Jet Production Rates in Association with W and Z Bosons in pp Collisions at √s = 7 TeV

Physics Analysis Summary in CERN Document Server: CMS-PAS-EWK-10-012


Abstract

We present a study of jet production in association with W and Z bosons in proton-proton collisions at √s = 7 TeV using the full 2010 data set collected by CMS corresponding to an integrated luminosity of 36 inverse-picobarns. We report the normalized inclusive rates of jets produced as well as the ratios σ(V + ≥ n-jets)/σ(V + ≥ (n-1)-jets) with a jet transverse energy threshold of 30 GeV. We present the first test of the Berends-Giele scaling at √s = 7 TeV.

Approved plots

(click on plots to get PDF versions)

Raw W and Z rates as a function of exclusive jet multiplicity

Jets are defined according to the anti-kT algorithm with a cone size ΔR=0.5

Jets are energy-calibrated particle-flow (PF) jets with transverse energy threshold at 30 GeV in the tracker acceptance |η|<2.4.

Simulation:

  • W signal: MadGraph + full CMS simulation (GEANT4), normalized to NNLO cross section
  • Z signal: MadGraph + full CMS simulation (GEANT4) and M(ll) > 50 GeV, normalized to NNLO cross section
  • top signal (ttbar and single top): MadGraph + full CMS simulation (GEANT4), normalized to NLO cross section
  • other backgrounds (QCD multi-jets): Pythia (NLO) + full CMS simulation (GEANT4)

cRawRates_W_e_30_log_new.png cRawRates_W_mu_30_log_new.png

Raw W event rate as a function of exclusive jet multiplicity, in the electron channel (left) and the muon channel (right), compared to the simulation

cRawRates_Z_e_30_log_new.png cRawRates_Z_mu_30_log_new.png

Raw Z event rate as a function of exclusive jet multiplicity, in the electron channel (left) and the muon channel (right), compared to the simulation

Signal extraction

Examples of W signal extraction

We present distributions of the transverse mass (computed from the lepton transverse momentum and the missing transverse momentum) and the multiplicity of b-tagged jets, for two inclusive jet multiplicity bins: ≥ 1-jet and ≥ 3-jets. The superimposed curves are projections of the unbinned maximum likelihood fit to the data with three components: signal, top background and other backgrounds.Electron channel:

pfMT_1-jets_e.png nB_1-jets_e.png

pfMT_3-jets_e.png nB_3-jets_e.png

Muon channel:

pfMT_1-jets_mu.png nB_1-jets_mu.png

pfMT_3-jets_mu.png nB_3-jets_mu.png

Examples of Z signal extraction

Zmass_1-jets_e.png Zmass_1-jets_mu.png

Di-lepton invariant mass distributions in the range 60 to 120 GeV in the inclusive jet multiplicity bin ≥ 1-jet, with, superimposed, the result of the unbinned maximum fit to the data, for the electron channel (left) and muon channel (right). The contribution of the background is small and cannot be seen in linear scale

Transverse energy of the leading jet in the event

cleadingJetPt_W_e_log_new.png cleadingJetPt_W_mu_log_new.png

Distribution of the leading jet transverse energy in W events, in the electron channel (left) and the muon channel (right)

cleadingJetPt_Z_e_log_new.png cleadingJetPt_Z_mu_log_new.png

Distribution of the leading jet transverse energy in Z events, in the electron channel (left) and the muon channel (right)

Inclusive jet multiplicity distributions

The following figures present, as a function of the inclusive number of jets n up to n=4, the cross sections σ(V + ≥ n-jets) normalized to the inclusive V cross section σ(V + ≥ 0-jets), and the ratio σ(V + ≥ n-jets)/σ(V + ≥ (n-1)-jets), for V = W and Z in the electron and muon channels. The error bars represent the total error in each jet multiplicity bin. Systematic uncertainties due to the jet energy scale and to the unfolding are represented by plain yellow and hashed blue bands, respectively. The cross-sections are not extrapolated to full acceptance. The data are compared to theory predictions obtained with MadGraph interfaced with Pythia (ME+PS) with two different tunes, D6T and Z2, as well as with Pythia with the Z2 tune.

