Measurement of top pair spin correlation using CDF Run II lepton+jets data
Speaker: David Mietlicki (CDF Collaboration) PDF
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 top quark charge at CDF
Speaker: Pavol Bartos (CDF Collaboration) PDF
Since the discovery of the top quark at Fermilab in 1995, the CDF collaboration has studied and measured many of its properties. One of the fundamental properties is the charge. The Standard Model predicts the top quark charge to be +2/3, but there is also an alternative theory arguing that the observed quark is a fourth generation quark with charge -4/3. We present the results of the top quark charge measurement via its decay products. A charge track weighting technique has been used to determine the b-jet charge and the CDF kinematic fitter has been exploited to determine the lepton - b-jet assignment in the lepton+jet case and an invariant mass cut in the dilepton topology.
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Measurement of the helicity fractions of $W$ bosons in $t\bar{t}$ production in dilepton channel at CDF
Speaker: Chang-Seon Moon (CDF Collaboration) PDF
We present a measurement of the helicity fractions of $W$ bosons
in the $t\bar{t}$ candidate events selected from final states
where both $W$ bosons are decaying leptonically. The analysis is
based on 5 fb$^{-1}$ of data collected by the CDF detector at
the Fermilab Tevatron in $p\bar{p}$ collisions at $\sqrt{s}$ =
1.96 TeV. The helicity fractions are determined by a comparison
of the cos$\theta*$ distribution between the momentum of the
charged lepton in the $W$ boson rest frame and the $W$ momentum
in top-quark rest frame with templates corresponding to
left-handed, right-handed and longitudinally polarized fractions
exclusively. This is the first measurement of the $W$ boson helicity fractions
in the dilepton channel using kinematic reconstruction at CDF.
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Measurement of the top quark width at CDF
Speaker: Jian Tang (CDF Collaboration) PDF
We present a measurement of the top quark width using 4.3/fb of
data collected with the CDF detector at Fermilab. We use a two
dimensional template method in the lepton+jet decay topology. The
observables are the reconstructed top quark mass from the
minimization of a $\chi^2$ for the overconstrained system, and
the invariant mass of the two jets from the W decays, which
provides an in situ improvement in the determination of the jet
energy scale. We build a Feldman-Counsin (FC) confidence belt
using Monte Carlo pseudo experiments to extract the top quark
width from data at the $95\%$ confidence level.
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Top quark mass measurement in the lepton+jets and dilepton channels at CDF using a template method
Speaker: Jian Tang (CDF Collaboration) PDF
We present a measurement of the top quark mass using the CDF
detector at the Fermilab Tevatron in the lepton + jets and two
leptons final states using a template method. In the lepton +
jets channel, we introduce a 3-dimensional template using
non-parametric kernel density estimation. Two of the observables
have been used in a previous analysis which are the reconstructed
top quark mass in each event obtained by minimizing a $\chi^2$
for the overconstrained kinematic system and dijet mass
of the hadronically decaying W boson in the same event sample, that
provides an in situ improvement in the determination of the jet
energy scale. The 3rd observable is the reconstructed top quark
mass with the 2nd best $\chi^2$ in the kinematic fit. In the
dilepton channel, we use the reconstructed top quark mass
determined using the neutrino weighting method and mT2, a
variable related with the transverse mass in events with two
missing particles. In order to increase the lepton acceptance in
the lepton+jet events, a new lepton category was included from
data collected by a trigger that requires the presence of missing
energy and two jets. By increasing the statistics and the
development of the 3-dimensional template method, we have
significant improved the final result.
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