculations, the resonances $f_0(980)$ and $f_0(1500)$ in the $π^+π^-$ and $π^0π^0$ spectra reveal themselves as dips.