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Experimental study of the decay KL → π+π−πo
Volume 28B, number 1
EXPERIMENTAL
PHYSICS LETTERS
STUDY
OF
THE
28October 1968
DECAY
K L
~
~+~-~o
P. B A S I L E , J . W . CItONIN *, B. T H E V E N E T , It. T U I t L A Y , S. Z Y L B E I t A J C H a n d A. Z Y L B E I t S Z T E J N D~parternent de Physique des Particules El$rnentaires, CEN, Saclay, F r a n c e Received 7 September 1968
F r o m a sample of 2446 K~ -~ ~'+Tr-rt° decays the study of pion energy s p e c t r a according to the squared m a t r i x element IMI 2 Ceil + 2a0(2T o - T m a x ) M K / r n 2 ] where T O is the 7r° kinetic energy, is p r e s e n t e d . We find a0 = - 0.188 ± 0.020, this value is compared with the ]AII = ~ rule selection.
In a n e x p e r i m e n t to s t u d y t h e c h a r g e d d e c a y m o d e s of K L a t S a t u r n e [1] we h a v e s e l e c t e d 3043 c a n d i d a t e s f o r K~, ~ ~ + n - v o . T h e d e t a i l s of t h e e x p e r i m e n t a r e g i v e n i n r e f . 1. T h e s e e v e n t s were chosen from the total sample by the requirem e n t t h a t t h e r a n g e of e a c h s e c o n d a r y b e l e s s t h a n o r e q u a l to t h e r a n g e of a p i o n . T h e d e c a y m o d e s KLe3 and KL~3 are largely eliminated by these means. W i t h i n t h i s s a m p l e we h a v e m a d e a n u m b e r of c u t s . A f i r s t c l a s s of c u t s i s g e o m e t r i c : t h e two charged particles must come from a common vert e x , m u s t not s c a t t e r off t h e m a g n e t p o l e p i e c e s , a n d m u s t not b e ~ - ~ d e c a y s in f l i g h t . The kinematic cuts listed below are then made: 1 °) T h e m o m e n t u m of t h e c h a r g e d p i o n s in t h e l a b o r a t o r y m u s t b e l a r g e r t h a n 50 M e V / c . P i o n s w i t h l e s s m o m e n t u m do not p e n e t r a t e t h e f i r s t p l a t e of t h e r a n g e s p a r k c h a m b e r a n d g i v e i n s u f ficient range information. 2 °) T h e e f f e c t i v e m a s s of t h e d i p i o n m u s t b e l e s s t h a n 375 MeV. 3 °) T h e q u a n t i t y (P'o)2 m u s t b e in t h e i n t e r v a l b e t w e e n - 7 × 103 a n d +33 × 103 ( M e V / c ) 2. (PS) 2 i s t h e s q u a r e of t h e i n c i d e n t K L m o m e n t u m i n a s y s t e m w h e r e t h e l o n g i t u d i n a l m o m e n t u m of t h e two charged particles is zero. T h e d i s t r i b u t i o n of ( P ' ) 2 f o r a l l e v e n t s a n d o those selected by the geometric and range cuts a r e s h o w n i n f i g u r e l a . A f t e r a l l c u t s , 2446 e v e n t s r e m a i n w h i c h h a v e b e e n u s e d in t h e a n a l y s i s . A Monte-Carlo calculation showed that the a* P r e s e n t a d d r e s s : P a l m e r Physical Laboratory, Princeton University, Princeton, New J e r s e y . 58
