High statistics measurement of the ωπ 0 transition form factor ” Spokespersons for the Experiment :

of Physics : We propose to perform a new measurement of the ωπ transition form factor (TFF) to explore the puzzling discrepancy between the existing experimental measurement and the numerous theoretical descriptions. Strong motivation to investigate this discrepancy comes from the close connection to the π TFF, needed for the data-driven approaches aiming to improve the precision of the Standard Model calculation of the anomalous magnetic moment of the muon. The statistics of the new A2 measurement will reduce the error of the TFF slope parameter with a factor 2.8, with respect to the previous A2 measurement. Additionally, unlike previous high statistics measurements of ωπ TFF from NA60, the A2 experimental setup provides an exclusive measurement with full control over background contributions. The collected data set can also be used for high statistics studies of η decays, such as the rare double radiative η → πγγ decay and the η → 3π Dalitz plot. Abstract of Equipment : The experiment will be performed at the tagged photon facility of MAMI using Crystal Ball/TAPS detector setup together with particle identification detector (PID) and multiwire proportional chambers (MWPCs). of Equipment : The experiment will be performed at the tagged photon facility of MAMI using Crystal Ball/TAPS detector setup together with particle identification detector (PID) and multiwire proportional chambers (MWPCs). MAMI Specifications : beam energy 1604 MeV beam polarization unpolarised Photon Beam Specifications : tagged energy range 630 – 1492 MeV photon beam polarization unpolarised Equipment Specifications : detectors Crystal Ball/TAPS, PID, MWPCs target liquid hydrogen Beam Time Request : set-up/test with beam 48 hours data taking 850 hours List of participating authors: • Institut für Physik, University of Basel, Switzerland D. Ghosal, N. Jermann, B. Krusche, A. Kaeser, C. Meier • Institut für Experimentalphysik, University of Bochum, Germany G. Reicherz • Helmholtz–Institut für Strahlenund Kernphysik, University of Bonn, Germany F. Afzal, R. Beck, A. Thiel, Y. Wunderlich • JINR, Dubna, Russia N.S. Borisov, I. Gorodnov, A. Lazarev, A. Neganov, Yu.A. Usov • SUPA School of Physics and Astronomy, University of Glasgow, UK S. Gardner, K. Livingston, I.J.D. MacGregor • Racah Institute of Physics, Hebrew University of Jerusalem, Israel G. Ron • Kent State University, Kent, USA D.M. Manley • Institut für Kernphysik, University of Mainz, Germany P. Achenbach, M. Biroth, F. Cividini, A. Denig, P. Drexler, M.I. Ferretti-Bondy, W. Gradl, L. Heijkenskjöld, V.L Kashevarov, P.P. Martel, E. Mornacchi, M. Ostrick, V. Sokhoyan, C. Sfienti, M. Thiel, A. Thomas, S. Wagner, J. Wettig • University of Massachusetts, Amherst, USA R.Miskimen • Institute for Nuclear Research, Moscow, Russia G. Gurevic • INFN Sezione di Pavia, Pavia, Italy A. Braghieri, S. Costanza, P. Pedroni • Department of Physics, University of Regina, Canada G.M. Huber • Mount Allison University, Sackville, Canada D. Hornidge • George Washington University, Washington, USA W.J. Briscoe, E.J. Downie, I.I. Strakovsky • Department of Physics, University of York, UK M. Bashkanov, D.P. Watts, D. Werthmüller • Rudjer Boskovic Institute, Zagreb, Croatia M. Korolija