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

TL;DR

This paper combines Monte Carlo simulations and analytical QCD approaches to accurately model Z boson plus heavy flavor jet production at the LHC, aiming to detect intrinsic charm in the proton through sensitive observables.

Contribution

It introduces a combined QCD approach and identifies new observables, like the double ratio, that enhance the search for intrinsic charm in proton structure.

Findings

Model describes ATLAS and CMS data well across rapidity regions.

Double ratio observable is sensitive to intrinsic charm contributions.

Proposed observables reduce theoretical uncertainties in IC detection.

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 kt-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 non-zero 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.