%
%  Top talk at UBC - Colloquium style
%
\documentstyle[epsfig,colordvi,top_debut]{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{The Debut of the Top Quark}

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

\vspace{0.5in}

\Red{Overview}

\tiny
\begin{itemize}
\item Boring Standard Model Stuff
\item What Does Dancing with the Top Quark Tell Us
\item Producing and Detecting Top
\item Sizing up the Top Quark
\item On to Run II
\end{itemize}

\tiny
\begin{flushright}
Work done in collaboration with Pierre Savard \\
and Andrew Robinson
\end{flushright}

\pagebreak
%
%  Intro to SM 
%
\tit{The Standard Model}

\small
The ingredients of the SM are
\tiny
\begin{itemize}
	\item 12 fermions
	\begin{itemize}
		\item 6 quarks (u, d, s, c, b, t)
		\item 6 leptons	($e^-$, $\nu_e$, $\mu$, $\nu_\mu$,
			$\tau$, $\nu_\tau$)
	\end{itemize}
	\item 3 electroweak bosons ($\W^+$, $W^-$, $Z^\circ$,
			$\gamma$)
	\item 8 gluons to describe the strong force
	\item ?? to describe gravity
\\[0.05in]
\end{itemize}

\small
Enormously successful paradigm since $\sim1975$
\tiny
\begin{itemize}
	\item Predicted rich phenomenology
	\item Accurate! (eg. $\delta_{M_z}/M_z \sim 8\times 10^{-5}$)
\\[0.05in]
\end{itemize}

\small
It predicted existence of top quark almost 20 years ago

\pagebreak
\tit{Why a Top Quark?}

In 1977, Lederman et al. reported a new resonance
\tiny
\begin{itemize}
	\item Mass of $9.54\pm0.04$~\GeVcc
	\item Decayed to $\mu^+\mu^-$\ pairs
	\item[$\Rightarrow$] A fifth quark
	\begin{itemize}
		\item Production rate $\Rightarrow$\ $Q=-1/3$
\\[0.05in]
	\end{itemize}
\end{itemize}

\small
Studies established that it should have a partner
\tiny
\begin{itemize}
	\item Certain types of decays didn't occur
	\begin{itemize}
		\item decays like $b\rightarrow \mu^+\mu^- d$\ not observed
	\end{itemize}
	\item $e^+e^-\rightarrow b\bar{b}$\ scattering suggested
	an $SU(2)$\ state
\end{itemize}

\pagebreak
\tit{The Top Quark Mass in the Standard Model}
\small
The SM ``needs'' a massive top quark
\tiny
\begin{itemize}
	\item Loop effects in SM driven by $M_{top}$
	\begin{itemize}
		\item $W/Z$\ boson mass ratio
		\item $b-\bar{b}$\ mixing
	\end{itemize}
\end{itemize}
\vspace{0.3in}
\vbox{
\vskip+0.0in
\hskip+3.0in
\special{psfile=physics_figures/mass_loops.eps  hscale= 50.0 vscale= 50.0}
\vskip-0.2in
}
\vspace{1.8in}
\vbox{
\vskip+0.0in
\hskip+0.0in
\special{psfile=figures/physics_figures/b_bbar_mixing.eps  hscale= 80.0 vscale= 80.0}
\vskip-0.0in
}

\small
However, no real information on $M_{top}$
\tiny
\begin{itemize}
	\item In 1983, new it had to be large ($\gessim 20$~\GeVcc)
	\item Searches limited by this mass scale
\end{itemize}
\pagebreak

%
\tit{SM Top Quark Phenomenology} 

\small
Top quarks decay via the weak force
\tiny
\begin{itemize}
	\item Predict $\sim100$\% $t\rightarrow W^+ b$
	\item For heavy top ($M_{top}\gessim 100-120$ \GeVcc), decays
	before it hadronises \\[0.1in]
\end{itemize}

