86 to be published.. Atomic Energy Commission... The different Mp/r+ regions chosen in K + and /r+ interactions reflect a slight systematic difference in the observed A mass.. No backgro
Trang 1Volume 18, number 1 P H Y S I C S L E T T E R S 1August1965
9 C.De Vries, R.Hofstadter, A.Johansson and R
Herman, Phys Rev 134 (1964) B 848
10 P.Stein, R.W.McAllister, B.D.McDaniel and
W M Woodward, Phys Rev Letters 9 (1962) 403;
P Stein, M Binkley, R~ W McAllister, B.D Mc-
Daniel and W M Woodward, Proc Intern Conf
at Stanford University (1963) p 373
11 B.Grossetete, preprint L A L O r s a y , to be pub- lished
12 J.R.Dunning J r , K.W.Chen A.A.Cone, G.Hart- wig, N F Ramsey, J.K Walker and R Wilson, Phys.Rev.Letters 13 (1964) 631
13 F.M.Renard, J T r ~ n Thanh V~n and M.Le Bellac, Orsay TH 86 (to be published)
* * * * *
O B S E R V A T I O N O F C O R R E L A T I O N S B E T W E E N V E C T O R - M E S O N
A N D B A R Y O N - R E S O N A N C E D E C A Y S *
G GOLDHABER, J L BROWN, I BUTTERWORTH, S GOLDHABER, A A HIRATA,
J A KADYK, B C SHEN a n d G H TRILLING
Depart~nent of Physics and Lawrence Radiation Labo~'atory, University of California, Berkeley, California
Received 24 June 1965
In our s t u d i e s of d o u b l e - r e s o n a n c e f o r m a t i o n
in the c h a n n e l
~ M + + - L p + ~ +' (i)
we have "observed marked angular correlations
between the decay angular distribution of the
vector meson and that of the ~, ~ baryon reso-
nance A++(1238) Here M + represents the ~+ or
K + meson and V ° the pO or K ~° vector-meson
resonance respectively As is well known [1-5],
for s m a l l v a l u e s of f o u r - m o m e n t u m t r a n s f e r
s q u a r e d , t the d e c a y a n g u l a r d i s t r i b u t i o n s at
the two v e r t i c e s f o r t h e s e r e a c t i o n s follow the
g e n e r a l f e a t u r e s of a p s e u d o s c a l a r m e s o n e x -
change model However, the a c t u a l d i f f e r e n t i a l
p r o d u c t i o n c r o s s s e c t i o n s d i s a g r e e s t r o n g l y
with s i m p l e exchange m o d e l s Two r e m e d i e s f o r
this difficulty with the p s e u d o s c a l a r m e s o n e x -
change m o d e l have b e e n s u g g e s t e d One h a s b e e n
the i n t r o d u c t i o n of f o r m f a c t o r s at the r e s p e c -
tive v e r t i c e s [6] The a l t e r n a t i v e h a s b e e n to
c o n s i d e r a b s o r p t i o n e f f e c t s due to i n i t i a l - and
f i n a l - s t a t e i n t e r a c t i o n s [7, 8] The a u g u l a r - c o r -
r e l a t i o n effects we have o b s e r v e d i n d i c a t e that
f i n a l - s t a t e i n t e r a c t i o n s play a n i m p o r t a n t r o l e
a n d t h e r e f o r e i m p l y the n e e d to c o n S i d e r a b s o r p -
tion effects
In this note we p r e s e n t e x p e r i m e n t a l d a t a
* Work done under the auspices of the U S Atomic
Energy Commission
76
showing the e x i s t e n c e of decay c o r r e l a t i o n s b e - tween the K *° a n d the A ++ r e s o n a n c e s ~ v e r y s i m -
l i a r to those o b s e r v e d b e t w e e n the po a n d A ++
r e s o n a n c e s [1, 2] T h e s e data come f r o m t h r e e
d i s t i n c t e x p e r i m e n t s , a l l c a r r i e d out in the Brook
h a v e n N a t i o n a l L a b o r a t o r y ' s 2 0 - i n c h b u b b l e c h a m -
b e r e x p o s e d i n the B r o o k h a v e n - Y a l e s e p a r a t e d
