Measurement of the ttbar production cross section with an in situ calibration of b-jet identification efficiency

A measurement of the top-quark pair-production cross section in ppbar collisions at sqrt{s}=1.96 TeV using data corresponding to an integrated luminosity of 1.12/fb collected with the Collider Detector at Fermilab is presented. Decays of top-quark pairs into the final states e nu + jets and mu nu + jets are selected, and the cross section and the b-jet identification efficiency are determined using a new measurement technique which requires that the measured cross sections with exactly one and multiple identified b-quarks from the top-quark decays agree. Assuming a top-quark mass of 175 GeV/c^2, a cross section of 8.5+/-0.6(stat.)+/-0.7(syst.) pb is measured.

Community, Power, and Colonialism: The U.S. Army in Southern Arizona and New Mexico, 1866-1886

Empire is central to U.S. history. When we see the U.S. projecting its influence on a global scale in today s world it is important to understand that U.S. empire has a long history. This dissertation offers a case study of colonialism and U.S. empire by discussing the social worlds, labor regimes, and culture of the U.S. Army during the conquest of southern Arizona and New Mexico (1866-1886). It highlights some of the defining principles, mentalities, and characteristics of U.S. imperialism and shows how U.S. forces have in years past constructed their power and represented themselves, their missions, and the places and peoples that faced U.S. imperialism/colonialism. Using insights from postcolonial studies and whiteness studies, this work balances its attention between discursive representations (army stories) and social experience (army actions), pays attention to silences in the process of historical production, and focuses on collective group mentalities and identities. In the end the army experience reveals an empire in denial constructed on the rule of difference and marked by frustration. White officers, their wives, and the white enlisted men not only wanted the monopoly of violence for the U.S. regime but also colonial (mental/cultural) authority and power, and constructed their identity, authority, and power in discourse and in the social contexts of the everyday through difference. Engaged in warfare against the Apaches, they did not recognize their actions as harmful or acknowledge the U.S. invasion as the bloody colonial conquest it was. White army personnel painted themselves and the army as liberators, represented colonial peoples as racial inferiors, approached colonial terrain in terms of struggle, and claimed that the region was a terrible periphery with little value before the arrival of white civilization. Officers and wives also wanted to place themselves at the top of colonial hierarchies as the refined and respectable class who led the regeneration of the colony by example: they tried to turn army villages into islands of civilization and made journeys, leisure, and domestic life to showcase their class sensibilities and level of sophistication. Often, however, their efforts failed, resulting in frustration and bitterness. Many blamed the colony and its peoples for their failures. The army itself was divided by race and class. All soldiers were treated as laborers unfit for self-government. White enlisted men, frustrated by their failures in colonial warfare and by constant manual labor, constructed worlds of resistance, whereas indigenous soldiers sought to negotiate the effects of colonialism by working in the army. As colonized labor their position was defined by tension between integration and exclusion and between freedom and colonial control.

Top Quark Mass Measurement in the lepton+jets Channel Using a Matrix Element Method and in situ Jet Energy Calibration

A precision measurement of the top quark mass m_t is obtained using a sample of ttbar events from ppbar collisions at the Fermilab Tevatron with the CDF II detector. Selected events require an electron or muon, large missing transverse energy, and exactly four high-energy jets, at least one of which is tagged as coming from a b quark. A likelihood is calculated using a matrix element method with quasi-Monte Carlo integration taking into account finite detector resolution and jet mass effects. The event likelihood is a function of m_t and a parameter DJES to calibrate the jet energy scale /in situ/. Using a total of 1087 events, a value of m_t = 173.0 +/- 1.2 GeV/c^2 is measured.