Improved measurement of absolute branching fraction of Ds+→τ+ν τ
Physical Review D - Particles, Fields, Gravitation and Cosmology 79:5 (2009)
Abstract:
We have studied the leptonic decay Ds+→τ+ντ, via the decay channel τ+→e+νeν̄τ, using a sample of tagged Ds+ decays collected near the Ds*±Ds peak production energy in e+e- collisions with the CLEO-c detector. We obtain B(Ds+→τ+ντ)=( 5.30±0.47±0.22)% and determine the decay constant fDs=(252.5±11.1± 5.2)MeV, where the first uncertainties are statistical and the second are systematic. © 2009 The American Physical Society.Measurement of B(Ds+→l+ν) and the decay constant fDs+ from 600 pb-1 of e+e- annihilation data near 4170 MeV
Physical Review D - Particles, Fields, Gravitation and Cosmology 79:5 (2009)
Abstract:
We examine e+e-→Ds-Ds*+ and Ds*-Ds+ interactions at 4170 MeV using the CLEO-c detector in order to measure the decay constant fDs+ with good precision. Previously our measurements were substantially higher than the most precise lattice based QCD calculation of (241± 3)MeV. Here we use the Ds+→+ν channel, where the + designates either a μ+ or a τ+, when the τ+→π+ν̄. Analyzing both modes independently, we determine B(Ds+→μ+ν)=( 0.565±0.045±0.017)%, and B(Ds+→τ+ν)=(6.42±0.81± 0.18)%. We also analyze them simultaneously to find an effective value of Beff(Ds+→μ+ν)=(0.591± 0.037±0.018)% and fDs+=( 263.3±8.2±3.9)MeV. Combining with the CLEO-c value determined independently using Ds+→τ+ν, τ+→e+νν̄ decays, we extract fDs+=( 259.5±6.6±3.1)MeV. Combining with our previous determination of B(D+→μ+ν), we extract the ratio fDs+/fD+=1.26±0.06±0.02. No evidence is found for a CP asymmetry between Γ(Ds+→μ+ν) and Γ(Ds-→μ-ν); specifically the fractional difference in rates is measured to be (4.8±6.1)%. Finally, we find B(Ds+→e+ν)<1.2×10-4 at 90% confidence level. © 2009 The American Physical Society.Measurement of cross sections for b jet production in events with a Z boson in pp̄ collisions at s=1.96TeV
Physical Review D - Particles, Fields, Gravitation and Cosmology 79:5 (2009)
Abstract:
A measurement of the b jet production cross section is presented for events containing a Z boson produced in pp̄ collisions at s=1.96TeV, using data corresponding to an integrated luminosity of 2fb-1 collected by the CDF II detector at the Tevatron. Z bosons are selected in the electron and muon decay modes. Jets are considered with transverse energy ET>20GeV and pseudorapidity |η|<1.5 and are identified as b jets using a secondary vertex algorithm. The ratio of the integrated Z+b jet cross section to the inclusive Z production cross section is measured to be 3.32±0.53(stat)±0.42(syst) ×10-3. This ratio is also measured differentially in jet ET, jet η, Z-boson transverse momentum, number of jets, and number of b jets. The predictions from leading-order Monte Carlo generators and next-to-leading-order QCD calculations are found to be consistent with the measurements within experimental and theoretical uncertainties. © 2009 The American Physical Society.Measurement of the tt̄ production cross section in 2fb-1 of pp̄ collisions at s=1.96TeV using lepton plus jets events with soft muon b tagging
Physical Review D - Particles, Fields, Gravitation and Cosmology 79:5 (2009)
Abstract:
We present a measurement of the tt̄ production cross section in pp̄ collisions at s=1.96TeV using events containing a high transverse momentum electron or muon, three or more jets, and missing transverse energy. Events consistent with tt̄ decay are found by identifying jets containing candidate heavy-flavor semileptonic decays to muons. The measurement uses a CDF run II data sample corresponding to 2fb-1 of integrated luminosity. Based on 248 candidate events with three or more jets and an expected background of 79.5±5.3 events, we measure a production cross section of 9.1±1.6pb. © 2009 The American Physical Society.Search for new physics in the μμ+e/μ+E T channel with a low-pT lepton threshold at the Collider Detector at Fermilab
Physical Review D - Particles, Fields, Gravitation and Cosmology 79:5 (2009)