b e a m [9] at the A.G.S The e x p e r i m e n t s involve the following r e a c t i o n s :
~+p , ~+~'~+p at 3.65 GeV/c [10] (2) K+p * K+~-~+p at 1.96 GeV/c [11] (3)
In r e a c t i o n (4) the K+p c h a n n e l was s e p a r a t e d
f r o m the K+n c h a n n e l by d e m a n d i n g that the labo-
r a t o r y m o m e n t u m of the n e u t r o n be l e s s than that
of the p r o t o n , a n d f u r t h e r , l e s s than 300 MeV/c With t h e s e c r i t e r i a , the m o m e n t u m d i s t r i b u t i o n
f o r the n e u t r o n a g r e e s w e l l with that g i v e n by the Hulth~n wave f u n c t i o n f o r the d e u t e r o n , and i t s
l a b o r a t o r y a n g u l a r d i s t r i b u t i o n i s a p p r o x i m a t e l y
i s o t r o p i c , showing that it i s r e a s o n a b l e to t r e a t
it a s a s p e c t a t o r to a r e a c t i o n on the p r o t o n as
t a r g e t
It h a s b e e n shown e a r l i e r that a p p r e c i a b l e
f r a c t i o n s of r e a c t i o n s (2) and (3) p r o c e e d v i a
d o u b l e - r e s o n a n c e f o r m a t i o n [10, 11] We note
h e r e that r e a c t i o n (4) i s a l s o d o m i n a t e d by K *° and A ++ p r o d u c t i o n a n d that a s i g n i f i c a n t p r o p o r - tion of the r e a c t i o n goes v i a t h e i r s i m u l t a n e o u s
p r o d u c t i o n i n a q u a s i - t w o - b o d y p r o c e s s This
m a y be s e e n f r o m fig 1, which shows the p h a s e -
Trang 2Volume 18, number 1 P H Y S I C S L E T T E R S 1 August 1965
s p a c e t r i a n g l e p l o t of % + v e r s u s MK+~ f o r the
d a t a at 2.3 G e V / c
The n u m b e r of e v e n t s i n v o l v e d in the t h r e e
e x p e r i m e n t s a r e 1784, 410 and 904, r e s p e c t i v e l y
Of t h e s e , the n u m b e r s a s s i g n e d to V ° A ++ "double
r e s o n a n c e " f o r m a t i o n a r e 555, 262 and 426, and
f i n a l l y , the n u m b e r s of e v e n t s w h i c h f u l f i l l o u r
s m a l l - f o u r - m o m e n t u m - t r a n s f e r cutoff c r i t e r i o n ,
t < 0.5 GeV 2, a r e 429, 124 and 248 r e s p e c t i v e l y ~
T h e s e l a s t t h r e e n u m b e r s c o r r e s p o n d to the s a m -
p l e w i t h w h i c h we a r e c o n c e r n e d h e r e
We h a v e c o m p a r e d the d a t a in r e a c t i o n s (3) and
(4) on K$°A ++ p r o d u c t i o n and find t h e m s u f f i c i e n t -
ly s i m i l a r to p e r m i t t h e i r c o m b i n a t i o n f o r g r e a t e r
s t a t i s t i c a l a c c u r a c y In what f o l l o w s we u s e the
c o m b i n e d d a t a f o r t h e s e r e a c t i o n s
To study the a n g u l a r c o r r e l a t i o n e f f e c t we show
S c a t t e r p l o t s of c o s ~ A v e r s u s c o s ~V w h e r e
t h e s e r e p r e s e n t the a n g l e s b e t w e e n the " i n c i d e n t "
p r o t o n and s c a t t e r e d p r o t o n in the A++ c e n t r e of
m a s s s y s t e m and the i n c i d e n t and outgoing M + in
the V ° c e n t r e of m a s s s y s t e m r e s p e c t i v e l y ( s e e
f i g s 2a and 3a) To obtain a q u a n t i t a t i v e m e a s u r e
of the o b s e r v e d c o r r e l a t i o n s , we h a v e p l o t t e d the
d e c a y a n g u l a r d i s t r i b u t i o n of the V ° m e s o n f o r
t h r e e i n t e r v a l s in c o s ~A T h e s e a r e the two
p o l a r i n t e r v a l s c o s ~A = - 1 0 to - 0 4 and +0.4 to
+ 1.0 and the e q u a t o r i a l i n t e r v a l - 0 4 to +0.4
