Jet-structure and the statistical model for electron-positron annihilation into hadrons

We consider a statistical model for electron-positron annihilation into hadrons, whose input single particle distribution function $\text{?(p)}$ is power behaved for large values of the momentum $\text{p, ?(p) ～ p}{}^{\mathrm{m?2}}$. Three classes can be distinguished, corresponding to m > 0, m = 0 and m < 0. The first two classes have asymptotically a spherically symmetric event structure, while for the case m < 0 we argue that energy-momentum conservation forces the events to be jet-like.