Production of New Quarks and Leptons at Proton - Colliders

The recent advent of the CERN proton-antiproton collider operating at an energy regime typified by the weak intermediate vector bosons has opened up prospects for detecting new, high-mass quarks and leptons. We evaluate t-quark production and decay mechanisms within the framework of the standard SU(3)(,c) x SU(2)(,L) x U(1)(,Y) model. The t signal at pp colliders is plagued by serious backgrounds, but systematic procedures involving transverse momentum cuts on decay products, and lepton isolation cuts, are proposed. It is shown that the t-quark signal is separable from background. Methods for determining the t-quark mass are discussed. Backgrounds due to higher -order QCD processes are shown to be manageable. Possible new fourth-generation quarks (a,v) are introduced, and detection possibilities are studied. Two cases of v-quark mass are particularly interesting: (1) overlapping generations (m(,v) < m(,t)) in which the v quark may be unusually long-lived and (2) supermassive quarks (m(,v) > M(,W) + m(,t)) which decay into real vector bosons. Electroweak W pair production and decay are evaluated as a benchmark to compare with fourth-generation quarks. Possibilities for detecting a new, fourth-generation heavy lepton L at pp colliders is investigated. Heavy leptons with m(,L) < 60 GeV should be detectable at the CERN collider. The L leptonic decay signal is shown to be hampered by backgrounds from W (--->) e and W (--->) (tau) (--->) e decay modes. The best L signal is the hadronic decay mode. The signal is two separate hard jets balanced by large missing transverse momentum. Four appendices involving technical details of our calculations are presented.