3rd Grenoble Top Workshop – October 25, 2008 Top Properties at Tevatron Run II 3rd Top Workshop _ Charles Plager UCLA For the CDF and DØ Collaborations Charles Plager 3rd Grenoble Top Workshop – October 25, 2008

New Era of Top Precision Physics! CDF and DØ now have more than forty (40 !!!) times as much integrated luminosity as we did when we discovered the top quark in Run I! With the data we have recorded, we are now able to have large, very pure top samples. For example, of the almost 50 results that CDF sent to the winter conferences, more than half were in top physics! Double B-Tag Lepton + Jets Candidates Charles Plager 3rd Grenoble Top Workshop – October 25, 2008

A Quick Note About Scale at the Tevatron Cross Sections at Ös = 1.96 TeV For those not intimately familiar with Tevatron high pT Physics: Top: 1 in 10 Billion Reducing and understanding backgrounds is the key. Charles Plager 3rd Grenoble Top Workshop – October 25, 2008

3rd Grenoble Top Workshop – October 25, 2008 Top Quark Review Fundamental question: Is it the truth, the Standard Model (SM) truth, and nothing but the truth? Did we really find the top quark? Is it the SM top quark? Is it only the SM top quark? The top quark is an ideal place to look for Beyond the Standard Model Physics! - tt Pair Lepton + Jets Decay _ Charles Plager 3rd Grenoble Top Workshop – October 25, 2008

What Can We Study About Top Quarks? _ Branching ratios Rare decays Non-SM decays Decay kinematics W helicity |Vtb| Top physics is very rich. Production cross section Production mechanism Resonance production Production kinematics Spin polarization Top charge Top spin Top mass Top width In today’s talk. Public Tevatron analyses. Charles Plager 3rd Grenoble Top Workshop – October 25, 2008

3rd Grenoble Top Workshop – October 25, 2008 Top Pair Decay Modes According to the SM, top quarks almost (?) always decay to Wb. When classifying the decay modes, we use the W decay modes: Leptonic Light leptons (e or ) Tauonic () Hadrons Charles Plager 3rd Grenoble Top Workshop – October 25, 2008

Top Pair Cross Section Measurements Why measure cross section? Theory has precise estimate(s - see next slide). New physics will affect different modes differently. E.g., t ! H+ b, H+ !   decay is not equally well reconstructed in all decay modes. Important to check assumptions and tools With b tagging, using neural net, etc. Need to understand sample composition for properties measurements. Cross section formula: Where: - number of observed events, - background estimate. - geometric acceptance, reconstruction efficiencies (e.g., lepton ID, b-tagging), and relevant branching fractions (e.g., W decays). - integrated luminosity. Charles Plager 3rd Grenoble Top Workshop – October 25, 2008

Theoretical Top Pair Cross Section Easy Question: What is the theory cross section for top pair production at the Tevatron (√s = 1.96 TeV)? Not-as-easy Answer: Depends on (in descending order of importance): Top mass. NLO vs NNLO parton distribution functions (PDF). Who you ask. NLO PDF and 175 GeV top mass: 6.7 pb. World average top mass !172.5 GeV ) +0.5 to +0.6 pb. NLO ! NNLO PDF: ) +0.2 to +0.3 pb. Cacciari et al. ! Kidonakis and Vogt: ) +0.1 pb. Charles Plager 3rd Grenoble Top Workshop – October 25, 2008

Lepton + Jets ANN Cross Section 7 input variables. Most sensitive variables: ∑ ET jets for ≥ 3rd jet HT (scalar sum of ET) Event selection: ≥ 3 jets 1 high pT electron or muon. High missing ET (consistent with missing  from W decay). No b tagging requirement. S ET ||max HT Charles Plager 3rd Grenoble Top Workshop – October 25, 2008

3rd Grenoble Top Workshop – October 25, 2008 ANN Cross Section Signal estimate from fit to Neural Network output. Dominant systematic uncertainties: QCD (multijet) modelling Parton Shower model Charles Plager 3rd Grenoble Top Workshop – October 25, 2008

Lepton +  Cross Section Selection requires 1 , 1 light lepton, and two high pT jets At least one jet identified b-tagged.  selection Three types: 1 track, no EM calorimeter clusters  ! - t 1 track, with EM clusters  ! - t + n 0 2 or more tracks  ! - - + t + n 0 Neural net designed to select real  s. One for each type Variables:  track quantities Hadronic and EM calorimeter energies Shower shapes Separate NN trained to reject electrons for type 2  s. Charles Plager 3rd Grenoble Top Workshop – October 25, 2008

Lepton +  Kinematic Results World’s Best Lepton +  Measurement! Charles Plager 3rd Grenoble Top Workshop – October 25, 2008

Top Pair Production Mechanism SM theory predicts 15% of top pair production from glue-glue annihilation. How can we determine the fraction?  between leptons in dilepton sample. Event kinematics e.g., cos (*), top quark speed () Use NN with lepton + jets sample Track density of tracks not in jets. Gluon jets have more associated tracks. Use lepton + jets sample Charles Plager 3rd Grenoble Top Workshop – October 25, 2008

Production Mechanism Results Dilepton result: Very statistics limited! Lepton + jets combination World’s First Dilepton Measurement! World’s Most Precise Measurement! Charles Plager 3rd Grenoble Top Workshop – October 25, 2008

