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CDF Collaboration

Publications and source records attributed to CDF Collaboration.

At least 289 records · Page 16Linked to original sources

arXiv2006

Search for Z'--> e^+e^- Using Dielectron Mass and Angular Distribution

We search for Z' bosons in dielectron events produced in ppbar collisions at sqrt{s}=1.96 TeV, using a 0.45 fb^(-1) dataset accumulated with the CDF II detector at the Fermilab Tevatron. To identify the Z' --> e^+e^- signal, both the dielectron invariant mass distribution and the angular distribution of the electron pair are used. No evidence of a signal is found, and 95% confidence level lower limits are set on the Z' mass for several models. Limits are also placed on the mass and gauge coupling of a generic Z', as well as on the contact interaction mass scales for different helicity structure scenarios.

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arXiv2006

Search for anomalous semileptonic decay of heavy flavor hadrons produced in association with a W boson at CDF II

We present a search for anomalous semileptonic decays of heavy flavor hadrons produced in association with a $W$ boson, in proton-antiproton collisions at sqrt{s}=1.96 TeV. We use 162 pb-1 of data collected with the CDF II detector at the Fermilab Tevatron Collider. We select events with one W boson and at least one jet with an identified secondary vertex. In the jets with a secondary vertex we look for a semileptonic decay to a muon. We compare the number of jets with both a secondary vertex and a semileptonic decay, and the kinematic properties of these jets, with the standard model expectation of W plus heavy flavor production and decay. No discrepancy is seen between the observation and the expectation, and we set limits on the production cross section of a B-like hadron with an anomalously high semileptonic branching ratio.

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arXiv2006

Measurement of $σ(Λ_b)/σ(B^0) \times BR(Λ_b\toΛ_cπ^-) / BR(B^0\to D^+π^-)$ in $p\bar{p}$ Collisions at $\sqrt{s}=1.96$ TeV

We present the first observation of the baryon decay $Λ_b\toΛ_cπ^-$ followed by $Λ_c\to p K^-π^+$ in 106 pb-1 of $p\bar{p}$ collisions at $\sqrt{s} = 1.96$ TeV in the CDF experiment. In order to reduce systematic error, the measured rate for $Λ_b$ decay is normalized to the kinematically similar meson decay $B^0\to D^+π^-$ followed by $D^+\toπ^+K^-π^+$. We report the ratio of production cross sections ($σ$) times the ratio of branching fractions (BR) for the momentum region integrated above $p_T > 6$ GeV/c and pseudorapidity range $|η| < 1.3$: $σ(p\bar{p}\to Λ_b X) / σ(p\bar{p}\to B^0 X) \times BR(Λ_b\toΛ_cπ^-) / BR(B^0\to D^+π^-) = 0.82 \pm 0.08(stat) \pm 0.11(syst) \pm 0.22 (BR(Λ_c\to p K^-π^+))$.

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arXiv2005

Search for charged Higgs bosons from top quark decays in \ppbar collisions at $\sqrt{s}=1.96$ TeV

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.

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arXiv2005

Search for Second-Generation Scalar Leptoquarks in $\bm{p \bar{p}}$ Collisions at $\sqrt{s}$=1.96 TeV

Results on a search for pair production of second generation scalar leptoquark in $p \bar{p}$ collisions at $\sqrt{s}$=1.96 TeV are reported. The data analyzed were collected by the CDF detector during the 2002-2003 Tevatron Run II and correspond to an integrated luminosity of 198 pb$^{-1}$. Leptoquarks (LQ) are sought through their decay into (charged) leptons and quarks, with final state signatures represented by two muons and jets and one muon, large transverse missing energy and jets. We observe no evidence for $LQ$ production and derive 95% C.L. upper limits on the $LQ$ production cross sections as well as lower limits on their mass as a function of $β$, where $β$ is the branching fraction for $LQ \to μq$.

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arXiv2005

Top Quark Mass Measurement Using the Template Method in the Lepton + Jets Channel at CDF II

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 (sqrt{s}=1.96 TeV) produce top/anti-top pairs, which decay to W^+W^-bbbar; events are selected where one W decays to hadrons, and one W decays to either e or mu plus a neutrino. The data sample corresponds to an integrated luminosity of approximately 318 pb^-1. A total of 165 ttbar 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 chi-squared 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.

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arXiv2005

Search for New Physics Using High Mass Tau Pairs from 1.96-TeV Proton-Antiproton Collisions

We present the results of a search for anomalous resonant production of tau lepton pairs with large invariant mass, the first such search using the CDF II Detector in Run II of the Tevatron $p\bar{p}$ collider. Such anomalous production could arise from various new physics processes. In a data sample corresponding to 195 pb$^{-1}$ of integrated luminosity we predict 2.8$\pm$0.5 events from Standard Model background processes and observe 4. We use this result to set limits on the production of heavy scalar and vector particles decaying to tau lepton pairs.

