Abstract
Measurements of differential cross sections dσ/dϕ* and double-differential cross sections d2σ/dϕ*d|y| for inclusive Z boson production are presented using the dielectron and dimuon final states. The kinematic observable ϕ* correlates with the dilepton transverse momentum but has better resolution, and y is the dilepton rapidity. The analysis is based on data collected with the CMS experiment at a centre-of-mass energy of 8 TeV corresponding to an integrated luminosity of 19.7 fb−1. The normalised cross section (1/σ) dσ/dϕ*, within the fiducial kinematic region, is measured with a precision of better than 0.5% for ϕ* < 1. The measurements are compared to theoretical predictions and they agree, typically, within few percent.
Highlights
Background estimationThe background contributions to the selected samples amount only to about 0.6% and 0.5% in the dielectron and dimuon channels, respectively
For the MadGraph signal as well as W+jets samples, the total inclusive cross sections are normalised to the values obtained from the theoretical predictions, computed using fewz (v2.0) [36] with the NNPDF3.0 set of parton distribution functions (PDF) [37]. fewz includes quantum chromodynamics (QCD) corrections up to NNLO and electroweak corrections up to next-to-leading order (NLO)
Measurements of the absolute differential cross sections dσ/dφ∗ and d2σ/dφ∗d|y| and the corresponding normalised differential cross sections in the combined dielectron and dimuon channels were presented for the dilepton mass range of 60 to 120 GeV
Summary
The central feature of the CMS apparatus is a superconducting solenoid of 6 m internal diameter, providing a magnetic field of 3.8 T. Within the solenoid volume are a silicon pixel and strip tracker, a lead tungstate crystal electromagnetic calorimeter (ECAL), and a brass and scintillator hadron calorimeter (HCAL), each composed of a barrel and two endcap sections. The steel and quartz-fibre Cherenkov hadron forward calorimeters extend the pseudorapidity coverage provided by the barrel and endcap detectors. Muons are measured in the gas-ionization detectors embedded in the steel flux-return yoke outside the solenoid, with detection planes made using three technologies: drift tubes, cathode strip chambers, and resistive-plate chambers. A more detailed description of the CMS detector, together with a definition of the coordinate system used and the relevant kinematic variables, can be found in ref. A more detailed description of the CMS detector, together with a definition of the coordinate system used and the relevant kinematic variables, can be found in ref. [21]
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