textfiles/bbs/KEELYNET/GRAVITY/grav6.asc

661 lines
33 KiB
Plaintext

(word processor parameters LM=8, RM=75, TM=2, BM=2)
Taken from KeelyNet BBS (214) 324-3501
Sponsored by Vangard Sciences
PO BOX 1031
Mesquite, TX 75150
There are ABSOLUTELY NO RESTRICTIONS
on duplicating, publishing or distributing the
files on KeelyNet except where noted!
October 6, 1991
GRAV6.ASC
--------------------------------------------------------------------
This file shared with KeelyNet courtesy of Tom Albion.
Tom operates the THC Online System in Canada at 604-361-4549.
--------------------------------------------------------------------
The Higgs Field
Title-> Armies of physicists struggle to discover proof of a
Scot's brainchild.. (Peter Higgs; Higgs boson) (study of
mass and the cause of heaviness)
Authors-> Mann, Charles C.
Twenty men in boots and hard hats pick their way through a
construction site a few hundred yards from the border between
Switzerland and France.
The morning is hot and dry for May, but the ground is nonetheless
muddy from the continued movement of bulldozers and trucks. The
center of activity is a vast hangarlike structure or, more
precisely, the pit at its center, more than 30 yards deep and almost
as wide, cut into the soft French soil.
A tall, stoop-shouldered man named Samuel C. C. Ting leads the
group. He is a physicist from the Massachusetts Institute of
Technology, a Nobel Prize winner. He wears dark suits, immaculately
clean, of no particular style, and dark ties, perfectly knotted, of
no particular hue. Authority rests lightly on his shoulders. He
and the people walking behind him are working on a colossal physics
experiment; they come from China, the United States and a dozen
other countries.
Known unromantically as L3, the experiment is designed to answer
what would appear to be a fundamental question:
Why are things heavy?
Why, in a gravitational field, do they have weight?
Or, as physicists would phrase the question: What is mass?
We think mass is created by the actions of a type of subatomic
particle known as the Higgs boson, named for Peter Higgs, the
Scottish physicist who was one of the first to predict its
existence. Yet scientists have never seen it, and are not certain
where to look.
Page 1
Ting thinks his experiment can find the Higgs, if it exists. He may
discover it, which could ultimately prove as significant an
achievement as splitting the atom. Then, too, the discovery might
just as well have no practical consequences. Or, the Higgs may not
exist, after all.
The wind, keening in the open struts of the elevator, follows the
scientists into the hole. Because nearby residents objected to the
ugliness of the construction, an earthen berm stands between the
hangar and the surrounding farms.
As the car descends, the berm sweeps out of view; then the Jura
Mountains, too, are hidden. By the end of the elevator ride, the
scientists have journeyed into a world of their own making. It is a
world some of them have never seen, despite having worked on the
experiment for years. Then, when the elevator finally stops, jaws
drop and a silence falls over the group.
Standing in the center of the pit is an octagon the size of an
office building, its huge side doors yawning open. It is an
electromagnet, made of more metal than the Eiffel Tower, wound with
hundreds of miles of cable.
Some of the scientists are startled, even dismayed, by what is not
there: the thousands of tons of equipment that remain to be stuffed
into the pit. The magnet and all the apparatus that goes with it
together constitute the heart of L3 - the detector that may, just
may, come up with the Higgs boson.
"When we first put the plans for this experiment down on paper, I
knew the dimensions were big," Ting says at last. Usually his voice
is toneless, careful, without edge even when administering the
sharpest rebuke; you keep thinking you have missed bits of
sentences. Now, however, he hesitates"But it isn't til you see it
that you get a feeling for how . . . big . . . it really is. I
went down here a couple of days ago and I thought, 'This is crazy.'
I thought, 'It can't be this size."'
Seeking an answer better than Aristotle's "Why are things heavy?"
Artistotle thought objects are pulled to earth because they wish to
return to it, and for much of Western history nobody came up with a
better explanation.
