On colour rearrangement in hadronicW ⁺W⁻ evemts

Abstract

We discuss the possibility of colour rearrangement in$e^ + e^ - \to W^ + W^ - \to q_1 \bar q_2 q_3 \bar q_4$ events, i.e that the original colour singlets$q_1 \bar q_2$ and$q_3 \bar q_4$ may be transmuted, for instance, into new singlets$q_1 \bar q_4$ and$q_3 \bar q_2$. The effects on event properties could be quite large if such a rearrangement would occur instantaneously, so that gluon emission would be restricted to each of the new singlets separately. We argue that such a scenario is unlikely for two reasons. Firstly, theW ⁺ andW ⁻ usually decay at separately. We argue that such a scenario is unlikely for two reasons. Firstly, theW ⁺ W ⁻ production, which leads to large relative phases for energetic radiation off the two constituents of a rearranged system, and a corresponding dampening of the QCD cascades. Secondly, within the perturbative scenario the colour transmutation appears only in order α ²_s and is colour-suppressed. Colour reconnection at longer time scales is quite feasible, however, and may affect the fragmentation phase. If so, the nature of non-perturbative QCD can be probed in a new way. We formulate several alternative toy models and use these to estimate the colour reconnection probability as a function of the event kinematics. Possible consequences for LEP 2 events are illustrated, with special attention to systematic errors inW mass determinations.