One of the great open problems in physics at the moment is the question of why the Universe has so much matter in it, and essentially no antimatter. If matter and antimatter (quarks and antiquarks, fundamentally) were created in equal amounts following the Big Bang, then all the matter and antimatter would annihilate, and the matter-filled Universe we see would not exist. A fundamental postulate of the laws of physics is CP-symmetry - that is, that the laws of physics are 'symmetrical' under CP-transformation (CP- as in a combination of both Charge and Parity operators.) In other words, basically, the laws of physics are "symmetrical" between matter and antimatter, since CP-symmetry is the symmetry between matter and antimatter. Particles and antiparticles should behave "symmetrically" in every way. However, as per the above, this isn't true. At least, it's not always true. There exists, therefore, some mechanism whereby CP-symmetry can be violated - CP-violation, an example of a symmetry violation in physics. The CP operator is the product of two: C for charge conjugation, which transforms a particle into its antiparticle, and P for parity, which creates the mirror image of a physical system. The strong interaction and electromagnetic interaction seem CP-invariant, but a slight degree of CP-violation is observed in weak interactions under certain conditions. The greater the degree of CP-violation present in the early Universe, the greater the amount of matter left in the Universe. Thus, the understanding of CP-violation plays an important role in cosmology, in explaining the amount of matter in the universe, which is a rather important quantity, from the point of view of physical cosmology. Quoteth Wikipedia a bit because I'm getting sick of writing and can't remember dates: From that last paragraph, of course, we arrive at Feynman's famous conjecture, which is absolutely true, that an antiparticle is a corresponding particle traveling backwards in time. That is indeed how Quantum Field Theory predicts the existence of antiparticles. The K0 (neutral K) meson (or Kaon) consists of a down quark and a strange antiquark - ds' - and its corresponding antiparticle K0' is of course made up of a strange and an anti-down, sd'. Similarly, the B0 is db', and the B0' is bd'. (B mesons, by definition, contain a b quark/antiquark, which is why they're named thus, and Kaons contain a strange combined with a non-strange quark.) These mesons can 'oscillate' back and forth - with a particle spontaneously turning into the antiparticle, and vice versa, like this: http://en.wikipedia.org/wiki/Image:Kaon-box-diagram.svg But the transition between particle and antiparticle and between antiparticle and particle don't occur at quite the same rate - because of the CP-violating term! Whilst CP-violation was first experimentally discovered, it was discovered in neutral Kaon interactions - but today, most experimental studies of CP-violation deal with the B-mesons. Two of today's best known particle physics experiments investigating CP-violation in the decay of B-mesons are the Belle and BaBar experiments - where B mesons are produced in electron-positron collisions using particle accelerators - the latter at the Stanford Linear Accelerator, and the former at an electron-positron synchrotron collider at KEK in Japan. The interaction points are surrounded by optimised detectors to watch the decay of the B-mesons created. When, say, a B0 decays into some stuff, say a K0 and a couple of leptons, the anti-reaction, a B0' decaying into the corresponding antiparticles, will occur, but at a different rate. The LHC-b detector experiment on the LHC is intended to be very similar in nature to these existing experiments - with similar goals. Well, I hope you found that interesting. Um, any questions?