by Suzanne Taylor Muzzin
March 19, 2010
This image of a full-energy
collision between gold ions
shows the paths taken by
thousands of subatomic particles produced during the impact.
New Haven, Conn.
For a brief instant, it appears, scientists at
Brookhaven National Laboratory on Long Island recently
discovered a law of nature had been broken.
Action still resulted in an equal and opposite reaction, gravity kept the
Earth circling the Sun, and conservation of energy remained intact. But for
the tiniest fraction of a second at the Relativistic Heavy Ion Collider
physicists created a symmetry-breaking bubble of space where parity no
Parity was long thought to be a fundamental law of nature.
states that the universe is neither right- nor left-handed - that the laws
of physics remain unchanged when expressed in inverted coordinates. In the
early 1950s it was found that the so-called weak force, which is
responsible for nuclear radioactivity, breaks the parity law.
However, the strong force, which holds
together subatomic particles, was thought to adhere to the law of parity, at
least under normal circumstances.
Now this law appears to have been broken by a team of about a dozen particle
physicists, including Jack Sandweiss, Yale's Donner Professor of
Physics. Since 2000, Sandweiss has been smashing the nuclei of gold
atoms together as part of the
STAR experiment at RHIC, a
2.4-mile-circumference particle accelerator, to study the law of parity
under the resulting extreme conditions.
The team created something called a quark-gluon plasma - a kind of "soup"
that results when energies reach high enough levels to break up protons and
neutrons into their constituent quarks and gluons, the fundamental building
blocks of matter.
Theorists believe this kind of quark-gluon plasma, which has a temperature
of four trillion degrees Celsius, existed just after the Big Bang,
when the universe was only a microsecond old.
The plasma "bubble" created in the collisions at
RHIC lasted for a mere millionth of a billionth of a billionth of a second,
yet the team hopes to use it to learn more about how structure in the
universe - from black holes to galaxies - may have formed out of the soup.
the gold nuclei, traveling at 99.999%
of the speed of light, smashed together, the plasma that resulted was so
energetic that a tiny cube of it with sides measuring about a quarter
of the width of a human hair would contain enough energy to power
the entire United States for a year.
It was the equally gargantuan magnetic field
produced by the plasma - the strongest ever created - that alerted the
physicists that one of nature's laws might have been broken.
"A very interesting thing happened in these
extreme conditions," Sandweiss says.
"Parity violation is very difficult
to detect, but the magnetic field in conjunction with parity violation
gave rise to a secondary effect that we could detect."
Sandweiss and the team - which includes Yale
physics research scientists Evan Finch, Alexei Chikanian and
Richard Majka - found that
quarks of a like sign moved together:
Up quarks moved along the magnetic field
lines, while down quarks traveled against them.
That the quarks could tell the difference in
directions suggested to the researchers that
symmetry had been broken.
The results were so unexpected that Sandweiss and his colleagues waited more
than a year to publish them, spending that time searching for an alternative
The physicist is still quick to point out that
the effect only suggests parity violation - it doesn't prove it - but the
STAR collaboration has decided to open up the research to scrutiny by other
"I think it's a real effect, but we'll know
more in the upcoming years," Sandweiss says.
Next, the team wants to test the result by
running the experiment at lower collision energies to see if the apparent
violation disappears when there is not enough energy to create the
necessary extreme conditions.
If the effect proves to be real, it could help scientists understand a
similar asymmetry that led to one of physics' most fundamental mysteries -
namely, why the universe is dominated by ordinary matter today when equal
amounts of matter and antimatter were created by the Big Bang.
Sandweiss, for one, is looking forward to some answers.
"I'd really like to see this evolve and find
out exactly what's going on," he says.