During alpha-decay , a nucleus decays by emitting an alpha-particle ( a helium nucleus ._2He^4) according to the equation ._Z^AX to ._(Z-2)^(A-4)Y+._2^4He+Q In this process, the energy released Q is shared by the emitted alpha-particle and daughter nucleus in the form of kinetic energy . The energy Q is divided in a definite ratio among the alpha-particle and the daughter nucleus . A nucleus that decays spontaneously by emitting an electron or a positron is said to undergo beta-decay .This process also involves a release of definite energy . Initially, the beta-decay was represented as ._Z^AX to ._(Z+1)^AY + e^(-)"(electron)"+Q According to this reaction, the energy released during each decay must be divided in definite ratio by the emitted e' (beta-particle) and the daughter nucleus. While , in alpha decay, it has been found that every emitted alpha-particle has the same sharply defined kinetic energy. It is not so in case of beta-decay . The energy of emitted electrons or positrons is found to vary between zero to a certain maximum value.Wolfgang Pauli first suggested the existence of neutrinoes in 1930. He suggested that during beta-decay, a third particle is also emitted. It shares energy with the emitted beta particles and thus accounts for the energy distribution.During beta^+ decay (positron emission) a proton in the nucleus is converted into a neutron, positron and neutrino. The reaction is correctly represented as