Measurement of pure electroweak production of a Z boson in association with forward/backward jets in proton-proton collisions at s1/2=8 TeV

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Abstract

The purely electroweak (EW) cross section for the production of two jets in association with a Z boson, in proton-proton collisions at √s=8 TeV, is measured using data recorded by the CMS experiment at the CERN LHC, corresponding to an integrated luminosity of 19.7-1. The electroweak cross section for the lljj final state (with l = e or μ and j representing the quarks produced in the hard interaction) in the kinematic region defined by Mll>50 GeV, Mjj>120 GeV, transverse momentum pTj>25 GeV, and pseudorapidity |ηj|<5, is found to be σEW(lljj)=174± 15(stat) ± 40(syst) fb, in agreement with the standard model prediction. The associated jet activity of the selected events is studied, in particular in a signal-enriched region of phase space, and the measurements are found to be in agreement with QCD predictions.

Click on a plot/table to get the pdf version of it.

Figures

Signal diagrams
Method I
Control distributions for Method I using di-muon events with two JPT jets. The contributions from the different background sources and the signal are shown stacked and data is super-imposed.
Method II
Simulation-based compatibility tests between the photon-based data-driven prediction for events with Mjj>750 GeV using the PF jet algorithm.The QCD γjj distribution contains the contribution from prompt and fake photons as estimated from simulation and it is compared to the simulated QCD Zjj sample. The bottom panel shows the ratio between the target distribution and the photon-based prediction. The estimated contributions to the uncertainty on the γ-based shape are shown separately in the bottom panel.
Distributions for the tag jets at pre-selection level. Both di-muon and di-electron plus two PF jets with Mjj>750 GeV events are used. The contributions from the different background sources and the signal are shown stacked and data is super-imposed. The bottom panels show the ratio of data to total prediction. The total uncertainty from the data-driven background prediction obtained from the photon control sample is shown as a shaded band in both the distribution and the bottom panel.
Measurements of the radiation patterns in multijet events in association with a Z boson
Study of the charged hadronic activity
Study of the third jet properties in a high purity region
Control distributions for the hadronic activity of events with Mjj>1250 GeV. For each distribution the insets show the result of the direct bin-by-bin background subtraction. The grey band in the bottom panels represents the total uncertainty assigned to the background.
Event display

Tables

Update: preliminary plots/tables of the paper to be submitted

Topic attachments
I Attachment History Action Size Date Who Comment
PDFpdf BDT_fit_Allystar.pdf r1 manage 17.9 K 2013-09-12 - 15:37 PedroSilva  
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PDFpdf Figure7_mumu_control.pdf r1 manage 45.8 K 2014-07-17 - 21:43 PedroSilva  
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PDFpdf Figure7_mumu_signal.pdf r1 manage 44.6 K 2014-07-17 - 21:43 PedroSilva  
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PDFpdf Figure8_mumu_signal.pdf r1 manage 43.1 K 2014-07-17 - 21:54 PedroSilva  
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PDFpdf Figure9_550to750.pdf r1 manage 46.2 K 2014-07-17 - 21:57 PedroSilva  
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PDFpdf Figure9_gt750.pdf r1 manage 46.5 K 2014-07-17 - 21:57 PedroSilva  
PNGpng Figure9_gt750.png r1 manage 51.9 K 2014-07-17 - 21:57 PedroSilva  
PDFpdf Mjj_fit_Allystar.pdf r1 manage 18.4 K 2013-09-12 - 15:37 PedroSilva  
PNGpng Mjj_fit_Allystar.png r1 manage 59.5 K 2013-09-12 - 12:51 PedroSilva  
PDFpdf Table1.pdf r1 manage 57.7 K 2013-09-12 - 13:07 PedroSilva  
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PDFpdf Table5_paper.pdf r1 manage 58.0 K 2014-07-17 - 21:26 PedroSilva  
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PNGpng bckg3_diagram.png r1 manage 15.2 K 2013-09-12 - 12:51 PedroSilva  
PDFpdf cosdPhi_vs_HT.pdf r1 manage 20.1 K 2013-09-12 - 15:36 PedroSilva  
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PDFpdf cosdPhi_vs_detajj.pdf r2 r1 manage 17.9 K 2013-09-12 - 23:14 PedroSilva  
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PDFpdf llmjjgt092_vbfcandjetdeta_closure.pdf r1 manage 18.3 K 2013-09-12 - 15:41 PedroSilva  
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PDFpdf mjjgt092_vbfcandjetdeta.pdf r1 manage 21.0 K 2013-09-12 - 15:43 PedroSilva  
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PDFpdf mjjgt092_vbfhardpt.pdf r1 manage 22.1 K 2013-09-12 - 15:43 PedroSilva  
PNGpng mjjgt092_vbfhardpt.png r1 manage 68.0 K 2013-09-12 - 13:47 PedroSilva  
PDFpdf nJets_vs_HT.pdf r1 manage 18.7 K 2013-09-12 - 15:36 PedroSilva  
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PDFpdf nJets_vs_detajj.pdf r2 r1 manage 17.7 K 2013-09-12 - 23:14 PedroSilva  
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PDFpdf rhophi.pdf r2 r1 manage 132.5 K 2013-09-12 - 17:43 PedroSilva  
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PDFpdf softHT3_vs_detajj.pdf r2 r1 manage 17.8 K 2013-09-12 - 23:14 PedroSilva  
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PDFpdf softHT3_vs_mjj.pdf r2 r1 manage 15.3 K 2013-09-12 - 23:14 PedroSilva  
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PDFpdf vbfz_diagram.pdf r1 manage 8.1 K 2013-09-12 - 15:46 PedroSilva  
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Topic revision: r9 - 2014-11-04 - PaoloAzzurri
 
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