\chapter{Afterword}

{\sl D. Amidei and R. Brock} \\

\noindent In the past year, a convincing case has emerged for an
extended evolution of the Fermilab collider. Why did we go through this
exercise when there are other opportunities in the world for future
accelerators?

Two recent and familiar examples of surprises in High Energy Physics 
illustrate a feature of research which deserves protection when future 
plans are considered. These surprises, which dominate much active work 
in our field, are the long lifetime of $B$ hadrons and the extremely large 
mass of the top quark. The efforts which eventually led to these 
understandings didn't come from strategic  
leaps, but rather from the accumulation of experimental results and 
techniques over time. No accelerators were proposed, planned, or
constructed to make these discoveries. Instead, hints and leads, accompanied 
by new detector technologies, were followed over many years to eventual 
discovery and understanding. This is an ``evolutionary path"
to scientific progress. The continued importance of results from CESR (the Cornell 
Electron Synchrotron Ring) is one of the excellent examples
of the success of 
the evolutionary approach in facility planning, and reminds us that 
continued investment and the establishment of {\em depth} with promising 
platforms ensures progress.  

Particularly applicable to our concerns in the 1990's are the following 
four points regarding the evolutionary path for High Energy
Physics:

\begin{enumerate}
\item The bottom quark and top quark stories referred to above represent the 
usual path toward scientific breakthrough. ``Throwing long'' is a strategy 
which has a place as a component of a broad, stable physics program. However, 
it cannot dominate a program in difficult times. 
\item As much as anything in science can come with a guarantee, success 
and surprise seem repeatedly to be the eventual outcomes of the evolutionary
approach in high energy physics.  
\item This sort of success doesn't happen accidentally. Rather, the guarantee
is underwritten by the mounting of topical experiments which attract the brightest
scientists, coupled with the means  to do those experiments in a timely way.  We call
this {\bf Following  the Physics}, as decidedly distinct from ``waiting for the
physics''.
\item The Fermilab program outlined here is a paradigm example of 
Evolutionary Physics at its best and it is feasible now.
\end{enumerate} 

Like other sciences, in High Energy Physics there are periodic and sometimes dramatic
advances in understanding. What's perhaps unique about our field is that these changes
occur primarily through massive efforts, each requiring many years and large sums of 
money.
This means that an historical perspective is necessary to see incremental progress.
If we pause and 
view the present 
from the standpoint of 10 to 15 years ago, our current
understanding of elementary particle physics would have looked unpredictably 
unfamiliar. Sensible planning would take into account that such unpredictability is 
a part of doing well planned scientific 
experiments and therefore would build in our ability 
to make a similar statement about a new physics landscape
15 years from now.
We need to prepare and 
defend a plan which combines the proper mix of sensible short term 
extrapolation, far--future opportunities, and faith in scientific 
unpredictability which is 
borne of a broad perspective.
This report forms the beginning of such a plan by 
describing a set of significant experiments all within the context of a 
feasible 
collider program. That 100 physicists began this exercise and that 70\% 
of them are authors of the individual detailed chapters is evidence of 
the excitement of the science and the commitment of the Tevatron community.

If resources are limited, and there is no expectation that this will not 
be the case for years, we should pay attention to the hints which exist 
and {\bf Follow the Physics}.
While the  precise  locations of  surprises can't be  predicted,  we are
fortunate  that  the  various  general areas  are  woven  together in an
increasingly correlated tapestry. The general threads are:

\begin{itemize}
	
\item {\bf Top and Electroweak physics, combining direct measurements and
indirect constraints from many different experiments.}\\
{\small \noindent If the Standard 
Model is correct, the generation of mass is related to at least two 
important length scales: the mass of the $W$ and $Z$, of $\approx 100$ GeV/c$^2$.
and the vacuum expectation value of $\approx 246$ GeV/c$^2$.  
That the top quark mass is nearly twice the former, and 
not far from the latter is probably a hint about the top quark 
which should  not be ignored.  
Many measurements are possible to probe these scales.}

\item {\bf Symmetry Breaking}\\
{\small \noindent Inherent within the Standard Model are explicit 
predictions, but also a set of underlying assumptions regarding the 
symmetry breaking mechanism. One of these predictions is the 
existence of a Higgs boson of indeterminate mass, playing the role of 
the quasiparticle of a possible phase transition. Other related
but different schemes, 
also encompass Standard Model predictions but are 
more general. Supersymmetry is a leading example of such an 
extension. A component of any electroweak ``prospecting'' will include 
emphasis on these anticipated themes.}


