Effects of Soft Gluons at High-Energy Colliders
In high energy particle collisions, gluons in the initial and final state dominate the properties of particle interactions. This occurs not only in the types of events commonly associated with gluon hard scatterings, but also in places where gluons have not usually been considered important. This thesis will discuss three such cases. First, at the high energy electron proton collider HERA, the gluon structure function of the photon contributes to the production of charmonium, the bound state of two charmed quarks. This contribution complicates the proposed measurement of the structure of the proton, but may allow a measurement of the structure of the photon. The presence of gluons in the photon complicates our picture of ep collisions. In pp collisions, the opposite occurs. It is often thought that only a small fraction of hadronic events can be described by QCD. But, at high energy, the behavior of the total hadronic cross section seems to be described by a perturbative approach. At energies above ~45 GeV the total cross section rises with energy. This rise can be associated with the increasing probability of hard interactions in hadronic collisions. This connection can be seen in the context of the eikonal method. The last section discusses the radiation of gluons in events where there is a hard scattering: W events. When W particles are produced, gluons are radiated. This radiation contributes energy to the hadrons which accompany the W. The energy radiated from the hard scatter, which is calculable, seems to account for most of the transverse hadronic energy seen in W events at the CERN collider. This may imply that some properties of the "underlying event" are determined by the calculable radiation of gluons, not by "soft" processes which we can't predict.
- Pub Date:
- January 1990
- Physics: Elementary Particles and High Energy