The Importance Of Matter Over Antimatter In The Universe

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We are living in a universe which is made of matter. However, according to the modern theories of cosmology, equal populations of matter and anti-matter should have been produced in the beginning of the universe. Then, a very natural and profound question arises; from where does the asymmetry between matter and anti- matter we are looking now come from?
A. Sakharov [1] pointed out that there are three essential elements to construct theories which can explain the excess of matter over antimatter in the universe:
1. departure from thermal equilibrium;
2. reactions that change baryon number have to occur in the early universe; and 3. the existence of CP violation.
Here, CP violation means there exists difference of properties between matter and antimatter. CP violation is thus one of essential elements in any attempt to understand the history of our universe.
Until 1964, physicist believed there was no difference between matter and anti- matter, despite antimatter has opposite-signed charge and internal quantum num- bers. In other words, it was believed that there was symmetry between matter and antimatter, that is CP symmetry. The violation of CP symmetry was (totally unex- pectedly) found in decays of neutral K mesons in 1964 [2]. Since then, an enormous effort has been done both theoretically and experimentally to reveal the origin of this phenomenon.
In 1973, Kobayashi and Maskawa (KM) [3] proposed a theory of quark mixing which can introduce CP violation within the framework of the Standard Model (SM) of elementary particle physics. They demonstrated that quark-flavor mixing matrix with measurable complex phase introduces CP violation into quark interactions. This requirement is satisfied if there are at least six flavors of qu...

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... there is such an effect, we should see opposite systematic effect between CP even and odd modes, since their asymmetry should be equal in magnitude but opposite in sign. This is an excellent check of the measurement procedure. For these reasons B0 → J/ψKL mode is as important as the Golden Mode in sin2φ1 measurement, although it is expected to have more background due to experimental difficulty in KL detection.
Apart from other charmonium+K0 modes (like ψ(2S)K0 or χc1K0), next mode to be used in the φ1 measurement is B0 → J/ψK∗0, where K∗0 decays into KS andπ0. Although this decay mode is CP eigenstate and its decay proceeds with the same quark diagram as the Golden Mode, both decay products have spin 1 and the final state is a mixture of CP odd and even states. We must use angular information of decay products to separate contributions from different CP components.

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