\small
Can be viewed as ``pure'' $\beta$\ decay
\tiny
\begin{eqnarray}
\Gamma_{\rm top} &=& {{G_F M_t^3}\over{8\sqrt{2} \pi}} 
   \left( 1 - {{M_W^2}\over{M_t^2}} \right)^2 
   \left( 1 + 2{{M_W^2}\over{M_t^2}} \right) \nonumber \\
&\sim& 175\ {\rm MeV}\ \left( {{M_t}\over{M_W}} \right)^3\ \sim\ 2\
{\rm GeV} \nonumber
\end{eqnarray}
\begin{itemize}
	\item Toponium doesn't have time to form
	\item $T$~mesons $\sim$\ degenerate (if there was time...)
\\[0.1in]
\end{itemize}

\small
Decay dominated by ``longitudinal $W^+$''
\tiny
\begin{itemize}
	\item Means the $W^+$\ prefers helicity 0
	\item Result of large top and $W^+$\ mass
\end{itemize}	

\pagebreak

\tit{The Hunt for the Top Quark}

\small
SM didn't tell us the top quark mass
\tiny
\begin{itemize}
	\item Search for evidence in $e^+e^-$\ and $p\bar{p}$\
	\begin{itemize}
		\item Rate decreases sharply with $M_{top}$
		\item By 1989, had set limit of $M_{top}>77$\ \GeVcc
\\[0.05in]
	\end{itemize}
\end{itemize}

\small
By 1992, had new measurements of $M_Z$\ and $M_W$
\tiny
\begin{itemize}
	\item SM predicted top quark with $M_{top} \gessim 140$~\GeVcc
	\item Only place to look was in high-energy $p\bar{p}$\ collisions
	\item Two experiments
	\begin{itemize}
		\item Collider Detector at Fermilab (CDF)
		\item \DZero
	\end{itemize}
\end{itemize}
\pagebreak

%
%  Its there
%
\tit{Discovery of Top}

\small
Hints of top production appeared as early as 1993
\tiny
\begin{itemize}
	\item CDF published a 61 page PRD in Sep 1994
	\item Gave ``cagey'' label to the reports
	\begin{itemize}
		\item ``Evidence for top quark production...''
	\end{itemize}
	\item \DZero's analysis not as definitive
\\[0.05in]
\end{itemize}

\small
With a factor of two more data, result was unequivocal
\tiny
\begin{itemize}
	\item April 1995, both collaborations announced discovery
	\item Confirmed SM predictions -- $M_{top} \sim
			170-190$~\GeVcc
	\item Gave us a ``free quark'' system to study
	\begin{itemize}
		\item[\Blue{$\Rightarrow$}] \Blue{New frontier in 
		particle physics}
	\end{itemize}
\end{itemize}
\pagebreak
%
%  Techniques
%
\tit{Reconstructing Top}

\small
Since top is pair-produced and $\beta$\ decays
\tiny
\begin{itemize}
	\item Expect to see 6 final state particles
\end{itemize}
\vspace{2.0in}
\vbox{
\vskip+7.8in
\hskip-2.0in
\special{psfile=figures/prd_plots/feynman_top_decay.ps  hscale=100.0
vscale=100.0}
\vskip-7.8in
}
\small
Life is normally not that easy -- in reality:

\begin{center}
\epsfysize=3.5in
\epsffile{physics_figures/ttbar_lepton_jets.eps}
\end{center}
\pagebreak
%
% Selecting top decays
%
\tit{Identifying Top Decays in $p\bar{p}$\ Collisions}

\small
In order to identify top candidates
\tiny
\begin{itemize}
	\item Search for $W\rightarrow l \nu_l$\ candidate
	\begin{itemize}
		\item Electron or muon with $P_T>20$~\GeVc
		\item Missing transverse energy $\mMEt>20$~GeV
	\end{itemize}
	\item Search for at least one $b$~jet
	\begin{itemize}
		\item Most effective tool is to find a secondary
		vertex
	\end{itemize}
	\item Some evidence of other $W$\ in event
	\begin{itemize}
		\item Either two more jets or another lepton
	\end{itemize}
\end{itemize}

\vbox{
\vskip+3.3in
\hskip+1.3in
\special{psfile=figures/run1b_blessed_plots/dil_57621_45230_tracking_only.eps
hscale= 90.0 vscale= 90.0}
\vskip 0.5in
}
\pagebreak

