Top Physics from Run 1 and Run 2 Prospects at CDF
Steven R. Blusk
for the CDF Collaboration
We present a summary of top quark physics results from Run 1 at CDF using the Run 1 data sample of 106 pb$^{-1}$. In addition to the precursory measurements of the top quark mass and $bar$ cross section, we have performed a number of other analyses which test the consistency of the $bar$ data sample with the standard model (SM). Deviations from SM expectations could provide hints for new physics. We find that the data are consistent with the SM. While the Run 1 data are statistically limited, we have shown that the systematic uncertainties are under control and thus have layed the groundwork for higher precision tests of the SM in Run 2. This report describes the Run 1 top quark analyses and expectations and prospects for top quark measurements in Run 2.
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\documentclass{ws-p10x7}

\newcommand{\et}{{\rm E}_{\scriptscriptstyle\rm T}}
\def \Et {{\rm E}_{\rm T}}
\def \Pt {{\rm P}_{\rm T}}
\newcommand{\met}{\mbox{$\protect \raisebox{.3ex}{$\not$}\et \ $}}
\newcommand{\ppbar}{p\bar{p}}
\newcommand{\qqbar}{q\bar{q}}
\newcommand{\ttbar}{t\bar{t}}
\newcommand{\bbbar}{b\bar{b}}
\newcommand{\ccbar}{c\bar{c}}
\newcommand{\bbar} {\bar{b}}   
\newcommand{\tbar} { \bar{{t}}  }                                
\def \mtop {$M_{top} \ $}
\newcommand{\gev}  { \rm GeV }
\newcommand{\gevc} { {\rm GeV}/c }
\newcommand{\gevcc}{ {\rm GeV}/c^{2} }


\begin{document}

\title{Top Physics from Run 1 and Run 2 Prospects at CDF}

\author{Steven R. Blusk, for the CDF Collaboration}

\address{University of Rochester, Rochester, New York 14628}

\twocolumn[\maketitle\abstract{
We present a summary of top quark physics results from Run 1 at CDF using the Run 1
data sample of 106 pb$^{-1}$. In addition to the precursory measurements of the top quark 
mass and $\ttbar$ cross section, we have performed a number of other analyses which 
test the consistency of the $\ttbar$ data sample with the standard model (SM). Deviations
from SM expectations could provide hints for new physics.
We find that the data are consistent with the SM. While the Run 1 data are
statistically limited, we have shown that the systematic uncertainties are under control 
and thus have layed the groundwork for higher precision tests of the SM in Run 2.
This report describes the Run 1 top quark analyses and expectations and prospects for
top quark measurements in Run 2. }]

