[tt] NYT: A Giant Takes On Physics' Biggest Questions

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A Giant Takes On Physics' Biggest Questions
CERN - Large Hadron Collider - Particle Physics
http://www.nytimes.com/2007/05/15/science/15cern.html
[Get the dead-tree version, if you can. This is fabulous stuff.]

By DENNIS OVERBYE

300 FEET BELOW MEYRIN, Switzerland The first thing that gets you is
the noise.

Physics, after all, is supposed to be a cerebral pursuit. But this
cavern almost measureless to the eye, stuffed as it is with an
Eiffel Towers worth of metal, eight-story wheels of gold fan-shape
boxes, thousands of miles of wire and fat ductlike coils, echoes
with the shriek of power tools, the whine of pumps and cranes, beeps
and clanks from wrenches, hammers, screwdrivers and the occasional
falling bolt. It seems no place for the studious.

The physicists, wearing hardhats, kneepads and safety harnesses, are
scrambling like Spiderman over this assembly, appropriately named
Atlas, ducking under waterfalls of cables and tubes and crawling
into hidden room-size cavities stuffed with electronics.

They are getting ready to see the universe born again.

Again and again and again 30 million times a second, in fact.

Starting sometime next summer if all goes to plan, subatomic
particles will begin shooting around a 17-mile underground ring
stretching from the European Center for Nuclear Research, or Cern,
near Geneva, into France and back again luckily without having to
submit to customs inspections.

Crashing together in the bowels of Atlas and similar contraptions
spaced around the ring, the particles will produce tiny fireballs of
primordial energy, recreating conditions that last prevailed when
the universe was less than a trillionth of a second old.

Whatever forms of matter and whatever laws and forces held sway Back
Then relics not seen in this part of space since the universe cooled
14 billion years ago will spring fleetingly to life, over and over
again in all their possible variations, as if the universe were
enacting its own version of the Groundhog Day movie. If all goes
well, they will leave their footprints in mountains of hardware and
computer memory.

We are now on the endgame, said Lyn Evans, of Cern, who has been in
charge of the Large Hadron Collider, as it is called, since its
inception. Call it the Hubble Telescope of Inner Space. Everything
about the collider sounds, well, large from the 14 trillion electron
volts of energy with which it will smash together protons, its cast
of thousands and the $8 billion it cost to build, to the 128 tons of
liquid helium needed to cool the superconducting magnets that keep
the particles whizzing around their track and the three million DVDs
worth of data it will spew forth every year.

The day it turns on will be a moment of truth for Cern, which has
spent 13 years building the collider, and for the worlds physicists,
who have staked their credibility and their careers, not to mention
all those billions of dollars, on the conviction that they are
within touching distance of fundamental discoveries about the
universe. If they fail to see something new, experts agree, it could
be a long time, if ever, before giant particle accelerators are
built on Earth again, ringing down the curtain on at least one
aspect of the age-old quest to understand what the world is made of
and how it works.

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If you see nothing, said a Cern physicist, John Ellis, in some sense
then, we theorists have been talking rubbish for the last 35 years.

Fabiola Gianotti, a Cern physicist and the deputy spokeswoman for
the team that built the Atlas, said, Something must happen.

The accelerator, Dr. Gianotti explained, would take physics into a
realm of energy and time where the current reigning theories simply
do not apply, corresponding to an era when cosmologists think that
the universe was still differentiating itself, evolving from a
primordial blandness and endless potential into the forces and
particles that constitute modern reality.

She listed possible discoveries like a mysterious particle called
the Higgs that is thought to endow other particles with mass, new
forms of matter that explain the mysterious dark matter waddling the
cosmos and even new dimensions of spacetime.

For me, Dr. Gianotti said, it would be a dream if, finally, in a
couple of years in a laboratory we are going to produce the particle
responsible for 25 percent of the universe.

Halfway around the ring stood her rival of sorts, Jim Virdee from
Imperial College London, wearing a hardhat at the bottom of another
huge cavern. Dr. Virdee is the spokesman, which is physics-speak for
leader, of another team, some 2,500 strong, with another giant
detector, the poetically named Compact Muon Detector, which was
looming over his shoulder like a giant cannon.

The prospect of discovery, Dr. Virdee said, is what sustained him
and his colleagues over the 16 years it took to develop their
machine. Without such detectors, he said, this field which began
with Newton just stops.

