1. 7/12/2015 Top Pairs Meeting 1 A template fit technique to measure the top quark mass in the l+jets channel Ulrich Heintz, Vivek Parihar

2. 7/12/2015Top Pairs Meeting2 Overview  OBJECTIVE: develop a fast algorithm for the measurement of the top quark mass in l + jets channel to complement the computing intensive matrix element technique.  currently studied a template fit method using only ttbar signal MC in the e + jets channel  results shown here are based on the output of HITFIT from Pieter Houben’s Monte Carlo data files (January version)  event selection is that used by the Ideogram analysis by Pieter and Michele.  templates are constructed using the mass for each event for which HITFIT obtains the lowest (positive) chi-squared.

3. 7/12/2015Top Pairs Meeting3 PART 1 Parametrization of Templates :

4. 7/12/2015Top Pairs Meeting4 m top =155 GeV 155 Templates m top =195 GeV m top =170 GeV

5. 7/12/2015Top Pairs Meeting5 Templates m top =195 GeV m top =170 GeV m top =155 GeV Each template is fitted with Landau convoluted with Gaussian + Pure Gaussian with a total of 7 parameters

6. 7/12/2015Top Pairs Meeting6 Fit Parameters  show that parameters vary smoothly with m top Landau * Gauss Landau * Gauss

7. 7/12/2015Top Pairs Meeting7 Fit Parameters Gaussian

8. 7/12/20158 2 D Simultaneous Fit  express the 7 parameters as functions of m top  fit all templates simultaneously Function used : Landau*Gaussian + Gaussian with total 7 internal parameters.

9. 7/12/20159 2 D Simultaneous Fit  results Landau* gauss parameters Width of Landau a0 - a1*(mtop-175) Most Probable a2 + a3*(mtop-175) Area a4*(1- a7) GSigma a5+ a6*(mtop-175) Pure Gaussian Norm a4*a7 Most Probable a8+ a9*(mtop-175) Sigma a10 a0 = 8.82 ; a1= 0.02 ; a2 = 162.82 ; a3 = 0.49 ; a4 = 4.69 ; a5 = 19.16 ; a6 = 0.17 ; a7 = 0.14 ; a8 = 175.32 ; a9 = 0.96 ; a10 = 11.6

10. 7/12/201510 2 D Simultaneous Fit  superimpose template parametrizations

11. 7/12/2015Top Pairs Meeting11 PART II  Ensemble Tests : -> 1000 ensembles with 200 ttbar events each, randomly picked from the data files. -> 1000 ensembles with 200 ttbar events each, randomly picked from the data files. -> parametrized templates used to calculate the negative log likelihood for each ensemble of 200 events. -> parametrized templates used to calculate the negative log likelihood for each ensemble of 200 events.

12. 7/12/2015Top Pairs Meeting12 Ensemble tests  - log likelihood plot and quadratic fit for a sample ensemble (m top = 155 GeV) The fit procedure, determines the measured top mass by, finding the minimum of the Log likelihood curve.

13. 7/12/2015Top Pairs Meeting13 Ensemble tests  Distributions of Measured (fitted) Top Mass (upper row) and Pulls (bottom row) ……

14. 7/12/2015Top Pairs Meeting14 154.4 GeV (3.31) 159.9 GeV(2.986) 165 GeV (2.919) 0.2046 (1.116) 0.0394 (1.002) 0.0171 (0.974)

15. 7/12/2015Top Pairs Meeting15 169.3 (3.2) 174.2 (3.289) 179.4 (3.339) 0.2428 (1.042) 0.2527 (1.03) 0.188 (1.041)

16. 7/12/2015Top Pairs Meeting16 185.2 GeV(4.467) 190.4 GeV (3.108)193.8 GeV (4.488) -0.0299 (1.377) -0.1098 (0.9465) 0.378 (1.292)

17. 7/12/2015Top Pairs Meeting17 Calibration Plots :

18. 7/12/2015Top Pairs Meeting18Results  using 200 ttbar signal events measure the top quark mass without bias measure the top quark mass without bias expected statistical uncertainty  3.2 GeV expected statistical uncertainty  3.2 GeV  next steps include backgrounds include backgrounds apply to p17 data apply to p17 data

19. 7/12/2015Top Pairs Meeting19 Back up