A neutron cannot directly produce a proton by adding an electron to its quark composition. The reason is that a neutron and a proton differ not only in their electric charge but also in their quark composition.
A neutron consists of three quarks: two down quarks (d) and one up quark (u), denoted as (udd). The electric charges of the down and up quarks are -1/3 and +2/3 respectively, adding up to a net charge of 0 for the neutron.
On the other hand, a proton consists of two up quarks and one down quark, denoted as (uud). The electric charges of the up and down quarks are +2/3 and -1/3 respectively, resulting in a net charge of +1 for the proton.
To convert a neutron into a proton, a process called beta decay is involved. Beta decay occurs when a down quark within the neutron undergoes a transformation into an up quark. This transformation is mediated by the weak nuclear force.
During beta decay, one of the down quarks within the neutron can change into an up quark. This process also involves the emission of a W- boson, which subsequently decays into an electron and an electron antineutrino. The electron is then released as a separate particle.
The resulting composition after beta decay is a proton (uud) and an electron. So, the neutron is transformed into a proton by changing the quark content rather than by simply adding an electron to the original quarks.