Hard production of a <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>Z</mml:mi></mml:math> boson plus heavy flavor jets at LHC and the intrinsic charm content of a proton

Abstract

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 ${k}_{\mathrm{T}}$ factorization at small $x$ and conventional collinear QCD at large $x$. A satisfactory description of the ATLAS and CMS data on the ${p}_{\mathrm{T}}$ 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 $y&gt;1.5$, 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 $|y|&lt;1.5$ and in the forward region $1.5&lt;|y|&lt;2.5$, 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.