An Explanation for the rho-pi Puzzle of J/psi and psi' Decays

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  • 6 January 1998
Abstract
We propose a new explanation for the longstanding puzzle of the tiny branching fraction of psi -> rho pi relative to that for J/psi -> rho pi. In the case of J/psi, we argue that this decay is dominated by a higher Fock state in which the ccbar pair is in a color-octet ^3S_1 state. The decay proceeds through the annihilation process c cbar -> q qbar and the formation of rho and pi involves the endpoints of the meson wavefunctions. In the case of the psi', we argue that the probability for the c cbar pair in this higher Fock state to be close enough to annihilate is suppressed by a dynamical effect related to the small energy gap between the mass of the psi' and the D Dbar threshold. Using data on the branching fractions into rho pi and K^* Kbar as input, we predict the branching fractions for all other vector/pseudoscalar decay modes of the psi'.

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