Search for Light Higgs Boson from Top Quark Decays at CDF
We present a search for light (with mass below 2m_b)
NMSSM pseudo-scalar Higgs boson A originating
from top quark decays t->H+b -> W*Ab
Under assumption that A decays into tau-tau,
we search in events with lepton + >=3 jets and >= 1 b-tag
for an additional isolated track in the Pt range from 3 to 20 GeV/c.
Using a fit to the isolated track Pt spectrum we derive limits on the branching
ratio of t->H+b for various H+ and A masses.
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Direct Measurement of the Top Quark Width at CDF
We present a measurement of the top quark width using ttbar lepton + jets events collected by the CDF II Detector from ppbar collisions at $\sqrt{s} =$ 1.96 TeV at the Fermilab Tevatron. From a data sample of integrated luminosity of 4.3 fb$^{-1}$, we identify 1011 $t\bar{t}$ candidate events. A reconstructed top quark mass and hadronic W boson mass are built per event and compared with templates of different top quark widths. We use a nonparametric kernel density estimation technique to derive two-dimensional probability density functions from simulated signal and background samples. By applying Feldman-Cousins approach, we establish an upper limit at 95$\%$ C.L. of $\Gamma_t <$ 7.6 GeV and a 68$\%$ C.L. range of 0.3 GeV $< \Gamma_t <$ 4.4 GeV for assumed top quark mass of 172.5 GeV$/c^2$.
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Search for Heavy Top-like Quarks Using Lepton Plus Jets Events in 1.96-TeV ppbar Collisions
In the 15 years since the discovery of top at the Tevatron data available has reached the point where we can perform in depth examinations of the top quark event sample for evidence of physics beyond the Standard Model. We present a search for a massive quark (t') decaying to Wq and thus mimicking the top quark decay signature. We use the reconstructed mass of the t' quark and the scalar sum of the transverse energies in the event to discriminate possible new physics from Standard Model processes, and set limits on a standard 4th generation t' quark.
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Measurement of top pair spin correlation using CDF Run II lepton+jets data
Top quark spin is one of the most interesting, yet not well-measured, quantities in top physics. Standard model top pair production through qq annihilation or gluon fusion produces a characteristic spin correlation which can be modified by exotic production mechanisms such as Z' bosons or KK gluons. According to the standard model, top quarks decay weakly before any hadronization processes take effect. This enables top quark spin information to be transmitted to the top quark decay products. We report on the observation and measurement of the t-tbar spin correlation using lepton+jet events in 4.5/fb of CDF data.
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Measurement of the ttbar Cross Section in the Lepton + Jets Channel Using Simultaneous Kinematic Fits in 2.7 fb-1 of CDF Data
We measure both the t\bar{t} cross section and the background
level of W+jets, QCD, and electroweak processes using a simultaneous
kinematic fit to the $b$-tagged lepton + jets data. This is the first
application of a procedure of this kind.
The top cross section and Monte Carlo simulation K factors for W+jets
processes are found to be in good agreement with existing measurements
using other procedures. This approach has an added advantage that many
systematic uncertainties are measured in-situ and inversely scale with
integrated luminosity.
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Latest CDF Results on the Measurement of W-Boson Polarization in Top-quark Decay
The top quark is the most massive fundamental particle observed by
experiment. Due to its large mass, the top quark decays before forming a bound
state and provides a unique opportunity to study the properties of a ``bare'' quark. In
the Standard Model (SM) the top quark decays via the weak interaction into a W boson
and a b quark most of the time, and the W boson is expected to have longitudinal,
left-handed and right-handed polarization fractions of ~0.70, ~0.30 and 0.0, respectively.
In beyond the SM scenarios, significant deviations from the SM expectation are possible
due to the presence of anomalous couplings in the tWb vertex.
I will present the latest CDF results probing the tWb vertex by measurement of W-Boson polarization
in top-pair decay.
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Measurement of the top pair production cross section in the dilepton
decay channel at CDF
We present a measurement of the $t\bar{t}$ production cross section in
$p\bar{p}$ collisions at $\sqrt{s}$ = 1.96 TeV using 5.1 fb$^{-1}$ of data
collected by the CDF detector at the Fermilab Tevatron. We use $t\bar{t}$
dilepton events reconstructed with missing transverse energy and jets
assuming top quark mass $m_t$ = 172.5 GeV/c$^2$.
We measure $$\sigma_{ t\bar{t}} = 7.40 \pm \mathrm{0.58_{stat} \pm 0.63_{syst} \pm
0.45_{lumi}\ pb}.$$ for pre-tagging signal candidate events
$$\sigma_{ t\bar{t}} = 7.25 \pm \mathrm{0.66_{stat} \pm 0.47_{syst} \pm
0.44_{lumi}\ pb}.$$ for b-tagging signal candidate events
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Measurement of the Top quark Mass at CDF using a Matrix Element Technique
We report an updated measurement of the top quark mass obtained from proton-antiproton collisions at a center-of-mass energy of 1.96 TeV at the Fermilab Tevatron using the CDF II detector. We calculate a signal likelihood using a matrix element integration method with a Quasi-Monte Carlo integration to take into account finite detector resolution and quark mass effects. We use a neural network discriminant to distinguish signal from backgrounds. Our overall signal probability is a 2-D function of mt and ΔJES, where ΔJES is a shift applied to all jet energies in units of the jet-dependent systematic error. We apply a cut to the peak value of individual event likelihoods in order to reduce the effect of badly reconstructed events. This measurement updates our previous measurements to use a dataset corresponding to 4.8 fb-1 of integrated luminosity, requiring events with a lepton, large missing ET, and exactly four high-energy jets in the pseudorapidity range |η| ≤ 2. In addition, for this analysis, we add a new class of events containing loose muons to increase the total data sample. We require that at least one of the jets is tagged as coming from a b quark, and observe 738 total events before and 630 events after applying our likelihood cut. We find mt = 172.6 ± 0.9 (stat.) ± 0.7 (JES) ± 1.1 (syst.) GeV/c2, or mt = 172.6 ± 1.6 (tot.) GeV/c2.
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Search For TTBAR Resonances In Multi-Jets At CDF
We present a blind search for resonant top-antitop pair production and
subsequent decay in the all-hadronic channel. We apply a powerful
reconstruction technique where the observed event kinematics are
constrained according to the full standard model top-antitop
production and decay matrix element.
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