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