Dr Farrukh Azfar

Abstract:

This Letter reports a measurement of the top quark mass, Mtop, in data from pp¯ collisions at s=1.96 TeV corresponding to 2.7 fb−1 of integrated luminosity at the Fermilab Tevatron using the CDF II detector. Events with the lepton+jets topology are selected. An unbinned likelihood is constructed based on the dependence of the lepton transverse momentum, PT, on Mtop. A maximum likelihood fit to the data yields a measured mass Mtop=176.9±8.0stat±2.7syst GeV/c2. In this measurement, the contribution by the jet energy scale uncertainty to the systematic error is negligible. The result provides an important consistency test for other Mtop measurements where explicit use of the jet energy is made for deriving the top quark mass.

Abstract:

We report the first observation of two Cabibbo-suppressed decay modes of the Bs0 meson. Using a sample of pp̄ collisions at √s=1.96TeV corresponding to 5.9fb-1 of integrated luminosity collected with the CDF II, the collider detector at the Fermilab Tevatron, we search for new Bs0 decay modes in a sample of events containing J/ψ→μ+μ - decays. We reconstruct a Bs0→J/ψK*(892)0 signal with K*(892)0→K+π-, observing a yield of 151±25 events with a statistical significance of 8.0σ. We also reconstruct a Bs0→J/ψKS0 signal with KS0→π+π-, observing a yield of 64±14 events with a statistical significance of 7.2σ. From these yields, we extract the branching ratios B(Bs0→J/ψK*(892)0)=(8. 3±3.8)×10-5 and B(Bs0→J/ψK0)=(3.5±0.8) ×10-5, where statistical, systematic, and fragmentation- fraction uncertainties are included in the combined uncertainty. © 2011 American Physical Society.

Abstract:

We report on a measurement of b-hadron lifetimes in the fully reconstructed decay modes B(+)→J/ψK(+), B⁰→J/ψK*(892)⁰, B⁰→J/ψK(s)⁰, and Λ(b)⁰→J/ψΛ⁰ using data corresponding to an integrated luminosity of 4.3 fb⁻¹, collected by the CDF II detector at the Fermilab Tevatron. The measured lifetimes are τ(B(+))=[1.639±0.009(stat)±0.009(syst)] ps, τ(B⁰)=[1.507±0.010(stat)±0.008(syst)] ps, and τ(Λ(b)⁰)=[1.537±0.045(stat)±0.014(syst)] ps. The lifetime ratios are τ(B(+))/τ(B⁰)=[1.088±0.009(stat)±0.004(syst)] and τ(Λ(b)⁰)/τ(B⁰)=[1.020±0.030(stat)±0.008(syst)]. These are the most precise determinations of these quantities from a single experiment.

Abstract:

We present a search for a new narrow, spin-1, high mass resonance decaying to μ(+)μ⁻+X, using a matrix-element-based likelihood and a simultaneous measurement of the resonance mass and production rate. In data with 4.6 fb⁻¹ of integrated luminosity collected by the CDF detector in pp collisions at √s=1960 GeV, the most likely signal cross section is consistent with zero at 16% confidence level. We therefore do not observe evidence for a high mass resonance and place limits on models predicting spin-1 resonances, including M>1071 GeV/c² at 95% confidence level for a Z' boson with the same couplings to fermions as the Z boson.

Abstract:

We report on a measurement of b-hadron lifetimes in the fully reconstructed decay modes B+→J/ψK+, B0→J/ ψK*(892)0, B0→J/ψKs0, and Λb0→J/ψΛ0 using data corresponding to an integrated luminosity of 4.3fb-1, collected by the CDF II detector at the Fermilab Tevatron. The measured lifetimes are τ(B+)=[1.639±0.009(stat)±0.009(syst)] ps, τ(B0)=[1.507±0.010(stat)±0.008(syst)]ps, and τ(Λb0)=[1.537±0.045(stat)±0.014(syst)]ps. The lifetime ratios are τ(B+)/τ(B0)=[1.088±0.009(stat)±0. 004(syst)] and τ(Λb0)/τ(B0)=[1.020±0.030(stat)±0. 008(syst)]. These are the most precise determinations of these quantities from a single experiment. © 2011 American Physical Society.