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Physics with W+jets at CDF towards better understanding of W+2jet process, with regard to the dijet resonant peak Koji Sato on behalf of CDF Collaboration KEK Theory Meeting on Particle Physics Phenomenology February 29, 2012 Slide 2 Contents Slide 3 INTRODUCTION Tevatron Accelerator and the CDF Experiment Slide 4 Tevatron Run II Slide 5 Tevatron Termination Tevatrons last beam was terminated on Sep 30, 2011. Slide 6 Tevatron Run II Luminosity History Typical Peak Luminosity : 4 10 32 cm 2 s -1. 8 pb -1 /week. Total Integrated Luminosity: Delivered: 11.8 fb -1. Recorded by CDF: 9.98 fb -1. 8.86 fb -1 with good silicon. Typical data taking efficiency of CDF: ~ 85% to the end. No significant drop after 10 years of running!! (CDF) Slide 7 Collider Detector at Fermilab Multi-purpose detector Tracking in 1.4 T magnetic field. Coverage | | WW/WZ Production in l jj Decay Mode Autumn 2009 analysis using 4.3 fb -1. e/ with Pt>20 GeV, | |25 GeV. 2 jets with Et>20GeV, | |30 GeV. (MET,j1)>0.4. Pt(jj)>40 GeV. Measured cross section: (WW+WZ)= 18.13.3(stat.) 2.5(syst) 1.1 Slide 12 DIJET MASS SPECTRUM IN W+2JETS Overview of the analysis and 4.3 fb -1 results Slide 13 Jet Definition Jets are clustered using JETCLU algorithm with R Dijet Mass Spectrum in l jj Final State Spring 2011 analysis using 4.3 fb -1. e/ with Pt>20 GeV, | |25 GeV. 2 jets with Et>30 GeV, | |30 GeV. (MET,j1)>0.4. Pt(jj)>40 GeV. An excess is seen. The W mass peak around 80 GeV does NOT look to be described very well. CDFs usual cut: Et jet >20 GeV Slide 18 Systematic Uncertainties Slide 19 Dijet Mass Spectrum in l jj Final State Spring 2011 analysis using 4.3 fb -1. e/ with Pt>20 GeV, | |25 GeV. 2 jets with Et>30GeV, | |30 GeV. (MET,j1)>0.4. Pt(jj)>40 GeV. An excess is seen. 3.2 deviation from estimated background, after considering the systematic uncertainties on background modeling. Slide 20 4.3 fb -1 with Different Cuts Jet Et>65 GeV Pt(jj)>40 GeV Jet Et>30 GeV Pt(jj)>40 GeV (nominal selection) Jet Et>30 GeV Pt(jj)>60 GeV Slide 21 A Web Post at CMS http://cmsdoc.cern.ch/~ttf/CDFDiJetScale/AnimatedDijet.gif Scale the background M jj distribution by up to 7%. The excess goes away if a 5% scale is assumed. In CDF analysis, JES shape uncertainty is considered in the final fit. However, this method will end up with 10% discrepancy in overall normalization. Author not known. I didnt find a description about this plot, either. We will revisit this plot later. Slide 22 STUDIES ON W+2JETS PROPERTIES Summer 2011 update with 7.3 fb -1 Slide 23 Summer 2011 update Summer 2011 update using 7.3 fb -1. Excess corresponding to 4 pb. Statistically 4.7 deviation from estimated background. 4.1 even when we consider systematic effect. D0 did not see such an excess. Slide 24 M jj Distribution by Lepton Type Electron:Muon: Slide 25 Some Kinematics 1 Slide 26 Some Kinematics 2 Slide 27 Some Kinematics 3 Slide 28 Some Kinematics 4 Slide 29 Crosscheck - Jet Energy Scale Largest systematic source, considered in the fit. Shifted JES by +2 which corresponds to a shift by 7% for the left plot. We still see a notable excess 4.1 . Plus, JES wont explain the discrepancy in angular distributions. Slide 30 Crosscheck Alternative Generator With alternative W+jets modeling with Sherpa 1.2.2. Slide 31 NLO Effect (4.3 fb -1 analysis) Ratio between MCFM and ALPGEN+PYTHIA was calculated as a function of M jj. Reweight ALPGEN sample by the obtained ratio. This procedure returned a statistical significance of 3.4 3.2 with nominal analysis . Slide 32 First pretag W+2jets analysis after the anomaly Slide 33 SM Higgs Search Status at CDF/Tevatron (these results will be updated very very soon) CDF excludes 156.5 < m H < 173.7 GeV/c 2 at 95% C.L. Tevatron excludes 156 < m H < 177 GeV/c 2 at 95% C.L. Slide 34 SM Higgs Properties at Tevatron bbWW mH135 GeV (high mass): Easiest to look for HWW with one or two W decaying to lepton. Slide 35 CDF Analyses Slide 36 Event Selection and Reconstruction Event selection: e/ with Pt>20 GeV, | |20 GeV. 2 jets with Et>20GeV, | |