When we started, we did not know how to do this experiment and did
not know if it would work, he said. Twenty-five hundred scientists
can work together. Our judge is not God or governments, but nature.
If we make a mistake, nature will not hesitate to punish us.

Game of Cosmic Leapfrog

The advent of the Cern collider also cements a shift in the balance
of physics power away from American dominance that began in 1993,
when Congress canceled the Superconducting Supercollider, a monster
machine under construction in Waxahachie, Tex. The supercollider,
the most powerful ever envisioned, would have sped protons around a
54-mile racetrack before slamming them together with 40 trillion
electron volts.

For decades before that, physicists in the United States and Europe
had leapfrogged one another with bigger, more expensive and,
inevitably, fewer of these machines, which get their magic from
Einsteins equation of mass and energy. The more energy that these
machines can pack into their little fireballs, the farther back in
time they can go, closer and closer to the Big Bang, the smaller and
smaller things they can see.Recalling those times, Dr. Evans said:
There was a nice equilibrium across the Atlantic. People used to
come and go.

Now, Dr. Evans said, The center of gravity has moved to Cern.

The most powerful accelerator now operating is the trillion-electron
volt Tevatron, colliding protons and their antimatter opposites,
antiprotons, at the Fermi National Accelerator Laboratory in
Batavia, Ill. But it is scheduled to shut down by 2010,

Cern was born amid vineyards and farmland in the countryside outside
Geneva in 1954 out of the rubble of postwar Europe. It had a twofold
mission of rebuilding European science and of having European
countries work together.

Today, it has 20 countries as members. Yearly contributions are
determined according to members domestic economies, and a result is
a stable annual budget of about a billion Swiss francs. The
vineyards and cows are still there, but so are strip malls and
shopping centers.

It was here that the World Wide Web was born in the early 1990s, but
the director-general of Cern, Robert Aymar, joked that the labs
greatest fame was as a locus of conspiracy in the novel Angels and
Demons, by the author of The DaVinci Code, Dan Brown. The lab came
into its own scientifically in the early 80s, when Carlo Rubbia and
Simon van der Meer won the Nobel Prize by colliding protons and
antiprotons there to produce the particles known as the W and Z
bosons, which are responsible for the so-called weak nuclear force
that causes some radioactive decays.

Bosons are bits of energy, or quanta, that, according to the weird
house rules of the subatomic world, transmit forces as they are
tossed back and forth in a sort of game of catch between matter
particles. The Ws and Zs are closely related to photons, which
transmit electromagnetic forces, or light.

The lab followed up that triumph by building a 17-mile-long ring,
the Large Electron-Positron collider, or Lep, to manufacture W and Z
particles for further study. Meanwhile, the United States abandoned
plans for an accelerator named Isabelle to leapfrog to the giant
supercollider in Texas.

Even before that supercollider was canceled, in 1993, however, Cern
physicists had been mulling building their own giant proton collider
in the Lep tunnel.

In 1994, after the supercollider collapse gave its own collider a
clear field, the Cern governing council gave its approval. The
United States eventually agreed to chip in $531 million for the
project. Cernalso arranged to borrow about $400 million from the
European Investment Bank. Even so, there was a crisis in 2001 when
the project was found to be 18 percent over budget, necessitating
cutting other programs at the lab. The colliders name comes from the
word hadron, which denotes subatomic particles like protons and
neutrons that feel the strong nuclear force that binds atomic
nuclei.

Whether the Europeans would have gone ahead if the United States had
still been in the game depends on whom you ask. Dr. Aymar, who was
not there in the 90s, said there was no guarantee then that the
United States would succeed even if it did proceed.

Certainly in Europe the situation of Cern is such that we appreciate
competition, he said. But we assume we are the leader and we have
all intention to remain the leader. And well do everything which is
needed to remain the leader.

To match the American machine, however, the Europeans, with a much
smaller tunnel 17 miles instead of 54 had to adopt a riskier design,
in particular by doubling the strength of their magnets.

In this business, society is prepared to support particle physics at
a certain level, Dr. Evans saids. If you want society to accept this
work which is not cheap, you have to be really innovative.

Cocktail Party Physics

The payoff for this investment, physicists say, could be a new
understanding of one of the most fundamental of aspects of reality,
namely the nature of mass.

This is where the shadowy particle known as the Higgs boson, a k a
the God particle, comes in.

