Search for a Fourth-Generation Quark More Massive than the Z0 Boson in pp¯ Collisions at √s=1.8TeV

Le résumé fourni par la source

We present the results of a search for pair production of a fourth-generation charge $\ensuremath{-}\frac{1}{3}$ quark $({b}^{\ensuremath{'}})$ in $\sqrt{s}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1.8\mathrm{TeV}$ $p\overline{p}$ collisions using $88{\mathrm{pb}}^{\ensuremath{-}1}$ of data obtained with the Collider Detector at Fermilab. We assume that both quarks decay via the flavor-changing neutral current process ${b}^{\ensuremath{'}}\ensuremath{\rightarrow}{\mathrm{bZ}}^{0}$ and that the ${b}^{\ensuremath{'}}$ mass is greater than ${m}_{Z}{+m}_{b}$. We studied the decay mode ${b}^{\ensuremath{'}}\overline{{b}^{\ensuremath{'}}}\ensuremath{\rightarrow}{Z}^{0}{Z}^{0}b\overline{b}$ where one ${Z}^{0}$ decays into ${e}^{+}{e}^{\ensuremath{-}}$ or ${\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$ and the other decays hadronically, giving a signature of two leptons plus jets. An upper limit on the ${\ensuremath{\sigma}}_{p\overline{p}\ensuremath{\rightarrow}{b}^{\ensuremath{'}}\overline{{b}^{\ensuremath{'}}}}\ifmmode\times\else\texttimes\fi{}[B({b}^{\ensuremath{'}}\ensuremath{\rightarrow}{\mathrm{bZ}}^{0}){]}^{2}$ is established as a function of the ${b}^{\ensuremath{'}}$ mass. We exclude at $95%$ confidence level a ${b}^{\ensuremath{'}}$ quark with mass between 100 and $199\mathrm{GeV}{/c}^{2}$ for $B({b}^{\ensuremath{'}}\ensuremath{\rightarrow}{\mathrm{bZ}}^{0})\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}100%$.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.