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arXiv2005

Precision Top Quark Mass Measurement in the Lepton + Jets Topology in ppbar Collisions at sqrt(s) = 1.96 TeV

We report two measurements of the top quark mass M_top using the CDF II detector at the Fermilab Tevatron in a 318 pb^-1 data sample observed in the lepton + jets final state. One method uses an event-based likelihood technique resulting in M_top = 173.2 +2.6/-2.4 (stat.) +/- 3.2 (syst.) GeV/c^2 or 173.2 +4.1/-4.0 GeV/c^2. The second method reconstructs a top quark mass in each event using the measured invariant mass of the hadronically decaying W boson to constrain the jet energy scale to obtain a value for M_top of 173.5 +3.7/-3.6 (stat.) +/- 1.3 (syst.) GeV/c^2 or 173.5 +3.9/-3.8 GeV/c^2. We take the latter, which is more precise, as our result.

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arXiv2005

Measurement of the Cross Section for $t\bar{t}$ Production in $p\bar{p}$ Collisions using the Kinematics of Lepton+Jets Events

We present a measurement of the top pair production cross section in $p\bar{p}$ collisions at $\sqrt{s}$=1.96 TeV. We collect a data sample with an integrated luminosity of 194$\pm$11 pb$^{-1}$ with the CDF II detector at the Fermilab Tevatron. We use an artificial neural network technique to discriminate between top pair production and background processes in a sample of 519 lepton+jets events, which have one isolated energetic charged lepton, large missing transverse energy and at least three energetic jets. We measure the top pair production cross section to be $σ_{t\bar{t}}= 6.6$$\pm 1.1 \pm 1.5$ pb, where the first uncertainty is statistical and the second is systematic.

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arXiv2005

Measurement of B(t->Wb)/B(t->Wq) at the Collider Detector at Fermilab

We present a measurement of the ratio of top-quark branching fractions R= B(t -> Wb)/B(t -> Wq), where q can be a b, s or a d quark, using lepton-plus-jets and dilepton data sets with integrated luminosity of ~162 pb^{-1} collected with the Collider Detector at Fermilab during Run II of the Tevatron. The measurement is derived from the relative numbers of t-tbar events with different multiplicity of identified secondary vertices. We set a lower limit of R > 0.61 at 95% confidence level.

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arXiv2005

Study of Jet Shapes in Inclusive Jet Production in ppbar Collisions at sqrt{s} = 1.96 TeV

We report on a study of jet shapes in inclusive jet production in $p \bar{p}$ collisions at $\sqrt{s} = 1.96 {\rm TeV}$ using the upgraded Collider Detector at Fermilab in Run II (CDF II) based on an integrated luminosity of $170 \rm pb^{-1}$. Measurements are carried out on jets with rapidity $0.1 < |Y^{\rm jet}| < 0.7$ and transverse momentum 37 GeV/c $< P_T^{\rm jet} < 380$ GeV/c. The jets have been corrected to the hadron level. The measured jet shapes are compared to leading-order QCD parton-shower Monte Carlo predictions as implemented in the PYTHIA and HERWIG programs. PYTHIA, tuned to describe the underlying event as measured in CDF Run I, provides a better description of the measured jet shapes than does PYTHIA or HERWIG with their default parameters.

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arXiv2005

Search for neutral MSSM Higgs bosons decaying to tau pairs in p-pbar collisions at sqrt(s)=1.96 TeV

We present a search for neutral supersymmetric Higgs bosons decaying to tau pairs produced in p-pbar collisions at sqrt(s) = 1.96 TeV. The data, corresponding to 310 pb^(-1) integrated luminosity, were collected with the CDF II detector at the Tevatron collider at Fermilab. No significant excess above the standard model backgrounds is observed. We set exclusion limits on the production cross section times branching fraction to tau pairs for Higgs masses in the range from 90 to 250 GeV/c^2.

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arXiv2005

Measurement of the $\ttbar$ Production Cross Section in $\ppbar$ Collisions at $\sqrt{s}=1.96 TeV Using Lepton Plus Jets Events with Semileptonic B Decays to Muons

We present a measurement of the $\ttbar$ production cross section using $194 \mathrm{pb^{-1}}$ of CDF II data using events with a high transverse momentum electron or muon, three or more jets, and missing transverse energy. The measurement assumes 100% $t\to Wb$ branching fraction. Events consistent with $\ttbar$ decay are found by identifying jets containing heavy flavor semileptonic decays to muons. The dominant backgrounds are evaluated directly from the data. Based on 20 candidate events and an expected background of 9.5$\pm$1.1 events, we measure a production cross section of $5.3\pm3.3^{+1.3}_{-1.0} \mathrm{pb}$, in agreement with the standard model.

