%
%  Single top talk at CAP Meeting, June 2000
%
\documentstyle[epsfig,colordvi,cap_00]{slides}

\input latex.macros
\input top.macros
\def\DZero{D$\mbox{0\kern-.55em /}$}
\def\mDZero{{\rm D}\mbox{0\kern-.55em /}}
\def\mGeVcc{{\rm GeV\, c^2}}
%

\newcommand{\tit}[1] {
        \begin{center}
        \normalsize
        \fbox{\Red{#1}} \vspace{.25in}
        \small
        \end{center}
}


\def\met{\mathbin{E\mkern - 11mu/_T}}

\begin{document}

\small

\tit{Search for Single Top Production}

\Start
\vspace{0.5in}
\begin{center}
Pekka Sinervo\\
{\it University of Toronto}
\end{center}

\vspace{0.5in}

\Red{Overview}

\tiny
\begin{itemize}
\item Standard Model Framework for Top
\item Single Top Production
\item Search in Run I Data
\begin{itemize}
	\item Technique
	\item Results
\end{itemize}
\item Prognostications for Run II
\\[0.2in]
\end{itemize}

\tiny
\begin{flushright}
Work done primarily by Sarah Wolinski \\
and Pierre Savard
\end{flushright}

\pagebreak
%
%  Intro to SM 
%
\tit{Top Quark Production}

\small
Top has been observed through the LO SM process
$$p\bar{p} \rightarrow t\bar{t}$$
\tiny
\small
\begin{eqnarray}
\sigma_{\mttbar} &=& 6.5^{+1.7}_{-1.4}\ {\rm pb} \nonumber
\end{eqnarray}

\begin{center}
\epsfysize=3.5in
\epsffile[30 140 520 630]{figures/top_physics/top_xs_cdf_d0.eps}
\end{center}

\tiny
\begin{itemize}
        \item Theory predictions range from 4.7 to 5.5 pb
\end{itemize}

However, this is not the only source of top quarks!

\pagebreak
%
%  Single Top Production
%
\tit{Single Top Production}

\small
Single top production is a much lower rate process
\tiny
\begin{itemize}
	\item Sensitive to $\Gamma_{t}$\ and $V_{tb}$
$$ {{|V_{tb}|^2}\over{
|V_{td}|^2 +
|V_{ts}|^2 +
|V_{tb}|^2}} = 0.99 \pm 0.29$$ 
	\item Also could have contributions from non-SM sources
			\\[0.05in]
\end{itemize}

\small
There are two primary SM production processes
\tiny
\begin{enumerate}
	\item $t$-channel $W-g$\ fusion $\Rightarrow W^+ b q$\ final state
	\item $s$-channel $W^\ast$\ process 
		$\Rightarrow W^+ b \bar{b}$\ final state
			\\[0.01in]
\end{enumerate}

\begin{center}
\epsfysize=3.0in
\epsffile[30 140 520 630]{figures/single_top/single_top_production_diagrams.ps}
\end{center}

\begin{itemize}
	\item Predicted cross sections are $1.7\pm0.3$\ and
$0.7\pm0.1$~pb
\end{itemize}
\pagebreak
%
%  Search for two processes
%
\tit{Search Technique}

\small
Kinematics of production processes different
\tiny
\begin{itemize}
	\item Use the same selection for both processes
	\begin{itemize}
		\item 1, 2 or 3 jets with $E_T>15$~Gev and $|\eta|<2.0$
		\item At least one $b$-tagged jet
		\item Require $140\le M_{top}\le 210$~\GeVcc
	\end{itemize}
	\item Fit $H_T$\ distribution with signal and background
terms
\begin{eqnarray}
	H_T \equiv \sum_{\rm partons} E_T
\nonumber
\end{eqnarray}
\end{itemize}
\tiny
\begin{center}
\begin{tabular}{lcc}
			&  $W^\ast$	&	$W$-gluon \\[0.05in]
\hline \\
$\sigma_{theory}$\ (pb)		&   $0.73\pm0.10$	&  $1.7\pm0.3$ \\
Integrated luminosity (\invpb)	&  $106\pm4$		&  $106\pm4$   \\
$W+n$~jet acceptance (\%)	&  $ 4.5\pm0.7$		&  $6.7\pm1.0$ \\
SVX $b$-tag efficiency (\%)	&  $37.5\pm3.1$		& $24.8\pm2.0$ \\[0.05in]
\hline \\
Number of expected events	&  $1.3\pm0.3$		&  $3.0\pm0.6$ \\
\end{tabular}
\end{center}

\vspace{.2in}
		
\pagebreak

\tit{Top Mass Reconstruction}

\vspace{.5in}

\begin{center}
\epsfysize=5.5in
\epsffile[30 140 520 630]{figures/single_top/single_top_top_mass.ps}
\end{center}

