EWK-10-008 Observation of W-gamma and Z-gamma final states

Abstract

We present the first measurement of Wγ and Zγ production in proton proton collisions at √s = 7 TeV, based on 36.1 pb⁻¹ 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 E_T^γ > 10 GeV and spatial separation from charged leptons ΔR(μ, γ) > 0.7. We find σ(pp → Wγ + X) × B(W → lν) = 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.

Main Caltech Contributions

• Group Skims
• Analysis Framework
• Photon energy scale and resolution from Z→μμγ
• Extraction of the aTGC limits
• Electron and muon Trigger Look-Up Tables

Results

• 2D aTGC limits:
  

• 1D aTGC limits:
  

• Wgamma photon Et spectrum:
  

• Zgamma photon Et spectrum:
  

• Radiation Amplitude Zero:
  

• Wgamma cross-section systematics:
  

• Zgamma cross-section systematics:
  

• m(llg) versus m(ll):
  

• Data-driven background estimate:
  

Important links and documents

• CADI page
• EWK-10-008 Full-text
• AN-10-279
• Material for Approval
• Twiki

Timeline

• Pre-Approval: Jan 25 in the EWK meeting, Slides
• Pre-approved on Jan 27, see Michael's message
• Approval: Feb. 23, in the General Meeting,approved
• CWR End: March 25
• As of March 6, responding to CWR comments before the Final Reading

-- Main.veverka - 2011-04-07