Colour Octet Contribution in Exclusive P-Wave Charmonium Decay into Octet and Decuplet Baryons

In the last years, the need of the colour octet state in inclusive P-wave charmonium decay has been firmly established. However, the implications of this in the corresponding exclusive reactions have not been fully recognized. We argue for the necessity of the colour octet in P- and higher-wave quarkonium decay. Using a set of phenomenologically constructed baryon wavefunctions, we consider the Chi_J decay into octet and decuplet baryon-antibaryon pair. By doing so, we subject the wavefunctions to a test of applicability. We show that the colour singlet component alone is insufficient to account for experimental measurements and only by including the colour octet contribution can the partial theoretical decay widths be brought into range of the data. By the present and earlier applications of the set of wavefunctions, they show themselves to be reasonable model wavefunctions at around the scale Q^2 \sim 10-20 GeV^2.Comment: 58 pages, 17 embedded PS figures, corrected typos, added appendix of numerical parameters, version to appear in Eur. Phys. J.