Observation of Wγ and Zγ production at √s = 7 TeV

EWK-10-008

Abstract

We present the first measurement of Wγ and Zγ production in proton proton collisions at √s = 7 TeV, based on 36 inverse-picobarns of data recorded at the LHC by the CMS detector. The electron and muon decay channels of the W and Z are used. We measure the cross sections for the photon transverse energy ET(γ)>10 GeV and spatial separation from charged leptons ΔR(l,γ)>0.7. We find σ(pp → Wγ+X) B(W → l\nu) = 55.9 5.0 (stat.) 5.0 (syst.) 6.1 (lumi.) pb and σ(pp → Zγ+X) B(Z → ll) = 9.3 1.0 (stat.) 0.6 (syst.) 1.0 (lumi.) pb, in agreement with standard model predictions. We also set the first limits on anomalous WWγ, ZZγ, and Zγγ trilinear gauge couplings at √s = 7 TeV.

Approved plots

Data-driven background determinations, W channel

Wg_Combined_Background_EBEE.png

Data-driven background determinations, Z channel

Zg_Combined_Background_EBEE.png

Wγ signal

wgamma_etg.png

Zγ signal

zgamma_etg.png

First indication of radiation amplitude zero at the LHC

raz.png

The radiation amplitude zero (RAZ) in Wγ production, which is manifestation of the interference between the s and t amplitudes contributing to that process, is seen at the LHC as a dip around zero in the distribution of the lepton-charge-signed difference in pseudorapidity between the lepton and the photon.

M(ll) versus M(llγ)

Zg_banana.png

In this representation, three main components contributing to the di-lepton+photon signal are distinguished:

  • along the horizontal band at the Z mass: Z to leptons with FSR photon
  • along the vertical band at the Z mass: ISR photon and Z to leptons - where anomalous neutral gauge couplings can contribute
  • other events: radiative Drell-Yan pairs, either ISR or FSR

