Please explain

The neutrino hypothesis was not invoked merely to provide a satisfactory solution to the energy conservation
problem associated with beta decay. It also provided a solution to a similar difficulty connected with
the conservation of angular momentum in beta decay. The neutron, proton ande lectron of each
have an angular momentum of + & or -3 in the usual units of hi277 (where h is Planck’s constant).
According to equation (1) it is impossible for angular momentum to be conserved. If, however, a neutrino
of spin +B or -+ units is produced with the beta particle, the well-known law of conservation ofangular momentum can be satisfied.

np + β- ... (1)