It was left for Kepler, Newton and their fellows to realize that
heaviness came from the interaction of gravity with some other
quality, which we today call "mass." It is the quality of an object
that causes it to have inertia: that means you have to use force to
get it moving if it is standing still, and you have to use force to
stop it if it is already moving.
You must use force whether you are on the surface of a planet or
floating weightless between the stars. Mass is a quality an object
always has; it is different from weight, which changes, or even
disappears, with changing circumstances.
Take an astronaut who, when he is on Earth, weighs 180 pounds. The
moon's gravitational field is only one-sixth as strong as Earth's,
so when that same astronaut is standing on the moon, he will feel he
only weighs one-sixth as much.
Page 2
When he is in free-fall in a spacecraft, we say he is "weightless."
His mass, however, is always the same 180 pounds.
Well into this century, physicists knew a lot about how mass behaved
but did not know whence it derived or, more simply, what it was.
"Mass is the great question of physics," says Abdus Salam, a Nobel
Prize-winning physicist who is director of the International Centre
for Theoretical Physics at Trieste. "We have fruitlessly banged our
heads against it for centuries."
Today the search for the origins of mass has become, to the dismay
of some researchers, one of the largest and most costly undertakings
in the history of science. On both sides of the Atlantic, thousands
of scientists and support staff are working to build the enormous
machines that will be used in the quest. The L3 group, led by 450
physicists from 39 institutions, is but one of six groups of
experimenters hoping to solve the mystery of mass.
The quest began, at least indirectly, during the 1950s, when
physicists first began to work out their grand unified theories,
schemes in which the four fundamental forces in nature are only
different manifestations of one and the same thing (SMITHSONIAN, May
1983).
Part of the idea is that each force has an agent, a subatomic
particle, that produces the effects we see. They are known
collectively as GAUGE BOSONS.
Photons, for example, "carry" the electromagnetic force, whether in
the form of light waves, radio waves, x rays or gamma rays, among
others. Mesons carry the strong force that holds the nucleus of an
atom together.
Scientists still have not seen gravitons, the particles postulated
to carry gravity; and until recently, physicists had not even seen
the particlcs, known as intermediate vector bosons or the W and Z
particles, that carry the weak force, an obscure force central to
the process of radioactive decay.
It was in the atmosphere of looking for unification theories that
physicists such as Salam and Sheldon Glashow, now of Harvard,
working independently, were toying with the idea that
electromagnetism and the weak force could be brought together and
seen as different manifestations of the same thing-the electroweak
force.
In the late 1950s, Glashow and Salam developed similar theories, but
hit the same stumbling block: while much of the mathematics in each
theory worked, there were major discrepancies between the particles
that carried the forces.
Photons have no mass at all; but even before they were actually
seen, W and Z particles were predicted to be heavy - very heavy.
(Many physicists had calculated their mass and had eventually come
up with a similar ballpark figure. Each W or Z weighs more than 80
times what an entire hydrogen atom does.)
Yet the equations of Glashow and Salam said that on some deeper
Page 3
level, the Ws and Zs should have no mass, like their sibling the
photon. "It was a problem," Glashow has admitted. "It was a bit
like saying a Ping-Pong ball and a bowling ball are somehow the
same thing."
By the early 1960s, Glashow had begun to look into other areas of
physics, but his childhood friend Steven Weinberg, now at the
University of Texas, and Salam each continued looking for a way to
describe the two forces as one.
At the same time, a Scottish theorist, Peter Higgs, was at the
University of Edinburgh working on a somewhat related problem. For
several years the shy, soft-spoken, excessively modest Higgs had
been investigating various aspects of field theory, which is the
notion that all of space is saturated by a field, much as the field
of a magnet saturates the region near it.
Like the field of a magnet, the hypothetical field Higgs created had
ephemeral particles that acted as its agents: these eventually came
to be known as "Higgs bosons."
Higgs had been engaged in intense doodling, fiddling with equations,
adding in one variable and taking out another to learn more about
the nature of his hypothetical field. It was at this point, around
1964, that he noticed something extraordinary.
