Tau anomaly and vectorlike families

The implications of a recently indicated increase in τ lifetime are discussed. It is stressed that the available experimental constraints (from δρ,${\mathrm{\epsilon }}_3$, and ${\mathrm{N}}_{\nu }$, etc.) are satisfied most naturally if the indicated τ anomaly is attributed to the mixing of the τ family with a heavy vectorlike family ${\mathrm{Q}}_{\mathrm{L},\mathrm{R}}^{\prime }$ with masses ∼200 GeV to 2 TeV, which is a doublet of SU(2${)}_{\mathrm{R}}$ and singlet of SU(2${)}_{\mathrm{L}}$, rather than with a heavy fourth family with standard chiral couplings. L↔R symmetry would imply that ${\mathrm{Q}}_{\mathrm{L},\mathrm{R}}^{\prime }$ is accompanied by the parity-conjugate family ${\mathrm{Q}}_{\mathrm{L},\mathrm{R}}$ which is a doublet of SU(2${)}_{\mathrm{L}}$ and singlet SU(2${)}_{\mathrm{R}}$. Two such vectorlike families, together with an increase in ${\mathrm{\tau }}_{\mathrm{\tau }}$, are, in fact, crucial predictions of a recently proposed supersymmetric composite model that possesses many attractive features, in particular, explanations of the origin of diverse scales and family replication. In the context of such a model, it is noted that an increase in ${\mathrm{\tau }}_{\mathrm{\tau }}$ due to mixing involving vectorlike families will necessarily imply a correlated decrease in neutrino counting ${\mathrm{N}}_{\nu }$ from the CERN ${\mathrm{e}}^{+}$ ${\mathrm{e}}^{\mathrm{-}}$ collider LEP from 3. Such a decrease in ${\mathrm{N}}_{\nu }$ would be absent, however, if the τ anomaly is attributed to a mixing involving a standard fourth family with chiral couplings. Because of the seesaw nature of the mass matrix of the three chiral and two vectorlike families, that arises naturally in the model, departures from universality in the first two families as well as in b¯b and ${\mathrm{\tau }}^{+}$ ${\mathrm{\tau }}^{\mathrm{-}}$ channels (linked to down flavors) are strongly suppressed, in accord with observations.