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A massive star collapses at the end of its life, emitting on the order of 10 58 neutrinos and antineutrinos in all lepton flavors. [2] The luminosity of different neutrino and antineutrino species are roughly the same. [3] They carry away about 99% of the gravitational energy of the dying star as a burst lasting tens of seconds.
A neutrino (/ nj uː ˈ t r iː n oʊ / new-TREE-noh; denoted by the Greek letter ν) is an elementary particle that interacts via the weak interaction and gravity. [2] [3] The neutrino is so named because it is electrically neutral and because its rest mass is so small that it was long thought to be zero.
Powerful bursts of electron neutrinos (ν e) with typical energies of the order of 10 MeV and duration of the order of 10 seconds are produced in the core of a red giant star as it collapses on itself via the "neutronization" reaction, i.e. fusion of protons and electrons into neutrons and neutrinos: p + e − → n + ν e.
The initial collapse of degenerate cores is accelerated by beta decay, photodisintegration and electron capture, which causes a burst of electron neutrinos. As the density increases, neutrino emission is cut off as they become trapped in the core.
This rebound produces a shock wave, at which point many of the previously produced electron neutrinos are ejected in what is called a neutrino burst. The energy carried away from the supernova by the neutrino burst weakens the shock, and matter falls into the remnant of the progenitor star.
The two neutrino production mechanisms convert the gravitational potential energy of the collapse into a ten-second neutrino burst, releasing about 10 46 joules (100 foe). [ 16 ] Through a process that is not clearly understood, about 1%, or 10 44 joules (1 foe), of the energy released (in the form of neutrinos ) is reabsorbed by the stalled ...
The two types of beta decay are known as beta minus and beta plus.In beta minus (β −) decay, a neutron is converted to a proton, and the process creates an electron and an electron antineutrino; while in beta plus (β +) decay, a proton is converted to a neutron and the process creates a positron and an electron neutrino. β + decay is also known as positron emission.
In the KATRIN experiment the spectrum around this end-point is measured with high precision to obtain the neutrino mass. Timeline of neutrino mass measurements by different experiments. [5] The beta decay of tritium is one of the least energetic beta decays. The electron and the neutrino which are emitted share only 18.6 keV of