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Astroparticle Physics

Since the mesons are unstable about 98.8% of all neutral pions (pi-0-mesons) with half-time decay approximately equal to decay into a pair of photons. Since the has zero charge and is composed of quark-antiquark pairs, it can decay electromagnetically. It requires two photons to conserve momentum. Since is positively charged particle it should decay into light charged lepton and appropriate neutrino, in 99.988% possibility this decay reaction implies division into and , respectively. This decay is caused as a result of weak interactions, thus have such average period of life of about. Talking about current nucleons reaction it is possible to conclude that this one is based on strong interaction using charged pi-minus-meson as a supportive particle. Chances of getting such reaction are defined in accordance with Heisenberg's Uncertainty Principle. In the result of charge exchange proton becomes neutron.

Meson consists of charm quark and up antiquark; -meson consists of charm quark and down antiquark;The energy in the rest frame of the after decay is represented by the next expression

Feynman Diagram showing a muon decaying by the weak interaction.Time Let us consider next expression and explain its components. Generally, this expression represents Fermi Theory of Weak Interaction.Where is Fermi coupling constant and represents the strength of Fermi's interaction ( the most precise experimental determination of the Fermi constant comes from measurements of the muon lifetime, which is inversely proportional to the square of (when neglecting the muon mass against the mass of the W boson); is the coupling constant of the weak interaction and it is dimensionless; - W-boson mass; The propagator gives the probability amplitude (used in describing the behaviour of systems) for a particle to travel from one place to another in a given time, or to travel with a certain energy and momentum. Since W boson has mass let us add propagator term, for small, it means propagator is constant.Integrating over the electron energy it is possible to obtain the muon decay rate:In the limit of the result always depends on the ratio and, hence, the Fermi Coupling constant is defined as , then it is possible to write the muon lifetime as . This means dependence of muon decay rate on. , the reactions flow in the result of weak interactions. Two last are forbidden because not all conservation laws’ requirements are met (changes of the electric charge Q, baryon charge B, electronic lepton Le muon). If the muons travel at nearly the speed of light then the distance traveled in a typical lifetime will be:, which means that particle will decay at the altitude of and wouldn’t reach the surface. In order to find speed, let us consider next expression: Then It means that velocity of mesons is exponentially approaching to the speed of …

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