If he added in his own field equations (and thus the Higgs bosons)
to equations somewhat analogous to those of Salam or Glashow, he
found that certain particles in the original equation behaved in an
astonishing fashion.
They began with zero mass and then mathematically "ate up"
other, unwanted particles in the field (ones that had made a mess of
the mathematics in the theory he was investigating) emerging with
mass.' (The unknown particles turned out to be the W and Z
particles, but Higgs did not know that at the time.)
Higgs published his findings - described by Glashow as a
"terrifically loony idea: an idea that nobody would ever have paid
attention to" - with little fanfare. Eventually, Salam and Weinberg
independently heard about his work and realized it might solve their
problem.
Each added Higgs' equations into the ones they had been working on
and - to their great delight - found that the particles that
acquired mass in Higgs equations corresponded to the W and Z
particles in their own. Higgs' hypothetical boson provided the
mechanism by which the electromagnetic and weak forces could finally
be seen as one.
Higgs bosons might have been entirely forgotten if a groundswell of
theoretical and experimental work in the 1970s had not led to the
acceptance of the electroweak theory - and to Nobel Prizes for
Glashow, Salam and Weinberg in 1979.
Four years later the W and Z were discovered by a team led by Carlo
Rubbia and Simon van der Meer, who quickly received Nobels for their
efforts. Today the electroweak theory is inscribed in the
Page 4
textbooks, except for one not-so-little worry: nobody has seen even
the slightest trace of the Higgs.
"And without the Higgs," jokes Paul Lecoq, a French member of the L3
collaboration, "Messrs. Glashow, Weinberg and Salam may eventually
have to give back those little prizes they got in Sweden."
In a long, high laboratory, Ulrich Becker wedges his way through a
forest of electronic equipment and the cables and welding equipment
necessary to hook it together. A big man with the square face and
wiry, stand-up hair of a friendly monster, Becker has been one of
Ting's chief collaborators for two decades.
Born and raised in the Federal Republic of Germany, he is now a
member of the international fraternity of science: citizen of West
Germany, resident of France, worker in Switzerland, taxpayer of the
United States. Like Ting, he is officially on the faculty of MIT
but, like Ting, he has spent the past decade traveling the globe in
quest of the Higgs.
"Put naively," Becker says "most of the progress in particle physics
for the past 20 years, this electroweak theory and everything else,
depends on the supposition - the guess - that there is this field,
the Higgs field, that saturates the whole Universe, and that
particles get their mass from interacting with it.
You might say it's a little like a magnet, with some kinds of metal
being more attracted than others. Particles that are more
'attracted' to the Higgs have more mass. The picture is very nice,
theoretically speaking - yet there 'is not one shred of evidence for
it."
Ting's L3 group is based at the European Organization for Nuclear
Research, still known to physicists around the world by its old
acronym, CERN. The main campus is in a suburb of Geneva, but the
laboratory has grown with physics itself: the L3 assembly area is in
France, a few miles from the Swiss border. (Customs is a constant
problem; recently, Becker recalls, he had to cross the frontier 12
times in a single afternoon; the border guard threatened to seize
his car if he came through again that day.)
A great circular tunnel connects the campus and the L3 pit; it
houses an almost completed particle accelerator called the LEP, the
Large Electron-Positron collider.
Accelerators are devices that smash subatomic particles into a
target or into one another with enormous energy; in the resultant
collisions, matter changes into energy and energy into matter, and
the flying fragments provide clues to the laws of nature.
They are usually built in the shape of a wheel; as particles move
around the circumference, they are boosted to higher and higher
speeds by powerful electric fields.
Electrons, which at rest are very light, can be pushed to within a
whisker of the speed of light. At such relativistic speeds,
however, the electron becomes heavy and difficult to turn in the
necessary continuous circle.
