Radiative decays of the J/$\psi$ and evidence for a new heavy resonance

Berkelman, Karl; Braunschweig, W.; Buschhorn, G.; Cords, D.; DASP Collaboration; de Boer, W.; Felst, R.; Gadermann, E.; Grindhammer, Guenter; Gunderson, B.; Hultschig, H.; Joos, P.; Koch, W.; Kotthaus, R.; Kotz, U.; Krehbiel, H.; Kreinick, D.; Lierl, H.; Ludwig, J.; Martyn, H.-U.; McNeely, W. A.; Mess, K. H.; Moffeit, K. C.; Oberlack, H.; Orito, S.; Petersen, A.; Poelz, G.; Pretzl, K.; Ringel, J.; Sander, H. G.; Sauerberg, K.; Schliwa, M.; Schmitz, Daniel; Schmueser, Peter; Sturm, W.; Suda, T.; Totsuka, Y.; Wallraff, W.; Wiik, B. H.; Wolf, G.; Yamada, S.

Radiative decays of the J/ $\psi$ and evidence for a new heavy resonance

Abstract

The three photon final state produced in e + e − collisions has been measured at the mass of the J ψ resonance using the nonmagnetic part of the double arm spectrometer DASP. The decays J ψ → ηγ, η'γ and π o γ were observed and their branching ratios are given. A four standard deviation signal was observed in the γγ mass spectrum at a mass of (2.83 ± 0.03) GeV. An upper limit is given for the direct decay J ψ → 3γ