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

Abstract

The differential cross sections for the process $\gamma \gamma \to {\pi }^0{\pi }^0$ have been measured in the kinematic range 0.6 GeV $<W<4.1$ GeV, $|\cos {\theta }^{\ast }|<0.8$ in energy and pion scattering angle, respectively, in the $\gamma \gamma$ 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. The differential cross sections are fitted in the energy region 1.7 GeV $<W<$ 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 ${\chi }_{c0}$ charmonium state and obtain the product of its two-photon decay width and branching fraction to ${\pi }^0{\pi }^0$. 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 ${\pi }^{+}{\pi }^{-}$ channel, and in addition we find that the cross section ratio, $\sigma ({\pi }^0{\pi }^0)/\sigma ({\pi }^{+}{\pi }^{-})$, is $0.32\pm 0.03\pm 0.05$ on average in the 3.1-4.1 GeV region.

22 pages, 10 figures

References in corpus (12)

• SVD Approach to Data Unfolding
• High statistics study of f_0(980) resonance in gamma gamma --> pi^+ pi^- production
• High-statistics measurement of neutral-pion pair production in two-photon collisions
• High-statistics measurement of neutral-pion pair production in two-photon collisions
• High statistics measurement of the cross sections of gamma gamma -> pi^+ pi^- production
• Measurement of the gamma gamma -> pi+ pi- and gamma gamma -> K+ K- processes at energies of 2.4 - 4.1 GeV
• The handbag contribution to gamma gamma to pi pi and K K
• Measurement of gamma gamma -> p p-bar production at Belle
• Two-Photon Widths of the chi_cJ States of Charmonium
• A study of gamma gamma -> Ks Ks production at energies of 2.4-4.0GeV at Belle
• gamma+gamma --> pi+pi, K+K : leading term QCD vs handbag model
• New Measurement of Exclusive Decays of the chi_c0 and chi_c2 to Two-Meson Final States

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