Introduction

In this chapter we are going to consider a few further phenomena that should be included in a realistic model for hadron production.

We start by considering heavy flavor fragmentation. There should be no production of heavy flavors in the fragmentation process itself because of the very strong suppression from the tunnelling process. Heavy quark jets will nevertheless occur when the heavy flavor is produced in a process where there is a large energy concentration, e.g. in an e+e– annihilation process. Then the first-rank hadron in the jet contains the heavy flavor and such a hadron will, in general, have a larger mass than the ordinary hadrons, which are made up from the lighter quark flavors, u, d and s. We have seen (cf. Chapter 9) that for the usual Lund fragmentation function a larger-mass hadron will have a ‘harder’ z-spectrum, i.e. the typical value of the fragmentation variable z will be closer to unity.

We will consider a number of different models, both those that tend to give 1 – z ∝ 1/M and those that give 1 – z ∝ 1/M2 for the first-rank hadron with large mass M. We will also consider a rather different treatment which leads to the so-called Peterson formula, for heavy quark fragmentation. The basic idea is to make use of the wave functions obtained in a lightcone-dynamical scenario.