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ISSN - 15507998, Physical Review D - Particles, Fields, Gravitation and Cosmology, 2009, vol. 80, p. -

High-statistics study of ηπ0 production in two-photon collisions

Uehara S., Watanabe Y., Nakazawa H., Adachi I., Aihara H., Arinstein K., Aulchenko V., Bakich A. M., Belous K., Bondar A., Bračko M., Browder T. E., Chang P., Chen A., Cheon B. G., Chistov R., Choi Y., Crnkovic J., Dalseno J., Dash M., Eidelman S., Epifanov D., Gabyshev N., Garmash A., Goldenzweig P., Ha H., Hayasaka K., Hayashii H., Horii Y., Hoshi Y., Hou W. S., Hyun H. J., Iijima T., Inami K., Ishikawa A., Itoh R., Iwasaki M., Iwasaki Y., Kang J. H., Kawai H., Kichimi H., Kiesling C., Kim H. O., Kim J. H., Kim Y. I., Kim Y. J., Ko B. R., Krokovny P., Kumar R., Kuzmin A., Kwon Y. J., Kyeong S. H., Lee S. H., Li J., Limosani A., Liu C., Liventsev D., Louvot R., Matyja A., McOnie S., Miyabayashi K., Miyata H., Miyazaki Y., Mizuk R., Mori T., Nagasaka Y., Nakano E., Nakao M., Nishida S., Nishimura K., Nitoh O., Ogawa S., Ohshima T., Okuno S., Palka H., Park C. W., Park H., Park H. K., Poluektov A., Sahoo H., Sakai Y., Schneider O., Schwanda C., Senyo K., Sevior M. E., Shapkin M., Shebalin V., Shen C. P.

The differential cross section for the process γγ→η π0 has been measured in the kinematic range 0.84GeV<W<4.0GeV, θ*|<0.8, where W and θ* are the energy and π0 (or η) scattering angle, respectively, in the γγ center-of-mass system. The results are based on a 223fb-1 data sample collected with the Belle detector at the KEKB e+e- collider. Clear peaks due to the a0(980) and a2(1320) are visible. The differential cross sections are fitted in the energy region 0.9GeV<W<1.46GeV to obtain the parameters of the a0(980). Its mass, width and ΓγγB(ηπ0) are measured to be 982.3-0.7-4.7+0.6+3. 1MeV/c2, 75.6±1.6-10.0+17.4MeV and 128-2-43+3+502eV, respectively. The energy and angular dependences above 3.1 GeV are compared with those measured in the π0π0 channel. The integrated cross section over θ*|<0. 8 has a W-n dependence with n=10.5±1.2±0.5, which is slightly larger than that for π0π0. The differential cross sections show a sin-4θ* dependence similar to γγ→π0π0. The measured cross section ratio, σ(ηπ0)/σ(π0π0)=0. 48±0.05±0.04, is consistent with a QCD-based prediction. © 2009 The American Physical Society.