Electron neutrinos

In the last decade, neutrino experiments have demonstrated that neutrinos are massive particles which may oscillate among three autostates. Such experiments [77-82] have evidenced the mass difference between the autostates, but not the neutrino mass scale value. The only way to determine the neutrino mass is the knowledge of the shape of the end point of energy spectrum in beta decays. In the hypothesis of the Majorana neutrino (neutrino coincides with antineutrino and its rest mass is different from zero), the measure of the decay half-life in the neutrinoless double-beta decay (DBD) would be necessary. A number of recent theoretical interpretations of neutrino oscillation experiments data imply that the effective Majorana mass of the electron neutrino (as measured in neutrinoless DBD) could be in the range 0.01 eV to the present bounds. 

According to most theoretical analyses of the present neutrino experiment results, next-generation DBD experiments with mass sensitivities of the order of lOmeV may find the Majorana neutrino with a non-zero effective electron neutrino mass, if the neutrino is self-conjugate and the neutrino mass spectrum is of the quasi-degenerate type or it has inverted hierarchy [83], Majorana massive neutrinos are common predictions in most theoretical models, and the value of a few 10 2cV predicted for its effective mass, if reached experimentally, will test its Majorana nature. 

This raises the burning question starting out from a simple substance (not to say elementary) made up of photons, electrons, neutrinos, neutrons and protons, what mechanisms exist for synthesising the many and varied nuclei to be found in nature This in turn raises the question where and when did these processes take place, and how do they fit together chronologically as the Universe has evolved ... 

Among electronic neutrino detectors is the great KAMIOKANDE experiment and its extension SUPERKAMIOKANDE. Spread out at the bottom of a mine in Japan, this device has directional sensitivity and it can thus be checked whether captured neutrinos do actually come from the Sun. 

In physics, speculative ideas often begin to seem much more reasonable when there is a theory to explain them. In 1933 Fermi advanced just such a theory, proposing that the electron and the neutrino were spontaneously created at the moment that a radioactive disintegration took place. At the same time, one of the neutrons in the nucleus was changed into a proton. Fermi showed that electron-neutrino production could be explained if one assumed the existence of a new force (now called the weak force). He concluded that the mass of the neutrino was probably near zero. This would explain why it hadn t been detected. 

Particles such as electrons and muons are not made up of quarks, and they are thus insensitive to the strong force. It is electrical attraction between unlike charges that binds electrons in atoms. Both electrons and muons belong to a class of particles called leptons, and there are six of them, just as there are six quarks. The six leptons are the electron, the muon, the tauon (named after the Greek letter tau), and three different kinds of neutrinos, which are called electron neutrino, muon neutrino, and tauon neutrino. 

Perhaps the most novel aspect of SNl987a is the detection [6,7] of neutrinos from the production and cooling of a compact remnant. One hopes this is only the beginning of a new field of astronomy. The analysis I present here [5], parallel to the analysis of many other authors [23-28], finds remnant binding energy 2.0 0.5 X 1053 ergs and remnant mass 1.2 to 1.7 Mq consistent with what one expects for neutron star generation. An upper limit of 10-15 eV may also be inferred for the electron neutrino mass. 

There are a number of other interesting limits to be drawn on neutrino properties by somewhat more sophisticated use of the supernova dynamics. Putting another neutrino-antineutrino pair [30], i.e., another two species, into any calculation of the neutron star cooling would probably accelerate this process unacceptably. Further, one can place an upper limit [5] of 45 eV on the mass of any species mixing with the electron neutrino, else no supernova mechanism would succeed, delayed or prompt. 

Tau neutrinos are emitted from the central part of the iron core together with the electron neutrinos because they are also in thermal equilibrium with matter there. When tau neutrinos decay on the way of... 

During the 1960s, L.M. Lederman, M. Schwartz, and J. Steinberger conducted the well-known two-neutnno experiment, which established a relationship between particles, muon and muon neutrinos, electron and electron neutrino, This later evolved into I he standard model of particle physics. The Nobel prize in physics was shared by these researchers in 1988. 

