We present a high-statistics measurement of differential cross sections and the total cross section for the process $\gamma \gamma \to {\pi }^0{\pi }^0$ in the kinematic range $0.6\mathrm{GeV}\le W\le 4.0\mathrm{GeV}$ and $|\cos {\theta }^{*}|\le 0.8$, where $W$ and ${\theta }^{*}$ are the energy and pion scattering angle, respectively, in the $\gamma \gamma$ center-of-mass system. Differential cross sections are fitted to obtain information on S, ${\mathrm{D}}_0$, ${\mathrm{D}}_2$, ${\mathrm{G}}_0$, and ${\mathrm{G}}_2$ waves. The G waves are important above $W\simeq 1.6\mathrm{GeV}$. The general behavior of partial waves is studied by fitting differential cross sections in a simple parametrization where amplitudes contain resonant contributions and smooth background. The ${\mathrm{D}}_2$ wave is dominated by the $f_2(1270)$ meson whose parameters are consistent with the current world averages. The ${\mathrm{D}}_0$ wave contains a $f_2(1270)$ component, whose fraction is fitted. For the S wave, the $f_0(980)$ parameters are found to be consistent with the values determined from our recent ${\pi }^{+}{\pi }^{-}$ data. In addition to the $f_0(980)$, the S wave prefers to have another resonance-like contribution whose parameters are obtained.

• Received 22 May 2008

DOI:https://doi.org/10.1103/PhysRevD.78.052004