mount of gg3 and Ke3 that can fall into the region of the geometric and kinematics cuts is less than 2% of the K ~3 sample. The M0nte-Carlo calculation of the expected distributions of the 3n events includes the geometric selection of the apparatus, the incident KL momentum spectrum, the counter trigger logic, multiple scattering and measurement errors, decays in flight, and in identical fashion all the cuts made for the real data. The Monte-Carlo then defines the relative efficiency as a function of position on the Dalitz plot, as well as other experimental distributions as modified by the apparatus. We have also evaluated the number of 3n events lost because of the misidentification of one of the pions as a lepton. In addition to the conditions on (p')2 and the effective mass we have found that the 3n events must satisfy the relations:
P±ni "-<110 MeV/c and I ,°±nI + *°±n21 < 140 MeV/c where P±niis the transverse component of a pion momentum. Further the two charged pions must each make an angle of less than 90o with the incident KL direction. Among the 17 000 identified leptonic decays observed we have found at most 125 events which could be in fact 3n decays. Figure Ib shows the tails of the (p,)2 distributions of events identified a s Kt~ 3 a n d Ke3. O n e c a n s e e t h a t a b o u t 60 K p 3 events from an excess above the Monte-Carlo c u r v e a n d a r e l i k e l y to b e 3n e v e n t s . In t h e a n a -
Volume 28B, n u m b e r 1
PHYSICS
28 October 1968
-•.N./phos
(Po) z DISTRIBUTIONS
Number
LETTERS
e spoce
of events
\ I
MONTEC A R L O nM~
>, o
I00C
MONTE CARLO K ~ rleO
0
-1o
-.1o
5
P~,V
dN (K~'ne'Ol
.c[ 0.5
n
N
\ ~
I
MONTECARLO
i
10
;
i
2g
I
40
30
T7° kinetic energy
I
S0
MeV
Fig. 2. /r ° s p e c t r u m / p h a s e space (2446 events). 50(
0
-20
-~0
'
()
'
~0
'
20
(,Po) 2WI 0-:3(MeV//c)
Fig. la. Distribution in (p~)2 of all experimental events. The continuous line is the expected distribution calculated by Monte-Carlo. The c r o s s hatched h i s t o g r a m r e p r e s e n t s the data which r e m a i n s a f t e r the cut Mef f < < 375 MeV and identification of the two charged pions by , 2 that we have range, mhe a r r o w indicates the cut in (Po) applied. lb. Detail of the tail of those events identified as Ktz 3 or Ke3. l y s i s w h i c h f o l l o w s we f i n d t h a t t h e l o s s of t h e s e e v e n t s d o e s not a l t e r o u r c o n c l u s i o n s . In fig. 2 we p r e s e n t t h e s p e c t r u m of k i n e t i c e n e r g y TTro of t h e n e u t r a l p i o n . T h e p o i n t s a r e o b t a i n e d b y d i v i d i n g t h e o b s e r v e d n u m b e r of e v e n t s i n e a c h b i n b y t h e n u m b e r e x p e c t e d on t h e b a s i s of a p u r e p h a s e s p a c e d i s t r i b u t i o n . W e h a v e f i t t e d o u r r e s u l t s to s e v e r a l m o d e l s w h i c h h a v e b e e n u s e d to p a r a m e t r i z e t h e d a t a . T h e s e f i t s a r e g i v e n in t a b l e 1. W e h a v e v e r i f i e d t h a t t h e a d d i t i o n of a c o r r e c t i o n to t a k e a c c o u n t of t h e l o s t K~3 e v e n t s d o e s not c h a n g e t h e a b o v e r e s u l t s . F o r e x a m p l e , w i t h t h e a d d i t i o n of t h e 125 c a n d i d a t e s f o r K~3 a m o n g Kt~ 3 a n d Ke3 e a c h w i t h a w e i g h t of 0.5, s i n c e o n l y
