First measurement of the polarization of W bosons with large transverse momentum in W+jets events at a pp collider

Abstract

The first measurement of the polarization of W bosons with large transverse momentum at a proton-proton collider is presented. The measurement is based on 36 inverse-picobarns of data recorded at √s = 7 TeV by the Compact Muon Solenoid detector at the LHC. Using both decays to electrons and muons, W bosons with a transverse momentum larger than 50 GeV are used to determine the left-handed, right-handed and longitudinal polarisation fractions (fL, fR, f0). We find (fL-fR)- = 0.226 0.031 (stat.) 0.050 (syst.) and f0- = 0.162 0.078 (stat.) 0.136 (syst.) for negatively charged W bosons and (fL-fR)+ = 0.300 0.031 (stat.) 0.034 (syst.) and f0+ = 0.192 0.075 (stat.) 0.089 (syst.) for positively charged W bosons. This establishes for the first time that W bosons produced in pp collisions are predominantly left-handed, as predicted by the Standard Model.

Approved plots

distribution of the LP variable for electrons

electron_MC_WHelicityFramePlots_MinusICVar.png

electron_MC_WHelicityFramePlots_PlusICVar.png

distribution of the LP variable for muons

muon_MC_WHelicityFramePlots_MinusICVar.png

muon_MC_WHelicityFramePlots_PlusICVar.png

electron results

electron_contour_minus.pngelectron_contour_plus.png

muon results

muon_contour_minus.pngmuon_contour_plus.png

Combined results

combined_contour_minus.pngcombined_contour_plus.png

-- GautierHamelDeMonchenault - 19-Mar-2011

Topic attachments
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PDFpdf combined_contour_minus.pdf r1 manage 42.4 K 2011-03-19 - 23:38 GautierHamelDeMonchenault  
PNGpng combined_contour_minus.png r1 manage 49.8 K 2011-03-19 - 23:37 GautierHamelDeMonchenault  
PDFpdf combined_contour_plus.pdf r1 manage 42.4 K 2011-03-19 - 23:28 GautierHamelDeMonchenault  
PNGpng combined_contour_plus.png r1 manage 49.8 K 2011-03-19 - 23:29 GautierHamelDeMonchenault  
PDFpdf electron_MC_WHelicityFramePlots_MinusICVar.pdf r1 manage 17.6 K 2011-03-19 - 23:38 GautierHamelDeMonchenault  
PNGpng electron_MC_WHelicityFramePlots_MinusICVar.png r1 manage 32.4 K 2011-03-19 - 23:39 GautierHamelDeMonchenault  
PDFpdf electron_MC_WHelicityFramePlots_PlusICVar.pdf r1 manage 17.5 K 2011-03-19 - 23:39 GautierHamelDeMonchenault  
PNGpng electron_MC_WHelicityFramePlots_PlusICVar.png r1 manage 32.7 K 2011-03-19 - 23:39 GautierHamelDeMonchenault  
PDFpdf electron_contour_minus.pdf r1 manage 42.1 K 2011-03-19 - 23:41 GautierHamelDeMonchenault  
PNGpng electron_contour_minus.png r1 manage 49.9 K 2011-03-19 - 23:41 GautierHamelDeMonchenault  
PDFpdf electron_contour_plus.pdf r1 manage 42.4 K 2011-03-19 - 23:42 GautierHamelDeMonchenault  
PNGpng electron_contour_plus.png r1 manage 50.3 K 2011-03-19 - 23:42 GautierHamelDeMonchenault  
PDFpdf muon_MC_WHelicityFramePlots_MinusICVar.pdf r1 manage 17.0 K 2011-03-19 - 23:40 GautierHamelDeMonchenault  
PNGpng muon_MC_WHelicityFramePlots_MinusICVar.png r1 manage 30.0 K 2011-03-19 - 23:40 GautierHamelDeMonchenault  
PDFpdf muon_MC_WHelicityFramePlots_PlusICVar.pdf r1 manage 17.0 K 2011-03-19 - 23:40 GautierHamelDeMonchenault  
PNGpng muon_MC_WHelicityFramePlots_PlusICVar.png r1 manage 30.2 K 2011-03-19 - 23:40 GautierHamelDeMonchenault  
PDFpdf muon_contour_minus.pdf r1 manage 42.4 K 2011-03-19 - 23:43 GautierHamelDeMonchenault  
PNGpng muon_contour_minus.png r1 manage 49.7 K 2011-03-19 - 23:43 GautierHamelDeMonchenault  
PDFpdf muon_contour_plus.pdf r1 manage 42.4 K 2011-03-19 - 23:43 GautierHamelDeMonchenault  
PNGpng muon_contour_plus.png r1 manage 49.7 K 2011-03-19 - 23:44 GautierHamelDeMonchenault  
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Topic revision: r1 - 2011-03-20 - GautierHamelDeMonchenault
 
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