Electron anti-neutrino

The synthesis of the light elements is sensitive to physical conditions in the early radiation-dominated era at temperatures T < 1 MeV, corresponding to an age r > 1 s. At these and higher temperatures, weak interactions rates Tweak > H were rapid compared to the expansion rate, and thus the weak interactions were in thermal equilibrium. In particular, the processes which interconvert neutrons and protons through scatterings with electrons (e ), positrons (e ), electron neutrinos (ve) and electron anti-neutrinos (v ), namely... 

The Urea process is essentially an electron capture followed by / -decay, with the emission of a neutrino and anti-neutrino pair, e.g. 

All the particles in Table 10.1 have spin. Quantum mechanical calculations and experimental observations have shown that each particle has a fixed spin energy which is determined by the spin quantum number s s = h for leptons and nucleons). Particles of non-integral spin are csWeA fermions because they obey the statistical rules devised by Fermi and Dirac, which state that two such particles cannot exist in the same closed system (nucleus or electron shell) having all quantum numbers the same (referred to as the Pauli principle). Fermions can be created and destroyed only in conjunction with an anti-particle of the same class. For example if an electron is emitted in 3-decay it must be accompanied by the creation of an anti-neutrino. Conversely, if a positron — which is an anti-electron — is emitted in the ]3-decay, it is accompanied by the creation of a neutrino. 

Since the 19S0s it has become clear that neutrinos exist as several types. In j3 decay an "anti-neutrino" is formed, while a "neutrino" is emitted in 0 decay. Both these neutrinos are now referred to as electron neutrinos, and respectively. 

In all reactions the lepton number must be conserved the total number of leptons minus antileptons on each side of a decay or reaction process must be the same. A similar law is valid for the quarks. In the reaction above several quantum numbers are obeyed (i) the charge is the same on both side, (ii) the lepton number is zero on both sides (none = electron minus anti-neutrino), (iii) the quark number is conserved. The elementary reactions in Figure 10.4 can all be described in terms of lepton and quark transformations. 

A beta particle, (3 , is an electron in all respects it is identical to any other electron. Following on from Section 1.1, the sum of the masses of the "Ni plus the mass of the (3 , and i>, the anti-neutrino, are less than the mass of "Co. That mass difference drives the decay and appears as energy of the decay products. What happens during the decay process is that a neutron is converted to a proton within the nucleus. In that way the atomic number increases by one and the nuclide drops down the side of the valley to a more stable condition. A fact not often realized is that the neutron itself is radioactive when it is not bound within a nucleus. A free neutron has a half-life of only 10.2 min and decays by beta emission ... 

The well-known proton, neutron, and electron are now thought to be members of a group that includes other fundamental particles that have been discovered or hypothesized by physicists. These very elemental particles, of which all matter is made, are now thought to belong to one of two families namely, quarks or leptons. Each of these two families consists of six particles. Also, there are four different force carriers that lead to interactions between particles. The six members or flavors of the quark family are called up, charm, top, down, strange, and bottom. The force carriers for the quarks are the gluon and the photon. The six members of the lepton family are the e neutrino, the mu neutrino, the tau neutrino, the electron, the muon particle, and the tau particle. The force carriers for these are the w boson and the z boson. Furthermore, it appears that each of these particles has an anti-particle that has an opposite electrical charge from the above particles. 

Elementary particles come in only two kinds quarks and leptons. There are only six quarks and six leptons, see Table 10.2. The leptons are the electron, e, the muon, fi, and the tauon (tau particle), t, and their respective neutrinos. The quarks and leptons are grouped together in three families (or generations) of two quarks and two leptons each. This makes 12 elementary building blocks, or 24 if one counts their anti particles Table 10.2 only refers to our matter (i.e. koino matter). The leptons and quarks all have different properties and names, sometimes also referred to as colors. The physical theory relating these particles to each other is therefore named Quantum Chromo Dynamics (QCD). 

All particles are divided into two groups quarks and leptons. Leptons include the electron, muon, tauon, and the corresponding neutrinos c /v, p /v, and -r"/v and their anti-particles e /v, and Muons are beheved to have... 

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