First measurement of the ratio of branching fractions B(Λb 0 →Λc+μ-ν̄μ)/B(Λb 0 →Λc+π-)
Physical Review D - Particles, Fields, Gravitation and Cosmology 79:3 (2009)
Abstract:
This article presents the first measurement of the ratio of branching fractions B(Λb0→Λc+μ-ν̄μ)/ B(Λb0→Λc+π-). Measurements in two control samples using the same technique B(B̄0→D+μ- ν̄μ)/B(B̄0→D+π-) and B(B̄ 0→D*(2010)+μ-ν̄μ)/ B(B̄0→D*(2010)+π-) are also reported. The analysis uses data from an integrated luminosity of approximately 172pb-1 of pp̄ collisions at s=1.96TeV, collected with the CDF II detector at the Fermilab Tevatron. The relative branching fractions are measured to be B(Λb 0→Λc+μ-ν̄μ)B(Λb 0→Λc+π-)=16.6±3.0(stat) ±1.0(syst)+2.6-3.4(PDG) ±0.3(EBR), B(B̄0→D+μ-ν̄μ) B(B̄0→D+π-)=9.9±1.0(stat) ±0.6(syst)±0.4(PDG)± 0.5(EBR), and B(B̄0→D*( 2010)+μ-ν̄μ)B(B̄0→D*( 2010)+π-)=16.5±2.3(stat) ±0.6(syst)±0.5(PDG)± 0.8(EBR). The uncertainties are from statistics (stat), internal systematics (syst), world averages of measurements published by the Particle Data Group or subsidiary measurements in this analysis (PDG), and unmeasured branching fractions estimated from theory (EBR), respectively. This article also presents measurements of the branching fractions of four new Λb 0 semileptonic decays: Λb0→Λc( 2595)+μ-ν̄μ, Λb0→Λc( 2625)+μ-ν̄μ, Λb0→Σc( 2455)0π+μ-ν̄μ, and Λb 0→Σc(2455)++π-μ-ν̄μ, relative to the branching fraction of the Λb0→Λc+μ- ν̄μ decay. Finally, the transverse-momentum distribution of Λb0 baryons produced in pp̄ collisions is measured and found to be significantly different from that of B̄0 mesons, which results in a modification in the production cross-section ratio σΛb0/σB̄0 with respect to the CDF I measurement. © 2009 The American Physical Society.Erratum: Search for high-mass e+e- Resonances in pp̄ collisions at s=1.96TeV (Physical Review Letters (2009) 102 (031801))
Physical Review Letters 102:5 (2009)
Search for maximal flavor violating scalars in same-charge lepton pairs in pp collisions at sqrt[s]=1.96 TeV.
Phys Rev Lett 102:4 (2009) 041801
Abstract:
Models of maximal flavor violation (MxFV) in elementary particle physics may contain at least one new scalar SU(2) doublet field Phi(FV)=(eta(0),eta(+)) that couples the first and third generation quarks (q_(1), q_(3)) via a Lagrangian term L(FV)=xi(13)Phi(FV)q(1)q(3). These models have a distinctive signature of same-charge top-quark pairs and evade flavor-changing limits from meson mixing measurements. Data corresponding to 2 fb(-1) collected by the Collider Dectector at Fermilab II detector in pp[over ] collisions at sqrt[s]=1.96 TeV are analyzed for evidence of the MxFV signature. For a neutral scalar eta(0) with m_(eta;(0))=200 GeV/c(2) and coupling xi(13)=1, approximately 11 signal events are expected over a background of 2.1+/-1.8 events. Three events are observed in the data, consistent with background expectations, and limits are set on the coupling xi(13) for m(eta(0)=180-300 GeV/c(2).Direct bound on the total decay width of the top quark in pp- collisions at s=1.96□□TeV
Physical Review Letters 102:4 (2009)
Abstract:
We present the first direct experimental bound on the total decay width of the top quark, t, using 955□□pb-1 of the Tevatrona's pp- collisions recorded by the Collider Detector at Fermilab. We identify 253 top-antitop pair candidate events. The distribution of reconstructed top quark mass from these events is fitted to templates representing different values of the top quark width. Using a confidence interval based on likelihood-ratio ordering, we extract an upper limit at 95% C.L. of "t<13.1□□GeV for an assumed top quark mass of 175□□GeV/c2. © 2009 The American Physical Society.Search for maximal flavor violating scalars in same-charge lepton pairs in pp̄ collisions at s=1.96TeV
Physical Review Letters 102:4 (2009)