Probing the linearly polarized gluons in unpolarized proton with heavy-quark pair production

N. Ya. Ivanov, A. V. Efremov, O. V. Teryaev

We consider the azimuthal $\cos \phi$ and $\cos 2\phi$ distributions and the Callan-Gross ratio $R=\mathrm{d}{\sigma }_L/\mathrm{d}{\sigma }_T$ in heavy-quark pair electroproduction, $lN\rightarrow l^{\prime}…