W Helicity Examines the nature of the tWb vertex, probing the structure of weak interactions at energy scales near the Electro-Weak Symmetry Breaking scale. Stringent test of V-A interaction in SM. Standard Model expectations: F0 = 0.7, F- = 0.3, and F+ = 0.0 V+A is Suppressed in the SM W- left-handed fraction F- = 0.3 t b W +1/2 -1/2 +1 W+ right-handed fraction F+ = 0.0 t W b +1/2 +1 -1/2 t W0 longitudinal fraction F0 = 0.7 W +1/2 b W Charles Plager 3rd Grenoble Top Workshop – October 25, 2008

3rd Grenoble Top Workshop – October 25, 2008 W Helicity Uses both dilepton and lepton + jets channels. Reconstruct cos (*) for leptonic W decays. Use: Kinematic fitter (LJ) Lepton pT (dilepton) Use hadronic W decay as well. We do not know which jet is from up-type quark decay, but can reconstruct | cos (*) | . Charles Plager 3rd Grenoble Top Workshop – October 25, 2008

3rd Grenoble Top Workshop – October 25, 2008 W Helicity Results Charles Plager 3rd Grenoble Top Workshop – October 25, 2008

3rd Grenoble Top Workshop – October 25, 2008 W Helicity Results Combines to CDF measurements, both using lepton + jets channel. Charles Plager 3rd Grenoble Top Workshop – October 25, 2008

Search for tt Resonances _ Search for tt Resonances Uses lepton + jets event selection: High pT lepton Missing transverse energy B-tag. Invariant mass reconstruction: Assume pT = MET Solve for Pz assuming W mass. Allows for events with less than three jets. Charles Plager 3rd Grenoble Top Workshop – October 25, 2008

Search for tt Resonances _ Search for tt Resonances For Z’ limits, assuming a lepto-phobic Z’ Br (Z’ ! tt) = 100% _ World’s Most Precise Measurement! Charles Plager 3rd Grenoble Top Workshop – October 25, 2008

Search for Invisible Top Decays It is the relative reconstruction efficiency  acceptance that determines the relative yield. is the relative acceptance when one top decays to the Wb while the other decays to the new decay, XY. is the relative acceptance when both top quarks decays to the new decay, XY. Compare expected yield to observed number of candidate events. Create Feldman-Cousins acceptance bands using number of observed events. t ! Zc, t ! gc, t ! c, t ! Invisible. What do we mean by “invisible?” Not (well) reconstructed as double b-tag lepton + jets. What would happen if there were a large branching fraction to an invisible decay? For example, Br (t ! Invisible) = 10%? Br (t ! Wb) = 90% P (tt ! Wb Wb) = 81% ) For a purely invisible decay, we should have an 19% deficit when we look at the L + J event yield for a given theoretical cross section. XY Charles Plager 3rd Grenoble Top Workshop – October 25, 2008

Feldman-Cousins Acceptance Bands Charles Plager 3rd Grenoble Top Workshop – October 25, 2008

Search for Invisible Top Decays Theory cross section from Cacciari et al. (hep-ph: 0804.2800) assuming CTEQ PDFs. World’s First Measurement! Charles Plager 3rd Grenoble Top Workshop – October 25, 2008

Search for the Top FCNC Decay t → Zq Top FCNC extremely rare in the SM: B(t → Zq) = O(10–14) Beyond SM: B(t → Zq) up to O(10–4), Any signal at Tevatron or LHC: New Physics. Signature: tt → Wb Zq (Z + ≥4 Jet). Dominant SM background: SM Z + Jets. Charles Plager 3rd Grenoble Top Workshop – October 25, 2008

Search for t → Zq: Ingredients ’ Charles Plager 3rd Grenoble Top Workshop – October 25, 2008

Search for t → Zq: Results Analysis method: Simultaneously fit mass 2 in 3 regions: Signal (B-tagged and Anti b-Tagged) Control ) Constrain shape & normalization of Z + jets background. Data compatible with background only. Feldman-Cousins limit with systematic uncertainties: 3.5 times better than best published limit (L3). World’s Best Measurement! Charles Plager 3rd Grenoble Top Workshop – October 25, 2008

3rd Grenoble Top Workshop – October 25, 2008 Looking Forward Top quark physics is becoming precision field. Almost all analyses (except mass) are still statistics limited. So far, most (but not all) things are frustratingly consistent with the SM. CDF and DØ each have many of the world’s best measurments: http://www-cdf.fnal.gov/ physics/new/top/top.html http://www-d0.fnal.gov/Run2Physics/ WWW/results/top.htm MZ’ (leptophobic) > 760 GeV (95% C.L.) Br (t ! Zq) < 3.7% (95% C.L.) Br (t ! Invisible) < 9% (95% C.L.) fgg < 38% (95% C.L.) … Lots of exciting top physics happening at the CDF and DØ. CDF, DØ, and the Tevatron are all running very well. A lot of room to grow. 2 fb-1 8 fb-1 Charles Plager 3rd Grenoble Top Workshop – October 25, 2008

New Era of Precision Top Physics! 2010 PDG Top Entry 2008 PDG Top Entry 2006 PDG Top Entry Charles Plager 3rd Grenoble Top Workshop – October 25, 2008

Top Physics Finally Makes Prime Time The Big Bang Theory! Mondays at 7:00 on CBS. Top Branching Fractions Top FCNC Charles Plager 3rd Grenoble Top Workshop – October 25, 2008

3rd Grenoble Top Workshop – October 25, 2008 Thank You! Charles Plager 3rd Grenoble Top Workshop – October 25, 2008

3rd Grenoble Top Workshop – October 25, 2008 Backup Slides Charles Plager 3rd Grenoble Top Workshop – October 25, 2008