\section{Introduction}%1
%
%   The longer version...
%
%	The top quarks was discovered only five years ago at the CDF~\cite{cdf-discovery}
%and D0~\cite{d0-discovery} Collaborations. Since that time, the full data samples 
%($\approx$105 pb$^{-1}$) have been analyzed and results published. Here we present Run 1
%results from the CDF experiment and discuss prospects for Run 2 which is to begin in less
%than one year. The CDF detector is described in detail in the references~\cite{cdf_det}.
%In short, it contains tracking and calorimetry for reconstructing jets, electrons, muons
%and neutrinos (through missing transverse energy, \met). B-quark jets are identified by 
%reconstructing displaced vertices in a silicon vertex detector (SVX tagging) or through identifying 
%soft leptons inside a jet consistent with a semileptonic b decay (SLT tag). 
%
%	In $\ppbar$ collisions at the Tevatron ($\sqrt{s}$=1.8 TeV), top-antitop quark pairs
%are produced through the strong interaction ($\approx$90\% $\qqbar$ annihilation,
%$\approx$10\% gluon fusion) with an expected cross section of 5.1 pb~\cite{ttbar-xs-theory}.
%Single top quarks are also expected to be produced through a t-W-b electroweak vertex with
%an expected total cross section of $\approx$1/2 that of $\ttbar$~\cite{singletop-xs-theory}.
%Within the SM, the top (antitop) quark is expected to decay with a lifetime of 
%$\approx~10^{-24}$ seconds into a W$^+$ (W$^-$) boson and a b ($\bbar$) quark 
%($\ttbar\to W^+ W^- b \bbar$). 
%$\ttbar$ final states are classified according to the decays modes of the two W bosons. Dilepton
%final states consist of events where both W bosons have decayed leptonically into either and 
%$e$ or $\mu$ plus a neutrino (BR=5\%). Lepton + jets final states include events where one of the
%W bosons decays leptonically and the other hadronically into two jets (BR=30\%). The All-Jets mode 
%includes events in which both W-bosons decay hadronically into pairs of jets (BR=44\%).
%
%    Dilepton events are selected by requiring 2 leptons ($e$ or $\mu$) with $\Pt>20 \gevc$,
%$\ge$2 jets with $\Pt>10~\gevc$ and \met > 25~$\gev$. Backgrounds are mainly from Drell-Yan,
%$Z\to\tau\tau$, misidentified/mismeasured leptons, and $WW$ production.
%Lepton+$\ge3$ jets events are defined by having
%one $e$ or $\mu$ with $\Pt>20~\gevc$, $\ge$3 jets with $\Pt>15~\gevc$ of which at least one must
%be SVX or SLT tagged, and \met > 20~$\gev$. Lepton + $\ge 4$ jets require a fourth jet with
%$\Pt>8~\gevc$ which results in a larger signal-to-background, and are used when either 
%higher purity or top mass reconstruction is required. Because of the higher purity of $\ttbar$ 
%in W+$\ge$4 jet events, we remove the $b$-tagging requirement if there are at least 4 jets with 
%$\Pt>15~\gevc$. The background is predominantly from non-$\ttbar$ W+jet production, with smaller 
%contributions mistags, $\bbbar$ and single top. The All-Jets mode requires no high $\Pt$ leptons, 
%no significant \met and $\ge$ 5 jets with at least one SVX b-tag. By far, the dominant
%background is from multi-jet production. Details of the selection criteria and backgrounds 
%can be found in the references~\cite{dil-xsec,ljet-xsec,allhad-mass-xsec}.
%

	In $\ppbar$ collisions at the Tevatron ($\sqrt{s}$=1.8 TeV), top quark pairs
are produced through the strong interaction with an expected cross section (at NLO) of 
5.1 pb~\cite{ttbar-xs-theory}. 
Single top quarks are also expected to be produced through a t-W-b electroweak vertex with
an expected total cross section of $\approx$1/2 that of $\ttbar$~\cite{singletop-xs-theory}.
Within the SM, the top quark is expected to decay with a lifetime of 
$\approx~10^{-24}$ seconds into a W boson and a b quark. 
$\ttbar$ final states are classified according to the decays modes of the two W bosons. Dilepton
final states consist of events where both W bosons decay to an $e$ or $\mu$ (BR=5\%). Lepton + jets 
final states include events where one of the W bosons decays leptonically ($e$ or $\mu$)
and the other hadronically (BR=30\%). The All-Jets mode includes events in which both W-bosons decay 
hadronically (BR=44\%). 

%    Dilepton events are selected by requiring 2 leptons ($e$ or $\mu$) with $\Pt>20 \gevc$,
%$\ge$2 jets with $\Pt>10~\gevc$ and \met > 25~$\gev$. Backgrounds are mainly from Drell-Yan,
%$Z\to\tau\tau$, misidentified/mismeasured leptons, and $WW$ production.
%Lepton+$\ge$ 3 jets events require one $e$ or $\mu$ with $\Pt>20~\gevc$, $\ge$3 jets with 
%$\Pt>15~\gevc$ of which at least one must be SVX or SLT tagged, and \met > 20~$\gev$. 
%Lepton + $\ge 4$ jets require a fourth jet with
%$\Pt>8~\gevc$ which results in a larger signal-to-background, and are used when either 
%higher purity or top mass reconstruction is required. Because of the higher purity of $\ttbar$ 
%in W+$\ge$4 jet events, we remove the $b$-tagging requirement if there are at least 4 jets with 
%$\Pt>15~\gevc$. The background is predominantly from non-$\ttbar$ W+jet production, with smaller 
%contributions mistags, $\bbbar$ and single top. The All-Jets mode requires no high $\Pt$ leptons, 
%no significant \met and $\ge$ 5 jets with at least one SVX b-tag. By far, the dominant
%background is from multi-jet production. Details of the selection criteria and backgrounds 
%can be found in the references~\cite{dil-xsec,ljet-xsec,allhad-mass-xsec}.

