Implications of theϒ(9.5)for gauge theories of weak interactions

Abstract

We analyze the implications of the discovery of the $\ensuremath{\Upsilon}(9.5)$, assumed to be a heavy-quark-antiquark bound state, for gauge theories of weak interactions and especially for neutrino reactions. Taking into account all present experimental constraints, we study the consequences of particular multiplet assignments of the new heavy quark in models based on the group SU(2) \ensuremath{\bigotimes} U(1) and higher gauge groups, in particular SU(3) \ensuremath{\bigotimes} U(1). In neutrino and antineutrino reactions in which this new quark is produced, its semileptonic decays will provide a key signal for its discovery. We specialize to the SU(3) \ensuremath{\bigotimes} U(1) model and give a careful analysis of multimuon events arising from the production of this heavy quark and the concomitant heavy lepton.