introduction-weak-interaction-volume-one

y J r
, and the weak leptonic current, containing such terms as (4 .4 .9) and
(4 .4 .10), and also possibly neutral and self-charged current terms, by ah~ .
Since in semileptonic processes, such as the neutron decay (3 .1 .1), the
hadronic current couples with the leptonic one, the former must be a charged
current, since at least the leptonic current terms (4 .4 .9) and (4 .4 .10) are
charged . This is expressed by saying that, for the hadronic current ,
A Q = 1
(5 .3 .1 )
A
so that when .J acts on a system, it raises the total charge of the hadron s
present by one unit of charms Since the current
also raises the charge o f
all leptons in a system by le, the Hamiltonian for semileptonic processe s
must be of the form
HI = (G4-2) ( . (x) J r (x)) + HHerm . conj . (5 .3.2 )
in order to obey charge conservation . As J r is evidently a
= — 1 (5.3.3)
current, the hadronic current may couple with itself to produce a Hamiltonia n
H I s (G/12) ( . _ (x) (x)) + Heim . conj . (5 .3 .4 )
(5 .3 .4) is thought to be responsible the pure hadron decays of strange particles ,
such as
pr (5 .3 .5 )
We note that the total weak Hamiltonian is probably of the current-current
form :
HI ( G/ J-2) (Tr (x) + r (x) ) . ( ~, (x) + J (x) ) (5 .3 .6 )
T
A useful method of summarizing our present knowledge of weak interaction coupling s
is the Puppi tetrahedron, which has, at its vertices,the currents :
p n (5 .3 .7 )
e+ v (5 .3 .8 )
e
P ( 5 .3 .9 )
r yr (5 .3 .10 )
There exists also a charge-conjugate Puppi tetrahedron (6), and the questio n
of whether vertices of this are coupled to those of the normal tetrahedron
was discussed in 4 .4 .
We now consider the assignments of the three important quantum numbers ,
Y, I and G. to the current i . Since both hypercharge-conserving and hypercharge-