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arXiv2005

Measurement of the Ratios of Branching Fractions B(Bs->Ds- pi+)/B(B0->D-pi+) and B(B+->D0bar pi+)/B(B0->D-pi+)

We report an observation of the decay Bs -> Ds- pi+ in p pbar collisions at sqrt(s) = 1.96 TeV using 115 pb^(-1) of data collected by the CDF II detector at the Fermilab Tevatron. We observe 83 +/- 11 Bs -> Ds- pi+ candidates, representing a large increase in statistics over previous measurements and the first observation of this decay at a p pbar collider. We present the first measurement of the relative branching fraction B(Bs -> Ds- pi+) / B(B0 -> D- pi+) = 1.32 +/- 0.18 (stat.) +/- 0.38 (syst.). We also measure B(B+ -> D0bar pi+) / B(B0 -> D- pi+) = 1.97 +/- 0.10(stat.) +/- 0.21(syst.), which is consistent with previous measurements.

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arXiv2005

Measurement of $b$ hadron masses in exclusive $J/ψ$ decays with the CDF detector

We measure the masses of $b$ hadrons in exclusively reconstructed final states containing a $J/ψ\toμ^-μ^+$ decay using $\rm 220 pb^{-1}$ of data collected by the CDF II experiment. We find: m(B^+) = 5279.10 \pm 0.41_{(stat.)} \pm 0.36_{(sys.)} MeVcc, m(B^0) = 5279.63 \pm 0.53_{(stat.)} \pm 0.33_{(sys.)} MeVcc, m(B^0_s) = 5366.01 \pm 0.73_{(stat.)} \pm 0.33_{(sys.)} MeVcc, m(Λ^0_b) = 5619.7 \pm 1.2_{(stat.)} \pm 1.2_{(sys.)} MeVcc. m(B^+) - m(B^0) = -0.53 \pm 0.67_{(stat.)} \pm 0.14_{(sys.)} MeVcc, m(B^0_s) - m(B^0) = 86.38 \pm 0.90_{(stat.)} \pm 0.06_{(sys.)} MeVcc m(Λ^0_b) - m(B^0) = 339.2 \pm 1.4_{(stat.)} \pm 0.1_{(sys.)} MeVcc. The measurements of the $B^0_s$, $Λ^0_b$ mass, $m(B^0_s)-m(B^0)$ and $m(Λ^0_b)-m(B^0)$ mass difference are of better precision than the current world averages.

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arXiv2005

Search for New High Mass Particles Decaying to Lepton Pairs in pbarp Collisions at sqrt(s)=1.96 TeV

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.

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arXiv2005

Search for Lambda_b -> p pi and Lambda_b -> p K decays in p-pbar collisions at sqrt(s) = 1.96 TeV

We report on a search for Lambda_b -> p pi- and Lambda_b -> p K- (and charge conjugate) decays in p-pbar collisions at sqrt(s) = 1.96 TeV using 193 pb-1 of data collected by CDFII experiment at the Fermilab Tevatron Collider. Data were collected using a track trigger that has been optimized to select tracks belonging to a secondary vertex that is typical of two body charmless decays of b-flavored hadrons, including Lambda_b baryons. As no Lambda_b signal was observed, we set the upper limits on the branching fractions BR(Lambda_b -> p h-) where h is K or pi, of 2.3x10-5 at 90% C.L. and 2.9x10-5 at 95% C.L.

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arXiv2005

A Search for Supersymmetric Higgs Bosons in the Di-Tau Decay Mode in Proton Anti-Proton Collisions at sqrt(s)=1.8 TeV

A search for direct production of Higgs bosons in the di-tau decay mode is performed with 86.3 +/- 3.5 pb^-1 of data collected with the Collider Detector at Fermilab during the 1994-1995 data taking period of the Tevatron. We search for events where one tau decays to an electron plus neutrinos and the other tau decays hadronically. We perform a counting experiment and set limits on the cross section for supersymmetric Higgs boson production where tan(beta) is large and m_A is small. For a benchmark parameter space point where m_A=100 GeV/c^2 and tan(beta)=50, we limit the production cross section multiplied by the branching ratio to be less than 77.9 pb at the 95% confidence level compared to the theoretically predicted value of 11.0 pb. This is the first search for Higgs bosons decaying to tau pairs at a hadron collider.

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