This thesis presents a study of the decays τ→eνν identified after a selection of τ+τ− events
produced in e+e− collisions at LEP. These collisions, predominantly
mediated by a Z0 boson, offer a good laboratory for the study of weak
current parameters. Moreover, the decays of the tau lepton, which proceed via a
W boson, increase the possibilities of our study. The experimental
observables, which imply an indirect knowledge of the coupling constants,
include the polarization asymmetry and the forward-backward polarization
asymmetry. The branching ratio of the electronic decay of the Ï„ lepton
(18.24±0.28±0.32)%) derives a measurement of the strong coupling
constant αs​ at the scale of the Z0 boson mass
(0.118−0.006+0.004​±0.006) and a test of lepton universality in weak
currents (gμ​gτ​​=1.000±0.014). The spectra of momenta and
electromagnetic energy depositions used as estimates of the energy of the
electron allow to measure the polarization asymmetries
(Pτ​=−0.16±0.09±0.05 and ApolFB​=−0.19±0.09±0.01) giving
subsequent values for the effective sin2θW​ (0.230±0.013 and
0.218±0.015).Comment: Doctoral thesis in spanish language. 172 pages including the index,
the introduction and the bibliography. A postscript version is available at
http://evalu0.ific.uv.es/lozano/phd_e.htm