Matter-antimatter asymmetry

A small degree of matter-antimatter asymmetry, with a baryon number B (ratio of net number of baryons Nb — N-g in a co-moving volume to the entropy S) in the range 10-11 to 10-8. 

The matter - antimatter asymmetry in the Universe and its relation to the underlying symmetries of Nature is of such fundamental importance that a number of large-scale experiments have been undertaken to search for cosmic antimatter. 

CP violation has been experimentally established also in B meson decays. However, the observed matter-antimatter asymmetry of the Universe requires additional sources of CP violation. 

After the discovery of parity violation the CP symmetry, i.e., the invariance of the physical laws against the simultaneous transformation of charge and space reflection, was still assumed to be exact. However, in 1964 Cronin and Fitch (Nobel Prize 1980) discovered (Christenson et al. 1964) that the weak interaction violates that as well, although this violation is tiny, not maximal, like that of the P invariance. CP violation makes it possible to differentiate between a world and an antiworld and may be related to the matter - antimatter asymmetry. 

On the interface of neighboring domains of baryonic and antibaryonic matter, quark—antiquark (proton-antiproton) annihilation would lead to the emission of hard X-rays. The absence of this signal makes it highly probable that even if antibaryons were present in the early, hot Universe they had disappeared before the CMBR was emitted. Therefore, the observed baryonic density actually proves the presence of a matter—antimatter asymmetry within the present horizon in our Universe (Rubakov and Shaposhnikov 1996 Riotto and Trodden 1999). 

The resolution of the matter-antimatter asymmetry problem is an issue of central importance in particle physics in the twenty-first century. 

Could that be so that the Universe was created with the preponderance of matter over antimatter We have no support for such hypothesis. Einstein remarked If that s the way God made the world then I don t want to have anything to do with Him [7]. Indeed, the contemporary Standard Model of Physics suggests that equal amounts of matter and antimatter were born during the Big-Bang. Where has the antimatter gone What causes the apparent asymmetry between matter and antimatter Obviously the antiparticles have been annihilated by particles - but apparently this process was not fully symmetric, since enough matter was left over for our Universe. We seem to be the result of an accident, caused by a a slight imperfection of Nature. 

Asymmetry of the time axis is the most likely cause of chirality, the other badly broken symmetry of Nature. Chirality is observed at a number of different levels, most notably in the structure of space-time, the constitution of matter and the structure of biologically active molecules. There is a selection rule that gradually relaxes with increasing complexity and decreasing quantum potential. At the lowest level space-time has an absolutely fixed chirality (time flow) which has never been observed to invert. Matter commonly occurs in one chiral form only, but antimatter, although less common is not unknown. The two chiral forms of matter annihilate when brought into contact. The two molecular chiral forms of biology appear to be of the same stability, both occur freely in Nature and interconversions under appropriate conditions are well known. 

For example, where is the antideuterium More generally, where is the antimatter At the microscopic level, that is, the level of fundamental particles that make up the Earth, Sun, and Milky Way, all evidence points to a clear symmetry between matter and antimatter yet, on the macroscopic level we observe an asymmetry—matter dominates the cosmos. Why should this be Did the... 

Quarks and antiquarks traverse the phase boundaries, which represent a potential barrier for them. As a consequence of the complex CP-violating phase in the Hamiltonian describing weak interactions, the reflection and transmission amplitudes for matter and antimatter turn out to be different leading to an asymmetry in the constitution of matter and antimatter inside the bubbles. 

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