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 a scalar or vector particle decaying into Zγ in p over(p, ̄) collisions at sqrt(s) = 1.96 TeV
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics 671:3 (2009) 349-355
Abstract:
We present a search for a narrow scalar or vector resonance decaying into Zγ with a subsequent Z boson decay into a pair of electrons or muons. The data for this search were collected with the DØ detector at the Fermilab Tevatron p over(p, ̄) collider at a center of mass energy sqrt(s) = 1.96 TeV. Using 1.1 (1.0) fb-1 of data, we observe 49 (50) candidate events in the electron (muon) channel, in good agreement with the standard model prediction. From the combination of both channels, we derive 95% C.L. upper limits on the cross section times branching fraction (σ × B) into Zγ. These limits range from 0.19 (0.20) pb for a scalar (vector) resonance mass of 600 GeV/ c2 to 2.5 (3.1) pb for a mass of 140 GeV/ c2.Search for maximal flavor violating scalars in same-charge lepton pairs in pp̄ collisions at s=1.96TeV
Physical Review Letters 102:4 (2009)
Abstract:
Models of maximal flavor violation (MxFV) in elementary particle physics may contain at least one new scalar SU(2) doublet field ΦFV=(η0,η+) that couples the first and third generation quarks (q1, q3) via a Lagrangian term LFV=ξ13ΦFVq1q3. These models have a distinctive signature of same-charge top-quark pairs and evade flavor-changing limits from meson mixing measurements. Data corresponding to 2fb-1 collected by the Collider Dectector at Fermilab II detector in pp̄ collisions at s=1.96TeV are analyzed for evidence of the MxFV signature. For a neutral scalar η0 with mη0=200GeV/c2 and coupling ξ13=1, ∼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 ξ13 for mη0=180-300GeV/c2. © 2009 The American Physical Society.Search for High-Mass e+e- Resonances in pp¯ Collisions at s=1.96 TeV
Physical Review Letters American Physical Society (APS) 102:3 (2009) 031801