Underground Lab To Probe Ratio of Matter To Antimatter

Wired reports on the Enriched Xenon Observatory 200, a particle detector scientists hope will answer the question of why there is significantly more matter than antimatter in the universe. Quoting: "The new detector will try to fill in the picture, determining basic features of [neutrinos], like their mass and whether or not they, unlike almost all other particles, are their own antiparticles. That quirk is why some scientists believe neutrinos could be the mechanism for the creation of our matter-filled universe. Almost all other particles have an antiparticle twin that, if it comes into contact with the particle, immediately annihilates it. But if neutrinos are their own antiparticles they could conceivably be knocked onto matter's 'team,' thereby causing the cascading win for matter over antimatter that we know occurred. As the Indian theoretical physicist G. Rajasekaran put it in a speech [PDF] earlier this year, neutrinos that are their own antiparticles would explain 'how, after [the] annihilation of most of the particles with antiparticles, a finite but small residue of particles was left to make up the present Universe.'"

Comments

How so?

[KasperMeerts]

Who says there is more matter than antimatter in the universe? Has anyone ever gone to the Andromeda galaxy? So how do we now it consists of normal matter? Doesn't matter react the same as antimatter in every possible way?

Questions for a physicist in this field

[kanweg]

Does antimatter attract matter or repulse it (could a double star, one of antimatter and one of matter, i.e. where the stars revolve around each other exist?).

Would it be a prerequisite that a big bang produces as much matter as antimatter?

Bert

Re:How can you tell?

[CRCulver]

I thought it wasn't possible to tell antimatter from matter from afar?

That's the premise in one of Larry Niven's old Beowulf Shaeffer stories (collected in Crashlander ). Shaeffer and a Steve Fosset-like millionaire come upon an isolated planet, only to discover to their dismay that it is made out of antimatter. Unfortunately, the relatively believable science ends there, because Niven's way of having them colonize it relies on a species of unobtainium

Re:To pick a nit

[The_Wilschon]

IIRC, standard model neutrinos are Dirac particles, which have well defined antiparticles. However, the hypothesis being tested is whether or not neutrinos are actually Majorana particles, which are invariant under charge conjugation (that is, they are precisely the same particle as their antiparticle.). It all comes down to representation theory and the Lorentz group (and friends). If we claim that charge conjugation is an interesting transformation to examine, then we must clearly describe exactly how each of our fields (particles) changes when we apply that transformation. Dirac and Majorana particles transform two different ways, and we don't know that our conjecture that all the fermions are Dirac particles is actually correct.