EWK-10-008 < Main

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

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---++ Abstract
We present the first measurement of W&gamma; and Z&gamma; production in proton proton collisions at &radic;s = 7 !TeV, based on 36.1 pb<sup>&#8722;1</sup> 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<sub>T</sub><sup>&gamma;</sup> > 10 !GeV and spatial separation from charged leptons &Delta;R(&mu;, &gamma;) > 0.7. We find &sigma;(pp &rarr; W&gamma; + X) &times; B(W &rarr; l&nu;) = 55.9 ± 5.0 (stat.) ± 5.0 (syst.) ± 6.1 (lumi.) pb and &sigma;(pp &rarr; Z&gamma; + X) &times; B(Z &rarr; 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 WW&gamma;, ZZ&gamma;, and Z&gamma;&gamma; trilinear gauge couplings at &radic;s = 7 !TeV.

---++ Main Caltech Contributions
   * [[https://twiki.cern.ch/twiki/bin/view/CMS/VGammaFirstPaper#Vgamma_Group_Skims][Group Skims]]
   * [[https://twiki.cern.ch/twiki/bin/view/CMS/VGammaFramework][Analysis Framework]]
   * Photon energy scale and resolution from Z&rarr;&mu;&mu;&gamma;
   * Extraction of the aTGC limits
   * [[https://twiki.cern.ch/twiki/bin/view/CMS/VGammaFirstPaper#Electron_Trigger_Look_up_Tables][Electron]] and [[https://twiki.cern.ch/twiki/bin/view/CMS/VGammaFirstPaper#W_munu_gamma][muon]] Trigger Look-Up Tables

---++ Results
   * 2D aTGC limits: <br />
     <img src="%ATTACHURLPATH%/fig6_aTGC_limits.png" alt="fig6_aTGC_limits.png" width='783' height='421' />

   * 1D aTGC limits: <br />
     <img src="%ATTACHURLPATH%/table3_aTGC_limits.png" alt="table3_aTGC_limits.png" width='622' height='110' />

   * Wgamma photon Et spectrum: <br />
     <img src="%ATTACHURLPATH%/fig2_phoEt_aTGC.png" alt="fig2_phoEt_aTGC.png" width='769' height='580' />

   * Zgamma photon Et spectrum: <br />
     <img src="%ATTACHURLPATH%/fig3_phoEt_aTGC_Z.png" alt="fig3_phoEt_aTGC_Z.png" width='769' height='555' />

   * Radiation Amplitude Zero: <br />
     <img src="%ATTACHURLPATH%/fig4_raz.png" alt="fig4_raz.png" width='780' height='584' />

   * Wgamma cross-section systematics: <br />
     <img src="%ATTACHURLPATH%/table1_Wsystematics.png" alt="table1_Wsystematics.png" width='759' height='506' />

   * Zgamma cross-section systematics: <br />
     <img src="%ATTACHURLPATH%/table2_Zsystematics.png" alt="table2_Zsystematics.png" width='704' height='380' />

   * m(llg) versus m(ll): <br />
     <img src="%ATTACHURLPATH%/fig5_m2_vs_m3.png" alt="fig5_m2_vs_m3.png" width='800' height='550' />

   * Data-driven background estimate: <br />
     <img src="%ATTACHURLPATH%/fig1_photonEt.png" alt="fig1_photonEt.png" width='797' height='391' />

---++ Important links and documents
   * [[http://cms.cern.ch/iCMS/analysisadmin/cadi?ancode=EWK-10-008][CADI page]]
   * [[http://cms.cern.ch/iCMS/analysisadmin/paperversions?analysis=EWK-10-008][EWK-10-008 Full-text]]
   * [[http://cms.cern.ch/iCMS/jsp/db_notes/showNoteDetails.jsp?noteID=CMS%20AN-2010/279][AN-10-279]]
   * [[https://twiki.cern.ch/twiki/bin/view/CMS/VGammaMaterialForApproval][Material for Approval]]
   * [[https://twiki.cern.ch/twiki/bin/viewauth/CMS/VGammaFirstPaper][Twiki]]

---++ Timeline
   * *Pre-Approval*: Jan 25 in the [[http://indico.cern.ch/conferenceDisplay.py?confId=122337][EWK meeting]], [[https://twiki.cern.ch/twiki/pub/CMS/VGammaFirstPaperReview/VG_preapproval_20110125.pdf][Slides]]
   * Pre-approved on Jan 27, see [[https://hypernews.cern.ch/HyperNews/CMS/get/EWK-10-008/8.html][Michael's message]]
   * *Approval*: Feb. 23, in the [[http://indico.cern.ch/conferenceDisplay.py?confId=123701][General Meeting]],[[https://hypernews.cern.ch/HyperNews/CMS/get/EWK-10-008/34.html][approved]]
   * *CWR* End: March 25
   * As of March 6, responding to CWR comments before the Final Reading


-- Main.veverka - 2011-04-07

Attachments

Topic attachments
I	Attachment	History	Action	Size	Date	Who	Comment
png	fig1_photonEt.png	r1	manage	67.3 K	2011-04-07 - 19:50	UnknownUser	Data-driven background estimate
png	fig2_phoEt_aTGC.png	r1	manage	83.3 K	2011-04-07 - 19:53	UnknownUser	Wgamma photon Et spectrum
png	fig3_phoEt_aTGC_Z.png	r1	manage	71.4 K	2011-04-07 - 19:54	UnknownUser	Zgamma photon Et spectrum
png	fig4_raz.png	r1	manage	61.0 K	2011-04-07 - 19:54	UnknownUser	Radiation Amplitude Zero
png	fig5_m2_vs_m3.png	r1	manage	135.8 K	2011-04-07 - 19:55	UnknownUser	m(llg) versus m(ll)
png	fig6_aTGC_limits.png	r1	manage	57.6 K	2011-04-07 - 19:56	UnknownUser	2D aTGC limits
png	table1_Wsystematics.png	r1	manage	78.9 K	2011-04-07 - 19:57	UnknownUser	Wgamma cross-section systematics
png	table2_Zsystematics.png	r1	manage	57.8 K	2011-04-07 - 19:58	UnknownUser	Zgamma cross-section systematics
png	table3_aTGC_limits.png	r1	manage	24.1 K	2011-04-07 - 19:58	UnknownUser	1D aTGC limits

Topic revision: r8 - 2011-05-17 - veverka

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