Dr Farrukh Azfar

Abstract:

We present a measurement of the tt̄ production cross section using events with one charged lepton and jets from pp̄ collisions at a center-of-mass energy of 1.96 TeV. A b-tagging algorithm based on the probability of displaced tracks coming from the event interaction vertex is applied to identify b quarks from top decay. Using 318pb-1 of data collected with the CDF II detector, we measure the tt̄ production cross section in events with at least one restrictive (tight) b-tagged jet and obtain 8.9-1.0+1.0(stat)-1.0+1.1(syst)pb. The cross section value assumes a top quark mass of mt=178GeV/c2 in the acceptance corrections. The dependence of the cross section on mt is presented in the paper. This result is consistent with other CDF measurements of the tt̄ cross section using different samples and analysis techniques, and has similar systematic uncertainties. We have also performed consistency checks by using the b-tagging probability function to vary the signal-to-background ratio and also using events that have at least two b-tagged jets. © 2006 The American Physical Society.

Abstract:

We report a measurement of the tt̄ production cross section using the CDF II detector at the Fermilab Tevatron. The analysis is performed using 311pb-1 of pp̄ collisions at s=1.96TeV. The data consist of events selected with six or more hadronic jets with additional kinematic requirements. At least one of these jets must be identified as a b-quark jet by the reconstruction of a secondary vertex. The cross section is measured to be σtt̄=7. 5±2.1(stat.)-2.2+3.3(syst.)-0.4+0.5(lumi.)pb, which is consistent with the standard model prediction. © 2006 The American Physical Society.

Abstract:

We present a measurement of RB, the ratio of the branching fraction for the rare decay D0→K+π- to that for the Cabibbo-favored decay D0→K-π+. Charge-conjugate decays are implicitly included. A signal of 2005±104 events for the decay D0→K+π- is obtained using the CDF II detector at the Fermilab Tevatron collider. The data set corresponds to an integrated luminosity of 0.35fb-1 produced in p̄p collisions at s=1.96TeV. Assuming no mixing, we find RB=[4.05±0.21(stat)±0.11(syst)] ×10-3. This measurement is consistent with the world average, and comparable in accuracy with the best measurements from other experiments. © 2006 The American Physical Society.

Abstract:

We describe a measurement of the top quark mass using events with two charged leptons collected by the CDF II detector from pp̄ collisions with s=1.96TeV at the Fermilab Tevatron. The likelihood in top quark mass is calculated for each event by convoluting the leading order matrix element describing qq̄→tt̄→blνlb̄l′νl′ with detector resolution functions. The presence of background events in the data sample is modeled using similar calculations involving the matrix elements for major background processes. In a data sample with integrated luminosity of 340pb-1, we observe 33 candidate events and measure Mtop=165.2±6.1(stat.) ±3.4(syst.)GeV/c2. This measurement represents the first application of this method to events with two charged leptons and is the most precise single measurement of the top quark mass in this channel. © 2006 The American Physical Society.

Abstract:

We present a measurement of the top quark pair production cross section in pp̄ collisions at s=1.96TeV using 318pb-1 of data collected with the Collider Detector at Fermilab. We select tt̄ decays into the final states eν+jets and μν+jets, in which at least one b quark from the t-quark decays is identified using a secondary vertex-finding algorithm. Assuming a top quark mass of 178GeV/c2, we measure a cross section of 8.7±0.9(stat)-0. 9+1.1(syst)pb. We also report the first observation of tt̄ with significance greater than 5σ in the subsample in which both b quarks are identified, corresponding to a cross section of 10.1-1.4+1.6(stat)-1.3+2.0(syst) pb. © 2006 The American Physical Society.