New G-parity violating amplitude in the J/Psi decay?
- Baldini Ferroli, R.
- De Mori, F.
- Destefanis, M.
- Maggiora, M.
- Pacetti, S.
- Yan, L.
- Bertani, M.
- Calcaterra, A.
- Felici, G.
- Patteri, P.
- Wang, Y. D.
- Zallo, A.
- Bettoni, D.
- Cibinetto, G.
- Farinelli, R.
- Fioravanti, E.
- Garzia, I.
- Mezzadri, G.
- Santoro, V.
- Savriã©, M.
- Bianchi, F.
- Greco, M.
- Marcello, S.
- Spataro, S.
- Carloni Calame, C. M.
- Montagna, G.
- Nicrosini, O.
- Piccinini, F.
DOIAbstract
The J/ψ meson has negative G parity so that, in the limit of isospin conservation, its decay into π+π- should be purely electromagnetic. However, the measured branching fraction B(J/ψ→π+π-) exceeds by more than 4.5 standard deviations the expectation computed according to BABAR data on the e+e-→π+π- cross section. The possibility that the two-gluon plus one-photon decay mechanism is not suppressed by G-parity conservation is discussed, even by considering other multipion decay channels. As also obtained by phenomenological computation, such a decay mechanism could be responsible for the observed discrepancy. Finally, we notice that the BESIII experiment, having the potential to perform an accurate measurement of the e+e-→π+π- cross section ...
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