High-statistics measurement of neutral-pion pair production in two-photon collisions

Abstract

We present a high-statistics measurement of differential cross sections and the total cross section for the process gamma gamma -> pi(0)pi(0) in the kinematic range 0.6 GeV <= W <= 4.0 GeV and vertical bar cos theta*vertical bar <= 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, D-0, D-2, G(0), and G(2) waves. The G waves are important above W similar or equal to 1.6 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 D-2 wave is dominated by the f(2)(1270) meson whose parameters are consistent with the current world averages. The 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.