Studies of high energy pp collisions

Abstract

The Standard Model of particle physics is examined in the context of high energy proton-antiproton collider experiments. The large energies available offer the possibility of producing new particles which may then be observed via their decay. Heavy quark production is examined through the production of unlike-sign lepton pairs. Methods for isolating several dilepton production mechanisms are given, including an eu signal for the top quark. Moreover, ψ production is shown to serve as a particularly clean tag for the production of particles containing b quarks. The possibility of observing a fourth generation heavy lepton via W decay is investigated. The hadronic decay mode leads to a promising signature of large missing accompanied by two hadronic jets and has a very healthy event rate. The monojet events found by the UA1 experiment are reviewed. Various extensions of the Standard Model are examined as possible explanations of these events. The first interpretation involves the production of SUSY particles. These are found to be compatible with the data if two squarks exist with mass 0(30GeV) and the gluino has mass > 0(60GeV). Secondly, interpretations based on four point effective interactions of the form qqZg are investigated, and are shown to be unable to account for the observed monojet rate. Finally, the production and decay of new heavy states (for example excited quarks) could account for the monojet data, but are found to predict large numbers of W + jet and γ + jet events which have not been seen.