WW  e ν 14 April 2007 APS April Meeting WW/WZ production in electron-neutrino plus dijet final state at CDFAPS April Meeting April 2007 Jacksonville, FL Anna Sfyrla (CDF Collaboration) University of Geneva, Switzerland

WW  e ν 14 April 2007 APS April Meeting WW/WZ Production 2 WW Production WZ Production WW/WZ observed so far only in the fully leptonic decay channel, in hadron colliders Aim of this analysis the observation in the semi-leptonic channel! X-Section Measurement comparison with SM theoretical predictions Triple gauge couplings (WWZ/ γ ) favorable channel for the triple gauge couplings due to the big branching ratio with respect to the leptonic channel Significant background for other interesting processes ex. H  WW Channel topologically similar to WH  l ν bb techniques developed in this analysis are also applicable there

WW  e ν 14 April 2007 APS April Meeting The CDF Detector A general purpose detector at TeV, FNAL Designed with the classic layered structure Central EM Calorimeter Central Outer Tracker (Drift Chambers) Central Inner Tracker (Silicon) Forward Calorimeter Muon Chambers Central Hadronic Calorimeter Main objects in this analysis Electrons Reconstructed in the Central EM Calorimeter using tracking information Neutrinos Missing transverse energy Jets Reconstructed in the calorimeter 3

WW  e ν 14 April 2007 APS April Meeting Event Selection & Backgrounds σ WW *BR = 12.4 pb *0.146 = 1.81 pb σ WZ *BR = 3.96 pb *0.07 = 0.28 pb σ W(e)jj = pb Signal/Background initially very poor Signal Definition Exactly 1 Central Electron Missing Transverse Energy > 25 GeV 2 or more Jets (P T >15GeV) Similar Event Topology (Backgrounds) W  e ν + jets W  τν + jets Z  ee + jets QCD t-tbar 4 W/Z W e ν jet

WW  e ν 14 April 2007 APS April Meeting Neural Network VAR 6 VAR 4 VAR 2 VAR 1 NN OUT 0 1 Analysis methodology – 1. Maximum Significance Gain [Significance = S/  (S+B)] Dijet Inv. Mass AFTER NN CUT INITIALLY Very Poor S/B VAR 3 VAR 5 5

WW  e ν 14 April 2007 APS April Meeting Dijet Inv. Mass Signal shape fixed using MC Background parameterization motivated by MC Both plugged into a likelihood fitter Background parameters and signal fraction given by likelihood fit to data Dijet Inv. Mass Overall parameterization  f s * ψ (x) + (1-f s )* φ (x) -2logQ CLs method A L Read 2002 J. Phys. G: Nucl. Part. Phys used to give the sensitivity of the analysis and the significance of the measurement 6 Analysis methodology – 2. S+B Hypothesis B-Only Hypothesis

WW  e ν 14 April 2007 APS April Meeting 7 Dijet invariant mass before NN training Overall S/  (S+B)=3. Signal region S/  (S+B)=3.5 Signal Region (MC) Signal Region

WW  e ν 14 April 2007 APS April Meeting 8 NN training JETNETNN Point of Maximum Significance Gain Signal BGR NN Input angles or angle-related variables NN Output as less correlated to the dijet invariant mass as possible

WW  e ν 14 April 2007 APS April Meeting 9 Gain of ~20% in significance!! Overall S/  (S+B)=3.4 Signal region S/  (S+B)=4.2 Signal Region Dijet invariant mass after NN training Expected significance ~4 σ

WW  e ν 14 April 2007 APS April Meeting Likelihood fit to data 10 P-value: ~ σ significance

WW  e ν 14 April 2007 APS April Meeting Measured Numbers Having used 1.29 fb -1 of data Measured Number of WW/WZ Events (m jj  [40,160]GeV) 266 ± 173 (stat) ± 40 (sys) Cross section (m jj  [40,160]GeV) σ  BR = (1.45 ± 0.95 (stat) ± 0.29 (sys)) pb Theoretical σ  BR = 2.1 ± 0.2 pb [BR : (W  e ν,W/Z  jj) ] 95%CL upper limit σ  BR(W  e ν,W/Z  jj) < 3.4 pb 11 Signal Fraction Jet Energy Scale10% Jet Resolution10% Background Shape3% Acceptance Jet Energy Scale3% ISR2% FSR10% W leptonic3% Cross section Total Signal Fraction15% Total Acceptance11% Luminosity6% Total Cross Section20% Systematics Summary

WW  e ν 14 April 2007 APS April Meeting Summary A search for WW/WZ in the semi-leptonic decay channel has been presented, using 1.29 fb -1 of the CDF data So far in the analysis Central electrons have been used in the lepton selection & the event selection is optimized with the use of a Neural Network A 2.7 σ significance measurement has been performed The measurement is statistically limited at this stage Next Steps in the analysis There is a lot of potential for improvement! Adding muons and forward electrons in the event selection and adding more data, the event yield can be more than doubled, introducing a large factor in the significance! Search for Anomalous Gauge Couplings will follow 12

WW  e ν 14 April 2007 APS April Meeting Backup

WW  e ν 14 April 2007 APS April Meeting DATA-MC agreement - NN output Point of Maximum Significance Gain 14