%
%  Some history
%
\tit{Status of Collider Experiments}

\small
CDF and \DZero\ collected $\sim100$~\invpb\ of data in 92-96
\tiny
\begin{itemize}
	\item 1.8 TeV $p\bar{p}$\ collisions
	\item Collected events with
	\begin{itemize}
		\item High $P_T$\ leptons ($P_T\gessim10$~\GeVc)
		\item $\MEt>25$~GeV
		\item High $P_T$\ jets ($P_T\gessim100$~\GeVc)
\\[0.05in]
	\end{itemize}
\end{itemize}

\small
Various studies have strengthen initial interpretation
\tiny
\begin{itemize}
	\item Different techniques used to look at the same data
	\begin{itemize}
		\item Kinematic distributions
		\item Neural network approaches
	\end{itemize}
	\item Verified that all decay modes appear to be OK
	\begin{itemize}
		\item See reasonable signals in $\tau$\ lepton final
states
		\item All hadronic modes are also understood
	\end{itemize}
\end{itemize}

\pagebreak
%
%  What do we have now
%
\tit{The Status of Top Today}

\small
CDF has now detected top in virtually all decay modes
\tiny
\begin{itemize}
	\item Lepton + Jets mode (for mass analysis)
	\begin{itemize}
		\item lepton $P_T>20$~\GeVc\ and $\mMEt>20$~GeV
		\item $\ge3$\ jets, $E_T>15$~GeV and $|\eta|<2$
		\item Require 1 $b$-tagged jet OR a 4th jet
		with $E_T>15$
		\item[\Blue{$\Rightarrow$}] \Blue{76 candidates}\
		(expect $31\pm7$\ bkg) \\[0.05in]
	\end{itemize}
%
	\item Dileptons
	\begin{itemize}
		\item 2 leptons with $P_T>20$~\GeVc
		\item Remove Drell-Yan and $Z^\circ$\ background
		\item[\Blue{$\Rightarrow$}] \Blue{9 candidates} 
		($2.4\pm0.5$\ events bkg) \\[0.05in]
	\end{itemize}

	\item All hadronic decays
	\begin{itemize}
		\item between 5 and 8 jets ($E_T > 15$~GeV and
		$|\eta|<2.0$)
		\item $\sum E_T > 300$\ GeV + additional kinematic
cuts
		\item[\Blue{$\Rightarrow$}] \Blue{Observe 187 $b$-tagged jets}
		($142\pm11$\ expected bkg)
	\end{itemize}

\end{itemize}

\small
Used these samples for top quark measurements
\pagebreak
%
%  What are the Interesting properties
%
\tit{What are the Interesting Top Properties?}

\tiny
\begin{itemize}
	\item Top Quark Mass
	\begin{itemize}
		\item SM constrains it to $M_W/M_Z$ 
		\item Important consistency check of theory
			\\[0.05in]
	\end{itemize}
	\item Top Quark Production Cross Section
	\begin{itemize}
		\item Predicted by QCD with less uncertainties than 
		$\sigma_b$
		\item Look for single top production 
			\\[0.05in]
	\end{itemize}
	\item Top Quark Decay Rates
	\begin{itemize}
		\item Measured $t\rightarrow W^+ b/
			t\rightarrow W^+ q$
		\item Searched for FCNC such as $t\rightarrow Z^\circ c$
			\\[0.05in]
	\end{itemize}
	\item Top Quark Decay Kinematics
	\begin{itemize}
		\item SM expects decay to be polarized
		\item Have made first measurement of polarization
	\end{itemize}
\end{itemize}

\pagebreak

%
%  Top Mass result
%
\tit{Top Quark Mass}

\small
Measurements now limited by systematic uncertainties
\tiny
\begin{itemize}
	\item Overall systematic uncertainty is $\sim 5$~\GeVcc
	\begin{itemize}
		\item Dominated by uncertainties in soft gluon 
		contributions and energy scale
	\end{itemize}
	\item Run I statistics limit systematic uncertainty 
\\[0.05in]
\end{itemize}

\begin{center}
\epsfysize=3.6in
\epsffile[30 140 520 630]{ljm_likfit1.ps}
\end{center}

