Measurements of differential cross sections for associated production of a W boson and jets in proton-proton collisions at s=8  TeV<

Abstract

Differential cross sections for a W boson produced in association with jets are measured in a data sample of proton-proton collisions at a center-of-mass energy of 8 TeV recorded with the CMS detector and corresponding to an integrated luminosity of 19.6 fb −1 . The W bosons are identified through their decay mode W → µν. The cross sections are reported as functions of jet multiplicity, transverse momenta, and the scalar sum of jet transverse momenta (H T ) for different jet multiplicities. Distributions of the angular correlations between the jets and the muon are examined, as well as the average number of jets as a function of H T and as a function of angular variables. The measured differential cross sections are compared with tree-level and higher-order recent event generators, as well as next-to-leading-order and next-tonext-to-leading-order theoretical predictions. The agreement of the generators with the measurements builds confidence in their use for the simulation of W+jets background processes in searches for new physics at the LHC. Published in Physical Review D asEvents are retained if they pass a trigger selection requiring one isolated muon with p T > 24 GeV and |η| < 2.1.Signal and background processes are generated with various state-of-the-art generators and passed through detector simulation based on GEANT4 [14] description of CMS. Each simulated sample is normalized to the integrated luminosity of the data sample. The simulated events are required to pass an emulation of the trigger requirements applied to the data. Trigger efficiencies in the simulation are corrected for differences with respect to the data. Simulations also include additional collisions in the same or adjacent bunch crossings (pileup, PU). To model PU, minimum-bias events generated with PYTHIA6 using the Z2* tune [15] are superimposed on the simulated events, matching the multiplicity of PU collisions observed in data, which has an average value of approximately 21.The W+jets signal process is simulated with the matrix element (ME) generator MADGRAPH 5.1.1 [1] interfaced with PYTHIA 6.426 using the Z2* tune for parton showering and hadronization. This sample of events, denoted MADGRAPH5+PYTHIA6 (denoted as MG5+PY6 in the figure legends), is produced with the CTEQ6L1 parton distribution function (PDF) set [16] √ (∆φ) 2 + (∆η) 2 < 0.4 around the direction of the muon candidate track are considered. The transverse momentum of the muon candidate is denoted by p µ T . Because neutral PU particles deposit on average half as much energy as charged PU particles, the contamination in the isolation cone from neutral particles coming from PU interactions is estimated as 0.5 ∑ PU p T and it is subtracted in the definition of I iso .

NNLO QCD Corrections to W+jet Production in NNLO JET

“…We start with results for W production, where one or more jets is explicitly required alongside the boson in the experimental analysis. The 19.6 fb −1 CMS data taken at 8 TeV used for this comparison is taken from [35] for the muonic decay channel in combined W ± production, where we use the notation W = W + + W − . The anti−k T jet algorithm is used, with radius parameter R = 0.5, and the central scale chosen for the predictions is .…”

“…Scale errors are treated as fully correlated between the W + and the W − when obtaining total rates for W production. The NNLO QCD distributions were independently calculated for all observables with a single jet at leading order in [35] using the method of N-jettiness subtraction [7], however a direct comparison cannot be immediately performed here as hadronisation effects have been applied to the N-jettiness results presented in [35].…”

“…Predictions at LO (green right-hatched), NLO (orange left-hatched), and NNLO (red cross-hatched) are compared to CMS data from Ref. [35]. Distributions normalised to NLO are shown in the lower panels.…”

“…The cross section differential in H T of the jets and the exclusive jet multiplicity N jets for W production compared to CMS data at 8 TeV . Predictions at LO (green right-hatched), NLO (orange left-hatched), and NNLO (red cross-hatched) are compared to CMS data from Ref [35]…”

Electroweak and QCD aspects in vector boson plus jets associated production with CMS

“…It is therefore crucial to measure the production cross section as a function of various kinematic variables with the highest possible precision. Here differential cross section measurements of vector boson production in association with jets in proton-proton collisions at √ s = 8 TeV [1,3] and 13 TeV [2,4] at the LHC is presented. Final states with a vector boson and jets can also be used to study electroweak initiated processes, such as pure electroweak production of the ll j j final state.…”