The decay τrightarrow f₁ π ν_τ in the Nambu--Jona-Lasinio model

The width of the decay $\tau\rightarrow f_1 \pi \nu_\tau$ has recently been measured by the BaBar experiment. The estimation of this width is given in the framework of the NJL model with the axial-vector mesons. Prediction is in agreement with the experimental data. It is shown that the $\pi-a_1$ transition contribution plays an important role and allows us to bring the NJL prediction to the data.