Ghostbusting
decay causing a neutron to change to a proton, and in the process release an electron. As a result, every time this collision happened, one of the Chlorine37 atoms changed to an Argon37 atom. Argon is a noble gas and very unreactive. It was therefore possible to separate and collect all of the Ar 37 isotopes created. Furthermore, Ar 37 is also radioactive and the amount could hence be measured easily using a Geiger counter. From here the collected data could be extrapolated to produce a remarkably accurate estimate of the number of neutrinos interacting with the experiment.
The process of beta decay inside the detector is illustrated most clearly in the Feynman diagram developed by Richard Feynman. Beta decay is critical in the detection of neutrinos.
Fig.2. Electron neutrino interaction
Feynman diagram
The diagram above ( fig.2) illustrates the beta decay of a neutron (n) decaying to a proton (p) when it interacts with neutrino. It shows one down quark (d) 3 changing to an up quark (u) when it interacts via the weak force 4 (indicated by the W- boson) as the [electron] neutrino (V e ) changes to an electron (e - ). When reversing the reaction you simply oppose the direction of the arrows and, as a result, the polarity of the particles involved invert, i.e. a proton is converted to a neutron under the influence of a positron to produce an anti-neutrino, this time the interaction is labelled with the W+ boson as the direction has been reversed. In this way Feynman considered antiparticles in an abstract way as their particle counterpart moving backward through time. Understanding this reaction is crucial in the detection andmapping of neutrino collisions as in practice the angle between the incoming antineutrino and outgoing electron is equal to zero. Charged particles (such as the electron) are able to be detected and as a result it is possible to find the energy and direction of neutrino, as it is also equal to the electron’s similar properties . The Davis experiment examined only solar neutrinos produced by the nuclear fusion process at the centre of the sun. Davis identified a discrepancy in the experimental data he had collected, between the number of solar neutrinos detected and the number that were predicted to be produced. Only a third of the neutrinos expected actually produced any measurable interference, even allowing for the rarity of 3 ‘ Any of a number of subatomic particles carrying a fractional electric charge, postulated as building blocks of the hadrons. Quarks have not been directly observed but theoretical predictions based on their existence have been confirmed experimentally. ’ – Oxford dictionaries. 4 ‘ The weak force, weak interaction or weak nuclear force, is the mechanism of interaction between subatomic particles that is responsible for the radioactive decay of atoms. ’
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