First observation of tau->3 pi eta nu(tau) and tau->f(1)pi nu(tau) decays

Abstract

We have observed new channels for tau decays with an eta in the final state. We study 3-prong tau decays, using the eta --> gamma gamma and eta --> 3 pi(0) decay modes and 1-prong decays with two pi(0)'s using the eta --> gamma channel. The measured branching fractions B(tau(-)-->pi(-)pi(-)pi(+)eta nu(tau)) = (3.4-(0.6)(0.5) +/- 0.6) x 10(-4) and B(tau(-) --> pi(-)2 pi(0) eta nu<(tau>)) = (1.4 +/- 0.6 +/- 0.3) x 10(-4). We observe clear evidence for f(1) --> eta pi pi substructure and measure B(pi(-) --> F-1 pi(-)nu(tau)) = (5.8(-1.3)(+1.4) +/- 1.8) x 10(-4). We have also searched for eta'(958) production and obtain 90% C.L. upper limits B(tau(-) --> pi(-)eta'nu(tau)) < 7.4 x 10(-5) 10-5 and B(tau(-) --> pi(-) --> pi(-)pi(0) eta'nu(tau)) < 8.0 x 10(-5).