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

Thesis/Dissertation · Tue Dec 01 00:00:00 EST 2009

DOI:https://doi.org/10.2172/963775· OSTI ID:963775

Lujan, Paul Joseph ^[1]

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

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/c², or m_t = 172.6 ± 1.6 (tot.) GeV/c².

• Research Organization: Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC02-07CH11359
• OSTI ID: 963775
• Report Number(s): FERMILAB-THESIS-2009-26; TRN: US0903275
• Country of Publication: United States
• Language: English

Related Subjects

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