Signatures of new particles at high energy colliders

Abstract

We discuss the experimental signatures of new particles, predicted by the Standard Model and by Super symmetry, in high energy proton-antiproton and, or, electron-positron colliders. A review of the theory of the Standard Model and of Supersymmetry, and a general discussion of collider physics are included. We review various Higgs boson production mechanisms, and consider one, Higgs boson production via Bremsstrahlung from electroweak gauge bosons, in detail. We find that the clearest signature is seen in the invariant mass distribution of the electron pair in the process ρρ → X (Z → He÷e־). However, the event rate is small, and, unless the Higgs boson can be identified from its decay products, such events may be misidentified as ordinary Z → e÷e־ events. We analyse UA1 jet-plus-large-missing-p┬ events in terms of a supersymmetric model with a light photino and with m≈ < m≈. If these events are due solely to scalar quark production, we find that, in our scenario, the scalar quarks must have a mass in the range 20 - 35 GeV, and the gluino mass must be greater than 0(60) GeV. We study the production of scalar electrons in e÷e־ collisions on and above the Z resonance. By calculating the cross-sections for e÷e־ → e÷eﻵﻵ־ we show that scalar electrons with mass above the beam energies (√s/2) can be identified. In particular, if a zino exists with mass m? &lt; /s-m?. , then zino production and decay can give a contribution which dominates the ﻵ-exchange contributions. In this case the presence of both the ẽ and Ž may be revealed by a distinctive signature in the electron momentum distribution.