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

Collaboration
•
Mar, 2009
22 pages
Published in:
  • Phys.Rev.D 79 (2009) 052009
e-Print:
DOI:
Report number:
  • KEK-PREPRINT-2008-50,
  • BELLE-PREPRINT-2009-4
Experiments:
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Abstract: (arXiv)
The differential cross sections for the process γγ→π0π0\gamma \gamma \to \pi^0 \pi^0 have been measured in the kinematic range 0.6 GeV <W<4.1< W < 4.1 GeV, ∣cos⁡θ∗∣<0.8|\cos \theta^*|<0.8 in energy and pion scattering angle, respectively, in the γγ\gamma\gamma center-of-mass system. The results are based on a 223 fb−1^{-1} data sample collected with the Belle detector at the KEKB e+e−e^+ e^- collider. The differential cross sections are fitted in the energy region 1.7 GeV <W<< W < 2.5 GeV to confirm the two-photon production of two pions in the G wave. In the higher energy region, we observe production of the χc0\chi_{c0} charmonium state and obtain the product of its two-photon decay width and branching fraction to π0π0\pi^0\pi^0. We also compare the observed angular dependence and ratios of cross sections for neutral-pion and charged-pion pair production to QCD models. The energy and angular dependence above 3.1 GeV are compatible with those measured in the π+π−\pi^+\pi^- channel, and in addition we find that the cross section ratio, σ(π0π0)/σ(π+π−)\sigma(\pi^0\pi^0)/\sigma(\pi^+\pi^-), is 0.32±0.03±0.050.32 \pm 0.03 \pm 0.05 on average in the 3.1-4.1 GeV region.
Note:
  • 22 pages, 10 figures
  • 14.40.Gx
  • 13.60.Le
  • 13.66.Bc
  • 13.20.Gd
  • 14.40.Cs
  • electron positron: inelastic scattering
  • channel cross section: energy dependence
  • cross section: ratio
  • photon photon: exclusive reaction
  • pi0: pair production