Abstract
A measurement of the production cross-section of Z bosons in pp collisions at $\sqrt{s} = 13$ TeV is presented using dimuon and dielectron final states in LHCb data. The cross-section is measured for leptons with pseudorapidities in the range $2.0 < \eta < 4.5$, transverse momenta $p_\text{T} > 20$ GeV and dilepton invariant mass in the range $60<m(\ell\ell)<120$ GeV. The integrated cross-section from averaging the two final states is \begin{equation*}\sigma_{\text{Z}}^{\ell\ell} = 194.3 \pm 0.9 \pm 3.3 \pm 7.6\text{ pb,}\end{equation*} where the first uncertainty is statistical, the second is due to systematic effects, and the third is due to the luminosity determination. In addition, differential cross-sections are measured as functions of the Z boson rapidity, transverse momentum and the angular variable $\phi^*_\eta$.
Highlights
Measurements of electroweak gauge boson production are benchmark tests of Standard Model processes at hadron colliders, and are of interest for constraining the parton distribution functions (PDFs) that describe the structure of the proton
The boson transverse momentum and φ∗η distributions can be used to test Monte Carlo modelling of additional higher-order radiation that arises from quantum chromodynamics (QCD)
The fiducial region used for the results presented here is the same as in previous measurements of Z boson production at LHCb [1,2,3,4,5, 13]
Summary
The LHCb detector [14, 15] is a single-arm forward spectrometer covering the pseudorapidity range 2 < η < 5, primarily designed for the study of particles containing b or c quarks. Global event cuts (GEC) are applied in the electron trigger in order to prevent events with high occupancy from dominating the processing time: events only pass the electron trigger if they contain fewer than 450 hits in the SPD detector No such requirement is made within the muon trigger. Results are compared to predictions from Powheg [27, 28] at O(αs) using the NNPDF3.0 PDF set, with the showering implemented using Pythia 8. Higher jet multiplicities are generated by a parton shower, implemented here using the Monash 2013 tune for Pythia 8
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