W plus jets in the electron channel

cWPlusJetsEt30_e.png

W plus jets in the muon channel

cWPlusJetsEt30_mu.png

Z plus jets in the electron channel

cZPlusJetsEt30_e.png

Z plus jets in the muon channel

cZPlusJetsEt30_mu.png

Test of Berends-Gele scaling

The Berends-Gele scaling states that the ratio C(n)=σ(V + ≥ n-jets)/σ(V + ≥ (n+1)-jets) is approximately constant for n≥1. To test this hypothesis, we perform a fit to the data with the constraint C(n)=α+βŚn. The result of the fits are represented in the (α,β) plane, separately for the electron and muon channels, and compared to the theory prediction from MadGraph interfaced with Pythia/Z2 (ME+PS).

The error ellipses represent 68% confidence regions (statistical only). Arrows indicate typical shifts due to systematic effects.

alphabetaW.png

alphabetaZ.png


-- GautierHamelDeMonchenault - 18-Mar-2011

Topic attachments
I Attachment History Action Size Date Who Comment
PDFpdf Zmass_1-jets_e.pdf r1 manage 16.1 K 2011-03-18 - 13:56 GautierHamelDeMonchenault  
PNGpng Zmass_1-jets_e.png r1 manage 31.9 K 2011-03-18 - 13:56 GautierHamelDeMonchenault  
PDFpdf Zmass_1-jets_mu.pdf r1 manage 16.3 K 2011-03-18 - 13:56 GautierHamelDeMonchenault  
PNGpng Zmass_1-jets_mu.png r1 manage 31.8 K 2011-03-18 - 13:56 GautierHamelDeMonchenault  
PDFpdf alphabetaW.pdf r1 manage 27.9 K 2011-03-18 - 13:53 GautierHamelDeMonchenault  
PNGpng alphabetaW.png r1 manage 30.1 K 2011-03-18 - 13:53 GautierHamelDeMonchenault  
PDFpdf alphabetaZ.pdf r1 manage 26.9 K 2011-03-18 - 13:53 GautierHamelDeMonchenault  
PNGpng alphabetaZ.png r1 manage 25.5 K 2011-03-18 - 13:53 GautierHamelDeMonchenault  
PDFpdf cRawRates_W_e_30_log_new.pdf r1 manage 16.0 K 2011-03-18 - 13:54 GautierHamelDeMonchenault  
PNGpng cRawRates_W_e_30_log_new.png r1 manage 31.9 K 2011-03-18 - 13:54 GautierHamelDeMonchenault  
PDFpdf cRawRates_W_mu_30_log_new.pdf r1 manage 16.0 K 2011-03-18 - 13:54 GautierHamelDeMonchenault  
PNGpng cRawRates_W_mu_30_log_new.png r1 manage 31.8 K 2011-03-18 - 13:54 GautierHamelDeMonchenault  
PDFpdf cRawRates_Z_e_30_log_new.pdf r1 manage 16.0 K 2011-03-18 - 13:54 GautierHamelDeMonchenault  
PNGpng cRawRates_Z_e_30_log_new.png r1 manage 31.3 K 2011-03-18 - 13:54 GautierHamelDeMonchenault  
PDFpdf cRawRates_Z_mu_30_log_new.pdf r1 manage 16.1 K 2011-03-18 - 13:54 GautierHamelDeMonchenault  
PNGpng cRawRates_Z_mu_30_log_new.png r1 manage 31.5 K 2011-03-18 - 13:54 GautierHamelDeMonchenault  
PDFpdf cWPlusJetsEt30_e.pdf r1 manage 16.3 K 2011-03-18 - 13:55 GautierHamelDeMonchenault  
PNGpng cWPlusJetsEt30_e.png r1 manage 35.5 K 2011-03-18 - 13:55 GautierHamelDeMonchenault  
PDFpdf cWPlusJetsEt30_mu.pdf r1 manage 16.3 K 2011-03-18 - 13:55 GautierHamelDeMonchenault  