\pagebreak
\tit{$H_T$\ Reconstruction}

\small
The variable $H_T$\ is an effective discriminator
\tiny
\begin{itemize}
	\item QCD Background
	\item \ttbar\ background
	\item Single top signal
\end{itemize}
\vspace{.5in}

\begin{center}
\epsfysize=5.0in
\epsffile{figures/single_top/ht_sig_bkgd.eps}
\end{center}

\pagebreak
%
%  Results of search
%
\tit{Results of Search}

\small
Observed 65 events in this sample
\tiny
\begin{itemize}
	\item Largest single background are mistags
	\begin{itemize}
		\item $t\bar{t}$\ itself is a \Red{problem}\ now
	\end{itemize}
\end{itemize}

\begin{center}
\begin{tabular}{lc}
Process			&	Event Yield \\[0.05in]
\hline \\
Mistags				&	$ 25.9\pm7.5$	\\
$W b \bar{b} + W c \bar{c}$	&	$ 28.7\pm7.5$	\\
$W c$				&	$ 17.2\pm6.2$	\\
Non-$W$\			&	$ 12.1\pm4.1$	\\
Miscellaneous			&	$  5.1\pm0.9$	\\
\hline \\
After $M_t$\ cut		&       $ 54\pm11$      \\
\hline \\
$t\bar{t}$			&	$ 8.4\pm2.7$	\\
$W$-gluon			&	$ 3.0\pm0.6$	\\
$W^\ast$			&	$ 1.3\pm0.3$	\\
\hline \\
Total expected			&	$67 \pm 11$	\\
Observed			&	   65    	\\
\end{tabular}
\end{center}

\small
Not yet sensitive to SM single top rate
\tiny
\begin{itemize}
	\item Can set limits on total single top rate
\end{itemize}
\pagebreak


%
%  Single top from W* production
%
\tit{Single Top Production Cross Section Limits}

\small
Use $H_T$\ distribution to fit signal and background shapes
\tiny
\begin{itemize}
	\item Set upper limit using a Bayesian technique
	\item Fit gives $\sigma_t < 13.5$~pb at 95\%\ CL
		\\[0.1in]
\end{itemize}

\begin{center}
\epsfysize=4.0in
\epsffile{figures/single_top/ht_data_mc.eps}
\end{center}

\small
Still well away from SM rate
\tiny
\begin{itemize}
	\item Can conclude that there is no huge anomaly
	\item It is a feasable measurement for Run II
	\begin{itemize}
		\item Can get $S/N = 2.9$\ on $W+2,3$\ jet sample
	\end{itemize}
\end{itemize}

\pagebreak
%
%  Wrap up
%
\tit{Run II Forecasts}

\small
Run II will start this summer at $\sqrt{s}=2.0$~TeV
\tiny
\begin{itemize}
	\item CDF will begin with engineering run (no SVX II)
	\item Both detectors will be completed by end of 2000
	\item Physics running will commence in 2001
\\[0.05in]
\end{itemize}

\small
Will be worth the wait
\tiny
\begin{itemize}
	\item Begin with $\sim 3$~\invfb/year per detector
	\item Finish up with $\sim 5$~\invfb/year 
	\item Literal ``Top Factory'' with 
	\begin{itemize}
		\item 300 dilepton events
		\item 3000 tagged lepton+jet events
		\item 1500 events in ``mass sample''
\\[0.05in]
	\end{itemize}
\end{itemize}

\small
Single top production 
\tiny
\begin{itemize}
	\item Measure $\sigma_t$\ with 10\%\ uncertainty
	\item Measure $V_{tb}$\ with 12\%\ uncertainty
\\[0.05in]
\end{itemize}

	
\pagebreak

\tit{Summary}

\small
Debut of top using Run I data coming to close
\tiny
\begin{itemize}
	\item Have seen that it looks much like a SM fermion
	\item Clearly observed through QCD $t\bar{t}$\ production
	\item Single top harder to extract
	\begin{itemize}
		\item 95\%\ CL upper limit of 
		$\sigma_t < 13.5$~pb at 95\%\ CL
			\\[0.05in]
	\end{itemize}
\end{itemize}

\small
All this sets the stage for Run II
\tiny
\begin{itemize}
	\item Run for 2-4 years, with goal of $\sim6$~\invfb
	\begin{itemize}
	\item[$\Rightarrow$] Increase top quark sample $\times 50$
	\item Should be able to measure single top production
	\begin{itemize}
		\item $S/N \sim 2$
		\item $\sigma_{t} \sim 10$\%
			\\[0.05in]
	\end{itemize}
	\end{itemize}
\end{itemize}

\end{document}
