Rubin-LSST

Abstract:

Using 180 pb -1 of data collected with the CDF II detector at the Tevatron, we measure the first two moments of the hadronic invariant mass-squared distribution in charmed semileptonic B decays. From these we determine the nonperturbative Heavy Quark Effective Theory parameters Λ and λ 1 used to relate the B meson semileptonic branching ratio to the CKM matrix element |V cb|. For a minimum lepton momentum of 0.7 GeV/c in the B rest frame we measure the first two moments of the D** → D (*)π component to be 〈m D**2〉 = (5.83 ± 0.16 stat ± 0.08 syst) GeV 2/c 4 and 〈(m D**2 - 〈m D**2〉) 2〉 = (1.30 ± 0.69 stat ± 0.22 syst) GeV 4/c 8. Combining these with the discrete mass terms from the D and D* mesons, we find the total moments to be 〈M Ξc2〉 - m̄ D2 = (0.467 ± 0.038 stat ± 0.068 syst GeV 2/c 4 and 〈(M Ξc2 - 〈M Ξc2〉) 2〉 = (1.05 ± 0.26 stat ± 0.13 syst) GeV 4/c 8, where m̄ D is the spin-averaged D mass. The systematic error is dominated by the uncertainties in the world-average branching ratios used to combine the D, D*, and D** contributions. The analysis makes no assumptions about the shape or resonant structure of the D** → D (*)π invariant mass distribution. © 2005 The American Physical Society.

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. In these events, heavy flavor quarks from top quark decay are identified with a secondary vertex tagging algorithm. From 162 pb^-1 of data collected by the Collider Detector at Fermilab, a total of 48 candidate events are selected, where 13.5 ± 1.8 events are expected from background contributions. We measure a tt̄ production cross section of 5.6-1.1^+1.2(stat.)-0.6^+0.9(syst.) pb. © 2005 The American Physical Society.