The authors report on analyses of tau lepton decays?− →?K−?{sub?} and?− →??−?{sub?}, with? →??−?°, using 470 fb−1 of data from the BABAR experiment at PEP-II, collected at center-of-mass energies at and near the?(4S) resonance. They measure the branching fraction for the?− →?K−?{sub?} decay mode,?({tau}− →?K−?{sub {tau}}) = (1.42 ± 0.11(stat) ± 0.07(syst)) x 10−4, and report a 95% confidence level upper limit for the second-class current process {tau}− →??−?{sub {tau}},?({tau}− →??−?{sub {tau}})

This dissertation measures an inclusive branching fraction of (13.9 +- 2.0/sub -2.4//sup +2.1/)% for the decay tau− .-->. nu/sub tau/.pi.−.pi.° + nh° where h° is a .pi.° or an eta and n greater than or equal to 1. The data sample, obtained with the TPC detector facility at PEP, corresponds to an integrated luminosity of 72 pb−1 at 29 GeV center of mass energy. The measured value for this branching fraction is somewhat greater than the theoretical prediction and, taking errors into account, resolves the present difference between the inclusive and the sum of the exclusive tau− branching fractions into one charged prong. In addition, a lower limit of 8.3% (95% CL) is placed on the branching fraction B(tau− .-->. nu/sub tau/.pi.−.pi.°.pi.°).

The {tau}{sup -} {yields} {pi}{sup -}{pi}{sup -}{pi}{sup +}{pi}{sup 0}{pi}{sup 0}{nu}{sub {tau}} and {tau}{sup -} {yields} 3h{sup -} 2h{sup +} {nu}{sub {tau}} decays have been studied using the BABAR experiment at the PEP-II e{sup +}e{sup -} storage ring. Preliminary branching fractions are given for the {tau}{sup -} {yields} {pi}{sup -}{pi}{sup -}{pi}{sup +}{pi}{sup 0}{pi}{sup 0}{nu}{sub {tau}} and to the sub-channels {tau}{sup -} {yields} {eta}{pi}{sup -} {pi}{sup 0}{nu}{sub {tau}} and {tau}{sup -} {yields} {omega}(782){pi}{sup -}{pi}{sup 0}{nu}{sub {tau}}. A preliminary upper limit is given on the branching fraction for the {phi}(1020){pi}{sup -}{pi}{sup 0}{nu}{sub {tau}} mode. In addition a preliminary measurement of the branching fraction of the {tau}{sup -} {yields} 3h{sup -}2h{sup +} {nu}{sub {tau}} decay (h = {pi}, K) is presented.

We present {tau}{sup -} lepton branching fraction measurements based on data from the TPC/Two-Gamma detector at PEP. Using a sample of {tau}{sup -} {yields} {nu}{sub {tau}}K{sup -}{pi}{sup +}{pi}{sup -} events, we examine the resonance structure of the K{sup -}{pi}{sup +}{pi}{sup -} system and obtain the first measurements of branching fractions for {tau}{sup -} {yields} {nu}{sub {tau}}K{sub 1}{sup -}(1270) and {tau}{sup -} {yields} {nu}{sub {tau}}K{sub 1}{sup -}(1400). We also describe a complete set of branching fraction measurements in which all the decays of the {tau}{sup -} lepton are separated into classes defined by the identities of the charged particles and an estimate of the number of neutrals. This is the first such global measurement with decay classes defined by the four possible charged particle species, e, {mu}, {pi}, and K.