	\item {\bf Generational Mixing among quarks and among leptons.}\\
{\small  \noindent Among the oddest of field--theoretic 
consequences is the apparent quantum mechanical mixing of  fundamental 
fermions of grossly differing 
mass scales which seems to be operative only in 
the quark sector. Why? The opportunities for studying 
this  
phenomenon in the bottom system and perhaps the top system have been well--documented.  
Further, the astrophysical motivations for continued investigation of this 
phenomenon 
in the lepton sector are similarly well--documented.}

	\item {\bf CP violation in the strange, bottom, and top(?) systems.}\\
	{\small   \noindent Large--scale CP 
violation in the bottom system is expected as in the strange system. What about
their 
$I_3=1/2$ partners, charm and top? While probably 
related to fermion mixing, this question stands alone as an experimental question, 
independent of models.}

	\item {\bf Spectroscopy and Rare Decays in the strange, charm, bottom, and top
systems.}\\   
{\small \noindent From the strange and charm to the bottom and now 
top systems, the ``onia'' of baryonic and mesonic spectroscopies and rare 
decays are always of interest. The study of the bottom sector will be 
with us for decades. With the top quark, 
we have the first quark
which will not hadronize, but remains bare\ldots it will not
likely form hadronic matter, like a lepton.   
This second top quark hint may provide  important
clues to new physics.}

	\item {\bf Hadronic Structure in both high and low $p_{\rm T}$
regimes.}\\    
{\small \noindent We tend to become excited about the 
extremes of the electroweak world. Could this be, in part,
related to our 
familiarity with a perturbative and straightforward diagrammatic language?
Experimentally 
accessible but much less well--understood, is the passage from the 
perturbative regime into the actual binding regimes.  The structure of 
hadrons and the many--body aspects of gluon and low--$x$ physics may become 
clearer with continued focus.  Of course, the  high 
$p_T$ extreme is always of great interest, with higher statistical precision
leading to probes of higher mass scales.}

	\item {\bf The Zoo}\\
	{\small \noindent This is the part of 
elementary particle physics which is always revolutionary, and
inherently
unpredictable. The unusual seems to happen on a periodic basis, albeit at a 
timescale which is long.
Because of that, we become complacent and 
tend toward a self--assured posture that we know what to expect.  But 
reflection over the past 40 years of this field reminds one of the ``who 
ordered {\it that}\ldots !'' aspects of digging deeper.  The muon, partons 
and scaling, weak neutral currents, CP violation, the tau, the strange quark, 
the huge top quark mass, and the bottom quark lifetime were all largely 
unanticipated. They were brought to prominence and shown to be true only 
by experimental 
skill and theoretical imagination.}
\end{itemize}

\noindent This is a list of broad themes, but it does surround what most would 
acknowledge to be 
the important general areas of elementary particle research. As befitting 
for the National High Energy Physics Laboratory:
\begin{center}
{\bf the 
Fermilab complex is 
guaranteed to impact each of these areas.}
\end{center}
From the collider to the fixed 
target area to the neutrino oscillation program, this facility offers 
significant short term gains and long term promise. Fermilab will 
allow us to weave a tight pattern in the physics tapestry presented above by 
following the physics as it develops within a vigorous and comprehensive program.
That this evolutionary path is {\sl completely} within the 
scope and control of the U.~S. program is crucial to the maintenance of 
the flexibity and autonomy which is befitting our history and 
traditional commitment to this field. \\
\\
\noindent \rule{6.5in}{1mm}

{\sl \noindent We have outlined here a program of research specifically for the 
Tevatron collider at Fermilab. It is rich in guaranteed physics (top, IVB), surprising 
in its reach to the next level (SUSY, Higgs, exotics), fertile in the different 
configurations which are feasible, stimulating to continued R\&D in accelerator
and detector technologies, and stable as a platform for the far 
future of high energy physics (ultra--high energy $pp$, or $p\bar{p}$, an 
$e^+ e^-$ linear collider, or 
a $\mu$--collider). Much work still remains to be done, but we hope that 
those who have not considered the evolutionary opportunities at the Fermilab 
complex will begin to look deeper with us. We urge our colleagues, the Fermilab 
management, the Department of Energy, the National Science Foundation, and 
members of Congress to take seriously a Physics Program for the United States 
which builds on the significant investment of millions of dollars 
and thousands of physicist--years to continue to {\bf Follow the Physics}.}