Measurement of the associated production of a Z boson with charm or bottom quark jets in proton-proton collisions at $\sqrt{s}=13~\mathrm{TeV}$

Ratios of cross sections, $\sigma$(Z + c jets)/$\sigma$(Z + jets), $\sigma$(Z + b jets)/$\sigma$(Z + jets), and $\sigma$(Z + c jets)/$\sigma$(Z + b jets) in the associated production of a Z boson with at least one charm or bottom quark jet are measured in pp collisions at $\sqrt{s}=13~\mathrm{TeV}$ using $35.9~\mathrm{fb}^{-1}$ of data collected by the CMS experiment at the CERN LHC. The fiducial volume of the measurement is defined by jet transverse momentum $p_{\mathrm{T}} > 30~\mathrm{GeV}$ and pseudorapidity $\left|{\eta}\right| < 2.4$. The Z bosons are selected within the mass range of 71 and $111~\mathrm{GeV}$ requiring leptons (electrons or muons) with $p_{\mathrm{T}} > 25~\mathrm{GeV}$ and $\left|{\eta}\right| <$ 2.4. Results on the inclusive and differential cross section ratios as functions of jet and Z boson transverse momentum are compared with predictions from leading and next-to-leading order perturbative QCD calculations. These are the first of a kind measurements at $13~\mathrm{TeV}$, and the measurement precision exceeds that of the current theoretical predictions.