Phenomenology of the Standard Model, and beyond, at high-energy colliders

Abstract

I review planned searches for the so far unobserved Higgs boson of the Standard Model of High Energy Physics. In particular a light 'intermediate' mass Higgs with mass in the range 80 GeV ≤ M(_H) ≤130 GeV will be hard to detect. I suggest several methods at planned future high energy particle colliders for observing this Higgs boson. At LEP I we have reasonable numbers of Higgs produced in association with a Z boson up to the limit imposed by phase space M(_H) ˂ √s - 100 GeV. Unfortunately if the Higgs is degenerate in mass with the Z boson we have large numbers of background events from double Z production. I investigate possible methods round this background. Firstly in polarizing the initial e+e- beams, and secondly in studying the differing topologies of the ZH signal, and ZZ background events. Moving on to the hadron super colliders the LHC and the SSC. These colliders typically produce very clean signals for 'heavy' Higgs. However for a light "'intermediate* mass Higgs all Higgs decays are either dominated by huge QCD backgrounds; or put very strong constraints upon our experimental apparatus. I investigate the signals and backgrounds for an alternative approach where rather than looking for the Higgs in isolation, we look for it produced in association with other heavy particles. Despite these production mechanisms having a far lower rate than isolated Higgs production they have far better signal to background ratios, which makes them look promising. Two modes in particular appear to give encouraging signals; WH production, and tiH production. Both these production modes can be detected in the isolated lepton and two photon channel.