In the Standard Model, a suite of equations describing all the
forces but gravity, which has held sway as the law of the cosmos for
the last 35 years, elementary particles are born in the Big Bang
without mass, sort of like Adam and Eve being born without sin.

Some of them (the particles, that is) acquire their heft, so the
story goes, by wading through a sort of molasses that pervades all
of space. The Higgs process, named after Peter Higgs, a Scottish
physicist who first showed how this could work in 1964, has been
compared to a cocktail party where particles gather their masses by
interaction. The more they interact, the more mass they gain.

The Higgs idea is crucial to a theory that electromagnetism and the
weak force are separate manifestations of a single so-called
electroweak force. It shows how the massless bits of light called
photons could be long-lost brothers to the heavy W and Z bosons,
which would gain large masses from such cocktail party interactions
as the universe cooled.

The confirmation of the theory by the Nobel-winning work at Cern 20
years ago ignited hopes among physicists that they could eventually
unite the rest of the forces of nature.

Moreover, Higgs-like fields have been proposed as the source of an
enormous burst of expansion, known as inflation, early in the
universe, and, possibly, as the secret of the dark energy that now
seems to be speeding up the expansion of the universe. So it is
important to know whether the theory works and, if not, to find out
what does endow the universe with mass.

But nobody has ever seen a Higgs boson, the particle that
personifies this molasses. It should be producible in particle
accelerators, but nature has given confusing clues about where to
look for it. Measurements of other exotic particles suggest that the
Higgss mass should be around 90 billion electron volts, the unit of
choice in particle physics. But other results, from the Lep collider
here before it shut down in 2000, indicate that the Higgs must weigh
more than 114 billion electron volts. By comparison, an electron is
half a million electron volts, and a proton is about 2,000 times
heavier.

Weve nearly ruled out the Standard Model, if you want to say it that
way, said John Conway, a Fermilab physicist. The new collider was
specifically designed to hunt for the Higgs particle, which is key
both to the Standard Model and to any greater theory that would
supersede it.

Theorists say the Higgs or something like it has to show up simply
because the Standard Model breaks down and goes kerflooey at
energies exceeding one trillion electron volts. If you try to
predict what happens when two particles collide, it gives nonsense,
explained Dr. Ellis of Cern, a senior theorist with the long white
hair and a bushy beard to prove it.

There is either a violation of probability or some new physics, Dr.
Ellis said.

Nima Arkani-Hamed of Harvard said he would bet a years salary on the
Higgs.

If the Higgs or something like it doesnt exist, Dr. Arkani-Hamed
said, then some very basic things like quantum mechanics are wrong.

A result, Dr. Gianotti said, is either we find the Higgs boson, or
some stranger phenomenon must happen.

Nightmares

If the Cern experimenters find the Higgs, Nobel Prizes will flow
like water. But just finding the elusive particle will not be enough
to satisfy the theorists, who profess to be haunted by a much deeper
problem, namely why the putative particle is not millions of times
heavier than it appears to be.

When they try to calculate the mass of the Higgs particle using the
Standard Model and quantum mechanics, they get what Dr. Ellis called
a very infinite answer.

Rather than a trillion electron volts or so, quantum effects push
the mass all the way up to 10 quadrillion trillion electron volts,
known as the Planck energy, where gravity and the other particle
forces are equal.

The culprit is quantum weirdness, one principle of which is that
anything that is not forbidden will happen. That means the Higgs
calculation must include the effects of its interactions with all
other known particles, including so-called virtual particles that
can wink in and out of existence, which shift its mass off the
scale.

As a result, if the Standard Model is valid for all energies, said
Joe Lykken, a Fermilab theorist, then you are in deep doodoo trying
to explain why the Higgs mass isnt a quadrillion times bigger than
it needs to be.

Another way to put it is to ask why gravity is so much weaker than
the other forces the theory wants them all to be equal.

Theorists can rig their calculations to have the numbers come out
right, but it feels like cheating. What we have to do to equations
is crazy, Dr. Arkani-Hamed said.

One solution that has been proposed is a new principle of nature
called supersymmetry that, if true, would be a bonanza for the Cern
collider.

It posits a relation between the particles of matter like electrons
and quarks and particles that transmit forces like photons and the W
boson. For each particle in one category, there is an
as-yet-undiscovered superpartner in the other category.

Supersymmetry doubles the world, Dr. Arkani-Hamed said.

