Beta Decay

In Nuclear Physics , beta decay is a type of Radioactive decay in which a Beta Particle (an Electron or a Positron ) is emitted. In the case of electron emission, it is referred to as "beta minus" (β⁻), while in the case of a Positron Emission as "beta plus" (β⁺).

In β⁻ decay, the Weak Interaction converts a Neutron into a Proton while emitting an electron and an Anti-neutrino :
:

n^0 
ightarrow p^+ + e^- + \bar{
u}_e

.

At the Fundamental level (as depicted in the Feynman Diagram below), this is due to the conversion of a Down Quark to an Up Quark by emission of a W Boson .

In β⁺ decay, a proton is converted into a neutron, a Positron and a Neutrino :
:

\mathrm{energy} + p^+ 
ightarrow n^0 + e^+ + {
u}_e

.

So, unlike beta minus decay, '''beta plus''' decay cannot occur in isolation, because the mass of the neutron alone is greater than the mass of the proton. '''Beta plus''' decay can only happen inside nuclei when the absolute value of the binding energy of the daughter nucleus is higher than that of the mother nucleus. The difference between these energies goes into the reaction of converting a proton into a neutron, a positron and a neutrino and into the kinetic energy of these particles.

In all the cases where β⁺ decay is allowed energetically (and the proton is a part of a nucleus with electron shells), it is accompanied by the Electron Capture process, when an atomic electron is captured by a nucleus with emission of neutrino:
:

\mathrm{energy} + p^+ + e^- 
ightarrow n^0 + {
u}_e

.
But if the energy difference between initial and final states is low, the Electron Capture can occur without being accompanied by positron emission.

If the proton and neutron are part of an Atomic Nucleus , these decay processes Transmute one chemical element into another. For example:

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Beta Decay