Measurement of the WZ production cross section in pp collisions at s=13 TeV

Abstract

The WZ production cross section in proton-proton collisions at √ s = 13 TeV is measured with the CMS experiment at the LHC using a data sample corresponding to an integrated luminosity of 2.3 fb −1 . The measurement is performed in the leptonic decay modes WZ → ν , where , = e, µ. The measured cross section for the range 60 < m < 120 GeV is σ(pp → WZ) = 39.9 ± 3.2 (stat) +2.9 −3.1 (syst) ± 0.4 (theo) ± 1.3 (lumi) pb, consistent with the standard model prediction.The CMS detector is described in detail elsewhere [8]. The key components for this analysis are summarized here. 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 superconducting solenoid volume are a silicon pixel and strip tracker, a lead tungstate crystal electromagnetic calorimeter (ECAL), and a brass and scintillator hadron calorimeter, which provide the pseudorapidity coverage |η| < 1.479 in a barrel section and 1.479 < |η| < 3.0 in two endcap sections. Forward calorimeters extend the coverage to |η| < 5.0. Muons are measured in gas-ionization detectors embedded in the steel flux-return yoke outside the solenoid.The first level of the CMS trigger system, composed of custom hardware processors, is designed to select the most interesting events in less than 4 µs using information from the calorimeters and muon detectors. The high-level-trigger processor farm decreases the event rate from almost 100 kHz to around 1 kHz, before data storage. Data and Monte Carlo samplesThis measurement uses a sample of proton-proton collisions collected in 2015 at √ s = 13 TeV. The integrated luminosity of the sample is 2.3 fb −1 . Several Monte Carlo (MC) event generators are used to simulate the signal and background processes.The WZ signal is generated at NLO in perturbative QCD with POWHEG 2.0 [9][10][11][12]. The ZZ production via qq annihilation is generated at NLO using POWHEG 2.0, while the gg → ZZ 2 4 Event reconstruction process is simulated at leading-order with MCFM 7.0 [13]. The Zγ, ttV (ttW, ttZ), tZ, and triboson events VVV (WWZ, WZZ, ZZZ) are generated at NLO with MADGRAPH5 AMC@NLO [14]. The ZZ samples are scaled to the cross section calculated at NNLO for qq → ZZ [15] (scaling k factor 1.1) and at NLO for gg → ZZ [16] (scaling k factor 1.7). The PYTHIA 8.175 [17] program is used for parton showering, hadronization, and underlying event simulation using the CUETP8M1 tune [18]. The NNPDF3.0 [19] set of parton distribution functions (PDFs) is used, unless otherwise specified.For all processes, the detector response is simulated using a detailed description of the CMS detector, based on the GEANT4 package [20], and the event reconstruction is performed with the same algorithms used for data. The simulated samples include additional interactions per bunch crossing (pileup) taken from minimum-bias events generated with PYTHIA. The simulated events are weighted so that the pileup distribution matches the measured one, with an average of about 11 pileup interactions p...

Measurements of the pp → WZ inclusive and differential production cross sections and constraints on charged anomalous triple gauge couplings at $$ \sqrt{s} $$ = 13 TeV

“…The result is in good agreement with the MATRIX next-to-next-to-leadingorder (NNLO) prediction [55,56], of σ NNLO (pp → WZ) = 49.98 +2.2% −2.0% pb. This result supersedes the result from the CMS Collaboration using data corresponding to a smaller integrated luminosity of 2.3 fb −1 [14]. A measurement in the fiducial region yields a value of σ fid (pp → WZ) = 257.5 +5.3 −5.0 (stat) +2.3 −2.0 (theo) +12.8 −11.6 (syst) ± 7.4 (lumi) fb, pointing to an excess over the POWHEG next-to-leading-order cross section σ POWHEG fid = 227.6 +9.4 −8.0 fb.…”

Search for electroweak production of charginos and neutralinos in WH events in proton-proton collisions at $$ \sqrt{s}=13 $$ TeV

“…As a result, the tail modeling systematic uncertainty for this background is taken to be the same as those evaluated in CR0b. An additional uncertainty of 12% is applied to the normalization of the WZ → νbb background, based on the CMS cross section measurement of inclusive WZ production at 13 TeV [79]. A unique aspect of the WZ → νbb background is that M bb peaks at the Z boson mass, at the lower edge of the M bb selection used in this analysis.…”

Polarization Observables in WZ Production at the 13 TeV LHC: Inclusive Case

“…. , 6, corresponding respectively to [86,96] [24] to define their total phase space. As expected, we see that the W fractions are almost unchanged while the Z fractions vary more visibly.…”