\small
The final Run I values are 
\tiny
\begin{eqnarray}
	M_{top} &=& 176.0 \pm 6.5 \ \mGeVcc\ {\rm (CDF)} \nonumber \\
	M_{top} &=& 172.1 \pm 7.1 \ \mGeVcc\ {\rm (\mDZero)} \nonumber \\
	M_{top} &=& 174.3 \pm 5.1 \ \mGeVcc\ {\rm (Run I)} \nonumber
\end{eqnarray}

\pagebreak

\begin{center}
\epsfysize=5.5in
\epsffile[30 140 520 630]{mw_vs_mtop_lep_slc.ps}
\end{center}

\pagebreak

%
%  Top Cross Section
%
\tit{Top Quark Production Cross Section}

\small
The cross section obtained by a fit to 
\tiny
\begin{itemize}
	\item Lepton + jets, dileptons and all hadronic event rates
	\item Depends on $M_{top}$\ because of acceptance
\end{itemize}

\small
\begin{eqnarray}
\sigma_{\mttbar} &=& 7.6^{+1.8}_{-1.5}\ {\rm pb} \nonumber
\end{eqnarray}

\begin{center}
\epsfysize=3.5in
\epsffile[30 140 520 630]{xs_theories.ps}
\end{center}

\small
Rarest process ever measured in hadron collider!
\tiny
\begin{itemize}
	\item Theory predictions range from 4.7 to 5.5 pb
\end{itemize}

\pagebreak
\tit{Comparison with \DZero}

Measurements by \DZero\ also quite consistent

\begin{center}
\epsfysize=5.5in
\epsffile[30 140 520 630]{run_i_xsec_table.ps}
\end{center}

\pagebreak

%
%  Top Quark Pt Distribution
%
\tit{Top Quark Transverse Momentum Distribution}

\small
SM predicts top quarks produced ``back-to-back''
\tiny
\begin{itemize}
	\item Broad $P_T$\ distribution -- $<P_T> \sim M_{top}/2$
	\item Non-SM predictions can be quite different
	\begin{itemize}
		\item Can test models (such as Top colour or ADD) 
\\[0.05in]
	\end{itemize}
\end{itemize}

\begin{center}
\epsfig{file=hill.eps}
\end{center}          

\small
Limited statistics are a problem
\tiny
\begin{itemize}
	\item Produce a set of confidence limits on 
${{d\sigma_t}\over{dP_T}}$
	\item Limited to large bins ($\Delta P_T = 75$~\GeVc)
\end{itemize}

\pagebreak

%
%  Event selection for Top Pt Measurement
%
\tit{Event Selection}

\vspace{0.25in}

\small
Use the ``standard'' lepton + jets event selection:
\tiny
\begin{itemize}
	\item Single isolated $e(\mu)$ having $P_T>20$~\GeVc\ and $|\eta|<1.0$
	\item $\met > 20$~GeV
	\item $\ge 4$~jets, 3 with $E_T>15$~GeV and $|\eta|<2.0$
	\begin{itemize}
		\item fourth with $E_T>8$~GeV, $|\eta|<2.4$
			\\[0.1in]
	\end{itemize}
\end{itemize}

\small
To increase the signal significance, require that 
\tiny
\begin{center}
$N_{\mathrm{jet15}} \ge 4$ \Red{or} $N_{tag} \ge 1$ .
\end{center} 

\small
Kinematically fit event, constraining $M_{top} = 175$~\GeVcc
\tiny
\begin{itemize}
	\item Require $\chi^2 < 10$
	\item[$\Rightarrow$] Left with 61 events 
\end{itemize}

\pagebreak

\tit{Measurement of $P_T$}

Measurements on lepton-side and jet-side are \Red{strongly
correlated!}

\begin{center}
\epsfig{file=correlations.eps}
\end{center}

\tiny
\begin{itemize}
\item Make measurement using only \Red{jet-side} top quarks
\end{itemize}

