We present the first measurement of the Bs-Bsbar oscillation frequency Delta m_s. We use 1 fb^-1 ... more We present the first measurement of the Bs-Bsbar oscillation frequency Delta m_s. We use 1 fb^-1 of data from p-pbar collisions at sqrt{s}=1.96 TeV collected with the CDF II detector at the Fermilab Tevatron. The sample contains signals of 3,600 fully reconstructed hadronic Bs decays and 37,000 partially reconstructed semileptonic Bs decays. We measure the probability as a function of proper decay time that the Bs decays with the same, or opposite, flavor as the flavor at production, and we find a signal consistent with Bs-Bsbar oscillations. The probability that random fluctuations could produce a comparable signal is 0.2%. Under the hypothesis that the signal is due to Bs-Bsbar oscillations, we measure Delta m_s = 17.31^{+0.33}_{-0.18} (stat.) +- 0.07 (syst.) ps^-1 and determine |Vtd/Vts| = 0.208^{+0.001}_{-0.002} (exp.) ^{+0.008}_{-0.006} (theo.).
A search for new particles (X) that decay to electron or muon pairs has been performed using appr... more A search for new particles (X) that decay to electron or muon pairs has been performed using approximately 200 pb**(-1) of pbarp collision data at sqrt(s)=1.96 TeV collected by the CDF II experiment at the Fermilab Tevatron. Limits on sigma(ppbar -> X)*BR(X -> ll) are presented as a function of dilepton invariant mass m(ll) > 150 GeV/c**2, for different spin hypotheses (0, 1, or 2). The limits are approximately 25 fb for m(ll) > 600 GeV/c**2. Lower mass bounds for X from representative models beyond the Standard Model including heavy neutral gauge bosons are presented.
This article presents a measurement of the top quark mass using the CDF II detector at Fermilab. ... more This article presents a measurement of the top quark mass using the CDF II detector at Fermilab. Colliding beams of protons and anti-protons at Fermilab's Tevatron ( √ s = 1.96 TeV) produce top/anti-top pairs, which decay to W + W − bb; events are selected where one W decays to hadrons, and the other W decays to either e or µ plus a neutrino. The data sample corresponds to an integrated luminosity of approximately 318 pb −1 . A total of 165 tt events are separated into four subsamples based on jet transverse energy thresholds and the number of b jets identified by reconstructing a displaced vertex. In each event, the reconstructed top quark invariant mass is determined by minimizing a χ 2 for the overconstrained kinematic system. At the same time, the mass of the hadronically decaying W boson is measured in the same event sample. The observed W boson mass provides an in situ improvement in the determination of the hadronic jet energy scale, JES. A simultaneous likelihood fit of the reconstructed top quark masses and the W boson invariant masses in the data sample to distributions from simulated signal and background events gives a top quark mass of 173.5 +3.7 −3.6 (stat. + JES) ± 1.3 (other syst.) GeV/c 2 , or 173.5 +3.9 −3.8 GeV/c 2 .
We report the results of a search for a charged Higgs boson in the decays of top quarks produced ... more We report the results of a search for a charged Higgs boson in the decays of top quarks produced in \ppbar collisions at a center-of-mass energy of 1.96 TeV. We use a data sample corresponding to an integrated luminosity of 193/pb collected by the upgraded Collider Detector at Fermilab. No evidence for charged Higgs production is found, allowing 95% C.L. upper limits to be placed on BR(t->H^+b) for different charged Higgs decay scenarios. In addition, we present in the MSSM (mH,tan beta) plane the first exclusion regions with radiative and Yukawa coupling corrections.
We report a measurement of the top quark mass using events collected by the CDF II Detector from ... more We report a measurement of the top quark mass using events collected by the CDF II Detector from ppbar collisions at \sqrt{s} = 1.96 TeV at the Fermilab Tevatron. We calculate a likelihood function for the top mass in events that are consistent with ttbar->bbar l^- \nubar b l^+ \nu decays. The likelihood is formed as the convolution of the leading-order matrix element and detector resolution functions. The joint likelihood is the product of likelihoods for each of 33 events collected in 340 pb^{-1} of integrated luminosity, yielding a top quark mass M_t = 165.2 +- 6.1 (stat.) +- 3.4(syst.) GeV/c^2. This first application of a matrix-element technique to ttbar->bbar l^- \nubar b l^+ \nu decays gives the most precise single measurement of M_t in dilepton events. Combined with other CDF Run II measurements using dilepton events, we measure M_{t} = 167.9 +- 5.2 (stat.) +- 3.7 (syst.) GeV/c^2.
We present the results of a search for new physics in the jets plus missing transverse energy dat... more We present the results of a search for new physics in the jets plus missing transverse energy data sample collected from 368 pb^{-1} of ppbar collisions at sqrt{s}=1.96 TeV recorded by the Collider Detector at Fermilab. We compare the number of events observed in the data with a data-based estimate of the Standard Model backgrounds contributing to this signature. We observe no significant excess of events, and we interpret this null result in terms of lower limits on the fundamental Planck scale for a large extra dimensions scenario.
