Determination of the η-transition form factor in the γp→pη→pγe⁺e⁻ reaction

Berghäuser, H. et al. (2011) Determination of the η-transition form factor in the γp→pη→pγe⁺e⁻ reaction. Physics Letters B, 701(5), pp. 562-567. (doi: 10.1016/j.physletb.2011.06.069)

Abstract

The Dalitz decay η→γe+e− has been measured using the combined Crystal Ball and TAPS photon detector setup at the electron accelerator MAMI-C. Compared to the most recent transition form-factor measurement in the e+e− channel, statistics have been improved by one order of magnitude. The e+e− invariant mass distribution shows a deviation from the QED prediction for a point-like particle, which can be described by a form-factor. Using the usual monopole transition form-factor parameterization, F(m2)=(1−m2/Λ2)−1, a value of Λ−2=(1.92±0.35(stat)±0.13(syst)) GeV−2 has been determined. This value is in good agreement with a recent measurement of the η Dalitz decay in the μ+μ− channel and with recent form-factor calculations. An improved value of the branching ratio BR(η→γe+e−)=(6.6±0.4(stat)±0.4(syst))⋅10−3 has been determined.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Glazier, Dr Derek and McGeorge, Dr John and MacGregor, Professor Douglas and Livingston, Dr Kenneth and Owens, Professor Robert and Annand, Dr John and Rosner, Professor Guenther
• Authors: Berghäuser, H., Metag, V., Starostin, A., Bartolomé, P.A., Akasoy, L.K., Annand, J.R.M., Arends, H.J., Bantawa, K., Beck, R., Bekrenev, V., Braghieri, A., Branford, D., Briscoe, W.J., Brudvik, J., Cherepnya, S., Demissie, B.T., Downie, E.J., Drexler, P., Dieterle, M., Filʼkov, L.V., Fix, A., Glazier, D.I., Heid, E., Hornidge, D., Jahn, O., Jude, T.C., Kashevarov, V.L., Knezevic, A., Kondratiev, R., Korolija, M., Kotulla, M., Koulbardis, A., Kruglov, S., Krusche, B., Lemmer, B., Lisin, V., Livingston, K., MacGregor, I.J.D., Maghrbi, Y., Manley, D.M., Martinez-Fabregate, M., McGeorge, J.C., McNicoll, E.F., Mekterovic, D., Micanovic, S., Mushkarenkov, A., Nefkens, B.M.K., Nikolaev, A., Novotny, R., Ostrick, M., Owens, R.O., Pedroni, P., Pheron, F., Polonski, A., Robinson, J., Prakhov, S.N., Rosner, G., Rostomyan, T., Schumann, S., Sober, D., Suarez, I.M., Supek, I., Tarbert, C.M., Thiel, M., Thomas, A., Unverzagt, M., Watts, D.P., Werthmüller, D., Zamboni, I., and Zehr, F.
• College/School: College of Science and Engineering > School of Physics and Astronomy
• Journal Name: Physics Letters B
• Publisher: Elsevier BV
• ISSN: 0370-2693
• Published Online: 28 June 2011