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12/12/2000
Weighty Stuff
As promised last week, I bit the bullet and am writing about the
Higgs boson, which brings us to Ricki Martin. He performed on
the Today show recently and drew a wildly enthusiastic
response, notably from younger females in the crowd. Let''s take
a few hundred of these young ladies place them in a large room.
I could cross through that room in 15 seconds. However, send in
Ricki Martin and a cluster of screaming fans are attracted to him.
It''s now very difficult for him to make any progress and he may
take 10 minutes or even an hour, if he makes it across at all!
For the heck of it, let''s call that initially uniformly distributed
bunch of girls a "Higgs field". This Higgs field fills the room
and there is a definite attractive force between the field of girls
and Ricki. I don''t know his weight, but suppose Ricki masses in
at 180 pounds. When that Higgs field clusters around him, he
effectively weighs a couple thousand pounds as he walks,
dragged back by the clustered field. You could call the couple
thousand pounds his "effective mass". At Bell Labs we talked
about the effective mass of electrons travelling through silicon.
In the silicon there are positively charged atoms that attract the
negative electron and the electron is slowed down, resulting in a
larger effective mass.
The attraction of our Higgs field of females to Ricki suggests
there''s some kind of force causing the attraction. I have no idea
what this force could be. However, the idea of fields and forces
is familiar, for example, in the area of magnetism. If we bring an
iron nail close to a strong magnet, there''s a strong force attracting
the nail to the magnet. We can see the pattern of the magnetic
field by putting a bar magnet under a piece of paper or cardboard
and sprinkling iron filings on the paper. Let''s now take a bold
step and pretend that our Higgs field uniformly fills not just a
room, but the whole universe! Naturally, our young ladies would
not survive in most places in the universe, so let''s get rid of them
but still keep some kind of attractive force. That''s what Peter
Higgs, a particle physicist at the University of Edinburgh,
proposed in the 1960s. We''ve said in earlier columns that a
vacuum really is not totally "nothing". If Higgs is correct, the
Higgs field is one of the things found even in the emptiest
reaches of space.
Now let''s pretend we''re outside our universe and drop a proton
into the universe. Let''s be silly and pretend also that the proton
has no mass when we drop it into the universe. When the proton
enters the universe, it''s traveling through that Higgs field and, as
with Ricki, the Higgs field is attracted to and "clusters" around
the proton. Now the cluster drags on the proton and gives it an
effective mass. Repeat this with an electron and we find the
clustering isn''t as strong. The electron has a much lower
effective mass than the proton. If you wonder why the
difference, it''s like the difference between Ricki and me. He''s
young and vibrant; I''m old and decrepit. We''re two different
particles.
Why this ridiculous pretending that the proton and electron have
intrinsically no mass? Being a simple minded individual, I have
always accepted the fact that everything I see around me has
some mass associated with it. On a personal level, my own mass
during the holidays tends to increase more than I would like. As
a scientist, I''ve never questioned that protons and electrons have
different masses. That''s just the way it is. But particle physicists
don''t take such things for granted and actually want to know why
the electron weighs less than the proton. They even want to be
able to calculate the masses of all the quarks and other particles
theoretically. If they succeed in doing that, it will be an
achievement that cuts to the very essence of what we''re made of.
Actually, for many years these physicists have not been happy
with the fact that things have any mass at all. It seems that their
theories treat the fundamental particles as having no mass. You
might say, "You idiots, you just aren''t smart enough and your
theories stink!" But there''s a catch. These guys are far from
being idiots. In the 1960s, for example, three guys, working
independently, came up with theories about a fundamental
problem, the so-called "electroweak" force. Suffice to say here
that the theories deal with the weak nuclear forces involved in
radioactivity. These fellows were Abdus Salam, working in
England, and Sheldon Glashow and Steven Weinberg working in
the U.S. The three shared the 1979 Nobel Prize in physics for
their work.
One of the key results of their work was the prediction of two
new particles they called W and Z bosons. I''ll tell you about
bosons shortly. These W and Z bosons were only figments of
their imaginative theories until the 1980s. Then, with higher
energies available in accelerators and the theory in hand, the
existence of the W and Z particles was confirmed. The W and Z
bosons are, relatively speaking, monstrous particles a hundred
times heavier than a proton. They "carry" the weak nuclear
forces and are intimately involved, for example in the sun''s
nuclear reactions.
