introduction-weak-interaction-volume-one

multiple scattering, which can simulate true Mott scattering . The metal
nuclei in the foil are polarized by applying a transverse magnetic field .
Any anisotropy in the distribution of scattered electrons may be checke d
by reversing the magnetic field and observing whether the preferential
scattering direction is correspondingly reversed . Usually, the parameter
D = ( N ( ep ) — s (~ + n))/(N(1) + N(c + 'R) )
= he a(0) sin , (3 .7 .21 )
where N(12) is the counting rate at angle ep to the beam and a(A) i s
the right—left asymmetry parameter, is measured in experiments . a(e )
must be calculated theoretically, the most important consideration s
tending to be nonunifoxmities in the beam striking the scatterer, th e
effects of multiple scattering within the scattering foil, and depolarizatio n
resulting from the finite extension of the source . Many experiments ,
using either the crossed—fields or double—scattering method, have been
performed, demonstrating that (58 )
h e
— v . (3 .7 .22)
Substituting this result in (3 .7 .19b), we have
(2 Re (c i s` cl))/(Ic i l
2
rt' I cil 2 ) = 1 ( i = V, A) .
(3 .7 .23a )
This is satisfied if and only if we se t
CI = Ci , (3 .7 .23b )
and since Ci 0, our result is incompatible with parity invariance
(3 .3 .20), and thus we are forced to conclude that beta decay is parit y
nonivariant .
An alternative method for measuring the longitudinal polarizatio n
of beta decay electrons is ;•;Oiler or electron—electron scattering . I t
has been found (59) that the cross—section for this process is dependent
upon the relative spin orientations of the interacting electrons . Using
the Born approximation; we find tha t
(6TT)/(61'1) (E 2 (1 + 6x + x 2 ) — 2E(l — x) + 1 — x 2 ) /
/ (8E2 — 2E(4 — 5X + X 2 ) + 4 — 6x + 2X 2 ) (3 .7 .24 )
1 . This assumes that only one virtual photon is ever exchanged .