Search for the production of the final states ${\mathrm{\tau }}^{+}$${\mathrm{\tau }}^{\mathrm{-}}$${\mathit{e}}^{+}$${\mathit{e}}^{\mathrm{-}}$, ${\mathrm{\tau }}^{+}$${\mathrm{\tau }}^{\mathrm{-}}$${\mathrm{\mu }}^{+}$${\mathrm{\mu }}^{\mathrm{-}}$, and ${\mathrm{\tau }}^{+}$${\mathrm{\tau }}^{\mathrm{-}}$${\mathrm{\pi }}^{+}$${\mathrm{\pi }}^{\mathrm{-}}$ in ${\mathit{e}}^{+}$${\mathit{e}}^{\mathrm{-}}$ collisions at √s =29 GeV

We have searched for the reaction ${\mathit{e}}^{+}$ ${\mathit{e}}^{\mathrm{-}}$→${\mathrm{\tau }}^{+}$ ${\mathrm{\tau }}^{\mathrm{-}}$ff¯, where f is either an electron, muon, or charged pion, at √s =29 GeV using the Mark II detector at the SLAC PEP storage ring. One candidate event is found while 2.3 events are expected from known processes. We would expect to see 11 events if the cross section for ${\mathit{e}}^{+}$ ${\mathit{e}}^{\mathrm{-}}$→${\mathrm{\tau }}^{+}$ ${\mathrm{\tau }}^{\mathrm{-}}$ff¯ at √s =29 GeV were enhanced by the factor of 4.7 which the ALEPH Collaboration reports for √s =91 GeV. We also look for ${\mathit{e}}^{+}$ ${\mathit{e}}^{\mathrm{-}}$→${\mathit{e}}^{+}$ ${\mathit{e}}^{\mathrm{-}}$ff¯ and ${\mathit{e}}^{+}$ ${\mathit{e}}^{\mathrm{-}}$→${\mathrm{\mu }}^{+}$ ${\mathrm{\mu }}^{\mathrm{-}}$ff¯, and for ${\mathit{e}}^{+}$ ${\mathit{e}}^{\mathrm{-}}$→${\mathrm{\tau }}^{+}$ ${\mathrm{\tau }}^{\mathrm{-}}$γ, using a similar analysis procedure, and see the number of events predicted by the standard model.