So, I shouldn''t have been surprised when I saw on the front page
of our newspaper that scientists are looking for what some have
called the "God" particle, the "Higgs boson". Today, as were the
W and Z bosons, the Higgs boson is only a figment of the
physicists'' theories. Nevertheless, the physics community will be
spending many millions of dollars in a quest to prove or disprove
its existence. Why? Whenever you have a field, there''s
generally a particle that goes with it. So, if there is such a thing
as the Higgs field, there should be a particle - the Higgs boson.
What is a boson? First, a boson is a particle that can transmit
forces. You''re dealing with zillions of bosons at this very minute
as you read this sentence! Those photons of light flooding
through your eyes are bosons. Unlike the monstrous W and Z
bosons, photons have no mass at all. Each photon can be
considered as a little wave packet having an electromagnetic
field associated with it. The field represents a force and the
energy depends on the wavelength or frequency. Shorter
wavelength blue light has more energy than longer wavelength
red light.
Bosons are gregarious. Remember 10 or 20 clowns emerging
from that small car in the circus? The electron, which is not a
boson, is antisocial, on the other hand. If you have a can of
tennis balls only three will fit in the can. Like electrons, they
don''t like to be crowded. If the tennis balls were bosons,
somehow you''d be able to pack as many as you wanted in the can
and the bosons would find a way to fit in. This is a very crude
analogy and I really should be talking quantum mechanics but
the idea is there. There''s another particle we''ve talked about that
is a boson and that''s the gluon. You may recall that gluons are
what holds the quarks together in a proton or neutron. Otherwise
we''d all fly apart! If we ever got ourselves together in the first
place. The gluons, like the photons have no mass.
Back to the Higgs field and Higgs boson and why all the fuss?
You probably know or have guessed that what the physicists are
saying is that the Higgs field is the fundamental source of all the
mass in the universe. When we said our electron and proton had
"effective masses" in the Higgs field, to us those effective masses
are the real, ordinary, everyday masses we love and cherish.
You might say, "If it''s the Higgs field that''s what gives
substance. Why worry about the Higgs boson?" Well, to
actually detect the Higgs field pervading our universe may be an
impossible task. But, if there is a Higgs boson that carries this
field and that particle can be found, it will be a monumental
confirmation of Peter Higgs'' hypothesis.
The Higgs boson, if it exists, is a very heavy particle. It may
even be heavier than an iron or even a uranium atom. You might
think, "Hey, that big a particle should be easy to spot." Not true!
When it comes to big fundamental particles, the problem is that
they aren''t stable and don''t hang around more than a few
zillionths of a second. Furthermore, in the particle accelerators,
you don''t typically see the particles themselves but only their
decay products. How to find the Higgs boson? The answer is
bigger, more powerful accelerators. Two candidates in the race
to find the Higgs are CERN in Switzerland and the Fermi
National Accelerator Facility just outside Chicago but it could be
years before any conclusive experiments are performed.
I must give credit to David Miller of University College in
London. He was one of the winners of a contest to come up with
the best one-page explanation of the Higgs boson. Being a Brit,
Miller used ex-Prime Minister Margaret Thatcher at a political
worker gathering. Before using Ricki, I was tempted to use Gore
or Bush but decided that the political workers would be too
exhausted to cluster! Miller likened the Higgs boson to the
spread of a rumor across the room. As the rumor traverses the
room, clustering of the young ladies themselves sweeps across
the room like a wave. This wave, involving the clustering of the
Higgs field itself is the Higgs boson. Miller points out that
detection of the Higgs boson would nail down the existence of
the Higgs field. But he also points out that the possibility that
we''re all in a Higgs field but there''s no such thing as a Higgs
boson. If not, we may never know for sure why we have mass.
I don''t know about you, but dealing with such weighty matters
has exhausted me. I''m going to take a nap and close my eyes to
those zillions of bosons. My wife read this and said she felt the
same way! Maybe I''ll write about hornet juice next week.
Allen F. Bortrum
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