- A new experiment is designed to answer
the most fundamental question about our Universe - why it is made of matter
and not antimatter.
-
- The BaBar experiment at the Stanford
Linear Accelerator Center in California will start work on Sunday. Beams
of matter and anti-matter will be smashed into each other and the fleeting
debris of the collisions examined.
-
- Just days later a similar Japanese experiment,
Belle, will also begin. Next year an upgrade to the world's most powerful
particle machine, the Tevatron at Fermilab near Chicago, will also begin
work on the problem.
-
- All the instruments will investigate
the tiny differences between matter and anti-matter.
-
- Great puzzle
-
- One of the great puzzles of the universe
is why it is mostly made of one kind of matter instead of equal amounts
of matter and anti-matter.
-
- Matter and anti-matter are counterparts.
Bring them together and they annihilate each other in a burst of energy.
-
- It is believed that the cosmos was formed
with equal amounts of matter and anti-matter but today the universe is
overwhelmingly made of matter. Anti-matter is rare.
-
- Results reported earlier this year from
Fermilab suggested that matter and anti-matter are not after all identical
"mirror images" of one another.
-
- This could explain why all the anti-matter
that existed at the Big Bang has disappeared.
-
- The phenomenon they think they spotted
is technically called direct Charge-Parity (CP) violation. It means that
particles behave differently if you swap matter for anti-matter and also
swap left and right.
-
- Physicists say that this "asymmetry"
would have been important during the first moments of the Big Bang and
may have resulted in almost all anti-matter being destroyed.
-
- The observation of direct CP violation
is an exciting one for physicists as it disagrees with all the currently
held theories about the nature of matter. BaBar and Belle will look further
into this puzzle.
-
- The race is on
-
- At BaBar intense beams of electrons and
their anti-matter equivalent, positrons, will be smashed into each other.
-
- In the energy liberated during the collision,
a short-lived particle called a B-meson is created as well as its anti-particle,
the B-bar (physicists put a line - or bar - over the symbol to represent
an antiparticle).
-
- After about one thousandth of a billionth
of a second, these particles decay into different particles. Measuring
the details of this decay process will reveal the intracacies of CP violation.
-
- Scientists position large detectors around
the point of impact of the electron-positron beam to measure this.
-
- The six by six metre detector surrounds
the impact point and captures the decay particles. It produces a computer
display showing where the B and B-bar particles are produced and charts
the millimetre they travel before they turn into other particles.
-
- Looking for CP violation however will
not be a swift task. It is estimated that BaBar will have to take data
for at least two years before its measurement will be accurate enough.
-
- By that time other teams, such as those
at the Japanese Belle detector and the Tevatron at Fermilab near Chicago
may have got the answer first.
|