\pagebreak

\tit{$P_T$ Response Functions}

\small
Measured $P_T$\ smearing using MC/detector simulation

\begin{center}
\epsfig{file=res4.eps}
\end{center}

\tiny
\begin{itemize}
	\item Use standard HERWIG MC calculations
	\item Most smearing arises from incorrect jet assignments
\end{itemize}
\pagebreak

\tit{Uncorrected $P_T$\  Distribution}

\begin{center}
\epsfig{file=smear.eps}
\end{center}

\tiny
\begin{itemize}
	\item 61 events pass selection criteria
	\item Background distribution normalized to estimated rate
	\begin{itemize}
		\item We estimate $N_{bgd}=24.6\pm 5.8$\ events
	\end{itemize}
\end{itemize}

\pagebreak

\tit{Resulting Fitted $P_T$\ Distribution}

\small
Perform unbinned likelihood fit to response functions and bkg shapes
\tiny
\begin{itemize}
	\item Fit tagged and untagged events with different templates
	\item Use ``bootstrap'' technique to minimize assumptions 
	about shape of $P_T$ spectrum \Red{within each true bin}
	\item Define
\begin{eqnarray}
		R_i \equiv {{\rm fraction\ in\ {\it i}th\ bin}\over{
			\sigma_{\mttbar}}} \nonumber
\end{eqnarray}
\end{itemize}
\small
Apply $P_T$-dependent acceptance correction
\tiny
\begin{itemize}
	\item Acceptance increases with $P_T$
\\[0.05in]
\end{itemize}

\tiny
\begin{eqnarray}
R_1 & = & 0.29^{+0.18}_{-0.18}\nonumber \\
R_2 & = & 0.42^{+0.18}_{-0.18}\nonumber \\
R_3 & = & 0.29^{+0.12}_{-0.10}\nonumber  \\
R_4 & = & 0.000^{+0.035}_{-0.000} \nonumber
\end{eqnarray}

\pagebreak

\tit{Confidence Level Interval on $R_4$}

Obtain \Red{$R_4^{\mathrm{fit}}=0$} (fraction of top with $P_T>225$~\GeVc)
\tiny
\begin{itemize}
	\item Use non-Bayesian technique to determine what we can
infer about ``true'' size of $R_4$
	\item Set a 95\%\ CL limit using a MC technique
	\begin{itemize}
		\item Analyze samples of MC events with varying $R_4^{\mathrm{true}}$. 
		\item Smear $R_4^{\mathrm{true}}$ in each with
		Gaussian distribution with a width equal to 
		systematic uncertainty
		\item Determine value of $R_4^{\mathrm{true}}$ where 
		only 5\% of the pseudo experiments have $R_4^{\mathrm{fit}}=0$
\\[0.03in]
	\end{itemize}
\end{itemize}

\tiny
\begin{center}
CDF PRELIMINARY\\
\begin{tabular}{|c|c|}
\hline
Systematic Effect & $\delta(R_4)$ \\
\hline
Background Model & $\pm 0.0028$ \\
Jet Energy Scale & ${}^{+0.0007}_{-0.0042}$ \\
No Initial State Radiation & $\pm 0.0045$ \\
Final State Radiation & $\pm 0.0095$ \\
Flat $P_T$ Spectrum & $\pm 0.0157$ \\
$m_t$ = 180~GeV & -0.0160 \\
\hline
\end{tabular}
\end{center}
\small

\pagebreak

\tit{95\% Confidence Level Upper Limit}

\begin{center}
\epsfig{file=find95.eps}
\end{center}

\vspace{0.25in}

\tiny
Agrees with result obtained by integrating the likelihood function
\begin{itemize}
	\item Without systematics, $R_4 < 0.109$ at 95\% CL
\end{itemize}

