Question

Research the neutrino using the Internet and report your findings. In a nuclear decay, the nucleus of an atom splits apart. Larger particles can be detected and their masses and velocities can be recorded. Explain how the existence and properties of the neutrino could be predicted using the conservation laws.

Answer 1

Neutrino, being chargeless and possesing very small mass compared to the nucleons, is very difficult to be detected by the detectors that are usually used to detect nucleons or other massive nuclei.

So, the first challange is to know if there is such a particle produced in agiven nuclear decay. Luckily, we have the very fundamental laws of conservation, conservation of energy(mass and energy in this case) and conservation of momentum, which confirms the existence of a particle even with such minor impressions.

For instance, a nucleus A decays and you detect particle B and C in your detectors. Now, if you see a all decay event, A --> B+C, for which the energy of B is detected as E (say), then according to law of conservation of mass and energy, the energy of all the particles C will be same, if B and C are the only particles produced in the decay. But if there is one more particle, which might not have been detected in the detectors, the You get a range of energies for the detected particle C, as the energy remaining(apart from B) will be shared between C and the other particle in different proportions for different events of decay.

This is the basic idea to know the existence of the neutrino. Now for its properties, we must have detectors of high energy resolution such that the energy of neutrino from the law of conservation is higher than the maximum error of the detectors. In this way we can extract the properties of the missing particle.

Beta decay is an excellent example for the scenario asked in question.