From: LARRY KLAES (ljk4_at_msn.com)
Date: Tue Sep 30 2003 - 10:00:00 PDT
Other Dimensions? She's in Pursuit
September 30, 2003
By DENNIS OVERBYE
BATAVIA, Ill. - Flap harder, urged the little girl with the
stopwatch.
One by one, the children stepped up and launched themselves
off the garden wall, flapping homemade wings with their
arms. Always with the same result.
Crash.
Only the girl herself, 7 years old, an aspiring dancer,
astronaut, wing maker and free spirit, could not jump - not
out of fear or lack of confidence in the wings she had
made, but because she could not time her own flight. "And I
didn't trust anybody to time it for me," she recalled. She
already had the soul of a scientist, as well as a knack for
leadership.
Crash.
Just before midnight on a recent summer night, the girl,
Dr. Maria Spiropulu, now 33 and a physicist affiliated with
the University of California at Santa Barbara, stepped
outside a South Side Chicago jazz club and climbed into a
cluttered Honda Civic. She was wearing black jeans, a black
sleeveless top, Nikes and three rings on her left hand.
Spewing noise from a leaky muffler, she drove into the
Illinois prairie, through the gates of the Fermi National
Accelerator Laboratory, or Fermilab, and past scattered
farmhouses too white and neat to be real farmhouses
anymore.
Mars' bloody stare was high in a hazy sky by the time she
parked outside a hulking shedlike building. Inside the
shed, the ground floor rimmed a huge pit three stories deep
and wide as a basketball court, littered with the toys of
industrial strength science - cranes, racks of electronics,
tool chests, cables, long magnets stacked like redwood
logs.
Behind a wall at one end of the pit, smack in the beam of
Fermilab's Tevatron, the world's biggest particle
accelerator, sat a three-story 5,000-ton assembly of
magnets, crystals, electronics, wires and computers known
as the Collider Detector Facility.
The C.D.F., as it is called, was perhaps the most exquisite
and expensive stopwatch ever built. Dr. Spiropulu was
hoping to use it to time not the flight of flapping little
cousins, but the flight of particles going right out of
this world altogether, disappearing into another dimension,
like a billiard ball popping straight up off the table or
the phantom voices conjured by 19th-century mediums.
The discovery would confirm some of the boldest and most
far-reaching theories in physics, which imply that nature
has 10 or 11 dimensions, not the 3 of space and 1 of time
that frame our normal experience.
In a control room upstairs, the air was humming with
imagined energy of a trillion volts; 50 computer screens
were lit up, and one laptop lay open on a desk.
The screens showed the progress three stories below where
36 batches of protons were whirling around a 4-mile
racetrack 40,000 times a second. Now, as a disembodied
computerized female voice ticked off every step of the
process, antiprotons, the antimatter mirror antagonists of
protons, were being inserted, batch by batch, into the same
racetrack but in opposite directions.
If all went well, protons and antiprotons would soon be
colliding millions of times a second, replicating a little
bit of the universe circa a trillionth of a second after
the Big Bang, annihilating one another in a fireball of
energy and spraying bits of matter and energy through the
C.D.F. and perhaps out of the world as we know it.
But there was nothing mystical about Dr. Spiropulu's mood.
As the minutes ticked down she was in nerd mode, hunched
over a computer terminal like a kid doing last-minute
homework. She was running a test to diagnose the health of
the detector, inserting false data into one end of the
labyrinth of wires, detectors, filters and programs that
must decide in a fleeting instant which few dozen of the
three million big bangs per second were interesting enough
to record and study, and then checking to see that it
emerged unscathed out the other end.
"It is like a physical checkup," she explained, admitting
that it was "extremely tedious." But it is with exacting
solicitude for the subtleties of measurement that Dr.
Spiropulu, a self-described "lab chick," has made her mark
in the physics world, combining a hard scientific
conservatism and personal exuberance that has prompted her
to deliver karate kicks in a physics talk
"Physics is not my job; it is my life," she says. "The
world is what you measure."
"Everybody is entitled to their own opinion," she likes to
say, "but they're not entitled to their own facts. The data
is the data."
So far, the fifth dimension has not been found. Nor has the
sixth, seventh, eighth, ninth or tenth.
On Sept. 19, after a year of preparation, Dr. Spiropulu,
Dr. Kevin Burkett of Harvard and half a thousand co-authors
reported that any spatial extra dimensions, if they exist,
must be curled up into circles smaller than a hundredth of
an inch to a trillionth of an inch or so across, depending
on how many there are and how they are configured.
The results complement those of a sister Fermilab team led
by Dr. Greg Landsberg of Brown and Dr. Ryan Hooper of Notre
Dame, who used another giant detector, known as D0, and
different methods.
Dr. Spiropulu vows that the search has only begun. If they
don't find extra dimensions, physics will find something
just as "crazy," either at Fermilab or at CERN's Large
Hadron Collider, which will turn on with seven times as
much energy in 2007, and may produce miniature black holes,
if the theory is right.
Dr. Spiropulu said she would move back to Geneva and CERN
early next year, where her career began, to help prepare
for a revolution she says "will blow our minds."
Born in Greece, the daughter of a businessman and a teacher
of fashion design, Dr. Spiropulu describes herself as a
demanding child. "I wasn't crazy, but annoying," she said,
asking too many questions. That impression, she said,
lingers today.
