Measurement of the top quark mass and pp̄→tt̄ cross section in the all-hadronic mode with the CDF II detector
Physical Review D - Particles, Fields, Gravitation and Cosmology 81:5 (2010)
Abstract:
We present a measurement of the top quark mass and of the top-antitop (tt̄) pair production cross section using pp̄ data collected with the CDF II detector at the Tevatron Collider at the Fermi National Accelerator Laboratory and corresponding to an integrated luminosity of 2.9fb-1. We select events with six or more jets satisfying a number of kinematical requirements imposed by means of a neural-network algorithm. At least one of these jets must originate from a b quark, as identified by the reconstruction of a secondary vertex inside the jet. The mass measurement is based on a likelihood fit incorporating reconstructed mass distributions representative of signal and background, where the absolute jet energy scale (JES) is measured simultaneously with the top quark mass. The measurement yields a value of 174.8±2.4(stat+JES)-1.0+1.2(syst)GeV/c2, where the uncertainty from the absolute jet energy scale is evaluated together with the statistical uncertainty. The procedure also measures the amount of signal from which we derive a cross section, σtt̄=7.2±0.5(stat)±1.0(syst) ±0.4(lum)pb, for the measured values of top quark mass and JES. © 2010 The American Physical Society.Trapping ultracold atoms in a time-averaged adiabatic potential
Physical Review A - Atomic, Molecular, and Optical Physics 81:3 (2010)
Abstract:
We report an experimental realization of ultracold atoms confined in a time-averaged, adiabatic potential (TAAP). This trapping technique involves using a slowly oscillating (∼kHz) bias field to time-average the instantaneous potential given by dressing a bare magnetic potential with a high-frequency (~MHz) magnetic field. The resultant potentials provide a convenient route to a variety of trapping geometries with tunable parameters. We demonstrate the TAAP trap in a standard time-averaged orbiting potential trap with additional Helmholtz coils for the introduction of the radio frequency dressing field. We have evaporatively cooled 5×104 atoms of Rb87 to quantum degeneracy and observed condensate lifetimes of longer than 3 s. © 2010 The American Physical Society.Search for technicolor particles produced in association with a W Boson at CDF.
Phys Rev Lett 104:11 (2010) 111802
Abstract:
We present a search for the technicolor particles rho{T} and pi_{T} in the process pp-->rho{T}-->Wpi{T} at a center of mass energy of sqrt[s]=1.96 TeV. The search uses a data sample corresponding to approximately 1.9 fb{-1} of integrated luminosity accumulated by the CDF II detector at the Fermilab Tevatron. The event signature we consider is W-->lnu and pi{T}-->bb, bc or bu depending on the pi{T} charge. We select events with a single high-p{T} electron or muon, large missing transverse energy, and two jets. Jets corresponding to bottom quarks are identified with multiple b-tagging algorithms. The observed number of events and the invariant mass distributions are consistent with the standard model background expectations, and we exclude a region at 95% confidence level in the rho{T}-pi{T} mass plane. As a result, a large fraction of the region m(rho{T})=180-250 GeV/c{2} and m(pi{T})=95-145 GeV/c{2} is excluded.Measurement of absolute branching fractions of inclusive semileptonic decays of charm and charmed-strange mesons
Physical Review D - Particles, Fields, Gravitation and Cosmology 81:5 (2010)
Abstract:
We have measured the inclusive semileptonic branching fractions of D0, D+, and Ds+ mesons. For these measurements, we have used the full CLEO-c open-charm data samples, 818pb-1 at ECM=3.774GeV, giving D0D̄0 and D+D- events, and 602pb -1 at ECM=4.170GeV, giving Ds*±Ds" events. We obtain B(D0→Xe+νe)=(6.46±0.09±0.11)%, B(D +→Xe+νe)=(16.13±0.10±0.29)%, and B(Ds+→Xe+νe)=(6.52±0.39±0.15)%, where the first uncertainties are statistical and the second are systematic. From these and lifetimes obtained elsewhere, we obtain the ratios of semileptonic decay widths Γ(D+→Xe+νe)/Γ(D0→Xe +νe)=0.985±0.015±0.024 and Γ(Ds+→Xe +νe)/Γ(D0→Xe+νe)=0.828±0. 051±0.025. The ratio of D+ and D0 is consistent with the isospin symmetry prediction of unity, and the ratio of Ds+ and D0 differs from unity, as expected. © 2010 The American Physical Society.Studying the Underlying Event in Drell-Yan and High Transverse Momentum Jet Production at the Tevatron
(2010)