The decays of the negative G-parity meson G-parity into even numbers of pions violate G-parity. Such decays, as well as other G-parity decays into hadrons, can be parametrized in terms of three main intermediate virtual states: one photon, one photon plus two gluons, and three gluons. Since the electromagnetic interaction does not conserve G-parity, G-parity decays into positive G-parity final states should be dominantly electromagnetic. Nevertheless, the one-photon contribution to J/ψ→π+π-, that can be estimated by exploiting the cross section σ(e+e-→π+π-), differs from the observed decay probability for more than 4.5 standard deviations. We present a computation of the ggγ amplitude based on a phenomenological description of the decay mechanism in terms of dominant intermediate states ηγ, η′γ, and f1(1285)γ. The obtained value is of the order of the electromagnetic contribution.
G-parity-violating amplitudes in the J/ψ→π+π- decay
Pacetti S.
2018
Abstract
The decays of the negative G-parity meson G-parity into even numbers of pions violate G-parity. Such decays, as well as other G-parity decays into hadrons, can be parametrized in terms of three main intermediate virtual states: one photon, one photon plus two gluons, and three gluons. Since the electromagnetic interaction does not conserve G-parity, G-parity decays into positive G-parity final states should be dominantly electromagnetic. Nevertheless, the one-photon contribution to J/ψ→π+π-, that can be estimated by exploiting the cross section σ(e+e-→π+π-), differs from the observed decay probability for more than 4.5 standard deviations. We present a computation of the ggγ amplitude based on a phenomenological description of the decay mechanism in terms of dominant intermediate states ηγ, η′γ, and f1(1285)γ. The obtained value is of the order of the electromagnetic contribution.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