There are six different kinds of leptons (light particles) (Table 1.6), and they can be arranged in three pairs. The electron (e), the muon (p,), and the tau lepton (t) each carry a charge of —e and have associated with them the electron (ve), muon (VjJ, and tau neutrinos (vT). These neutrinos are electrically neutral and have small or zero rest mass. The actual mass of the neutrinos is a subject of current research (see Chapter 12). The electron neutrino is seen in nuclear phenomena such as (3 decay, whereas the other neutrinos are involved in higher energy processes. 

The symbol ve indicates the antiparticle of the electron neutrino.) In this equation, the number of leptons on the left is zero, so the number of leptons on the right must also be zero. This equivalence can only be true if we assign a lepton number L of 1 to the electron (by convention) and L = — 1 to the ve (being an antiparticle). Consider the reaction... 

The direct observational evidence for the occurrence of neutrino oscillations came from observations with the Cerenkov detectors. The SNO detector found one-third the expected number of electron neutrinos coming from the sun in agreement with previous work with the radiochemical detectors. The Super Kamiokande detector, which is primarily sensitive to electron neutrinos, but has some sensitivity to other neutrino types found about one-half the neutrino flux predicted by the standard... 

There are three known flavors of neutrinos the electron neutrino z/e, the muon neutrino and the tau neutrino ur. They are so named because they are produced or destroyed in concomitance with the electron, the muon, and the tau lepton, respectively. 

Even if they progressively slow down, they could rim a virtual world in their minds much like a computer runs a program, and the Diffuse Ones would not perceive any slowdown. This means that although the physical Universe is a black emptiness of electrons, neutrinos, and leptons, a rich virtual Universe could unfold from within. 

One is based on a study of the possibility of the conversion of muonium f/i+e -system) to antimuonium (p e+-svstem) [12]. This is possible in the case of non-conservation of electronic charge (i.e. the number of electrons and electronic neutrinos minus the number of positrons and antineutrinos) and muonic charge (i.e. the number of muons and muonic neutrinos minus the number of their antiparticles). Both must be conserved separately with the Standard Model. 

The nonzero mass of the neutrino also can explain why the measured flux of the solar neutrinos is a few times smaller than the one predicted by the theory of thermonuclear generation of solar energy. If mv 0, the electron neutrinos may transform into other types of neutrinos4 that are not recorded by the modern detectors. 

The nucleons inside a radioactive nucleus contained in a molecule interact with the electron-neutrino field and undergo the / transition—a transformation of a neutron into a proton accompanied by the emission of a / electron and a neutrino.5 The weak interaction does not affect the electron shell and the other nuclei of the molecule. For them the / decay is an instantaneous change (a jump) in the charge of the radioactive nucleus by unity. Besides this, the nucleus obtains a recoil momentum due to the emission... 

Another group of fundamental particles are the leptons (light particles), comprising also three families, electron and electron neutrino, muon and muon neutrino, tau particle and tau neutrino. Properties of the leptons are summarized in Table 3.3. The most important particles of this group are the electron and the electron neutrino, which are both stable. 

Electron neutrino V e OtollO- stable 0 Electron antineutrino, i,. 

Nuclides with an excess of protons exhibit P decay. A proton in the nucleus is converted into a neutron, a positron and an electron neutrino, as indicated in Table 5.1. The atomic number decreases by one unit, and the mass number remains unchanged. As in the case of P decay, the energy of the decay process is obtained by eq. (5.10). But because now Z2 — Zi — 1, it follows that ... 

Taking into account the formation of electron neutrinos in addition to the emission of electrons and positrons, respectively, the following equations are valid for p and P decay. 

After about 1 second, the universe was made up of a plasma of protons, neutrons, electrons, neutrinos, and photons, but the temperature was too high to allow the formation of atoms. This plasma and the extremely high energy caused fast nuclear reactions. As the temperature dropped to about 10 K, the following reactions occurred within a... 

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