\vspace{-0.20in}
\section{$\ttbar$ Cross Section}%2

   Cross section measurements have been made in all three decay 
channels. In the dilepton channel~\cite{dil-xsec}, we observe 9 events with an 
expected background of 2.5$\pm$0.5 events, which leads to a $\ttbar$
cross section of $8.2^{+4.4}_{-3.4}$ pb. In the lepton+$\ge$3 jets
channel, there are 29 (25) events which are SVX (SLT) tagged with expected backgrounds 
of 8.1 (13.2) events, leading to a measurement of $5.7^{+1.9}_{-1.5}$ pb~\cite{ljet-xsec}. 
For the All-Jets mode, we measure $7.6^{+3.5}_{-2.7}$ pb~\cite{allhad-mass-xsec}. Results 
from all three channels are combined to obtain a $\ttbar$ cross section of 
$6.5^{+1.7}_{-1.4}$ pb~\cite{ptohos} which is within one standard deviation from 
the theoretical prediction.

\vspace{-0.15in}
\section{Top Quark Mass}%3

   The most precise measurements in the top quark sector thus far have been in the mass.
In the dilepton channel, we use a weighting technique which compares the
observed \met in each event to the expected value as a function of the assumed top mass.
Using a likelihood technique we extract a top mass of \mtop=167.4$\pm$11.4~$\gevcc$~\cite{dil-mass}.
In the lepton+$\ge$4 jets events, we perform a 2C fit of the final state particles to the decay 
chain, which results in a measured top mass of $176.1\pm7.4~\gevcc$~\cite{ljet-mass}.
Full reconstruction of events in the All-Jets mode is also performed from which we 
measure \mtop=186.0$\pm 11.5~\gevcc$~\cite{allhad-mass-xsec}. 
The result from combining all three measurements is
$176.1\pm 6.6~\gevcc$, roughly 35 times the mass of the next heaviest quark!


%In the dilepton channel, the presence of two neutrinos results in too few constraints for 
%explicit mass reconstruction. Instead, we rely on a weighting technique which compares the
%observed \met in each event to the expected value as a function of the assumed top mass.
%Using this procedure, a {\it most likely} top mass per event is extracted and the resulting 
%distribution of {\it most likely} masses in data are compared to a Monte Carlo simulation of 
%top events for input top masses in the range from 120 to 220 $\gevcc$. The data are fit using 
%a likelihood procedure from which we find \mtop=167.4$\pm$11.4~$\gevcc$~\cite{dil-mass}. 
%The lepton+$\ge$4 
%jets events are fully constrained by the measurements of the four momenta of the lepton, jets, 
%and \met. We form a $\chi^2$ which allows the measured energies to fluctuate within their
%uncertainites subject to the constraints of the decay process. Comparing the reconstructed mass
%spectrum from data to Monte Carlo simulation yields \mtop=$176.1\pm7.4~\gevcc$~\cite{ljet-mass}. 
%Full reconstruction of events in the All-Jets mode is also performed by requiring at least 
%6 jets from which we measure \mtop=186.0$\pm 11.5~\gevcc$~\cite{allhad--mass-xsec}. 
%The result from combining all three measurements is
%$176.1\pm 6.6~\gevcc$, roughly 35 times the mass of the next heaviest quark!


