[Congressional Record Volume 140, Number 51 (Tuesday, May 3, 1994)]
[Senate]
[Page S]
From the Congressional Record Online through the Government Publishing Office [www.gpo.gov]
FERMILAB COMPLETES THE BUILDING BLOCKS OF MATTER
Mr. SIMON. Mr. President, I rise today to recognize a special
milestone in science and our understanding of nature. Scientists at
Illinois' own Fermilab have found the first direct evidence of the top
quark, the sixth and last component of a standard model of matter that
explains the relationships between subatomic particles.
Since the fifth quark was seen at Fermilab in 1977, scientists around
the world have searched for the elusive other half of the pair. I am
proud to say that the 2,000 men and women of Fermilab have the honor of
once again claiming the prize. Those in Congress who have supported
U.S. leadership in science have a right to be proud as well.
Programs such as that at Fermilab have not only contributed greatly
to our knowledge, but have provided the tools and skills of our best
science to their communities and the hundreds of students and
researchers that carry the scientific vision from Illinois to
communities across the Nation.
We congratulate them on their accomplishment and wish them every
success in their continuing research. I ask unanimous consent that the
full text of the attached article from the New York Times be included
in the Record.
There being no objection, the article was ordered to be printed in
the Record, as follows:
[From the New York Times, Apr. 26, 1994]
Top Quark, Last Piece in Puzzle of Matter, Appears To Be in Place
(By William J. Broad)
The quest begun by philosophers in ancient Greece to
understand the nature of matter may have ended in Batavia,
Ill., with the discovery of evidence for the top quark, the
last of 12 subatomic building blocks now believed to
constitute all of the material world.
An international team of 439 scientists working at the
Fermi National Accelerator Laboratory will announce the
finding today, bringing nearly two decades of searching to a
dramatic conclusion.
The Fermilab discovery, if confirmed, would be a major
milestone for modern physics because it would complete the
experimental proof of the grand theoretical edifice known as
the Standard Model, which defines the modern understanding of
the atom and its structure. The finding is likely to produce
waves of intellectual satisfaction for physicists around the
world and to give American physics a significant boost.
The discovery in all likelihood will never make a
difference to everyday life, but it is a high intellectual
achievement because the Standard Model, which it appears to
validate, is central to understanding the nature of time,
matter and the universe.
``The exciting thing is that this is the final piece of
matter as we know it, as predicted by cosmology and the
Standard Model of particle physics,'' Dr. David N. Schramm, a
theoretical physicist at the University of Chicago, said in
an interview, ``It's the final piece of that puzzle.''
Dr. Hans A. Bethe, a Nobel Laureate in physics at Cornell
University, said the finding was ``a very big deal'' that
``makes the whole picture of subnuclear particles much more
believable and better established.''
``We've needed the top quark,'' he said. ``it figures in
all our calculations for further processes, and none of them
would be right if it weren't there.''
If the top quark could not be found, the Standard Model of
theoretical physicists would collapse, touching off an
intellectual crisis that would force scientists to rethink
three decades of work in which governments around the globe
had invested many billions of dollars.
All matter is made of atoms, but nearly a century ago
physicists discovered that atoms, long considered to be the
smallest units of matter, were themselves composed of
smaller, subatomic particles like protons and neutrons. But
these particles later showed signs of being made of yet
smaller building blocks.
The field was plunged into confusion for many years until a
grand unifying theory pioneered by Dr. Murray Gell-Mann, a
physicist at the California Institute of Technology, sought
to explain the structure of particles like protons and
neutrons in terms of new units that he whimsically named
quarks.
His theory called for the existence of six different kinds
of quarks, named up and down, charm and strange, top and
bottom. The quark family parallels a six-member family of
lighter particles, known as leptons, that includes the
electron.
Various combinations of these 12 particles are thought to
make up everything in the material world. In addition to
matter, the universe contains potent forces like
electromagnetism and gravity, and perhaps many other exotic
particles as yet to be discovered.
Five of the six quarks were eventually found but the sixth
remained painfully absent. For nearly two decades rival teams
of scientists around the world have sought the top quark by
performing ever-more-costly experiments on increasingly large
machines that accelerate tiny particles almost to the speed
of light and then smash them together in a burst of energy.
The resulting fireball can yield clues to nature's most
elementary building blocks.
The team at Fermilab, which includes scientists from the
United States, Italy, Japan, Canada and Taiwan, cautioned
that the evidence they had gathered over the past year and a
half for the top quark would be convincing to many scientists
but not definitive. They said further work would be needed to
firmly establish the top quark and its attributes.
``Some people will say, `Hey, nice piece of physics but you
need more data to make sure,' '' said Dr. Melvyn J. Shochet,
a physicist at the University of Chicago who worked on the
Fermilab experiment and is a spokesman for the discovery
team. ``To that I can only agree.''
``We don't have a discovery,'' said a senior Fermilab
official, who spoke on the condition of anonymity. ``We have
evidence. It's good evidence. It's tightening up to where the
top quark lives. The next step is to get more events.''
