Colour Octet Contribution in Exclusive P-Wave Charmonium Decay into Proton-Antiproton

TL;DR

This paper investigates the role of colour octet contributions in exclusive P-wave charmonium decay to proton-antiproton, providing theoretical arguments and explicit calculations to clarify their necessity.

Contribution

It offers the first explicit calculation of Chi_J ---> p p̄ decay including colour octet contributions, clarifying their importance in exclusive decay processes.

Findings

Colour octet contributions are significant in exclusive P-wave charmonium decay.

Infrared divergence issues are resolved by including colour octet states.

Explicit calculations support the necessity of colour octet in exclusive decays.

Abstract

In inclusive P-wave charmonium decay, to cancel infrared divergence in the colour singlet contribution requires the inclusion of the colour octet which becomes degenerate with the former in the infrared limit. In the corresponding exclusive decay, such an infrared divergence does not exist. On this ground, it becomes doubtful whether the colour octet is needed in exclusive reactions. A contradiction in the underlying picture, however, would result once all strong decay channels are summed. We provide an answer to this question in support of the colour octet with theoretical arguments as well as an explicit calculation of Chi_J ---> p \bar p.