Matter-antimatter annihilation

Some particles created in the early moments following the big bang were destroyed by the process of matter/antimatter annihilation... 

The origin of X-rays, 7-ray bursts and radiowaves that pervade the Galaxy is as mysterious as the cosmic-ray sources. Evidence is mounting that in most cases these phenomena are linked to violent explosions, thought to include neutron-star quakes, quark nuggets, supernovae, matter-antimatter annihilation, clumping of quasars and colliding stars. Of all space radiations radio phenomena have been studied in most detail. 

Most of their interesting conclusions find a simple explanation in matter-antimatter annihilation through the vacuum interface, as proposed here. 

This process, which is characteristic of matter-antimatter collisions, is called annihilation and is another example of the interchange of the forms of matter. 

Early stages of the universe are listed in Table 15.2. Primeval matter was merging into elementary particles, huge amounts of energy were released and the big bang immediately caused a rapid expansion of the universe. Within about 1 s the temperature decreased markedly, matter and antimatter annihilated each other, quarks combined into mesons and baryons and enoimous amounts of energy were liberated causing further expansion. Formation of the first protons and leptons is assumed after about 1 s, when the temperature of the early universe was about lO K. 

A unique situation of the passage of positrons through an absorber is that as a positron loses its energy by interaction with electrons of the absorber atoms and comes to almost rest, it combines with an electron of an absorber atom. At this instant, both particles (/ + and e ) are annihilated as a result of matter-antimatter encounter to produce two photons of 511 keV, which are emitted in opposite directions ( 180°) (Fig. 1.6). This process is called the... 

A positron and an electron annihilate because (a) they have the same energy (b) they have opposite momentum or (c) it is matter-antimatter encounter ... 

All the particles mentioned have their anti-particles (designated by a bar above the particle symbol), except the photon and the mesons, who are their own antiparticles. We may think about antimatter as consisting of antiprotons and antineutrons in an antinucleus surrounded by antielectrons (i.e. positrons). Superficially, there would be no way to distinguish such antimatter from our matter (sometimes called koino matter). It has been proposed that the universe is made up of matter and antimatter as a requirement of the principle of symmetry. In that case some galaxies, which perhaps can be observed, should be made up of antimatter. When such antimatter galaxies (or material expelled fi-om them) collide with koino matter galaxies, both types of matter are annihilated and tremendous amounts of energy released. 

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). 

It is because of the rarity of antimatter that we cannot use annihilation of matter as a source of kinetic energy, heat, light, and other forms of energy. Of course, scientists can create antimatter, hut they have to supply the energy to create it. Wlien the created... 

At the Installation, Sakharov worked with many colleagues, in particular Yakov Zcldnvich and David Frank-Kamenetskii. Sakharov made key contributions to the Soviets first full-fledged H-bomb, tested in 1955. He also made many contributions to basic physics, perhaps the most important being his thesis that the universe is composed of matter (rather than all matter having been annihilated against antimatter) is likely to be related to charge-parity (CP) noninvariance. 

A few years later the antielectron was found, and almost 30 years later, the antiproton. Antimatter indeed exists in nature, as Dirac predicted from Einstein s work. This theoretical prediction was one of the greatest intellectual achievements of science. Today, beams of antimatter are produced in many laboratories they run in carefully evacuated tubes m order not to hit any ordinary matter until they reach their target, where they annihilate with the target substance. 

Sufficient atomic particle research has been accomplished to warrant discussion of possible methods of applying energy available from particle mass annihilation to rocket propulsion. Complete conversion of matter to energy would allow exhaust velocities near that of light to be obtained from a propulsion device. Antimatter, by definition is matter made up of antiparticles, such as antineutrons, negatrons (antiprotons), and positrons (anheledrons). An annihilation property is known to exist between particles with one particle termed the anhparticle of the other. 

In the quantum field theories that describe the physics of elementary particles, the vacuum becomes somewhat more complex than previously defined. Even in empty space, matter can appear spontaneously as a result of fluctuations of Ihe vacuum. It may be pointed, out, for example, that an electron and a positron, or antielectron, can be created out of the void, Particles created in this way have only a fleeting existence they are annihilated almost as soon as they appear, and their pressure can never be detected directly. They are called virtual particles in order to distinguish them from real particles. Thus, the traditional definition of vacuum (space with no real particles in it) holds. In their excellent paper, the aforementioned authors discuss how, near a superheavy atomic nucleus, empty space may become unstable, with the result that matter and antimatter can be created without any input of energy. The process may soon be observed experimentally. 

In this connection Alfven proposed the annihilation of matter and antimatter as a possible source of energy, but also other mechanisms, in particular, some form of release of gravitational energy were examined. 

As far as we can see into the Universe, we don t observe any primordial antimatter. Within the limits of our present observational horizon the Universe is seen to contain only matter and no antimatter. The presence of cosmic antimatter would lead to observable traces of annihilation however the measurements of the extragalactic 7 ray flux indicate an absence of annihilation radiation, and the microwave background spectrum lacks a corresponding distortion. These findings preclude the existence of a significant amount of antimatter within tens of Megaparsecs, which is the scale of super-clusters of galaxies. 

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. 

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