Title: Measurement of B _c production cross section in p$$\bar{p}$$ collisions at √s = 1.96 TeV

A measurement of the tmore » $$\bar{t}$$ pair production cross section is presented using 162 pb ^-1 of data collected by the CDF experiment during Run II at the Tevatron. t$$\bar{t}$$} events in the lepton+jets channel are isolated by identifying electrons and muons, reconstructing jets and transverse missing energy, and identifying b jets with a secondary vertex tagging algorithm. The efficiency of the algorithm is measured in a control sample using a novel technique that is less dependent on the simulation. For a top quark mass of 175 GeV/c ² , a cross section of σ _t$$\bar{t}$$ = 5.6$$+1.2\atop{-1.1}$$(stat.)$$+0.9\atop{-0.6}$$(syst.)pb is measured.« less

Processes at hadron colliders, such as the production of jets, are described by the Quantum Chromodynamics theory (QCD). Precise descriptions of processes involving jets in association with a vector boson have nowadays large relevance as they represent irreducible background to other Standard Model (SM) processes and searches for new physics. The experimental study and understanding of the b-jet production in association with a Z boson are crucial for many reasons. For one side, it is the most important background for a light Higgs boson decaying into a bottom-antibottom quark pair and produced in the ZH mode.This is one of the most promising channels for the Higgs search at Tevatron in particular since the latest results have excluded the high mass region (MH > 127 GeV/c ² ). For another side the signature of b-jets and a Z boson is also background to new physics searches, such as supersymmetry, where a large coupling of the Higgs boson to bottom quarks is allowed. The produ ction cross section measurement of b-jets in events with a Z boson has already been performed at hadron colliders, at the Tevatron by CDF and D0 experiments and are now pursued at the LHC by ATLAS and CMS. In particular the CDF measurement was performed with only 2 fb ^-1 and was limited by the statistical uncertainty. This PhD thesis presents a new measurement of themore » $$Z/\gamma^* + b$$-jet production cross section using the complete dataset collected by CDF during the Run II. $$Z/\gamma^*$$ bosons are selected in the electron and muon decay modes and are required to have 66 < MZ < 116 GeV/c ² while jets, reconstructed with the MidPoint algorithm, have to be central (|Y| < 1.5) with pT > 20 GeV/c . The per jet cross section is measured with respect to the $$Z/\gamma^*$$ inclusive and the $$Z/\gamma^* +$$ jets cross sections. Results are compared to leading order (LO) event generator plus parton shower and next-to-leading order (NLO) predictions corrected for non perturbative effects such as hadronizat ion and underlying event. Differential distributions as a fu! nction of jet transverse moment and jet rapidity are also presented together with the comparison to NLO pQCD predictions for different renormalization and factorization scales and various PDF sets.« less

We present the measurement of the tmore » $$\bar{t}$$ cross section in the lepton plus jets channel with ≥ 1 and ≥ 2 secondary vertex tags. We use the scalar sum of transverse energies of the event (H _T) to discriminate t{bar t} from the other backgrounds. We also use the transverse mass of the leptonic W-boson (M$$W\atop{T}$$) to further reduce the Non-W backgrounds. We use a combination of data and Monte Carlo to estimate the backgrounds from electroweak processes, single top, fake leptons, W+ Light Flavor fake tags, and real W+ Heavy Flavor production. We obtain a value of σ _≥1 = 8.7$$+0.9\atop{-0.9}$$(stat)$$+1.2\atop{-0.9}$$(sys) pb for the ≥1 tag cross section, and σ _≥2 = 8.7$$+1.8\atop{-1.6}$$(stat)$$+1.9\atop{-1.3}$$(sys) pb for the ≥2 tag cross section. The authors also present a measurement of the t$$\bar{t}$$ cross section by fitting the N _jet spectrum. They combine the =1 and ≥2 tag cross sections to obtain σ _t$$\bar{t}$$ = 8.9$$+0.9\atop{-0.9}$$(stat)$$+1.4\atop{-1.3}$$(syst)pb.« less

I present a measurement of the tmore » $$\bar{t}$$ production cross section at √s = 1.96 TeV using 2034 pb ^-1 of CDF Run II data using events with a high transverse momentum electron or muon, three or more jets, and missing transverse energy. The measurement assumes a t → Wb branching fraction of 100 percent. Events consistent with t$$\bar{t}$$ decay are found by identifying jets containing heavy-flavor semileptonic decays to muons. The dominant backgrounds are evaluated directly from the data. Based on 248 candidate events and an expected background of 86.8 ± 5.6 events, I measure a production cross section of 8.7 ± 1.1$$+0.9\atop{-0.8}$$ ± 0.6 pb, in agreement with the Standard Model.« less

A cross section measurement for the production of W ⁺W ^- is performed. Differential measurements are reported as a function of jet multiplicity and transverse energy. The inclusive cross section is measured to be σ(pmore » $$\bar{p}$$→W+W ^-+X=14.0±0.6(stat)$$+1.2\atop{-1.0}$$(syst)±0.8(lumi)±0.8(lumi) pb, consistent with the Standard Model prediction. Additionally, a search for the Higgs boson is performed in the final state of W+W ^- with two or more associated jets. Limits on the production cross section are set at the 95%95% confidence level, and combined with limits from related analyses. Both analyses use data collected by the CDF II detector from 9.7fb ^-1 of luminosity.« less