\vspace{-0.15in}
\section{The $\ttbar$ Invariant Mass ($M_{\ttbar}$)}%4

The $M_{\ttbar}$ analysis~\cite{mttbar} proceeds in a similar way to the top mass analysis.
To improve the resolution on the four momenta of the final state particles (and thus $M_{\ttbar}$),
we constrain the top quark mass to 175 $\gevcc$ in the fit. We also require when we remove
this constraint that the fitted top quark mass lie in the range from 150-200 $\gevcc$. 
%The data are shown in Fig.~\ref{fig:mttbar} along with the standard model prediction. The background 
%is constrained to the expected value and the $\ttbar$ contribution is normalized to account for 
%the remainder of the data. Since there is no clear excess we set 95\% confidence level (CL) limits 
%on the production for narrow resonances decaying to $\ttbar$. 
The data do not show an excess above the SM prediction, and we therefore present
limits on the cross section times branching ratio (see Fig.~\ref{fig:mttbar-limits}).
%Those limits, as a function of 
%the mass of the heavy object are shown in Fig.~\ref{fig:mttbar-limits}. The data are compared to
%the predictions for a leptophobic topcolor $Z^{\prime}$~\cite{zprime1,zprime2}. 
At the 95\% confidence level (CL), 
the data rule out a topcolor $Z^{\prime}$ with mass less than 480 (780) $\gevcc$ and natural width
equal to 0.012 (0.04) $M_{Z^{\prime}}$.


%\begin{figure}%1
%\epsfxsize120pt
%\figurebox{120pt}{120pt}{mttbar.ps}
%\caption{The observed $\ttbar$ invariant mass spectrum in the lepton+$\ge$4 jets 
%data (points) compared to simulation of standard model $\ttbar$ and W+jets (dashed line). 
%The dotted line shows the W+jets contribution.}
%\label{fig:mttbar}
%\end{figure}

\begin{figure}%2
\epsfxsize160pt
\vspace{-0.25in}
\figurebox{120pt}{160pt}{mttbar-limits.ps}
\vspace{-0.4in}
\caption{The 95\% CL limits on $\sigma_X\dot BR(X\to\ttbar)$ as a function of
the mass of $X$ for two different values of the full width of the heavy object. The data are 
compared to the prediction for a leptophobic topcolor $Z^{\prime}$ for full widths of 0.012 
$M_{Z^{\prime}}$ and 0.04 $M_{Z^{\prime}}$.}
\label{fig:mttbar-limits}
\end{figure}

\vspace{-0.15in}
\section{Top $\Pt$}%5

Like the $M_{\ttbar}$ analysis, we use $l$+4 jet data and constrain the top quarks mass to 
175 $\gevcc$. Because of the strong correlation between the top and antitop quarks' $\Pt$,
we use only the hadronically decaying top quark. We measure
the fraction of top quarks produced in four bins of true $\Pt$: 0-75 $\gevcc$, 
75-150 $\gevcc$, 150-225 $\gevcc$, and 225-300 $\gevcc$. First, we determine initial 
response functions which give the distribution of reconstructed $\Pt$ in each of the four 
true $\Pt$ bins. The data are then fit to a combination of the
four Monte Carlo (MC) reconstructed $\Pt$ distributions using an iterative procedure to minimize 
the sensitivity of the final result to the initial assumptions of the true top $\Pt$ distribution.
Within the limited statistics, the data are consistent with  
SM expectations. We measure the 95\% CL limit for the fraction of top 
quarks with true $\Pt$ larger than 225 $\gevc$ to be 0.114.


%The results for the fraction of top quarks in the four bins of true $\Pt$ are as follows:
%0-75 $\gevc$: $0.29^{+0.18}_{-0.18}(st)^{+0.08}_{-0.08}(sy)$; 
%75-150 $\gevc$: $0.42^{+0.18}_{-0.18}(st)^{+0.05}_{-0.07}(sy)$;
%150-225 $\gevc$: $0.29^{+0.12}_{-0.10}(st)^{+0.06}_{-0.05}(sy)$;
%225-300 $\gevc$: $0.000^{+0.035}_{-0.000}(st)^{+0.019}_{-0.00}(sy)$. 

