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arXiv · hep-ph/9610265

Colour-octet contributions to exclusive charmonium decays

J. Bolz·P. Kroll·G. A. Schuler
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Abstract

We investigate the theoretical uncertainties of $P$-wave charmonium decays into two pions, $χ_{\c J}\rightarrow π^+π^-$, $π^0π^0$. Constraining the pion distribution-amplitude from the recent precise data on $F_{πγ}(Q^2)$, we find an order-of-magnitude discrepancy between data and prediction. The disagreement persists even after inclusion of transverse 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 $|\c \cbar \g >$ of the $χ_{\c J}$ wave function is actually not power suppressed with respect to the usual colour-singlet decay arising from the dominant $|\c \cbar >$ Fock state. An explicit calculation yields an agreement with the data for a very reasonable value for the single extra non-perturbative parameter.

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J. Bolz, P. Kroll, G. A. Schuler. 1996-10-07. Colour-octet contributions to exclusive charmonium decays. https://doi.org/10.1016/s0370-2693(96)01515-8

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