Tau neutrino

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... 

If tau neutrinos emitted from SN1987A decayed outside the star, the 7-ray burst following the //-burst could be expected. Therefore observation of the /-ray burst from SN1987A imposes a strict... 

We assumed that tau neutrinos are emitted from their neutrino-sphere with the speotrum of Fermi-Dirac distribution with zero ohemical potential determined by the temperature at the neutrino-sphere. This temperature is estimated to be 5 MeV from the spectrum calculated by Wilson and his collaborators. 

Fig. 1 Constraints on mass and lifetime of tau neutrinos. For details, see in the text.

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. 

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. 

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. 

In 1956, after a four-year search, U.S. physicists F. Reines (1918-1998) and C. L. Cowan (1919-1974) finally succeeded in detecting neutrinos produced by the Savannah River Reactor in South Carolina. By 1962, a particle accelerator at Brookhaven National Laboratory was generating enough neutrinos to conduct detection experiments. Over several months, physicists observed a few dozen neutrino events and found that there were at least two types of neutrinos. The first one discovered was dubbed the electron neutrino, and the second the muon neutrino. Proof of a long-suspected third type of neutrino, the tau neutrino, were first found in late 1998. 

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. 

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