Search for top-quark decays to realWbosons at the Fermilab Tevatron collider

Abstract

We propose ways in which eventual signals from heavy-top-quark decays into on-shell or nearly-on-shell W bosons may be discriminated more sharply from background at the Fermilab Tevatron p¯p collider. For single-lepton t¯t signals, the principal background from direct W production cannot be eliminated by acceptance cuts alone, but the signal/background ratio can be greatly increased by requiring a high jet multiplicity n. Top-quark signals can be detected and $m_t$ can be measured via enhancements in the single-lepton event rates at high n, or via a peak in the invariant mass of the three hardest jets at high n. A t¯t signal can be extracted up to $m_t$=150 GeV (180 GeV) from selected data with n≥3 (n≥4) jets. For two-lepton t¯t signals, the principal standard-model backgrounds from b¯b,c¯c and Drell-Yan dilepton production can all be removed by cuts. The remaining backgrounds from direct $W^{+}$ $W^{\mathrm{-}}$ and Drell-Yan τ¯τ production can be suppressed to a level well below the t¯t signals, for the whole of the mass range up to $m_t$=200 GeV allowed for the standard model. Eventual t¯t signals can be confirmed by characteristic dynamical distributions. An integrated luminosity of 10 ${\mathrm{pb}}^{\mathrm{-}1}$ (100 ${\mathrm{pb}}^{\mathrm{-}1}$) would be enough to detect top quarks up to $m_t$=120 GeV (200 GeV).