There are six kinds of quarks : up, down, strange, charm, bottom and top. Similarly, there are six leptons : the electron, muon, tau and the three neutrinos. There are also antimatter copies of these twelve particles that differ only in their charge.
Antimatter particles should in principle be perfect mirror images of their normal companions. Take for instance particles known as mesons , which are made of one quark and one anti-quark.
Neutral mesons have a fascinating feature: they can spontaneously turn into their anti-meson and vice versa. In this process, the quark turns into an anti-quark or the anti-quark turns into a quark. But experiments have shown that this can happen more in one direction than the opposite one—creating more matter than antimatter over time. Among particles containing quarks, only those including strange and bottom quarks have been found to exhibit such asymmetries—and these were hugely important discoveries.
The very first observation of asymmetry involving strange particles in allowed theorists to predict the existence of six quarks—at a time when only three were known to exist. The discovery of asymmetry in bottom particles in was the final confirmation of the mechanism that led to the six-quark picture.
Both discoveries led to Nobel Prizes. Both the strange and bottom quark carry a negative electric charge. The only positively charged quark that in theory should be able to form particles that can exhibit matter-antimatter asymmetry is charm.
Theory suggests that if it does, then the effect should be tiny and difficult to detect. It's thrilling to learn more about how the universe works. As they travel through the Earth, these particles oscillate between different physical properties electron, muon and tau known as flavors. The T2K collaboration found a mismatch in the way neutrinos and antineutrinos oscillate by recording the numbers that reached Super- K with a flavor different from the one they had been created with.
More precise measurements are needed to confirm these findings. However, these measurements do strengthen previous observations and pave the way toward a future discovery. If confirmed by future studies, these findings would represent a groundbreaking advance toward understanding the fundamental reason for the predominance of matter over antimatter in our universe.
Recently, HEP studied two versions of the same particle. One version contained a charmed quark and an antimatter version of an up quark, called the anti-up quark. The other version had an anti-charm quark and an up quark. Using LHC data, they identified both versions of the particle, well into the tens of millions, and counted the number of times each particle decayed into new byproducts. Adds Polyakov, "Particles might look the same on the outside, but they behave differently on the inside.
That is the puzzle of antimatter. The rules for the oscillations and decays are given by a theoretical framework called the Cabibbo-Kobayashi-Maskawa CKM mechanism. It predicts that there is a difference in the behaviour of matter and antimatter, but one that is too small to generate the surplus of matter in the early universe required to explain the abundance we see today.
Our recent result from the LHCb experiment is a study of neutral B 0 S mesons, looking at their decays into pairs of charged K mesons. The B 0 S mesons were created by colliding protons with other protons in the Large Hadron Collider where they oscillated into their anti-meson and back three trillion times per second.
The collisions also created anti-B 0 S mesons that oscillate in the same way, giving us samples of mesons and anti-mesons that could be compared. We counted the number of decays from the two samples and compared the two numbers, to see how this difference varied as the oscillation progressed. There was a slight difference — with more decays happening for one of the B 0 S mesons.
And for the first time for B 0 S mesons, we observed that the difference in decay, or asymmetry, varied according to the oscillation between the B 0 S meson and the anti-meson. In addition to being a milestone in the study of matter-antimatter differences, we were also able to measure the size of the asymmetries.
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