G-parity violating amplitudes in the J/ψ→ π⁺ π^- decay

2016/11/14 by Ferroli, Rinaldo Baldini, Mangoni, Alessio, Pacetti, Simone
#81V35 #FOS: Physical sciences #High Energy Physics - Phenomenology (hep-ph)

paper · doi:10.48550/arxiv.1611.04437

Abstract

The decays of the negative G-parity meson J/ψ 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, J/ψ 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.

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