Phenomenology of $\tau^- \rightarrow \pi^- \nu_{\tau} \gamma$ using LCSR

We present the study of radiative tau decay ($\tau^- \rightarrow \pi^- \nu_\tau \gamma$), computing the structure dependent contribution using Light Cone Sum Rules. This decay includes the same form factors as the radiative pion decay with the crucial difference that the momentum transfer squared, $t$, between the pion-photon system is positive, which makes these form factors timelike and also as $t$ can now take values upto $m_\tau^2$ , it can produce real hadronic resonances. The analytical form for these form factors has been calculated using light cone sum rules method and the invariant mass-spectrum in the $\pi-\gamma$ system and the decay width are presented. The structure dependent parameter, $\gamma$, the ratio of the axial to vector form factor is found to be in good agreement with the experimental determination.