Study of weak vacuum polarization in $Z \to 2l \gamma$

The goal of the work was to perform a search of weak vacuum polarization in the channel $Z \to 2l \gamma$ using $20 \text{ fb}^{-1}$ of $pp$ collision data collected by the ATLAS experiment in 2012 at 8 TeV. The ratio of the distribution of an invariant mass of $l\gamma$ obtained from experimental data to the MC distribution from the experimental data was used for the search of the effect. Total significance of weak vacuum polarization signal in the invariant mass distribution of $l \gamma$ in only one of four channels has some significance. First studies indicate that an evidence of about $3.5 \sigma$ can be reached. The parameters, amplitude and phase, determined from the fit are different in each channel and thus inconclusive.