An Important thing to know. The Top Quark The Top Quark Mass An Important thing to know. 11/24/2018 B. Todd Huffman - Oxford

t Z W b c s d u   e   e The Top Quark The Standard Model The top quark was discovered only 10 years ago Existence is required by the SM, but striking characteristics: its mass is surprisingly large Studied only at the Tevatron The Standard Model Particle Masses t Z W b c s d u   e   e 11/24/2018 B. Todd Huffman - Oxford

Why measure the Top Quark Mass? Related to standard model observables and parameters through loop diagrams Consistency checks of SM parameters Precision measurements of the Mtop (and MW) allow prediction of the MHiggs Constraint on Higgs mass can point to physics beyond the standard model Summer 2005 11/24/2018 B. Todd Huffman - Oxford

Final State from Leading Order Diagram Dilepton Channel Final State from Leading Order Diagram What we measure Branching fraction: 5% (lepton = e or ) Final state: 2 leptons, 2 b quarks, 2 neutrinos Combinatorial background: 2 combinations 2 neutrinos: under constrained, kinematically complicated to solve Mtop S:B = 2:1 and 20:1 requiring 1 identified b tag 11/24/2018 B. Todd Huffman - Oxford

Final State from Leading Order Diagram Lepton+Jets Channel Final State from Leading Order Diagram What we measure Branching fraction: 30% (lepton = e or ) S:B = 1:4 to 11:1 depending on the b-tagging requirement Combinatorial background: 12 (0 b tag), 6 (1 b tag), and 2 (2 b tags) 1 neutrino: over constrained Most precise Mtop measurements 11/24/2018 B. Todd Huffman - Oxford

Final State from Leading Order Diagram All Jets Channel Final State from Leading Order Diagram What we measure Branching fraction: 44% Huge amount of background S:B = 1:8 after requiring at least 1 b-tag jet Combinatorial background: 90 combinations Backgrounds mainly from multi-jet QCD production 11/24/2018 B. Todd Huffman - Oxford

Robust program of top quark mass measurements Top Quark Mass at CDF Robust program of top quark mass measurements Many measurements in all the different channels -> consistency Different methods of extraction with different sensitivity -> confidence Combine all channels and all methods -> precision 11/24/2018 B. Todd Huffman - Oxford

CDF Measurement (~350pb-1) Mtop Different statistical and systematical sensitivities in each channel Other sources arise from the assumptions employed to infer Mtop: Initial state and final state radiation Parton distribution functions b-jet energy scale Generators Background modeling and composition b-tagging efficiency MC statistics Systematics dominated by the uncertainty on parton energies (Jet Energy Scale, JES) CDF Measurement (~350pb-1) Statistical (GeV/c2) Jet En. Scale (GeV/c2) Other syst. (GeV/c2) Dilepton 6 3 2 Lepton+Jets 4 1 All Jets 5 11/24/2018 B. Todd Huffman - Oxford

Jet Energy Scale Jet energy scale Determine the energy of the quarks produced in the hard scattered We use the Monte Carlo and data to derive the jet energy scale Jet energy scale uncertainties Differences between data and Monte Carlo from all these effects 11/24/2018 B. Todd Huffman - Oxford

In-situ Measurement of JES Additionally, we use Wjj mass resonance (Mjj) to measure the jet energy scale (JES) uncertainty Constrain the invariant mass of the non-b-tagged jets to be 80.4 GeV/c2 Mjj Measurement of JES scales directly with statistics! 11/24/2018 B. Todd Huffman - Oxford

Data and Monte Carlo W-jet pT b-jet pT ttbar pT Mttbar Ask Lucio about this set of plots. ttbar pT Mttbar 11/24/2018 B. Todd Huffman - Oxford

In this Talk Lepton + jets: Template analysis Lepton + jets: Matrix Element Lepton + jets: Decay Length All Hadronic: Ideogram Missing Di-leptons…cannot go into detail on everything! 11/24/2018 B. Todd Huffman - Oxford

Mtop Lepton+Jets Results

Detected Top Candidate Silicon Detector Results 11/24/2018 B. Todd Huffman - Oxford

Top Mass - Guessing Jets What you get if you always guess correctly, vs just trying all possible combinations. You cannot ‘pick the best one’….since you do not know the mass which one is ‘best’?? 11/24/2018 B. Todd Huffman - Oxford

Run Monte carlo with various mass hypotheses. Top Mass - Templates Run Monte carlo with various mass hypotheses. These are used as ‘templates’ that can be compared to data using the c2 difference between data and the template. 11/24/2018 B. Todd Huffman - Oxford

Top Mass – Background Templates Use W+Jet background with fake electron and mistagged b to check that jet shapes are OK in MC. Then use MC to generate a ‘background’ mass plot. 11/24/2018 B. Todd Huffman - Oxford

Template Analysis Reconstructed mtop and mjj from data are compared to templates of various true Mtop and JES (jet energy uncertainty shift) using an unbinned likelihood Uses all four samples to increase sensitivity 2 b tags 1 b tag (T) 1 b tag (L) 0 b tag Expected S:B 10:1 4:1 1:1 0.6:1 Expected Number of Events ( tt = 6.1pb) 47 104 64 no a priori estimate Data (680 pb-1) 57 120 75 108 11/24/2018 B. Todd Huffman - Oxford