The experiment was run on Fermilab's Tevatron, a four-mile,
circular accelerator in an underground tunnel that hurls
counterrotating beams of protons and antiprotons at each
other with a combined energy of 1.8 trillion electron-
volts. It is currently the highest-energy accelerator in
the world. The detector that gathered the evidence is the
size of a large house and weighs 5,000 tons. A 150-page
manuscript describing the work was mailed on Friday to
Physical Review, the world's pre-eminent journal of
physics.
Dr. Schochet, the team spokesman, said the mass of the top
quark, its most important attribute, was calculated to be 174
billion electron-volts, with an uncertainty range of plus or
minus 17 billion electron-volts.
``That's quite heavy,'' he said. ``It's almost as heavy as
an entire gold atom. It's by far heavier than any other
elementary particle that's been observed, which is why it's
taken so long to find.''
As Fermilab, which is run by the Federal Department of
Energy, reports the finding today, simultaneous announcements
are to be made in Rome, Tokyo, Ottawa and Taipei.
Dr. Gell-Mann took the word quark from a line in
``Finnegans Wake'' by James Joyce: ``Three quarks for Muster
Mark.'' So too, Dr. Gell-Mann predicted that quarks in normal
matter came in groups of three. Protons would be made of two
up quarks and one down quark; neutrons of two down quarks and
one up quark. Dr. Gell-Mann's ideas were radical and strongly
resisted, partly because the fractional charges of his quarks
seemed implausible. But his theories explained much, and were
soon partly confirmed by particle discoveries. In 1969 he won
the Nobel Prize in Physics.
Low-mass quarks, the up and down, are the only ones thought
to ordinarily exist in this world. Physicists believe that
the higher-mass ones, charm and strange, top and bottom, were
present naturally only for a tiny fraction of a second at the
beginning of time during the Big Bang--the primordial
explosion thought to have given rise to the universe. Top
quarks, having the highest mass of all, are believed to have
vanished from the universe after existing for less than a
billionth of a second.
Thus, a time machine is needed to see most quarks. Particle
acclerators slam together tiny bits of matter to create
intense fireballs almost as hot as those that existed at the
beginning of time, creating streams of nature's most
rudimentary particles.
In 1977, when the bottom quark was discovered at Fermilab
in a particle accelerators, physicists calculated that its
top-quark companion would have a mass of 13.5 billion
electron-volts, making it an easy target for any number of
accelerators then planned around the world.
In July 1984, a European team of 151 scientists headed by
Dr. Carlo Rubbia announced that it had confirmed the
existence of the top quark, calling it a major breakthrough.
That fall, Dr. Rubbia won the Nobel Prize in Physics for
other discoveries. But it turned out that his top-quark claim
was premature. The particle was far heavier, and more
difficult to detect, than had generally been anticipated.
a kind of alchemy
Physicists at Fermilab have been hunting the top quark for
nearly two decades, looking at increasingly high energies.
The process, they say, is like slamming together two tennis
balls and trying to find a bowling ball in the rubble--a hint
of the top quark's huge mass. The tennis balls can create
things heavier than themselves because of their high
energies, a kind of alchemy first suggested by Einstein in
his famous law of equivalence between matter and energy.
The rub is the rarity of collisions that make top quarks.
Dr. Shochet, the experiment team's spokesman, said many
billions of proton-antiproton collisions were needed to
produce just one top quark and that even then, subtle clues
to its existence might be lost amid a clutter of spurious
signals. The quarks themselves exist for only a fraction of a
second, and cannot be detected directly. Their presence is
inferred from ghostly showers of particles produced as they
perish.
Dr. Shochet said the team's evidence gathered over a year
and a half amounted to 15 clues from 12 collisions. Those
results, he added, were about twice as high as expected from
false positives in the background noise. He said really
nailing down the top quark would require a mass of evidence
three or four times above background levels.
Dr. Claudio Campagnair, a team physicist, said in a
Fermilab brochure: ``Rather than one `Eureka!' event, top
discovery will come by accumulating a lot of different
evidence, bit by bit. You could compare discovering top with
what happens in a courtroom in a case where there's no
smoking gun and you must convince the jury by the accumulated
weight of circumstantial evidence.''
A separate team of 420 scientists at Fermilab is now using
a different detector in an effort to confirm the first team's
findings during the Tevatron's current 18-month run. Its
work, and that of the original team, should be eased somewhat
by recent accelerator improvements that will increase the
number of collisions.
Fermilab is also completing a $230 million upgrade of the
Tevatron that should sharply increase the collision rate,
perhaps producing hundreds or thousands of top-quark
candidates. It should be completed by 1998 or 1999.
After that, the only other accelerator power enough to join
the hunt would be one under consideration at CERN, Europe's
premier accelerator laboratory, on the border of France and
Switzerland. Known as the Large Hadron Collider, it might be
completed by the year 2005.
If the top quark has indeed been discovered at Fermilab,
particle physicists will turn their attention to other
enigmas, such as why all matter has mass. In the United
States, such questions were to be addressed by the
superconducting supercollider, which was to have measured 54
miles around and cost up to $11 billion. In October, Congress
canceled the half-built machine in Waxahachie, Tex., calling
it an inordinate drain on the Federal budget.
American inventors are now trying to create small,
innovative accelerators in lieu of the big machine.
``Any new particle that's found'' in the years ahead, said
Dr. Schramm of the University of Chicago, ``is going to be
exotic in a much greater way than any quark.''
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