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04-08-2004, 03:26:03

Physicists Discover Dramatic Difference In Behavior Of Matter Versus Antimatter
Date: 2004-08-03

Physicists Discover Dramatic Difference In Behavior Of Matter Versus
Today, physicists conducting the BaBar experiment at the Stanford Linear
Accelerator Center (SLAC), a Department of Energy laboratory operated by
Stanford University, announced exciting new results demonstrating a
dramatic difference in the behavior of matter and antimatter. They
submitted their results to the journal Physical Review Letters for online

SLAC‚s PEP-II accelerator collides electrons and their antimatter
counterparts, positrons, to produce an abundance of exotic heavy particle
and anti-particle pairs known as B and anti-B mesons. These rare forms of
matter and antimatter are short-lived, decaying in turn to other lighter
subatomic particles, such as kaons and pions, which are observed in the
BaBar experiment.
„If there were no difference between matter and antimatter, both the B
meson and the anti-B meson would exhibit exactly the same pattern of
decays. However, our new measurement shows an example of a large
difference in decay rates instead,š said BaBar spokesman Marcello Giorgi,a
physicist at Istituto Nazionale di Fisica Nucleare (INFN) and the
University of Pisa.
By sifting through the decays of more than 200 million pairs of B and
anti-B mesons, BaBar experimenters have discovered striking
matter-antimatter asymmetry. „We found 910 examples of the B meson
decaying to a kaon and a pion, but only 696 examples for the anti-B
mesons,š Giorgi explained.
While BaBar and other experiments have observed matter-antimatter
asymmetries before, this is the first instance in B decays of a difference
obtained by simply counting up the number of matter and antimatter decays,
a phenomenon known as direct charge parity (CP) violation.
„We have observed a clear, strong signal for asymmetrical behavior of
matter and antimatter resulting from the direct CP violation mechanism,š
said James Olsen of Princeton University, one of the leaders of the
The new observation of a 13 percent preference for the B meson over the
anti-B meson dwarfs a similar effect observed in kaons at only a tiny rate
of 4 parts in a million. „The effect we have measured with B mesons is
roughly 100,000 times stronger than for kaons,š Olsen said. „The pattern
of different types of matter-antimatter asymmetries is starting to come
together into a coherent picture.š
When the universe began with the big bang, matter and antimatter were
present in equal amounts. But all observations indicate that we live in a
universe made only of matter. What happened to the antimatter?
Subtle differences between the behavior of matter and antimatter must be
responsible for the matter-antimatter imbalance that developed in our
universe. But our current knowledge of these differences is incomplete and
insufficient to account for the observed matter domination. CP violation
is one of the three conditions outlined by Russian physicist Andrei
Sakharov to account for the observed imbalance of matter and antimatter in
the universe.
"This is another great scientific achievement for the B-factory at SLAC,"
said Raymond L. Orbach, Director of the Department of Energy's Office of
Science. "The new result from BaBar, and related measurements at other
accelerators around the world, continue to improve our understanding of CP
violation and ultimately may tell us why the visible universe is only
„The new measurement is very much a result of the outstanding performance
of SLAC‚s PEP-II accelerator and the efficiency of the BABAR detector,š
Giorgi said. „The accelerator is now operating at 3 times its design
performance and BaBar is able to record about 98 percent of collisions.š
„This is an exciting and beautiful resultųit probes a key mechanism
underlying the structure and behavior of matter,š said SLAC Director
Jonathan Dorfan. „The observation of the direct CP violation effect in B
decays is a significant step forward in assembling the pieces of the
puzzle of matter versus antimatter.š
Some 600 scientists and engineers from 75 institutions in Canada, China,
France, Germany, Italy, the Netherlands, Norway, Russia, the United
Kingdom, and the United States are working on BaBar. SLAC is funded by the
Department of Energy‚s Office of Science.
Editor's Note: The original news release can be found here.

This story has been adapted from a news release issued by Stanford Linear
Accelerator Center.

04-08-2004, 03:38:19
Someone please help TCO.

self biased
04-08-2004, 04:00:40

04-08-2004, 04:15:21
madder n anti-madder r diffr'nt

The Mad Monk
04-08-2004, 05:36:07
Try reversing the polarity.

04-08-2004, 05:46:33
So it's just another demonstration of CP violation?

The Mad Monk
04-08-2004, 07:01:15
If they don't decay as often, does that imply that antimatter should be more stable than matter?

...and does that imply that the known universe is really, really weird?

04-08-2004, 07:07:02
No. There's nothing like "antimatter is more stable than matter" here.

Just one decay pathway happens preferentially for certain particles than their antiparticles.

That in itself has always struck me as a bit odd.

Also, there's something known as the "CPT thm" which says that the product of the C, P and T reversal operators leaves everything looking the same.

What's really odd to me is that if CP is violated and CPT is conserved then T should be violated, which means that time is preferential in one direction...

Sir Penguin
04-08-2004, 07:54:47
Whatever happened to that guy who said that time isn't quantized?


The Mad Monk
04-08-2004, 08:06:22
which means that time is preferential in one direction...

You mean, like the way the universe never appears to...rewind?

04-08-2004, 09:18:59
Does any of this matter?

self biased
04-08-2004, 15:58:50
own goal.

04-08-2004, 16:16:16
Originally posted by The Mad Monk
You mean, like the way the universe never appears to...rewind?

More basic than that. :)

The general appearance of time going forward is not that great a mystery. There is one beginning state and many possible end states. That's all timeflow is....

09-03-2006, 01:58:02
I must have been drinking or am getting old...or someone had my user name. Don't remember posting this.

09-03-2006, 02:09:53

Frozen Frog
09-03-2006, 03:26:17
Originally posted by self biased
own goal.

Do you live for this?

Frozen Frog
09-03-2006, 03:26:45

09-03-2006, 07:42:48
I almost joined that experiment. Just decided to do this one instead.


09-03-2006, 09:49:17
Does this matter?

09-03-2006, 10:09:16
Wasn't it agreed that this supposedly universal event horizon we call time, is purely an historical measure...

09-03-2006, 13:24:44
Originally posted by Funko
Does this matter? :hmm:

09-03-2006, 14:13:57
Originally posted by TV4Fun
Someone please help TCO.

god help me i agree with tv4fun

and by 'help' you mean 'shoot' right?

The Mad Monk
10-03-2006, 01:44:24
It anti matters.

10-03-2006, 04:38:19
Ya Kenna change the laws of physics!


The Mad Monk
03-04-2006, 18:19:46
Possibly the most ironic line in television history.

09-04-2006, 20:06:17
NASA sux. Except Herb Henricks and his optical fiber work at Langley. He made some of the first MUX/DEMUX in the early 80s and I dorked around with him as a high school student.

09-04-2006, 20:36:09
Be careful. My money comes from NASA...

09-04-2006, 20:52:53
oh...and that too. ;)

09-04-2006, 20:53:46
In fact...I think they oughta add a travel stipend and some unconditional $$. :)

09-04-2006, 21:10:47

10-04-2006, 02:00:22
Originally posted by The Mad Monk

...and does that imply that the known universe is really, really weird?

This is news? It doesn't take a gaziilion dollars of equipment and 600 scientists to work that one out. :confused:

The Mad Monk
10-04-2006, 08:03:49
But it does to prove it scientifically.


Dyl Ulenspiegel
10-04-2006, 08:27:41
She blinded me with!