\pagebreak

\tit{Magnitude of Various Systematics}

\small
Have used combination of MC and data to estimate 
systematic uncertainties
\tiny
\begin{itemize}
	\item Largest relates to how well we ``unfold'' data
	\item But dominated by statistical uncertainties
\\[0.05in]
\end{itemize}
\tiny
\begin{center}
CDF PRELIMINARY
\begin{tabular}{|c|ccccc|}
\hline
\hline
Syst. & $\delta R_1$ & $\delta R_2$ & $\delta R_3$ & $\delta R_4$ &$ \delta (R_1+R_2)$\\
\hline
$m_t$ & ${}^{+0.026}_{-0.000}$ & ${}^{+0.00}_{-0.027}$ &
${}^{+0.023}_{-0.000}$& ${}^{+0.000}_{-0.018}$& ${}^{+0.006}_{-0.012}$ 
\\
ISR & $\pm 0.016$ & $\pm 0.011 $& $\pm 0.005 $& $\pm 0.005$ &$\pm 0.007$\\
FSR & $\pm 0.038$ & $\pm 0.023 $& $\pm 0.010 $& $\pm 0.005$& $\pm 0.015$\\
JES & ${}^{+0.020}_{-0.028}$& ${}^{+0.037}_{-0.006}$& ${}^{+0.000}_{-0.008}$& ${}^{+0.000}_{-0.003}$& ${}^{+0.014}_{-0.000}$\\
$Q^2$ & $\pm 0.025$& $\pm 0.008$& $\pm 0.008$& $\pm 0.010$ & $\pm
0.016$ \\
$P_T$ & $\pm 0.032$& $\pm 0.045$& $\pm 0.055$& $\pm 0.016$& $\pm 0.036$ \\
Acceptance  & ${}^{+0.010}_{-0.023}$& ${}^{+0.013}_{-0.012}$& ${}^{+0.016}_{-0.014}$& ${}^{+0.000}_{-0.000}$& ${}^{+0.025}_{-0.011}$\\
\hline
\hline
\end{tabular}
\end{center}

\small

\pagebreak

\begin{center}
\Red{Top Quark Differential Cross Section}
\end{center}
\small
\begin{eqnarray}
R_1+R_2 & = & 0.72^{+0.13}_{-0.13}\mathrm{(stat)}
^{+0.06}_{-0.06}\mathrm{(syst)}\nonumber \\[0.10in]
R_4 & < & 0.114~\mathrm{at~95\%~C.L.}  \nonumber
\end{eqnarray}
\begin{center}
\epsfysize=4.0in
\epsffile{sm.eps}
\end{center}
\tiny
\begin{center}
\begin{tabular}{|c|l|}
\hline
$P_T$ Bin & Measured Fraction of Top Quarks \\
\hline
$0<P_T<75$~GeV/c & $R_1 = 0.29^{+0.18}_{-0.18}\mathrm{(stat)}
^{+0.08}_{-0.08}\mathrm{(syst)}$\\
$75<P_T<150$~GeV/c & $R_2= 0.42^{+0.18}_{-0.18}\mathrm{(stat)}
^{+0.05}_{-0.07}\mathrm{(syst)}$\\
$150<P_T<225$~GeV/c & $R_3= 0.29^{+0.12}_{-0.10}\mathrm{(stat)}
^{+0.06}_{-0.05}\mathrm{(syst)}$\\
$225<P_T<300$~GeV/c & $R_4=0.000^{+0.035}_{-0.000}\mathrm{(stat)}
^{+0.019}_{-0.000}\mathrm{(syst)}$\\
\hline
\end{tabular}
\end{center}

\pagebreak

%
%  Wrap up
%
\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 But top mass scale is enigmatic
			\\[0.05in]
\end{itemize}

\small
All this sets the stage for Run II
\tiny
\begin{itemize}
	\item Will start data taking sometime in 2000 (April-Sep?)
	\item Run for 2-4 years, with goal of $\sim2$~\invfb
	\begin{itemize}
	\item[$\Rightarrow$] Increase top quark sample $\times 50$
			\\[0.05in]
	\end{itemize}
\end{itemize}

\small
By the time next generation collider turns on,
\tiny
\begin{itemize}
	\item Top will be pretty well-studied
	\begin{itemize}
		\item Reveal some property that points toward a more 
		complete theory?
		\item Will at least be an important background
	\end{itemize}
	\item Will be able to reconstruct millions at the LHC!
	\begin{itemize}
		\item It will become the ``high-statistics'' probe of
	the next energy scale
	\end{itemize}
\end{itemize}

\end{document}