These superpartners cancel out all the quantum effects that make the
Higgs mass skyrocket. Supersymmetry is the only known way to manage
this, Dr. Lykken said.

Because Higgs bosons are expected to be produced very rarely, it
could take at least a year or more for physicists to confirm their
discovery at the collider. But some supersymmetric particles, if
they exist, should be produced abundantly and could thus pop out of
the data much sooner. Suppose a gluino exists at 300 billion
electron volts, Dr. Arkani-Hamed said, referring to a putative
superpartner. We could know the first day if they exist.

For several years, supersymmetry has been a sort of best bet to be
the next step beyond the Standard Model, which is undefeated in
experiments but has enormous gaps. The Standard Model does not
include gravity or explain why, for example, the universe is matter
instead of antimatter or even why particles have the masses they do.

In the end, Michelangelo Mangano, a theorist at Cern, said, The
standard model prediction cant be the end of the story.

Supersymmetry also fixes a glitch in the age-old dream of explaining
all the forces of nature as manifestations of one primordial force.
It predicts that at a high enough energy, all the forces
electromagnetic, strong and weak have identical strengths.

If supersymmetry is right, unification works, Dr. Ellis said.

But there is no direct evidence for any of the thousands of versions
of supersymmetry that have been proposed. Indeed, many theorists are
troubled that its effects have not already shown up in precision
measurements at accelerators.

It doesnt smell good, Dr. Arkani-Hamed said. Physicists say the best
indirect evidence for supersymmetry comes from the skies, where the
galaxies have been found to be swaddled by clouds of invisible dark
matter, presumably unknown particles left over from the Big Bang.
Dark matter is a very physical argument. Dr. Ellis said. If you take
astrophysics seriously, there has to be some unseen stuff out there.

On the menu of discoveries, there is always None of the Above. As
Dr. Gianotti put it: Nature has chosen another solution. This will
be great.

There are indeed other potential solutions that go by the name of
Technicolor or the Little Higgs. But what if the collider sees
nothing?

That, Dr. Ellis said, would be interesting for the theorists, who
would have to retool and try to think even deeper thoughts about
quantum mechanics and relativity, but bad for the experimentalists.
Without any results, they would be unlikely to obtain financing for
the next big machine planned, the $7 billion International Linear
Collider.

A worse nightmare, several theorists said, would be seeing just the
Higgs, but nothing else. That would leave them where they are, stuck
in the Standard Model, with no answer to their embarrassing
fine-tuning problem, no dark matter and no clue to a better theory.

To add to the confusion, according to the Standard Model, the Higgs
can have only a limited range of masses without severe damage to the
universe. If it is too light, the universe will decay. If it is too
heavy, the universe would have blown up already. According to Dr.
Ellis, there is a magic value between 160 billion and 180 billion
electron volts that would ensure a stable universe and require no
new physics at all.

But that would leave theorists with nothing more to do and a world
in which basic questions would remain forever unanswered.

Dr. Ellis said, I cant believe God would push the button on a theory
like that.

But, he conceded, For the I.L.C., a boring Higgs is better than
nothing.

Sunken Cathedrals

There was more than birds singing and trees blooming outside the
main Cern cafeteria in March to suggest that springtime for physics
was approaching.

Some 300 feet beneath the warming grass, the magnets that are the
guts of the collider, thick as tree trunks, long as boxcars,
weighing in at 35 tons apiece, were strung together like an endless
train stretching away into the dim lamplight and around a gentle
curve.

A technician on his way to a far sector of the collider ring
bicycled past.

When you fold in the technology combined with the scale, said Peter
Limon, a Fermilab physicist on duty here, I dont think anything on
Earth or in space that we know about beats it.

Running through the core of this train, surrounded by magnets and
cold, were two vacuum pipes, one for protons going clockwise, the
other counterclockwise. Traveling in tight bunches along the twin
beams, the protons will cross each other at four points around the
ring, 30 million times a second. During each of these violent
crossings, physicists expect that about 20 protons, or the parts
thereof quarks or gluons will actually collide and spit fire. It is
in vast caverns at those intersection points that the knee-padded
and hardhatted physicists are assembling their detector, or sunken
cathedrals in the words of a Cern theorist, Alvaro de Rujula, to
capture the holy fire.Two of the detectors are specialized. One,
called Alice and led by Jurgen Schukraft of Cern, is designed to
study a sort of primordial fluid, called a quark-gluon plasma, that
is created when the collider smashes together lead nuclei.