Template Analysis Results Using 360 candidate events in 680 pb-1 we measure Using in-situ JES calibration results in 40% improvement on JES Better sensitivity than the previous world average! 11/24/2018 B. Todd Huffman - Oxford

Matrix Element Analysis Technique Optimizes the use of kinematic and dynamic information Build a probability for a signal and background hypothesis Likelihood simultaneously determines Mtop, JES, and signal fraction, Cs: 11/24/2018 B. Todd Huffman - Oxford

Matrix Element Analysis Technique For a set of set measured variables x: JES sensitivity comes from W resonance –this too is in the fit. All permutations and neutrino solutions are taken into account Lepton momenta and all angles are considered well measured Background probability is similar, no dependence on Mtop W(x,y) is the probability that a parton level set of variables y will be measured as a set of variables x (parton level corrections) dn is the differential cross section: LO Matrix element f(q) is the probability distribution than a parton will have a momentum q 11/24/2018 B. Todd Huffman - Oxford

Cross-check Monte Carlo with Data Compare Data and Monte Carlo calculating the invariant mass of 2 and 3 jets Signal probability evaluated at Mtop=174.5 GeV/c2 and JES=1 and using the most probable configuration Excellent agreement found between data and Monte Carlo 11/24/2018 B. Todd Huffman - Oxford

Better sensitivity than the previous world average! Results Using the 118 candidates in 680 pb-1 our Mtop is: with JES = 1.019  0.022 (stat) Better sensitivity than the previous world average! 11/24/2018 B. Todd Huffman - Oxford

New technique – B Decay Length The method has been published by C. Hill et al. at PRD 71, 054029 B hadron decay length  b-jet boost  Mtop Uses the average transverse decay length of the b-hadrons <Lxy> Relies on tracking, no JES and uncorrelated with other measurements 11/24/2018 B. Todd Huffman - Oxford

Mtop All Jets Results

All Jets Main challenges in this channel: Selection and events Small signal fraction S:B = 1:8 after requiring at least 1 identified b-jet Large combinatorial background: 90 combinations Selection and events ET/  ( ET) < 3 (GeV)1/2 ET  280 GeV nb-tag  1 Exactly 6 jets Ideogram method from the Delphi experiment for the W mass measurement, used in a Run II preliminary D0 for top mass measurement in lepton+jets channel Expected Events (310 pb-1) Multi-jets (light) 182 Multi-jets (heavy flavor) 68 Total background 240 tt (6.1 pb) 40 Data 290 11/24/2018 B. Todd Huffman - Oxford

Ideogram Overview Define a 2D event likelihood as Weight each combination with kinematical and b-tagging information: wi Extract from kinematical fit to mtop and manti-top  m1, m2, 1,2, 2 Sm calculated convoluting Briet-Wigners and Gaussian resolution functions Scomb combinatorial background from Monte Carlo 11/24/2018 B. Todd Huffman - Oxford

Template Shapes Using the two fitted masses gives a good separation Template for combinatorial background Template for background Signal, correct combination Using the two fitted masses gives a good separation between signal and background 11/24/2018 B. Todd Huffman - Oxford

Similar statistical sensitivity as the lepton + jets channel Results Using 310 pb-1 and 290 candidates we measure First Tevatron Run II all jets Mtop measurement Systematically limited! Similar statistical sensitivity as the lepton + jets channel 11/24/2018 B. Todd Huffman - Oxford

Summary of Mtop Results CDF Measurement Extracted value (GeV/c2) Statistical (GeV/c2) JES (GeV/c2) Other syst (GeV/c2) Lepton+Jets: Template (680pb-1) 173.4 1.7 1.8 1.3 Lepton+Jets: ME(680pb-1) 174.1 2.0 1.5 Lepton+Jets: Decay Length (750pb-1) 183.9 +15.7 -13.9 0.3 5.6 Dilepton: Matrix Element (750pb-1) 164.5 4.5 2.6 All Jets: Ideogram (310pb-1) 177.1 4.7 4.3 1.9 We compare (confidence and consistency) and combine (precision) 11/24/2018 B. Todd Huffman - Oxford

Combining Mtop Results Excellent results in each channel Combine them to improve precision Include Run-I results Account for correlations Use BLUE (NIM A270 110, A500 391) Matrix Element analysis in lepton+jets not yet included. Working to understand statistical correlations with Template analysis 2.6 CDF April’06 (750 pb-1) 11/24/2018 B. Todd Huffman - Oxford

Future We surpassed our Run II goal of measuring to 3 GeV/c2 precision Have made extrapolations based on present methods Upper limit: Only (stat) improves with luminosity Lower limit: Everything improves with luminosity Reality: likely somewhere in between With full Run-II dataset CDF should measure Mtop to < 1% 11/24/2018 B. Todd Huffman - Oxford

Conclusions What has been shown. First Run-II determination in all-jets channel Multiple methods and channels Observed consistency builds confidence CDF combined CDF should reach 1% precision with full Run-II data set Tevatron combination better still 11/24/2018 B. Todd Huffman - Oxford

Conclusions Present uncertainties on Mtop and MW help constrain MHiggs to about 40% MHiggs/ MHiggs Best fit favors light MHiggs where CDF/D0 are sensitive where difficult for LHC Mtop will continue to shrink New CDF/D0 MW expected soon... MW will also shrink We'll continue to squeeze SM, will it hold? 11/24/2018 B. Todd Huffman - Oxford