C o n v e r s e l y c o s ~A h a s a l s o b e e n p l o t t e d f o r the
s a m e t h r e e i n t e r v a l s of c o s ~V" T h e s e d i s t r i b u -
t i o n s a r e shown in f i g s 2 b - g and 3 b - g The
~' The c r i t e r i a used to define the double-resonance r e -
gions are: reaction (2): 1120 MeV ~< M p + ~< 1320 MeV,
650 MeV < M + _ ~< 850 MeV; reactions (3) and (4):
/ r /r
1130 MeV~ < Mp#+ ~< 1300 MeV, 840 MeV ~< MK+/r- ~<
940 MeV The different Mp/r+ regions chosen in K + and
/r+ interactions reflect a slight systematic difference
in the observed A mass No background corrections
were made because triangle plots showed that at
t ~< 0.5 GeV 2, background to double-resonance p r o -
duction is small In reaction (2) each of the two a
p~io~i indistinguishable/r+~s was in turn combined
with the proton to see if Mp/r+ lay in the A region If
so the other/r+ was combined with the/r- to see if
M ~ / r - lay in the p region Of 555 events, 489 had
Mp/r+ in the A region and M/r~._ in t h e p region with
Mlyff~ and M/r+~r- outside these respective regions,
and the former combinations have been used An ad-
ditional 56 had both M + and M + in the A region
but only one/r ~r- combination in the p region This
together with the appropriate Mp~+ have been used
For 10 events both Mp~+ and Mp~÷ lay in the A r e -
gmn, and both/rs/r and/rh/r in t h e p region• Here
both combinatior~s have bgen used with half weight
Incidentally, these ten events all have cos ~ p < -0.4
c u r v e s shown in t h e s e f i g u r e s r e p r e s e n t the b e s t
f i t to the e x p a n s i o n [(cos ~) = A + B c o s ~ +
C cos2ot The c o e f f i c i e n t s n o r m a l i z e d to A = 1.0
a r e l i s t e d in t a b l e s 1 and 2 The f i t s a r e good, and h i g h e r - o r d e r t e r m s a r e not r e q u i r e d
F o r a p u r e p s e u d o s c a l a r m e s o n e x c h a n g e no
a n g u l a r i n f o r m a t i o n can be t r a n s m i t t e d b e t w e e n
v e r t i c e s , and h e n c e one e x p e c t s no c o r r e l a t i o n to
o c c u r Thus e a c h of the t h r e e d i s t r i b u t i o n s in
c o s ~V and c o s o~ A would h a v e to be i d e n t i c a l
A s m a y be r e a d i l y noted by e x a m i n i n g f i g s 2 and
3, two d i s t i n c t d i f f e r e n c e s in the t h r e e d i s t r i b u -
t i o n s f o r c o s ~ A a r e : (a) The d i s t r i b u t i o n s in c o s ~A c o r r e s p o n d i n g
to the two p o l a r r e g i o n s of c o s ~V show a m a r k e d
d i f f e r e n c e The d i s t r i b u t i o n in c o s ~A w h i c h g o e s
w i t h c o s ~V in the i n t e r v a l 0.4 to 1.0, i e , c o r -
A
>
¢lJ
-I-
Q
1 6 0 0
1 4 0 0
1200
1000
1 6 0 0
1 4 0 0
2 0 0
1 0 0 0
600
K + d -~ K + T r - T r + p (n) 2 3 G e V / c
( o )
~ ~ 9 0 4 e v e n t s " ~:
• ~ ;.~ i o •
• , " " - = - ~ , ~ ? : ~
• " 4 " - ~,
t_< 0 • 5 G e V 2 ( b ) ~ 4 3 3 e v e n t s
• " -~ ~
M ( K + ~ r - ) ( M e V ) Fig 1 (a) Triangle plot of %/r+ versus MK+ ~ - for r e - action (4); (b) same as (a) but with t ~< 0.5 GeV 2
Trang 3Volume 18, number 1 P H Y S I C S L E T T E R S 1 August 1965
.:'.::.; (o~ : ': ::.'~.~:~-::? -: :' :,-~
:.-._ - • .:: ", .:.',! ~.:
cl "" "" "" " ' i " : " " " " ' " " ' "
° - o ~ , : : ; - o ~ : , ' :)
" ~ ' : " : " : : :" ~ I , , ~ ' ~ • " " " " " " ' " " '
40 (~) ~
i-I.O
~o
z
5O
40
30
0
C o s ~ p
20
!)1 i ~ l i , _
X f ~ _
oA.,co~ ~-, i.oj
i i [ i i i
