Beta decay parity

The Hamiltonian considered above, which connmites with E, involves the electromagnetic forces between the nuclei and electrons. However, there is another force between particles, the weak interaction force, that is not invariant to inversion. The weak charged current mteraction force is responsible for the beta decay of nuclei, and the related weak neutral current interaction force has an effect in atomic and molecular systems. If we include this force between the nuclei and electrons in the molecular Hamiltonian (as we should because of electroweak unification) then the Hamiltonian will not conuuiite with , and states of opposite parity will be mixed. However, the effect of the weak neutral current interaction force is mcredibly small (and it is a very short range force), although its effect has been detected in extremely precise experiments on atoms (see, for... 

A negatron emitted during beta decay has its spin aligned away from the direction of its emission (its angular momentum vector is antiparallel to its momentum vector) and hence has a negative helix, but an emitted positron has positive helix. It is because of the absence of beta particles with both positive and negative helix in both types of beta-emission processes that parity is not conserved in beta decay. 

Table 2 lists the selection rules for beta decay the entry A means that for die indicated spin and parity change llie transition is allowed 1, means that it is first forbidden II, second forbidden. .. 

Hudson, Experimental Test of Parity Conservation in Beta Decay, Physical Review 103, 1413-1414 (1957). 

C. Wu, E. Ambler, R. Ha3rward, D. Hoppes, R. Hudson, Experimental test of parity conservation in beta decay, Phys. Rev. 105 (1957) 1413-1415. 

No levels of the proton-unstable nucleus are known. levels are obtained from the (dp), (den) and (hol) reactions. The beta decay of to the 0 ground state is first forbidden, but transitions to the 7.12 and 6.14 MeV negative parity states are allowed, and the subsequent gamma radiation has been detected. The spin of is therefore probably 2". The isotopic spin allowed transition between the 7.12 and 6.14 MeV levels was not observed and the difference in intensity between the beta-spectrum components and the subsequent radiations is attributed to experimental uncertainties in the measurement of the former. 

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