Page 5
It takes huge amounts of electrical power to keep bending the beam
of electrons, which keep losing energy in the form of x rays as they
are forced to turn. To smooth out the turns, accelerators have
become bigger and bigger around, not to mention more and more
costly. The old proton accelerator at Brookhaven National
Laboratory on New York's Long Island is just half a mile around, the
main accelerator ring at the Fermi National Accelerator Laboratory
in Batavia, Illinois, is nearly 4 miles around.
The LEP in Geneva, when it is commissioned in July, will be 17 miles
around; the largest in the world. Someday it may be eclipsed in its
turn by the planned Superconducting Super Collider (SSC) in West
Texas, which will have a circumference of about 53 miles - and which
some investigators think may ultimately have the best chance of
finding the Higgs.
The LEP will achieve extraordinary energy levels in two ways. First,
instead of having the beam smash into stationary targets, the LEP
will have two beams moving in opposite directions.
It will be the difference between a car running into a tree and one
car colliding head-on with another. Second, the electrons will
collide with their antimatter counterpart, positrons, producing
total annihilation.
Some collisions will produce Zs, the neutral agents of the weak
force. A few of these, theory predicts, will fall apart into Higgs
bosons, which in turn will decay into a spray of other particles.
The Zs and Higgses will live so briefly - trillionths of a
trillionth of a second - that they will be impossible to see
directly. But the end product, the spray of other particles, can be
seen by complex detectors, and from it the researchers hope to infer
the existence and properties of the Higgs (pp. 106-07).
When the accelerator cranks up this summer, four experiments, all
multimillion-dollar collaborations, will begin work. L3 is the
biggest, the most expensive and the most directly aimed at the
Higgs.
The project began in 1979, when Ting, Becker and a small number of
other physicists started designing an ambitious machine, a detector,
that they hoped would trap the Higgs if, indeed, it exists.
"We asked CERN for the biggest hole they would give us," coleader
Hans Hofer of Zurich says. "It turned out that we could fill it up
completely with a detector the size of a four-story building." This
is the octagon in the pit, a massive tube stuffed with electronics.
Electrons and positrons will collide at its center; different
detector parts will measure different particles flying outward from
the violence.
"I hope," Becker says drily, "that Mr. Higgs is pleased by how much
trouble we have gone to in trying to find his little particle." His
train of thought is interrupted by the screech of a million
fingernails being dragged across a million blackboards as CERN
workers drag a 20-foot-high metal rack across the concrete floor.
"You know," Becker shouts over the noise "nobody sees Higgs! He
Page 6
just sits up there in Edinburgh! My graduate students come to me
all the time, asking me 'Who is this man Higgs?' Does he really
exist?"'
On the wall behind Becker is a painting of an object vaguely
resembling a Ferris wheel, It is the section of the detector to
which Becker has devoted nearly ten years of his life; the completed
structure is more than 30 feet in diameter, yet measures the
trajectories of particles called muons to within a thousandth of a
millimeter. Within the wheel is a lacework of laser lights, each
centered on a photosensitive cell.
Like an onion, Becker explains, the detector consists of layers of
instruments, each intended to measure a specific type of particle.
Each layer takes years of work, costs millions of dollars and
requires delicate negotiations among the dozens of institutions and
nations involved. Each brings unexpected benefits to industry: by
giving one order to a company that made plastic whiskers for teddy
bears, for example, L3 launched the firm into the fiber-optics
business.
As Becker speaks, fatigue informs his voice; he has accumulated a
quarter of a million miles in air travel. There are shadows under
his eyes and he often finds he needs to vent his frustrations by
working on his car.
"Nobody would choose to work this way, on projects so big," he says
"But we have to, if we're going to chase after something like the
Higgs. And, obviously, we have to hope the people at Stanford don't
get there ahead of us."
Frustration and fury in a California lab
A group of men and women gather, shirtsleeved and disheveled, early
one June morning at a laboratory just south of San Francisco.
Outside, the California sky is as blue as heaven; inside, the light
is dim and migraine green. In a chair against the wall slumps a
round-faced man with bags beneath his tired eyes: the Nobel
Prizewinning physicist and Stanford Linear Accelerator Center (SLAC)
director, Burton Richter, who has designed the project on which they
are working. He has staked the rest of his career, and those of
everyone else in the room, on its completion.