%\begin{table}%1
%\caption{Fractions of top events in each bin of true $\Pt$. 
%The first pair of uncertainties are statistical and the second set are 
%systematic.}\label{tab:toppt}
%\begin{tabular}{|c|c|c|c|} 
%\hline 
% \raisebox{0pt}[12pt][6pt]{$\Pt$ Bin} &  \raisebox{0pt}[12pt][6pt]{Measured fraction} \\
%\hline
%$0-75~\gevc$     & $0.29^{+0.18}_{-0.18}(st)^{+0.08}_{-0.08}(sy)$ \\
%$75-150~\gevc$   & $0.42^{+0.18}_{-0.18}(st)^{+0.05}_{-0.07}(sy)$ \\
%$150-225~\gevc$  & $0.29^{+0.12}_{-0.10}(st)^{+0.06}_{-0.05}(sy)$ \\
%$225-300~\gevc$  & $0.000^{+0.035}_{-0.000}(st)^{+0.019}_{-0.00}(sy)$ \\
%\hline
%\end{tabular}
%\end{table}

\vspace{-0.15in}
\section{W Helicity in Top Decays}

  The V-A structure of the t-W-b vertex results in a specific prediction for the W
polarization in top decays. At tree level, we expect the fraction of longitudinal $W$
bosons, $F_0$, to be 70.1$\pm$1.6\%. The $\Pt$ spectrum of the leading lepton is sensitive to
the W polarization. Using MC distributions of longitudinal and left-handed W's,
we fit the data to extract the fraction $F_0$. Using both the lepton+jets and dilepton
data samples, we measure $F_0=91\pm 37(stat)\pm 13$\%~\cite{w-hel}. 

\vspace{-0.15in}
\section{Rare Decays}

    The FCNC decays $t\to Zq$ and $t\to\gamma q$ are strongly suppressed in the S.M.
at the level of $\sim$10$^{-12}$, and therefore an observation of such events is a
signature of new physics. We have performed searches for these decays~\cite{rare-decays}
and find one event in each channel, consistent with background expectations. We therefore
set 95\% CL limits of 33\% and 3.2\% respectively for these two FCNC decays.

\vspace{-0.15in}
\section{Single Top Production}

   We have searched for single top in the lepton+jets data. One analysis searches for events in
both the W-gluon fusion and the s-channel $W^*$ processes. We select W+1,2,3 jet events which
have a SVX b-tag and a top invariant mass, $M_{l\nu b}$ in the range 140 to 210 $\gevcc$. 
We observe 65 events with an expected background of 62.5$\pm$11.5 events. We expect to 4.3 signal
events. Fitting the $H_T=\sum \et (lepton, \met, jets)$ distribution in data to MC 
signal and background distributions, we extract a cross section limit of 13.5 pb at 95\% CL. 
A second analysis which looks just for the W-gluon
fusion process selects W+2 jet events with an SVX tag and the same cut on $M_{l\nu b}$. An 
interesting and exploitable feature of these events is that, unlike the backgrounds, the 
product of the leading lepton's charge ($Q$) and the pseudorapidity of the untagged jet 
($\eta$) peaks at positive $Q\times\eta$. We observe 15 events with an expected background 
of 12.9$\pm$2.1 events (we expect 1.2$\pm$0.3 signal events). From a fit of the 
$Q\times\eta$ distribution in data to MC signal and background distributions, we extract 
a 95\% CL limit of 15.4 pb.

