1205.3249 (The Belle Collaboration et al.)

Measurement of gamma gamma* --> pi0 transition form factor at Belle    [PDF]

The Belle Collaboration, S. Uehara, Y. Watanabe, H. Nakazawa, I. Adachi, H. Aihara, D. M. Asner, T. Aushev, A. M. Bakich, K. Belous, V. Bhardwaj, B. Bhuyan, M. Bischofberger, A. Bondar, G. Bonvicini, A. Bozek, M. Bracko, T. E. Browder, M. -C. Chang, A. Chen, P. Chen, B. G. Cheon, K. Chilikin, I. -S. Cho, K. Cho, Y. Choi, J. Dalseno, Z. Dolezal, Z. Drasal, S. Eidelman, D. Epifanov, J. E. Fast, M. Feindt, V. Gaur, N. Gabyshev, Y. M. Goh, B. Golob, J. Haba, K. Hayasaka, H. Hayashii, Y. Horii, Y. Hoshi, W. -S. Hou, H. J. Hyun, T. Iijima, A. Ishikawa, R. Itoh, M. Iwabuchi, Y. Iwasaki, T. Iwashita, T. Julius, J. H. Kang, T. Kawasaki, C. Kiesling, H. J. Kim, H. O. Kim, J. B. Kim, J. H. Kim, K. T. Kim, M. J. Kim, Y. J. Kim, B. R. Ko, S. Koblitz, P. Kodys, S. Korpar, R. T. Kouzes, P. Krizan, P. Krokovny, A. Kuzmin, Y. -J. Kwon, J. S. Lange, S. -H. Lee, J. Li, Y. Li, J. Libby, C. -L. Lim, C. Liu, Y. Liu, Z. Q. Liu, D. Liventsev, R. Louvot, D. Matvienko, K. Miyabayashi, H. Miyata, Y. Miyazaki, G. B. Mohanty, A. Moll, T. Mori, N. Muramatsu, Y. Nagasaka, E. Nakano, M. Nakao, Z. Natkaniec, S. Nishida, K. Nishimura, O. Nitoh, S. Ogawa, T. Ohshima, S. Okuno, S. L. Olsen, Y. Onuki, P. Pakhlov, G. Pakhlova, H. K. Park, K. S. Park, T. K. Pedlar, R. Pestotnik, M. Petric, L. E. Piilonen, K. Prothmann, M. Rohrken, S. Ryu, H. Sahoo, K. Sakai, Y. Sakai, T. Sanuki, Y. Sato, V. Savinov, O. Schneider, C. Schwanda, R. Seidl, K. Senyo, O. Seon, M. E. Sevior, M. Shapkin, C. P. Shen, T. -A. Shibata, J. -G. Shiu, B. Shwartz, A. Sibidanov, F. Simon, J. B. Singh, P. Smerkol, Y. -S. Sohn, A. Sokolov, E. Solovieva, M. Staric, T. Sumiyoshi, Y. Teramoto, K. Trabelsi, T. Tsuboyama, M. Uchida, Y. Unno, S. Uno, Y. Usov, P. Vanhoefer, G. Varner, A. Vinokurova, V. Vorobyev, C. H. Wang, P. Wang, M. Watanabe, K. M. Williams, E. Won, Y. Yamashita, C. Z. Yuan, C. C. Zhang, Z. P. Zhang, V. Zhilich, V. Zhulanov, A. Zupanc

We report a measurement of the process gamma gamma* --> pi0 with a 759 fb^{-1} data sample recorded with the Belle detector at the KEKB asymmetric-energy e+e- collider. The pion transition form factor, F(Q^2), is measured for the kinematical region 4 GeV^2 <~ Q^2 <~ 40 GeV^2, where -Q^2 is the invariant mass squared of a virtual photon. The measured values of Q^2|F(Q^2)| agree well with the previous measurements below Q^2 ~= 9 GeV^2 but do not exhibit the rapid growth in the higher Q^2 region seen in another recent measurement, which exceeds the asymptotic QCD expectation by as much as 50%.

View original: http://arxiv.org/abs/1205.3249