.r , , , T I I
I0
0 ' : i : : ; : : ; :
u : ; : ' , ; : : : : ( d )
30
I0
N i i
I
C o s CtK*
(¢)
10.4sCos %Js 1.0 J
C o s a A
Fig 2 and 3 Study of t h e p ° A ++ system and Re K*°A ++ system
(a) Scatter plot of cos ~ A v e r s u s cos ~ respectively cos OtK*
(b) - (d) angular distribution in cos ~ p or cos (Y~K* for various
intervals in cos (~A as Indicated, and(e) -(g) angular distribu-
tion in cos (~A for various intervals in cos ~ p or cos ~K* as i n -
dicated
r e s p o n d i n g to f o r w a r d decay of the v e c t o r m e s o n
(or f o r w a r d s c a t t e r i n g of the i n c i d e n t m e s o n )
shows a d i s t r i b u t i o n c o n s i s t e n t with that expected
for p u r e p s e u d o s c , ] ~ r m e s o n exchange, i.e.,
/(cos ~A) = 1 + 3 c o s 2 ~ A T h u s , a s i d e f r o m a
s m a l l a s y m m e t r y effect p r e s u m a b l y r e l a t e d to
the w e l l - k n o w n m i n o r p h a s e s h i f t s i n the ~r+p
s c a t t e r i n g , the 4 ++ r e s o n a n c e a p p e a r s c o m -
p l e t e l y a l i g n e d i n a c c o r d a n c e with p s e u d o s c a l a r
m e s o n exchange m o d e l On the o t h e r hand, f o r
cos (~V in the i n t e r v a l - 1 0 to - 0 4 , i e , b a c k -
w a r d decay of the v e c t o r m e s o n r e l a t i v e to the
d i r e c t i o n of the i n c i d e n t m e s o n , the d i s t r i b u -
t i o n s in cos '~A s h o w / ( c o s ~A) m u c h c l o s e r to
i s o t r o p y The effects on the cos ~ V d i s t r i -
b u t i o n of choosing d i f f e r e n t r a n g e s of cos ~A
i s l e s s m a r k e d (10) The d i s t r i b u t i o n i n cos ~'A c o r r e s p o n d - ing to the e q u a t o r i a l r e g i o n in cos ~ V d i f f e r s
f r o m the t h e o r e t i c a l v a l u e for p u r e p s e u d o -
s c a l a r m e s o n exchange However, in the
e q u a t o r i a l r e g i o n the c o n t r i b u t i o n of the vec-
t o r - m e s o n decay i s e x p e c t e d to be m i n i m a l
T h e r e f o r e n o n - p - w a v e t e r m s in the m e s o n -
m e s o n s c a t t e r i n g a m p l i t u d e a n d i n c o h e r e n t
b a c k g r o u n d a r e r e l a t i v e l y m o r e i m p o r t a n t The d e p a r t u r e s s e e n i n t h i s r e g i o n m a y thus not be too s u r p r i s i n g
We have a l s o looked f o r c o r r e l a t i o n s b e - tween ~V and ~ the T r e i m a n - Y a n g a n g l e s
at the two d e c a y v e r t i c e s a s w e l l a s between
~ V and cos ~A and ~PA a n d cos ot V No s i g -
n i f i c a n t c o r r e l a t i o n e f f e c t s w e r e o b s e r v e d for these q u a n t i t i e s
In addition to the above e f f e c t s we note
s o m e dependence of the f o u r - m o m e n t u m
t r a n s f e r on cos ~V" In both pO and K *o p r o - duction, f o r w a r d d e c a y of the m e s o n r e s o -
n a n c e i s a s s o c i a t e d with a s o m e w h a t s h a r p e r
f o u r - m o m e n t u m - t r a n s f e r d i s t r i b u t i o n than i s
b a c k w a r d decay
When we f i r s t o b s e r v e d the c o r r e l a t i o n effect in p°A++ p r o d u c t i o n [1], we could not
r u l e out the p o s s i b i l i t y that it was r e l a t e d to Bose s y m m e t r i z a t i o n f o r the two 7r + m e s o n s
o c c u r r i n g in the f i n a l s t a t e The p r e s e n t ob-
s e r v a t i o n of the s a m e effect in K*°A ++ p r o - duction m a k e s it u n l i k e l y that Bose s y m m e -