\vspace{-0.2in}
\section{Run 2 Expectations}
\vspace{-0.1in}

   Run 2 will provide $\approx$40-50 times more $\ttbar$ events than Run 1. In addition to a 
large reduction in statistical uncertainties, systematic uncertainties such as the jet energy 
scale and MC modelling will also be reduced. For example, the large 
sample of $Z\to\bbbar$ events can be used to check the $b-jet$ energy scale. The invariant mass
of the two untagged jets in double SVX tagged W+4 jet events can be used to check the light quark 
jet energy scale. A comparison of extra jets in a high purity top sample can be used to put 
constraints on gluon radiation in the MC simulation. Moreover, we expect to undertake new physics
analyses in Run 2, such as studying the spin correlations in $\ttbar$ events.
Given the size of the Run 2 data sample, we have made projections for the precision we can expect
for a variety of measurements. Some of these projections are given in Table~\ref{tab:run2proj}.
Run 2 and a future Run 3 will clearly provide very rich top samples with which to probe the SM and 
beyond.



\begin{table}%1
\caption{Projections for the expected precision for measurements with an integrated luminosity 
of 2 $fb^{-1}$.}\label{tab:run2proj}
\begin{tabular}{|c|c|c|c|} 
\hline 
Measurement &  Precision \\
\hline
\mtop 				& 1.5\%  \\
$\ttbar$ cross section  	& 9\%    \\
Single top cross section	& 24\%   \\
$V_{tb}$ (from Single top)	& 13\%   \\
$F_0$				& 5.5\%  \\
$\sigma*BR(X\to\ttbar )$	& 0.1 pb at 1 TeV \\
$ BR(t\to \gamma c)$		& $<$2.8x10$^{-3}$ \\
$ BR(t\to Zc)$			& $<$1.3x10$^{-2}$ \\
$ BR(t\to Hb)$			& $<12$\% \\
\hline
\end{tabular}
\end{table}

\vspace{-0.15in}
\section*{Acknowledgments}
\vspace{-0.1in}
   We thank the Fermilab staff and our CDF collaborators for their vital 
contributions to these physics analyses.

 
\begin{thebibliography}{99}

%\bibitem{cdf-discovery} F. Abe {\it et al.,} Phys. Rev. Lett. {\bf 74}, 
%        2626 (1995).
%\bibitem{d0-discovery} S. Abachi {\it et al.,} Phys. Rev. Lett. {\bf 74}, 
%        2632 (1995).

\bibitem{ttbar-xs-theory} 
E. Berger and H. Contopanagos, {\it Phys. Rev.} D {\bf 57}, 253 (1998), {\it and references therein}.

\bibitem{singletop-xs-theory} 
T. Stelzer, Z. Sullivan and S. Willenbrock, {\it Phys. Rev.} D {\bf 58}, 
094021 (1998), {\it and references therein}.

%\bibitem{cdf_det} F.Abe {\it et al.,} {\it Nucl. Instrum. Methods} A {\bf 271},  387 (1988).

\bibitem{dil-xsec} 
F. Abe {\it et al.,} Phys. Rev. Lett. {\bf 80}, 2779 (1998).
\bibitem{ljet-xsec}
F. Abe {\it et al.,} Phys. Rev. Lett. {\bf 80}, 2773 (1998).
\bibitem{allhad-mass-xsec}
F. Abe {\it et al.,} Phys. Rev. Lett. {\bf 79}, 1992 (1997).

\bibitem{ptohos} F. Ptohos (for the CDF Collaboration), Proceedings of the 
        International Europhysics Conference on High Energy Physics 99, 
        Tampere, Finland, July 17, 1999.

\bibitem{dil-mass}
F. Abe {\it et al.,} Phys. Rev. Lett. {\bf 82}, 271 (1999).

\bibitem{ljet-mass}
T. Affolder {\it et al.,} preprint hep-ex/0006028 (submitted to {\it Phys. Rev.} D);
F. Abe {\it et al.,} Phys. Rev. Lett. {\bf 80}, 2767 (1998).

\bibitem{mttbar}
T. Affolder {\it et al.,} preprint hep-ex/0003005 (accepted in Phys. Rev. Lett.)

%\bibitem{zprime1}
%C. T. Hill {\it Phys. Lett.} B {\bf 345}, 483 (1995); 
%C. T. Hill and S. J. Parke {\it Phys. Rev.} D {\bf 49}, 4454 (1994).

%\bibitem{zprime2}
%R. M. Harris, C. T. Hill and S. J. Parke, Fermilab-FN-687, hep-ph/9911288 (1999).