As a young girl she dreamed of being an astronaut, but the
Greek air force academy did not accept women, so she went
to Aristotle University of Thessaloniki and majored in
physics. "I knew my life was as an experimental physicist,"
she said.
After graduation, she borrowed $500 from her father and
went to CERN, where she got a job as a technical assistant.
>From there, she went to Harvard for her Ph.D. in particle
physics. Most of those years were spent at Fermilab,
serving a gritty apprenticeship on and in the giant C.D.F.
She played drums and sang for a Fermilab band called Drug
Sniffing Dogs until she was expelled for not attending
rehearsals.
There was a dark period, she acknowledges, in 1996, when
two close friends, both Greek scientists, died - one in a
car accident, the other on Swissair Flight 111 that crashed
off Nova Scotia.
She said the memory of those days still hurt. "I can fight
and fight," she said, "but there are a bunch of things that
nothing can turn them around. Death is one."
For her doctoral thesis, she developed a kind of blind
analysis similar to that used in drug trials to search the
accelerator's output for evidence of a desperately sought
phenomenon known as supersymmetry.
If supersymmetry, generally regarded as the next great
thing in particle physics, is true, there is a whole set of
ghostlike elementary particles yet to be discovered. But
how to sort their signatures from known phenomena that can
mimic them?
Dr. Spiropulu's strategy was to set aside "in a box" the
data that might show the new particles. Then she analyzed
the rest of the data, which presumably did not contain any
"new physics," and used the results to predict how many
"background events" should show up when the box was finally
"opened."
Knowledge of this background is crucial if you don't want
your big discovery to turn out to be a mirage.
When she opened the box three years ago in front of her
C.D.F. colleagues, her calculations turned out to be dead
on. That meant no supersymmetry. Yet.
"Everybody else was clapping, and I was about to cry," she
said then. But at least with no arresting claim to defend,
she could focus on her dissertation.
After graduation Dr. Spiropulu joined the University of
Chicago and applied her expertise to the search for extra
dimensions.
It might seem obvious that we live in a world of three
spatial dimensions and one of time. But physicists have
become enamored of string theory, the "theory of
everything," which posits that nature is ultimately
composed of tiny vibrating strings. And the theory only
makes mathematical sense if space-time actually has 10
dimensions.
To explain the discrepancy between theory and experience,
string theorists have posited that the extra dimensions are
rolled up, like the pile on a carpet, into little circles
or six-dimensional balls, less than a trillionth the size
of an elementary particle.
In 1998, however, three theorists - Dr. Nima Arkani-Hamed
of Harvard, Dr. Savas Dimopoulos of Stanford and Dr. Gia
Dvali of New York University - suggested that if some of
these extra dimensions were larger, as much as a
millimeter, it could explain one of the enduring mysteries
of physics. Why is gravity is so weak compared with the
other fundamental forces of nature?
That this is so can be seen by the fact that a plywood
board, held together by electromagnetic forces between
atoms, is enough to counter the gravitational pull of the
entire Earth on a human body: we don't regularly fall
through the floor.
Supersymmetry is one way to shore up this mathematical gap,
but large extra dimensions, they said, might be another.
Suppose, they said, that gravity is actually comparable to
the other forces in strength and only appears weaker
because it is diluted by propagating through the extra
dimensions, while the other forces are confined to the
ordinary three dimensions.
In the so-called A.D.D. version, after the authors above,
the extra dimensions are little circles. But in another
version, developed by Dr. Lisa Randall of Harvard and Dr.
Raman Sundrum at Johns Hopkins, one of the extra dimensions
can be infinite.
If any of these ideas are right, it means that even with
Fermilab's Tevatron, physicists may be nibbling at the
energies that produce black holes or strings.
In ordinary physics, such effects occur only at the
so-called Planck energy, 1019 billion electron volts, at
which space-time itself appears bumpy and the paradoxical
rules of quantum mechanics have to be applied to gravity.
Physicists would need an accelerator the size of a galaxy -
and a budget to match - to get there.
Dr. Spiropulu and Dr. Burkett have focused on one
possibility, namely that the collision of a proton and an
antiproton - or of the quarks and gluons inside of them -
will produce a graviton, the hypothesized particle of force
that carries gravity.
In ordinary physics, all gravitons would be massless like
the photon that carries light. But a graviton's motion in
the extra dimensions would look like extra mass or energy,
Dr. Spiropulu said.
And that mass would be conspicuous by its disappearance.
"Once I make my 6-D graviton, it heads off into the extra
dimensions," she explained. In the detector's strict
bookkeeping, it would look as if energy were disappearing
from a collision.
So far the missing gravitons are, well, still missing. But,
Dr. Spiropulu says, "It's interesting that we can have
limits already, and not just sit and wring our hands."
Her analysis was based on Tevatron data obtained from 1992
to 1996. The machine has since been upgraded to produce
slightly more energetic, brighter beams.
There are still four more years for her or the D0 team to
grab the brass ring before CERN's new collider takes over.
One afternoon in August, as the beams hummed and banged
downstairs, some events interesting to have survived
winnowing by Dr. Spiropulu's "trigger" programs were being
flashed, one after another, on a pair of computer screens
in the control room. They appeared as spiky tracks or as
bumps of energy going in different directions.
To a particle physicist, these were familiar old friends.
Here, Dr. Spiropulu said, was probably a J/Psi particle,
whose discovery in 1974 had led