t r i z a t i o n is the d o m i n a n t f a c t o r Thus the a n g u l a r c o r r e l a t i o n effect i s
p r o b a b l y r e l a t e d to f i n a l - s t a t e i n t e r a c t i o n s ~
It i s i m p o r t a n t to note that the i n t r o d u c t i o n
of f o r m f a c t o r s to e x p l a i n p r o d u c t i o n a n g u -
l a r d i s t r i b u t i o n s does n o t help i n the i n t e r -
p r e t a t i o n of c o r r e l a t i o n effects On the o t h e r hand, f i n a l - s t a t e i n t e r a c t i o n s f o r m an i n t e -
g r a l p a r t of t h e a b s o r p t i o n m o d e l , a n d a suffi-
c i e n t l y detailed m o d e l m i g h t hopefully e x p l a i n both effects
In an a t t e m p t to identify the d y n a m i c o r i g i n
of the f i n a l - s t a t e i n t e r a c t i o n s we have looked at
m a s s d i s t r i b u t i o n s of a l l r e l e v a n t two- a n d t h r e e -
p a r t i c l e s y s t e m s a s f u n c t i o n s of cos ~V" Al- though the m a s s d i s t r i b u t i o n s in a l l t h e s e s y s t e m s
a r e s t r o n g l y c o r r e l a t e d to c o s CtV, it i s not p o s -
t An alternative approach has been considered by Gold- haber [12] This involves exchange of two pseudosca- lar mesons In such a case, correlation effects are
n o longer e~vluded, even without invoking final-state interactions
78
Trang 4V o l u m e 18, n u m b e r 1 P H Y S I C S L E T T E R S 1 August 1965
Table 1
E x p a n s i o n c o e f f i c i e n t s o f / ( c o s ~A) a n d / ( c o s ~ as functions of the p o l a r and e q u a t o r i a l i n t e r v a l s in cos c ~ and cos c~A, r e s p e c t i v e l y A l s o shown is the ( F - B ) / ( F + B) r a t i o The v a r i a t i o n of the expansion coefficient ~
f o r I(cos ~A) with c o s ~ p i n d i c a t e s the c o r r e l a t i o n effect d i s c u s s e d in t h e text T h e 429 e v e n t s a n a l y z e d
h e r e c o r r e s p o n d to channel (2) f o r t < 0.5 GeV ~ They a r e i l l u s t r a t e d in fig 2
Coefficients f o r A ++ decay
Coefficients f o r p c decay
T a b l e 2
E x p a n s i o n c o e f f i c i e n t s o f / ( c o s uA) a n d / ( c o s UK*) a s functions of the p o l a r and e q u a t o r i a l i n t e r v a l s in
cos ~K* and cos UA r e s p e c t i v e l y Also shown is the (F - B) / (F + B) r a t i o The v a r i a t i o n of the expansion coeffie,ent f o r / ( c o s ~ 5 ) with cos ~K* i n d i c a t e s the c o r r e l a t i o n effect d i s c u s s e d in the text The 372 events
• n~lyzed h e r e c o r r e s p o n d to e b , n n e l s (3) and (4) for t -,< 0.5 GeV 2 They a r e i l l u s t r a t e d in fig 3
Coefficients f o r A ++ decay
Coefficients f o r K *° decay
s i b l e , f r o m o u r e x p e r i m e n t a l d a t a , t o s i n g l e o u t
o n e s p e c i f i c p r o c e s s t h a t i d e n t i f i e s t h e f i n a l - s t a t e
i n t e r a c t i o n i n v o l v e d T h u s c o m p l e t e u n d e r s t a n d -
i n g of t h e c o r r e l a t i o n e f f e c t m u s t a w a i t f u r t h e r
s t u d y , b o t h f r o m t h e t h e o r e t i c a l a n d e x p e r i m e n -
t a l p o i n t s o f v i e w
A l t h o u g h w e h a v e s t r e s s e d h e r e c e r t a i n s i g -
n i f i c a n t s i m i l a r i t i e s i n K *o a n d p c p r o d u c t i o n ,
o n e m a j o r d i f f e r e n c e i s e v i d e n t f r o m t h e c o e f f i -
