Upper limit for the decay τ→ηπν

Abstract The semi-hadronic decay of the τ→ηπν has been studied in the reaction e + e − →τ + τ − at center-of-mass energies between 14.0 and 46.8 GeV with the CELLO detector at PETRA. No evidence for the decay has been found with an upper limit of 1.4% at 90% CL for the branching ratio τ→ηπν. This is in contradiction to a recent measurement of this final state at the 5% level. In the standard model this decay is strongly suppressed.