COLOR-OCTET CONTRIBUTIONS TO EXCLUSIVE CHARMONIUM DECAYS

We investigate the theoretical uncertainties of P-wave charmonium deca ys into two pions, chi(cJ) --> pi(+)pi(-), pi(0) pi(0). Constraining t he pion distribution-amplitude from the recent precise data on F-pi ga mma(Q(2)), we find an order-of-magnitude discrepancy between data and prediction. The-disagreement persists even after inclusion of transver se degrees of freedom and Sudakov suppressions. We propose the colour- octet mechanism as the solution to the puzzle. The colour-octet decay contribution arising from the higher Fock component \c(c) over barg$] of the chi(cJ) wave function is actually not power suppressed with res pect to the usual colour-singlet decay arising from the dominant \<c(c )over bar>] Fock state. An explicit calculation yields an agreement wi th the data for a very reasonable value for the single extra non-pertu rbative parameter.