c i e n t s g i v e n i n t a b l e s 1 a n d 2, n a m e l y , t h e l a r g e
f o r w a r d - b a c k w a r d a s y m m e t r y i n p c d e c a y [13]
i s t o b e c o n t r a s t e d w i t h a s m a l l a s y m m e t r y i n
K * ° d e c a y W e h a v e e x a m i n e d t h e l a t t e r a s y m -
m e t r y a s t h e K+~ - m a s s t r a v e r s e s t h e r e s o n a n c e
r e g i o n F i g 4 s h o w s t h e d e p e n d e n c e of t h e r a t i o
are the n u m b e r s of events in which the K + is emitted forward and b a c k w a r d in the K+Tr - centre
of mass T h e slight a s y m m e t r y can be inter- preted as due to the presence of a small, slowly varying, s - w a v e phase shift in the K+Tr - system This is to be contrasted with pc decay, w h e r e the
a s y m m e t r y r e m a i n s constant through the entire resonance region and consequently can not be in- terpreted in the s a m e way
W e would like to acknowledg~ helpful discus- sions and communications with A S Goldhaber and F Selleri W e wish to thank R Shutt for m a k - ing the 20-inch bubble c h a m b e r available to us,
Trang 5Volume 18, number 1 P H Y S I C S L E T T E R S 1 August 1965
> 120
~J
o I00
( z
,,, 80
0.1
G, 60
"5
" 40
E
Z
20
0
0.6
0.4
+0.2
I.i ba
0
-0.2
( a )
L
t - 0 5 G e V 2
.F
I
~ - - i I
4
7
.L
t. I
M ( K * 7 / " - ) ( M e V )
Fig 4 Distribution of the ( F - B ) / ( F +B) ratio for K *°
decay versus the KT# - mass distribution Data are from
reactions (3) and (4)
the A G S c r e w u n d e r K G r e e n and J S p i r o a s
w e l l a s the 2 0 - i n c h bubble c h a m b e r c r e w and in
p a r t i c u l a r H B r o w n f o r h e l p i n g with o u r r u n at
B r o o k h a v e n At B e r k e l e y we w i s h to thank o u r own scanning, m e a s u r i n g and c o m p u t i n g staff, in
p a r t i c u l a r , E m m e t t B u r n s , L o r a Ludwig, J a m e s
M i l l e r a n d B r y c e S h e l d o n
Refe~'ences
1 G.Goldhaber, Conf.on particle and high energy Physics (Boulder, Colorado, 1964) unpublished
2 Aachen-Berlin-Birmingham -Bonn-Hamburg-London
(I C ) -Mffnchen Collaboration, Phys Rev 138 (1965)
B 897
3 G Goldhaber, W Chinowski, S Goldhaber, W Lee and T.OtHalloran, Physics Letters 6 (1963) 62
4 R Kraemer, L.Madanmky, I Miller, A P e v s n e r ,
C Richardson, R Singh and R Zdanis, Prec Athens Topical Conf on Recently discovered resonant p a r - ticles, eds B A Munir and L J Gallaher (University
of Ohio, Athens, Ohio, 1963)p.130
5 M F e r r o - L u z z i , R.George, Y.Goldschmidt-Cler- mont, V P Henri, B Jongejans, D.W.G Leith,
G R Lynch, F Muller and J M Perreau, Nuovo Cimente, to be published
6 See e g , E F e r r a r i and F S e l l e r i , Suppl.del Nuovo Cimento 24 (1962) 453
7 K Gottfried and J D Jackson, Nuovo Cimento 34 (1964) 735;
J D Jackson, Rev Mod Phys., to be published
8 L.Durand and Y.T.Chiu, P h y s R e v L e t t e r s 12 (1964) 399; 13 (1964) 45E
9 C.Baltay, J.Sandweiss, J.Sanford, H.Brown, M Webster and S Yamamoto, Nucl Instr and Methods
20 (1963) 37
10 G.Goldhaber, J L B r o w n , S.Goldhaber, J.A.Kadyk,
B C Shen and G H Trilling, Phys Rev Letters 12 (1964) 336
11 W Chinowsky, G G o l ~ a b a r , S Goldhaber, W Lee and T O'Halloran, Phys Rev Letters 9 (1962) 330
12 A.S.Goldlmber, Phys.Rev.135 (1964) B508
13 G Goldhaber, in Second Coral Gables Conf on Symmetry principles at high energy, ede B Kursu- noglu, A Perlmutter and I Sakmar (W H Freeman and Company, San Francisco, 1965) p 34
80