We present the first measurement of the Bs-Bsbar oscillation frequency Delta m_s. We use 1 fb^-1 ... more We present the first measurement of the Bs-Bsbar oscillation frequency Delta m_s. We use 1 fb^-1 of data from p-pbar collisions at sqrt{s}=1.96 TeV collected with the CDF II detector at the Fermilab Tevatron. The sample contains signals of 3,600 fully reconstructed hadronic Bs decays and 37,000 partially reconstructed semileptonic Bs decays. We measure the probability as a function of proper decay time that the Bs decays with the same, or opposite, flavor as the flavor at production, and we find a signal consistent with Bs-Bsbar oscillations. The probability that random fluctuations could produce a comparable signal is 0.2%. Under the hypothesis that the signal is due to Bs-Bsbar oscillations, we measure Delta m_s = 17.31^{+0.33}_{-0.18} (stat.) +- 0.07 (syst.) ps^-1 and determine |Vtd/Vts| = 0.208^{+0.001}_{-0.002} (exp.) ^{+0.008}_{-0.006} (theo.).
A search for new particles (X) that decay to electron or muon pairs has been performed using appr... more A search for new particles (X) that decay to electron or muon pairs has been performed using approximately 200 pb**(-1) of pbarp collision data at sqrt(s)=1.96 TeV collected by the CDF II experiment at the Fermilab Tevatron. Limits on sigma(ppbar -> X)*BR(X -> ll) are presented as a function of dilepton invariant mass m(ll) > 150 GeV/c**2, for different spin hypotheses (0, 1, or 2). The limits are approximately 25 fb for m(ll) > 600 GeV/c**2. Lower mass bounds for X from representative models beyond the Standard Model including heavy neutral gauge bosons are presented.
This article presents a measurement of the top quark mass using the CDF II detector at Fermilab. ... more This article presents a measurement of the top quark mass using the CDF II detector at Fermilab. Colliding beams of protons and anti-protons at Fermilab's Tevatron ( √ s = 1.96 TeV) produce top/anti-top pairs, which decay to W + W − bb; events are selected where one W decays to hadrons, and the other W decays to either e or µ plus a neutrino. The data sample corresponds to an integrated luminosity of approximately 318 pb −1 . A total of 165 tt events are separated into four subsamples based on jet transverse energy thresholds and the number of b jets identified by reconstructing a displaced vertex. In each event, the reconstructed top quark invariant mass is determined by minimizing a χ 2 for the overconstrained kinematic system. At the same time, the mass of the hadronically decaying W boson is measured in the same event sample. The observed W boson mass provides an in situ improvement in the determination of the hadronic jet energy scale, JES. A simultaneous likelihood fit of the reconstructed top quark masses and the W boson invariant masses in the data sample to distributions from simulated signal and background events gives a top quark mass of 173.5 +3.7 −3.6 (stat. + JES) ± 1.3 (other syst.) GeV/c 2 , or 173.5 +3.9 −3.8 GeV/c 2 .
We report the results of a search for a charged Higgs boson in the decays of top quarks produced ... more We report the results of a search for a charged Higgs boson in the decays of top quarks produced in \ppbar collisions at a center-of-mass energy of 1.96 TeV. We use a data sample corresponding to an integrated luminosity of 193/pb collected by the upgraded Collider Detector at Fermilab. No evidence for charged Higgs production is found, allowing 95% C.L. upper limits to be placed on BR(t->H^+b) for different charged Higgs decay scenarios. In addition, we present in the MSSM (mH,tan beta) plane the first exclusion regions with radiative and Yukawa coupling corrections.
We report a measurement of the top quark mass using events collected by the CDF II Detector from ... more We report a measurement of the top quark mass using events collected by the CDF II Detector from ppbar collisions at \sqrt{s} = 1.96 TeV at the Fermilab Tevatron. We calculate a likelihood function for the top mass in events that are consistent with ttbar->bbar l^- \nubar b l^+ \nu decays. The likelihood is formed as the convolution of the leading-order matrix element and detector resolution functions. The joint likelihood is the product of likelihoods for each of 33 events collected in 340 pb^{-1} of integrated luminosity, yielding a top quark mass M_t = 165.2 +- 6.1 (stat.) +- 3.4(syst.) GeV/c^2. This first application of a matrix-element technique to ttbar->bbar l^- \nubar b l^+ \nu decays gives the most precise single measurement of M_t in dilepton events. Combined with other CDF Run II measurements using dilepton events, we measure M_{t} = 167.9 +- 5.2 (stat.) +- 3.7 (syst.) GeV/c^2.
We present the results of a search for new physics in the jets plus missing transverse energy dat... more We present the results of a search for new physics in the jets plus missing transverse energy data sample collected from 368 pb^{-1} of ppbar collisions at sqrt{s}=1.96 TeV recorded by the Collider Detector at Fermilab. We compare the number of events observed in the data with a data-based estimate of the Standard Model backgrounds contributing to this signature. We observe no significant excess of events, and we interpret this null result in terms of lower limits on the fundamental Planck scale for a large extra dimensions scenario.
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Papers by Paul Kato