How to measure the linear polarization of gluons in unpolarized proton using the heavy-quark pair production

In recent papers [1, 2], two new ways have been proposed to probe the linear polarization of gluons in unpolarized proton: using the azimuthal asymmetries and Callan-Gross ratio in heavy-quark pair leptoproduction, lN → l′QQ̅X. In this talk, we discuss in details the sensitivity of the QCD predictions for the azimuthal cos φ and cos 2φ asymmetries to the contribution of linearly polarized gluons inside unpolarized proton, where the azimuth φ is the angle between the lepton scattering plane (l, l′) and the heavy quark production plane (N, Q). Our analysis shows that the azimuthal distributions under consideration vary from 0 to 1 depending on the value of the gluonic counterpart of the Boer- Mulders function, $h_{1}^{ \bot g}$. We conclude that the cos φ and cos 2φ asymmetries in heavy-quark pair production in DIS processes are predicted to be large in wide kinematic ranges and sensitive to the contribution of linearly polarized gluons.

Heavy quark production in pA collisions: The double parton scattering contribution

In this paper, we estimate the double parton scattering (DPS) contribution for the heavy quark production in pA collisions at the LHC. The cross-sections for the charm and bottom production are estimated using the dipole approach, taking into account the saturation effects, which are important for high energies and for the scattering with a large nucleus. We compare the DPS contribution with the single parton scattering one and demonstrate that in the case of charm production, both are similar in the kinematical range probed by the LHC. Predictions for the rapidity range analyzed by the LHCb Collaboration are also presented. Our results indicate that the study of the DPS contribution for the heavy quark production in pPb collisions at the LHC is feasible and can be useful to probe the main assumptions of the approach.