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 pp 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 thorn c production in the central region of vertical bar y vertical bar < 1.5 and in the forward region 1.5 < vertical bar y vertical bar < 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.