# Precision measurement of the top quark mass in the lepton + jets channel using a matrix element method with Quasi-Monte Carlo integration

## Abstract

This thesis presents a measurement of the top quark mass obtained from p$$\bar{p}$$ collisions at √s = 1.96 TeV at the Fermilab Tevatron using the CDF II detector. The measurement uses a matrix element integration method to calculate a t$$\bar{t}$$ likelihood, employing a Quasi-Monte Carlo integration, which enables us to take into account effects due to finite detector angular resolution and quark mass effects. We calculate a t$$\bar{t}$$ likelihood as a 2-D function of the top pole mass m _{t} and Δ _{JES}, where Δ _{JES} parameterizes the uncertainty in our knowledge of the jet energy scale; it is a shift applied to all jet energies in units of the jet-dependent systematic error. By introducing Δ _{JES} into the likelihood, we can use the information contained in W boson decays to constrain Δ _{JES} and reduce error due to this uncertainty. We use a neural network discriminant to identify events likely to be background, and apply a cut on the peak value of individual event likelihoods to reduce the effect of badly reconstructed events. This measurement uses a total of 4.3 fb ^{-1} of integrated luminosity, requiring events with a lepton, large E _{T}, and exactly four high-energy jets in the pseudorapidity range |η| < 2.0, of which at least one must be tagged as coming from a b quark. In total, we observe 738 events before and 630 events after applying the likelihood cut, and measure m _{t} = 172.6 ± 0.9 (stat.) ± 0.7 (JES) ± 1.1 (syst.) GeV/c ^{2}, or m _{t} = 172.6 ± 1.6 (tot.) GeV/c ^{2}.

- Authors:

- Univ. of California, Berkeley, CA (United States)

- Publication Date:

- Research Org.:
- Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)

- Sponsoring Org.:
- USDOE

- OSTI Identifier:
- 963775

- Report Number(s):
- FERMILAB-THESIS-2009-26

TRN: US0903275

- DOE Contract Number:
- AC02-07CH11359

- Resource Type:
- Thesis/Dissertation

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; ACCURACY; B QUARKS; FERMILAB COLLIDER DETECTOR; FERMILAB TEVATRON; INTERMEDIATE BOSONS; LEPTONS; LUMINOSITY; MATRIX ELEMENTS; NEURAL NETWORKS; QUARKS; RESOLUTION; T QUARKS; Experiment-HEP

### Citation Formats

```
Lujan, Paul Joseph.
```*Precision measurement of the top quark mass in the lepton + jets channel using a matrix element method with Quasi-Monte Carlo integration*. United States: N. p., 2009.
Web. doi:10.2172/963775.

```
Lujan, Paul Joseph.
```*Precision measurement of the top quark mass in the lepton + jets channel using a matrix element method with Quasi-Monte Carlo integration*. United States. doi:10.2172/963775.

```
Lujan, Paul Joseph. Tue .
"Precision measurement of the top quark mass in the lepton + jets channel using a matrix element method with Quasi-Monte Carlo integration". United States.
doi:10.2172/963775. https://www.osti.gov/servlets/purl/963775.
```

```
@article{osti_963775,
```

title = {Precision measurement of the top quark mass in the lepton + jets channel using a matrix element method with Quasi-Monte Carlo integration},

author = {Lujan, Paul Joseph},

abstractNote = {This thesis presents a measurement of the top quark mass obtained from p$\bar{p}$ collisions at √s = 1.96 TeV at the Fermilab Tevatron using the CDF II detector. The measurement uses a matrix element integration method to calculate a t$\bar{t}$ likelihood, employing a Quasi-Monte Carlo integration, which enables us to take into account effects due to finite detector angular resolution and quark mass effects. We calculate a t$\bar{t}$ likelihood as a 2-D function of the top pole mass mt and ΔJES, where ΔJES parameterizes the uncertainty in our knowledge of the jet energy scale; it is a shift applied to all jet energies in units of the jet-dependent systematic error. By introducing ΔJES into the likelihood, we can use the information contained in W boson decays to constrain ΔJES and reduce error due to this uncertainty. We use a neural network discriminant to identify events likely to be background, and apply a cut on the peak value of individual event likelihoods to reduce the effect of badly reconstructed events. This measurement uses a total of 4.3 fb-1 of integrated luminosity, requiring events with a lepton, large ET, and exactly four high-energy jets in the pseudorapidity range |η| < 2.0, of which at least one must be tagged as coming from a b quark. In total, we observe 738 events before and 630 events after applying the likelihood cut, and measure mt = 172.6 ± 0.9 (stat.) ± 0.7 (JES) ± 1.1 (syst.) GeV/c2, or mt = 172.6 ± 1.6 (tot.) GeV/c2.},

doi = {10.2172/963775},

journal = {},

number = ,

volume = ,

place = {United States},

year = {Tue Dec 01 00:00:00 EST 2009},

month = {Tue Dec 01 00:00:00 EST 2009}

}