1304.0671 — arXiv2

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

hep-ex

/ Published

Apr 2, 2013

/ Updated

Aug 27, 2013

/ Categories

hep-ex hep-ph nucl-ex

/ Links

/ Authors

WASA-at-COSY Collaboration, :, P. Adlarson, W. Augustyniak, W. Bardan, M. Bashkanov, F. S. Bergmann, M. Berłowski, H. Bhatt, A. Bondar

and 107 more authors

M. Büscher, H. Calén, I. Ciepał, H. Clement, D. Coderre, E. Czerwiński, K. Demmich, E. Doroshkevich, R. Engels, W. Erven, W. Eyrich, P. Fedorets

, F. Goldenbaum

, C. -O. Gullström

, F. Hauenstein

, L. Heijkenskjöld

, F. Hinterberger

, G. Kemmerling

, P. Marciniewski

, B. Mariański

, U. -G. Meißner

, M. Mikirtychiants

, H. -P. Morsch

, I. Ozerianska

, E. Perez del Rio

, P. Pluciński

, G. Sterzenbach

, H. Stockhorst

, A. Trzciński

, J. Zabierowski

, M. J. Zieliński

, J. Złomańczuk

, P. Żuprański

/ Abstract

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-->ppπ^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 20 MeV <M_U< 100 MeV. This result together with other recent experimental limits significantly reduces the M_U vs. ε^2 parameter space preferred by the measured value of the muon anomalous magnetic moment.