Schematic diagram of elementary particles. (ShutterStock)
Scientists have discovered that all particles that can be detected have their corresponding antiparticles, i.e., particles with identical properties, but with opposite charges. Scientists refer to these two types of matter as positive matter and antimatter, respectively. It is also believed that when positive matter meets antimatter it will “annihilate” and disappear into a single energy.
However, according to the theory of the birth of the universe in the Big Bang, the Big Bang will generate equal amounts of positive and antimatter. Then the encounter between the two will all be annihilated. However, today we see the universe, almost no trace of antimatter, so far scientists only in some radioactive decay processes and cosmic rays found in some antimatter. So where did antimatter go, and what happened after the Big Bang? This has been one of the biggest puzzles in physics.
Recently, the European Organization for Nuclear Research (CERN), which has the world’s largest particle gas pedal, has discovered a little new clue that can explain this doubt in the study of positive and antimatter.
Scientists have come up with a rough explanation for the problem, suggesting that after the Big Bang, in that hot and dense state, there must have been some kind of change process that made it easier to produce positive matter, leading to a small surplus of positive matter compared to antimatter. As the universe cooled down, all the antimatter was destroyed by annihilation with an equal amount of positive matter, and finally the surplus of positive matter, generated the universe we see now.
Exactly what process leads to a surplus of positive matter is still unclear and has been a question physicists have been drilling into for the past few decades.
What has the new study found? It has to start with the known differences between positive and antiparticle oscillations, and positive and antiparticle decays.
Decay differences in the oscillation process of positive and negative particles
Quarks are now the most fundamental particles that scientists have traced to make up matter. Scientists start from quarks to study the difference between positive and anti-matter. There are six flavors of quarks: up, down, top, bottom, charm and strange, and each flavor of quark has its corresponding antiquark.
The protons and neutrons in the nucleus of ordinary matter consist of up and down quarks, while other quarks are produced by high-energy physics processes, such as the Large Hadron Collider at the European Organization for Nuclear Research.
Scientists call particles consisting of a quark and an antiquark mesons and have found four neutral mesons (B⁰s, B⁰, D⁰ and K⁰) to be special. in 1960, scientists observed for the first time that these mesons are able to spontaneously turn into their own antiparticles and back again, meaning that there is a back and forth oscillation between positive and negative particles.
Since they are unstable, at some stage of the oscillation process they will decay into more stable particles, and there are subtle differences in the decay process of positive and anti-mesons. The Cabibbo-Kobayashi-Maskawa matrix (CKM) is the framework theory that describes the oscillations and decay laws.
The theory proposes that there is slightly more positive matter due to the difference in the decay of positive and negative particles during the oscillations, but this difference is not enough to explain the surplus of positive matter in the universe today.
Therefore, scientists are still searching for exactly what other unknown underlying physical processes are necessary to explain this mystery.
What is the new discovery?
The Large Hadron Collider (LHCb) at CERN studies the decay of B⁰s mesons into a pair of charged K mesons. Different proton collisions produce B⁰s mesons that can oscillate back and forth between themselves and antiparticles 3 trillion times per second.
In addition to producing B⁰s mesons, collisions of different protons also produce antiparticles of B⁰s mesons, which also undergo similar oscillations. The researchers thus compared the properties of the ortho- and anti-mesons.
It turns out that one of the mesons has a slightly higher decay rate. The study says this is the first observation to find an asymmetry in the decay of the positive and anti-B⁰s mesons, which occur during the oscillations.
The study says the finding is a milestone in the study of the difference between positive and negative matter, and that they measured the magnitude of the asymmetry. This data helps to measure several parameters that refine the theory.
Lars Eklund, a professor of particle physics at the University of Glasgow in the United Kingdom, said investigating the mechanism of positive and negative matter asymmetry from several different angles will help scientists find the fundamental answer to the puzzle. “Studying at the level of the smallest particles is the best way for us to understand the universe on a large scale.”
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