2008/10/02 by I. Adachi, Belle Collaboration, Adachi, I.
Physics and Astronomy · #FOS: Physical sciences #High Energy Physics - Experiment (hep-ex) #High-Energy Particle Collisions Research #Nuclear physics research studies #Quantum Chromodynamics and Particle Interactions #hep-ex
paper · pdf · doi:10.48550/arxiv.0810.0334
19 pages 8 figures, ICHEP08 conference paper
arxiv created 2008/10/02 · openalex publication_date 2008/10/02 · arxiv updated 2009/12/01 · openalex created_date 2019/07/30 · openalex updated_date 2026/07/28
The differential cross section for the process γγ→ π0 π0 has been measured in the kinematic range 0.6 GeV < W < 4.1 GeV, |cos θ^*|<0.8 in energy and pion scattering angle, respectively, in the γγ center-of-mass system. The results are based on a 223 fb-1 data sample collected with the Belle detector at the KEKB e+ e- collider. Using the data with W > 1.4 GeV, we obtain results on light-quark resonances and charmonia. We also compare the observed angular dependence and ratios of cross sections for neutral-pair and charged-pair production to QCD models. Differential cross sections are fitted in the energy region, 1.4 \GeV < W < 2.2 \GeV, with a simple model where partial waves consist of resonances such as f2'(1525), f2(1950) and f4(2050) and smooth backgrounds. In the higher energy region, we observe production of the χc0 charmonium state and obtain the product of its two-photon decay width and the branching fraction to π0π0. The energy and angular dependences above 3.1 GeV are compatible with those measured in the π+π- channel, and in addition we find that the cross section ratio, σ(π0π0)/σ(π+π-), is 0.32 ± 0.03 ± 0.05 on average in the 3.1-4.1 GeV region.