PNGpng cWPlusJetsEt30_mu.png r1 manage 36.0 K 2011-03-18 - 13:55 GautierHamelDeMonchenault  
PDFpdf cZPlusJetsEt30_e.pdf r1 manage 16.3 K 2011-03-18 - 13:55 GautierHamelDeMonchenault  
PNGpng cZPlusJetsEt30_e.png r1 manage 36.2 K 2011-03-18 - 13:55 GautierHamelDeMonchenault  
PDFpdf cZPlusJetsEt30_mu.pdf r1 manage 16.4 K 2011-03-18 - 13:55 GautierHamelDeMonchenault  
PNGpng cZPlusJetsEt30_mu.png r1 manage 37.4 K 2011-03-18 - 13:55 GautierHamelDeMonchenault  
PDFpdf cleadingJetPt_W_e_log_new.pdf r1 manage 22.8 K 2011-03-18 - 13:53 GautierHamelDeMonchenault  
PNGpng cleadingJetPt_W_e_log_new.png r1 manage 38.8 K 2011-03-18 - 13:53 GautierHamelDeMonchenault  
PDFpdf cleadingJetPt_W_mu_log_new.pdf r1 manage 22.8 K 2011-03-18 - 13:53 GautierHamelDeMonchenault  
PNGpng cleadingJetPt_W_mu_log_new.png r1 manage 38.6 K 2011-03-18 - 13:53 GautierHamelDeMonchenault  
PDFpdf cleadingJetPt_Z_e_log_new.pdf r1 manage 21.1 K 2011-03-18 - 13:54 GautierHamelDeMonchenault  
PNGpng cleadingJetPt_Z_e_log_new.png r1 manage 35.6 K 2011-03-18 - 13:54 GautierHamelDeMonchenault  
PDFpdf cleadingJetPt_Z_mu_log_new.pdf r1 manage 21.3 K 2011-03-18 - 13:54 GautierHamelDeMonchenault  
PNGpng cleadingJetPt_Z_mu_log_new.png r1 manage 36.0 K 2011-03-18 - 13:54 GautierHamelDeMonchenault  
PDFpdf nB_1-jets_e.pdf r1 manage 13.9 K 2011-03-18 - 13:55 GautierHamelDeMonchenault  
PNGpng nB_1-jets_e.png r1 manage 26.7 K 2011-03-18 - 13:55 GautierHamelDeMonchenault  
PDFpdf nB_1-jets_mu.pdf r1 manage 13.9 K 2011-03-18 - 13:55 GautierHamelDeMonchenault  
PNGpng nB_1-jets_mu.png r1 manage 26.6 K 2011-03-18 - 13:55 GautierHamelDeMonchenault  
PDFpdf nB_3-jets_e.pdf r1 manage 13.8 K 2011-03-18 - 13:55 GautierHamelDeMonchenault  
PNGpng nB_3-jets_e.png r1 manage 26.5 K 2011-03-18 - 13:55 GautierHamelDeMonchenault  
PDFpdf nB_3-jets_mu.pdf r1 manage 13.9 K 2011-03-18 - 13:55 GautierHamelDeMonchenault  
PNGpng nB_3-jets_mu.png r1 manage 26.5 K 2011-03-18 - 13:56 GautierHamelDeMonchenault  
PDFpdf pfMT_1-jets_e.pdf r1 manage 18.7 K 2011-03-18 - 13:56 GautierHamelDeMonchenault  
PNGpng pfMT_1-jets_e.png r1 manage 37.0 K 2011-03-18 - 13:56 GautierHamelDeMonchenault  
PDFpdf pfMT_1-jets_mu.pdf r1 manage 18.9 K 2011-03-18 - 13:56 GautierHamelDeMonchenault  
PNGpng pfMT_1-jets_mu.png r1 manage 36.8 K 2011-03-18 - 13:56 GautierHamelDeMonchenault  
PDFpdf pfMT_3-jets_e.pdf r1 manage 17.3 K 2011-03-18 - 13:56 GautierHamelDeMonchenault  
PNGpng pfMT_3-jets_e.png r1 manage 39.5 K 2011-03-18 - 13:56 GautierHamelDeMonchenault  
PNGpng pfMT_3-jets_mu.png r1 manage 37.3 K 2011-03-18 - 16:29 GautierHamelDeMonchenault  
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