Richter, as it happens, shared his Nobel with Sam Ting in 1976 for
their separate but simultaneous discovery of yet another subatomic
particle, the J or Psi (SMITHSONIAN, July' 1975).
Silent as stone, Richter watches as, one after another, his
colleagues recount the small, infuriating problems of the day
before. Blown electronics. Inappropriate settings. Cooling
difficulties. Human error. The list goes on and on. The project
is more than a year behind schedule, and Richter's fury is as
palpable in the room as a heavy fog.
"We're getting close," says Andrew Hutton, the tall, bearded
Englishman acting as program deputy. "Close enough to proceed as if
we were going to start for real."
Page 7
"Not as if," Richter says. His voice is quiet, but his vehemence is
unmistakable. "We are starting. It is real. We can't wait anymore
on this. From now on, if something goes wrong, work around it. You
can't do science waiting for everything to work right. I want us to
start taking data at 4 Em."
Hutton smiles. "You heard the man," he says. "In eight hours,
we'll try to make history."
Like their rivals at CERN, the scientists at Stanford are working on
a particle accelerator. Known as the SLAC Linear Collider (SLC),
the device is as intricate and baffling as an Escher drawing.
Richter, its designer, had a hand in the original design of the LEP
When he discovered that the United States would not pay for such a
gigantic machine, he tried to come up with a smaller device that
would do the same work, and at a fraction of the cost of a circular
collider. The linear collider is the result.
Shaped somewhat like a two-mile-long tennis racket, it sends two
pulses of particles - electrons and positrons - racing down the
handle and around opposite sides of the head until they meet with
soundless violence at the top.
For most of the Journey, the particles move in a straight line and
do not lose energy by giving off x rays as they are forced to turn.
That means the machine can be much smaller, and hence more quickly
and inexpensively built, than a conventional accelerator. Many
physicists believe that the SLAC Linear Collider is a prototype for
future machines.
On the other hand, the two bunches of particles must collide on the
first pass, instead of having many chances as they spin millions of
times around a ring. The challenge is enormous: make two particle
aggregations, each the thickness of a human hair, each traveling at
a fraction less than the speed of light, smash together at the
precise center of a detector.
Although construction began after the LEP, the hope was to finish
the Stanford accelerator more than a year sooner, giving physicists
there the first chance to find a Higgs. If all goes well, the
machine's design will have been one of the most daring and
successful gambles in recent science, and physicists in the United
States will have leapfrogged their friends and competitors in
Europe. If, that is, all goes well.
"There is a bare chance we can find the Higgs first," says Patricia
Burchat, a young experimentalist at Stanford. "Like them, we will
make Zs, some of which will decay into Higgses. The question is
whether our machine will make enough Zs, and that, I'm afraid, is
not at all clear."
"To get this project approved by the government," Richter says, "we
cut the budget to the point where there was some doubt we would be
able to build the machine. It was a risk, but with the U.S. budget
deficit, it was the only way we could get the money."
The result is a bricolage, new equipment attached to another
accelerator that was built in the 1960s. The jumble of old and new
Page 8
systems is an engineer's nightmare: like an exotic sports car, it
works fine on blocks in the garage, but develops new problems on the
road. The linear collider is now months behind, and every moment of
additional delay further cuts the Americans' chances of getting
there first.
At 4 that afternoon, Richter appears at the main control center for
the first test run. Ninety minutes later, he is forced to leave in
frustration: the machine is not working. With Richter gone, the
staff continues to work before the computer screens lining one end
of the long, dimly lighted room.
The only sounds are the peeping of computer signals, the hush of air
conditioning and the occasional murmur of a dismayed voice. At a
chair in the center, Hutton marks the log. A Briton, he is one of
the relatively few scientists to work both in California and in
Switzerland.
