1304.0671 (WASA-at-COSY Collaboration et al.)

Search for a dark photon in the $π^0 \to e^+e^-γ$ decay    [PDF]

WASA-at-COSY Collaboration, :, P. Adlarson, W. Augustyniak, W. Bardan, M. Bashkanov, F. S. Bergmann, M. Berłowski, H. Bhatt, A. Bondar, M. Büscher, H. Calén, I. Ciepał, H. Clement, D. Coderre, E. Czerwiński, K. Demmich, E. Doroshkevich, R. Engels, W. Erven, W. Eyrich, P. Fedorets, K. Föhl, K. Fransson, F. Goldenbaum, P. Goslawski, A. Goswami, K. Grigoryev, C. -O. Gullström, F. Hauenstein, L. Heijkenskjöld, V. Hejny, F. Hinterberger, M. Hodana, B. Höistad, A. Jany, B. R. Jany, L. Jarczyk, T. Johansson, B. Kamys, G. Kemmerling, F. A. Khan, A. Khoukaz, S. Kistryn, J. Klaja, H. Kleines, B. Kłos, M. Krapp, W. Krzemień, P. Kulessa, A. Kupść, A. Kuzmin, K. Lalwani, D. Lersch, L. Li, B. Lorentz, A. Magiera, R. Maier, P. Marciniewski, B. Mariański, U. -G. Meißner, M. Mikirtychiants, H. -P. Morsch, P. Moskal, B. K. Nandi, H. Ohm, I. Ozerianska, E. Perez del Rio, N. Piskunov, P. Pluciński, P. Podkopał, D. Prasuhn, A. Pricking, D. Pszczel, K. Pysz, A. Pyszniak, C. F. Redmer, J. Ritman, A. Roy, Z. Rudy, S. Sawant, S. Schadmand, A. Schmidt, T. Sefzick, V. Serdyuk, N. Shah, B. Shwartz, M. Siemaszko, R. Siudak, T. Skorodko, M. Skurzok, J. Smyrski, V. Sopov, R. Stassen, J. Stepaniak, E. Stephan, G. Sterzenbach, H. Stockhorst, H. Ströher, A. Szczurek, T. Tolba, A. Trzciński, R. Varma, G. J. Wagner, W. Wȩglorz, A. Wirzba, M. Wolke, A. Wrońska, P. Wüstner, P. Wurm, A. Yamamoto, J. Zabierowski, M. J. Zieliński, W. Zipper, J. Złomańczuk, P. Żuprański, M. Żurek

The presently world largest data sample of pi0 --> gamma e+e- decays containing nearly 5E5 events was collected using the WASA detector at COSY. A search for a dark photon U produced in the pi0 --> gamma U --> gamma e+e- decay from the pp-->pp\pi^0 reaction was carried out. An upper limit on the square of the U-gamma mixing strength parameter epsilon^2 of 5e-6 at 90% CL was obtained for the mass range 30 MeV View original: http://arxiv.org/abs/1304.0671