Hard production of a Z boson plus heavy flavor jets at LHC and the intrinsic charm content of a proton

The cross section of associated production of a Z boson with heavy flavor jets in p p collisions is calculated using the Sherpa Monte Carlo generator and the analytical combined QCD approach based on k_T factorization at small x and conventional collinear QCD at large x . A satisfactory description of the ATLAS and CMS data on the p_T spectra of Z bosons and c jets in the whole rapidity, y , region is shown. Searching for the intrinsic charm (IC) contribution in these processes, which could be visible at large y >1.5 , we study observables very sensitive to nonzero IC contributions and less affected by theoretical QCD scale uncertainties. One of such observables is the so-called double ratio, the ratio of the differential cross section of Z +c production in the central region of |y |<1.5 and in the forward region 1.5 <|y |<2.5 , divided by the same ratio for Z +b production. These observables could be more promising for the search of IC at LHC as compared to the observables considered earlier.