Thursday, August 12, 2010

CP-Violation For Neutrinos

I'm a bit late in reporting this, but better late than never.

It appears that there's a first sighting of possible CP-violation in the lepton sector. An analysis of the MiniBooNE experiment seems to suggest that the flavor oscillation for neutrino and antineutrino differs from each other.

A team of physicists including some from MIT has found surprising differences between the flavor-switching behavior of neutrinos and antineutrinos. If confirmed, the finding could help explain why matter, and not antimatter, dominates our universe.

“People are very excited about it because it suggests that there are differences between neutrinos and antineutrinos,” says Georgia Karagiorgi, an MIT graduate student and one of the leaders of the analysis of experimental data produced by the Booster Neutrino Experiment (MiniBooNE) at the Fermi National Accelerator Laboratory.
 This would be very exciting indeed.

Still, I'm going to nitpick this report a bit for a possible misleading information.

Neutrinos, elementary particles generated by nuclear reactions in the sun, suffer from an identity crisis as they cross the universe, morphing between three different “flavors.” Their antimatter counterparts (which are identical in mass but opposite in charge and spin) do the same thing.
 If you read this carefully, you'll get the impression that antineutrinos are counterpart to neutrinos (which is true), and have opposite charge and spin. Of course, this would be in error because neutrinos are neutral. The passage is describing "antimatter" in general, but the way it is written makes it sound as if this is a description of antineutrinos. If someone who didn't know any better understood it that way, then he/she will become confused later on when the article gets it right:

In an effort to help nail down the number of neutrinos, MiniBooNE physicists send beams of neutrinos or antineutrinos down a 500-meter tunnel, at the end of which sits a 250,000-gallon tank of mineral oil. When neutrinos or antineutrinos collide with a carbon atom in the mineral oil, the energy traces left behind allow physicists to identify what flavor of neutrino took part in the collision. Neutrinos, which have no charge, rarely interact with other matter, so such collisions are rare.
 Communicating to the public is a very tough task where our words and how we convey the message can make a difference. Hopefully, this apparent contradiction doesn't diminish the message. This comment is not really a criticism of the article. It is easy to do such a thing, and I know I've done it myself where I know what I intended to write, but it came out differently after I've written it.



S.D said...

There is another recent experiment indicating CP violation.

bbbl67 said...

Another interesting development of this finding is that it could lead to the discovery of newer flavours of neutrinos, such as the "sterile" neutrino. A sterile neutrino is an important component in many different versions of Dark Matter theories, as well as competing modified gravity theories.