"We've done enough to show that the principle works," he says. "You
can make the bunches collide, and the next generation of
accelerators will be based on this one. But the curious thing is
that a future triumph will not be enough to make the lab look good
today. For that, we need to get this machine functioning ahead of
our friends in Europe, and to get some physics done."
Hutton laughs tiredly; he has been working for a long time without
much sleep. "I must say that right now it would be really nice-
truly nice-if a Z turned up on the screen."
They broke their hearts in San Francisco
A punishing heat wave blankets San Francisco Bay at the end of July,
forcing the region to ration water. Faced with record 100-degree
temperatures, the Stanford accelerator's components begin to
malfunction. Water pumps break down. Flow switches give up the
ghost. Microprocessors burn out. The 8 A.M. meetings become
sweaty litanies of disaster.
Five weeks after Richter ordered the machine to be turned on for
real, the laboratory has managed to accumulate a bare 21 hours of
data, Not a single Z has been seen. To make it worse, the Europeans
are ahead of schedule; in an initial test, their accelerator has
taken seven minutes to reach the goals scheduled to be achieved in
seven days.
Richter has taken to haunting the control room. His face looks, says
one friend, as if he were barely restraining himself from biting his
fingernails. More and more, it is apparent that the jury-rigged
machine was built too quickly and too cheaply. Richter is spending
much time huddling with scientists like Martin Breidenbach, the
wiry, intense leader of the principal experiment.
Weeks before, Breidenbach had been happily splayed on his back,
wrench in hand, beneath the team's detector; now he is being drawn
to the accelerator itself, for without the machine there will be no
particles to detect, no discoveries to make.
Back in his office at CERN, Sam Ting tells the delegation from the
Soviet Union "I don't know what your rules are. I don't even care.
Page 9
What I am saying is this: when the announcement of a discovery is
made, the people on the podium are the ones who get the credit. If
you want your scientists to get the credit they deserve, you will
have to change your policies about not letting them work outside the
Soviet Union. Obviously, the choice is up to you, not me." He
smiles. "I am just a scientist, a lone professor at MIT".
For the first time in the meeting, the Soviets laugh. Whatever they
think of their rules, experience has taught them that they are not
dealing with lone professors at MIT. The face of physics has
changed and research is now performed by huge collaborations, run by
men with fierce and powerful wills. Richter, at Stanford, is one;
Ting, at CERN, is another.
A moment later Ting says, "Nobody has spent all this time and money
on these projects to do ordinary physics. I will consider this
experiment to be an utter failure if someone finds the Higgs before
we do or if we make a technical mistake that prevents us from making
a major discovery." Tapping the symbol for the Higgs boson that he
has written on the blackboard, Ting repeats the words slowly. "A .
. . major discovery."
As the new year begins, tensions are running high at both CERN and
Stanford. The California team is still testing, but hoped to have
the machine on-line as early as March.
In Geneva, physicists have finished installing the components of
their massive detector, are hoping to begin testing in late winter
or early spring, and plan to have the machine up and running by
fall.
In Scotland, serenity reigns. Sitting in his small office at the
University of Edinburgh, Peter Higgs listens to the details of the
gargantuan effort to find the particle whose existence he
hypothesized so many years ago. "Of course I'm flattered by it
all," he says. Afternoon light comes in the window, the same light
that is filling the rolling hills outside with the colors of
sunset"Of course I like it when they give seminars on the search for
the Higgs and so on. And of course I think it's important to look
for. But-you want to know the truth -, When I consider the huge
sums going for this, the lifetimes spent on the search, I can't help
but think: 'Good heavens, what have I done?"'
--------------------------------------------------------------------
If you have comments or other information relating to such topics
as this paper covers, please upload to KeelyNet or send to the
Vangard Sciences address as listed on the first page.
Thank you for your consideration, interest and support.
Jerry W. Decker.........Ron Barker...........Chuck Henderson
Vangard Sciences/KeelyNet
--------------------------------------------------------------------
If we can be of service, you may contact
Jerry at (214) 324-8741 or Ron at (214) 242-9346
--------------------------------------------------------------------
Page 10