Constraints on anomalous triple gauge couplings

WWγ vertex

wwg.png

ZZγ and Zγγ vertices

zvg.png

-- GautierHamelDeMonchenault - 20-Mar-2011

Topic attachments
I Attachment History Action Size Date Who Comment
PDFpdf PhoEta.pdf r1 manage 15.2 K 2011-03-20 - 22:27 GautierHamelDeMonchenault  
PNGpng PhoEta.png r1 manage 30.7 K 2011-03-20 - 22:27 GautierHamelDeMonchenault  
PNGpng PhoPt_Barrel.png r1 manage 31.5 K 2011-03-20 - 22:26 GautierHamelDeMonchenault  
PDFpdf PhoPt_Endcap.pdf r1 manage 14.0 K 2011-03-20 - 22:26 GautierHamelDeMonchenault  
PNGpng PhoPt_Endcap.png r1 manage 31.6 K 2011-03-20 - 22:26 GautierHamelDeMonchenault  
PNGpng Wg_Combined_Background_EBEE.png r1 manage 29.2 K 2011-03-20 - 22:29 GautierHamelDeMonchenault  
PDFpdf Wg_Combined_Background_EBEE_Log.pdf r1 manage 11.1 K 2011-03-20 - 22:29 GautierHamelDeMonchenault  
PNGpng Wg_Combined_Background_EBEE_Log.png r1 manage 28.7 K 2011-03-20 - 22:29 GautierHamelDeMonchenault  
PDFpdf WgammaYields_combined.pdf r1 manage 27.9 K 2011-03-20 - 22:16 GautierHamelDeMonchenault  
PNGpng WgammaYields_combined.png r1 manage 29.1 K 2011-03-20 - 22:16 GautierHamelDeMonchenault  
PDFpdf ZGtoEEG_Bkg.pdf r1 manage 15.6 K 2011-03-20 - 22:12 GautierHamelDeMonchenault  
PNGpng ZGtoEEG_Bkg.png r1 manage 21.0 K 2011-03-20 - 22:11 GautierHamelDeMonchenault  
PDFpdf ZGtoEEG_Bkg_StatSyst.pdf r1 manage 15.6 K 2011-03-20 - 22:11 GautierHamelDeMonchenault  
PNGpng ZGtoEEG_Bkg_StatSyst.png r1 manage 21.0 K 2011-03-20 - 22:11 GautierHamelDeMonchenault  
PDFpdf ZGtoEEG_Eta.pdf r1 manage 14.7 K 2011-03-20 - 22:11 GautierHamelDeMonchenault  
PNGpng ZGtoEEG_Eta.png r1 manage 21.8 K 2011-03-20 - 22:10 GautierHamelDeMonchenault  
PDFpdf ZGtoEEG_Mee.pdf r1 manage 14.6 K 2011-03-20 - 22:10 GautierHamelDeMonchenault  
PNGpng ZGtoEEG_Mee.png r1 manage 28.7 K 2011-03-20 - 22:09 GautierHamelDeMonchenault  
PDFpdf ZGtoEEG_Meeg.pdf r1 manage 15.6 K 2011-03-20 - 22:09 GautierHamelDeMonchenault  
PNGpng ZGtoEEG_Meeg.png r1 manage 28.4 K 2011-03-20 - 22:09 GautierHamelDeMonchenault  
PDFpdf Zg_Combined_Background_EBEE.pdf r1 manage 11.5 K 2011-03-20 - 22:31 GautierHamelDeMonchenault  
PNGpng Zg_Combined_Background_EBEE.png r1 manage 29.4 K 2011-03-20 - 22:31 GautierHamelDeMonchenault  
PDFpdf Zg_Combined_Background_EBEE_Log.pdf r1 manage 11.0 K 2011-03-20 - 22:32 GautierHamelDeMonchenault  
PNGpng Zg_Combined_Background_EBEE_Log.png r1 manage 30.2 K 2011-03-20 - 22:32 GautierHamelDeMonchenault  
PDFpdf Zg_banana.pdf r1 manage 1042.4 K 2011-03-20 - 22:13 GautierHamelDeMonchenault  
PNGpng Zg_banana.png r1 manage 68.0 K 2011-03-20 - 22:12 GautierHamelDeMonchenault  
PDFpdf ZgammaYields_combined.pdf r1 manage 26.6 K 2011-03-20 - 22:14 GautierHamelDeMonchenault  
PNGpng ZgammaYields_combined.png r1 manage 28.2 K 2011-03-20 - 22:14 GautierHamelDeMonchenault  
PDFpdf Zgmass.pdf r1 manage 6.3 K 2011-03-20 - 22:12 GautierHamelDeMonchenault  
PNGpng Zgmass.png r1 manage 25.8 K 2011-03-20 - 22:12 GautierHamelDeMonchenault  
PDFpdf Zmass.pdf r1 manage 6.3 K 2011-03-20 - 22:07 GautierHamelDeMonchenault  
PNGpng Zmass.png r1 manage 26.9 K 2011-03-20 - 22:07 GautierHamelDeMonchenault  
PNGpng pfMET.png r1 manage 34.0 K 2011-03-20 - 22:21 GautierHamelDeMonchenault  
PDFpdf pfMT.pdf r1 manage 17.2 K 2011-03-20 - 22:20 GautierHamelDeMonchenault  
PNGpng pfMT.png r1 manage 36.0 K 2011-03-20 - 22:20 GautierHamelDeMonchenault  
PDFpdf pfmet_sihih.pdf r1 manage 13.1 K 2011-03-20 - 22:20 GautierHamelDeMonchenault  
PNGpng pfmet_sihih.png r1 manage 30.9 K 2011-03-20 - 22:20 GautierHamelDeMonchenault  
PNGpng photonPt_ee.png r1 manage 19.6 K 2011-03-20 - 22:19 GautierHamelDeMonchenault  
PDFpdf raz.pdf r1 manage 11.4 K 2011-03-20 - 22:17 GautierHamelDeMonchenault  
PNGpng raz.png r1 manage 25.1 K 2011-03-20 - 22:17 GautierHamelDeMonchenault  
PDFpdf wgamma_etg.pdf r1 manage 13.1 K 2011-03-20 - 22:29 GautierHamelDeMonchenault  
PNGpng wgamma_etg.png r1 manage 33.3 K 2011-03-20 - 22:29 GautierHamelDeMonchenault  
PDFpdf wwg.pdf r1 manage 9.3 K 2011-03-20 - 22:16 GautierHamelDeMonchenault  
PNGpng wwg.png r1 manage 26.6 K 2011-03-20 - 22:15 GautierHamelDeMonchenault  
PDFpdf zgamma_etg.pdf r1 manage 11.3 K 2011-03-20 - 22:15 GautierHamelDeMonchenault  
PNGpng zgamma_etg.png r1 manage 36.1 K 2011-03-20 - 22:15 GautierHamelDeMonchenault  
PDFpdf zvg.pdf r1 manage 10.5 K 2011-03-20 - 22:08 GautierHamelDeMonchenault  
PNGpng zvg.png r1 manage 33.6 K 2011-03-20 - 22:08 GautierHamelDeMonchenault  
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Topic revision: r1 - 2011-03-20 - GautierHamelDeMonchenault
 
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