The other, LHCb, is led by Tatsuya Nakada of Cern and the Swiss
Federal Institute of Technology in Lausanne. It is designed to hunt
for subtle differences in matter and antimatter that could help
explain how the universe, which was presumably born with equal
amounts of both, came to be dominated by matter.

The other two, the aforementioned Atlas and Compact Muon Solenoid,
or C.M.S. for short, are the designated rival workhorses of the
collider, designed expressly to capture and measure every last spray
of particle and spark of energy from the proton collisions.

The rivals represent complementary strategies for hunting the Higgs
particle, which is expected to disintegrate into a spray of lesser
particles. Exactly which particles depends on how massive the Higgs
really is.

One telltale signature of the Higgs and other subatomic cataclysms
is a negatively charged particle known as a muon, a sort of heavy
electron that comes flying out at nearly the speed of light.
Physicists measure muon momentum by seeing how much their paths bend
in a magnetic field.

It is the need to have magnets strong enough and large enough to
produce measurable bending, physicists say, that determines the
gigantic size of the detectors.

The Compact Muon Solenoid, built by Dr. Virdees group, weighs 12,000
tons, the heaviest instrument ever made. It takes its name from a
massive superconducting electromagnet that produces a powerful field
running along the path of the protons.

Conversely, the magnetic field on Atlas wraps like tape around the
proton beam. The Atlas collaboration has been led from its start by
Peter Jenni of Cern. At150 feet long and 80 feet high, Atlas is
bigger than its rival, but it is much lighter, about 7,000 tons,
about as much as the Eiffel Tower. The physicists like to joke that
if you threw it in the ocean in a plastic bag it would float.

The two detectors have much in common, including onion layers of
instruments to measure different particles and the ability to cope
with harsh radiation and vast amounts of data. Dr. Virdee compared
the central C.M.S. detector, made of strips of silicon that record
the passage of charged particles, to a 60-megapixel digital camera
taking 40 million pictures a second. We have to time everything to
the nanosecond, he said

To manage this onslaught the teams computers have to perform triage,
and winnow those events to a couple hundred per second. That is
dangerous, Dr. Gianotti said, because we are looking for something
rare. The Higgs occurs once in every trillion events, she said.

Contending Armies

The competition between Atlas and the C.M.S. is in keeping with a
long tradition of having rival teams and rival detectors at big
experiments to keep each other honest and to cover all the bets. As
Dr. Mangano put it, If you screw it up, others are here to crucify
you.

At the Fermilab Tevatron, the teams, several hundred strong, are
called CDF and D0. In the glory years 20 years ago at Cern, they
were called UA1 and UA2. Over the years, as the machines have grown,
so have the groups that built them, from teams to armies, 1,800
people from 34 countries for Atlas and 2,520 from 37 countries for
the C.M.S. The other two experiments Alice with 1000 scientists, and
LHCb with 663 are only slightly smaller.

Robert Cousins of U.C.L.A. and C.M.S. joked that he was old enough
so that after 25 years in the business half my friends are on Atlas,
the others on C.M.S. Dr. Jenni said all 1,800 Atlas scientists would
have their names on the first papers out of the collider, adding:
The people who work in the pit make as important a physics
contribution as those who end up in front of the computers. This is
a big step in energy. Its new territory, and thats in the end why
everyone is excited.

At the end of the day, Dr. Mangano said, unless there is a major
problem both machines will perform. It will come down to sociology,
he said. How quickly can they analyze the data? How do you
manipulate and analyze the data? The process of understanding is
long.

There could be new phenomena, he added, new particles that theorists
have not thought of.

Dr. Mangano pointed out that it had been a long time since
high-energy physicists had made a fundamental discovery. And back
then, when Dr. Rubbia was doing his Nobel work, there were
well-defined theories of what would be found. Now, everything will
be new.

There are many students who have never seen data, Dr. Mangano said.
I dont know how much longer we can keep going like that.

What comes out of the Large Hadron Collider, he said, will determine
the future of the field.

Dr. Arkani-Hamed said the tension was keeping him awake at night.
Nobody knows how this is going to go, he said. Thats what makes it
so cool. The experiment itself is so spectacular.

Sipping an espresso in his office, Dr. Mangano refused to consider
the possibility of failure. Its like saying suppose you drive into a
tree on the way home, he said. Lets hope we get home safely and we
see something.