%\bibitem{toppt-models}
%T. G. Rizzo, preprint hep-ph/9902273;
%E. Simmons, preprint hep-ph/9908511;
%K. Lane {\it Phys. Rev.} D {\bf 52}, 1546 (1995). 

\bibitem{toppt}
T. Affolder {\it et al.,} to be submitted to {\it Phys. Rev. Lett.}

\bibitem{w-hel}
T. Affolder {\it et al.,} {\it Phys. Rev. Lett.} {\bf 84} 216 (2000).

\bibitem{rare-decays}
T. Affolder {\it et al.,} {\it Phys. Rev. Lett.} {\bf 80} 2525 (1998).

\end{thebibliography}
 
\end{document}


%%%%%%%%%%%%%% End of ws-p10x7.tex %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%


hep-ex0009050.extracted_bib
\begin{thebibliography}{99}

%\bibitem{cdf-discovery} F. Abe {\it et al.,} Phys. Rev. Lett. {\bf 74}, 
%        2626 (1995).
%\bibitem{d0-discovery} S. Abachi {\it et al.,} Phys. Rev. Lett. {\bf 74}, 
%        2632 (1995).

\bibitem{ttbar-xs-theory} 
E. Berger and H. Contopanagos, {\it Phys. Rev.} D {\bf 57}, 253 (1998), {\it and references therein}.

\bibitem{singletop-xs-theory} 
T. Stelzer, Z. Sullivan and S. Willenbrock, {\it Phys. Rev.} D {\bf 58}, 
094021 (1998), {\it and references therein}.

%\bibitem{cdf_det} F.Abe {\it et al.,} {\it Nucl. Instrum. Methods} A {\bf 271},  387 (1988).

\bibitem{dil-xsec} 
F. Abe {\it et al.,} Phys. Rev. Lett. {\bf 80}, 2779 (1998).
\bibitem{ljet-xsec}
F. Abe {\it et al.,} Phys. Rev. Lett. {\bf 80}, 2773 (1998).
\bibitem{allhad-mass-xsec}
F. Abe {\it et al.,} Phys. Rev. Lett. {\bf 79}, 1992 (1997).

\bibitem{ptohos} F. Ptohos (for the CDF Collaboration), Proceedings of the 
        International Europhysics Conference on High Energy Physics 99, 
        Tampere, Finland, July 17, 1999.

\bibitem{dil-mass}
F. Abe {\it et al.,} Phys. Rev. Lett. {\bf 82}, 271 (1999).

\bibitem{ljet-mass}
T. Affolder {\it et al.,} preprint hep-ex/0006028 (submitted to {\it Phys. Rev.} D);
F. Abe {\it et al.,} Phys. Rev. Lett. {\bf 80}, 2767 (1998).

\bibitem{mttbar}
T. Affolder {\it et al.,} preprint hep-ex/0003005 (accepted in Phys. Rev. Lett.)

%\bibitem{zprime1}
%C. T. Hill {\it Phys. Lett.} B {\bf 345}, 483 (1995); 
%C. T. Hill and S. J. Parke {\it Phys. Rev.} D {\bf 49}, 4454 (1994).

%\bibitem{zprime2}
%R. M. Harris, C. T. Hill and S. J. Parke, Fermilab-FN-687, hep-ph/9911288 (1999).

%\bibitem{toppt-models}
%T. G. Rizzo, preprint hep-ph/9902273;
%E. Simmons, preprint hep-ph/9908511;
%K. Lane {\it Phys. Rev.} D {\bf 52}, 1546 (1995). 

\bibitem{toppt}
T. Affolder {\it et al.,} to be submitted to {\it Phys. Rev. Lett.}

\bibitem{w-hel}
T. Affolder {\it et al.,} {\it Phys. Rev. Lett.} {\bf 84} 216 (2000).

\bibitem{rare-decays}
T. Affolder {\it et al.,} {\it Phys. Rev. Lett.} {\bf 80} 2525 (1998).

\end{thebibliography}