one half can be true I~3 events, one finds a 0 = = - 0 . 1 8 0 + 0.020, a s h i f t w e l l w i t h i n t h e e r r o r . T h e v a l u e g i v e n f o r a 0 i s to b e c o m p a r e d w i t h e x i s t i n g m e a s u r e m e n t s [4- 5]. T h e k n o w l e d g e of o n l y t h e K L d i r e c t i o n a n d t h e m o m e n t a of t h e two c h a r g e d p a r t i c l e s d o e s not p e r m i t a u n i q u e s o l u t i o n f o r t h e e n e r g y of t h e charged pions in the K L rest system. The geome t r y of t h e a p p a r a t u s f a v o r s d e c a y s f o r w h i c h t h e d i f f e r e n c e b e t w e e n t h e two p o s s i b l e s o l u t i o n s i s s m a l l . In 80% of t h e e v e n t s t h e d i f f e r e n c e b e t w e e n t h e two s o l u t i o n s i n t h e e n e r g y of a c h a r g e d p i o n i s l e s s t h a t 10 M e V . In a l l t h e a n a l y s i s t h a t f o l l o w s we h a v e s u c c e s sively considered the following cases: 1) E * i i - e n e r g y of c h a r g e d p i o n s f o r s o l u t i o n w i t h t h e l o w e r m o m e n t u m K L. 2) E ' i S - e n e r g y of c h a r g e d p i o n s f o r t h e s o l u t i o n w i t h t h e h i g h e r m o m e n t u m K L. 3) E * i - m e a n of t h e two a b o v e s o l u t i o n s . If w e d e v e l o p l i n e a r l y t h e ~± s p e c t r a a s ddTTr± N _ I 1 + 2 a + ( 2 T ~ ± - T m a x ) ~ 2 1 x phase space we find t h e r e s u l t s g i v e n in t a b l e 2. O n e s e e s in t a b l e 2 t h a t t h e c h a r g e d s l o p e s a r e s e n s i t i v e to t h e c h o s e n s o l u t i o n . T h i s e f f e c t a p p e a r s to b e m o s t s e n s i t i v e to t h e e v e n t s a t low m o m e n t u m . If we r e m o v e t h e f i r s t two p o i n t s we f i n d f o r t h e averaged solution: a + = 0.077 ± 0 . 0 0 4 a- = 0.078 ± 0.004 T h e s e v a l u e s a r e in a g r e e m e n t f r o m t h e r e l a t i o n In01 = 2 aft=.
with those obtained 59
Volume 28B, number 1
PHYSICS
LETTERS
28 October 1968
Table 1. F o r m of matrix element 1.
Value of p a r a m e t e r
Linear: [2]
1 + olTyO/MK 1 + 2ao(2T~.O2.
Tmax)MK/m2
Quadratic
1 + OlTrfO/MK + ~ (TriO/MK) 2 3.
X2/degrees of freedom
(7-resonance: [3]
ol
= -6.12 ~=0.40
ao
= -0.188 :L 0.020
0.56
OL
= -6.00 ± 0.5
fl
= -8.6 ± 4.5
0.64
M0- = (380 + 416)MeV _
0.68
F(~ = (150 ~ 17)MeV Table 2.
w i t h t h e s e v a l u e s w e find t h e r a t i o s :
a +
a-
Lower solution
0.077 ~ 0.010
0.070 ± 0.009
Upper solution
0.080 ~ 0.008
0.078 ± 0.006
Mean solution
0.085 :~ 0.006
0.072 e 0.003
- a ( + - 0) / 2a(+ + - ) = 0.97 ± 0.13 and a(+-
W e h a v e a l s o l o o k e d a t t h e a s y m m e t r y in t h e Dalitz plot. A statistically significant asymmetry w o u l d i n d i c a t e a v i o l a t i o n of CP. W e find:
0) / a ( +
0 0)
= 0.76 ± 0 . 1 0 .
T h e f i r s t r a t i o i s c o m p a t i b l e w i t h t h e I Al[ = ½ r u l e ; t h e s e c o n d r a t i o d i s a g r e e s , but we s h o u l d e m p h a s i z e t h a t f u r t h e r m e a s u r e m e n t s on a(+ 0 0) a r e n e c e s s a r y [4] b e f o r e a f i r m c o n c l u sion can be drawn.
R = I NF~+>E~- -_ NEv+E~_ + N E~+~-~ i s t h e n u m b e r of e v e n t s in t h e I{ L r e s t frame~ ~wi~h E ~ > / ~ . T h i s r e s u l t i s i n s e n s i t i v e to t h e c h o i c e of s o l u t i o n . T h e v a l u e a(+ - 0) f o u n d in t h i s e x p e r i m e n t c a n b e u s e d to c h e c k t h e r e l a t i o n s b e t w e e n s l o p e s of t h e I~ L and g + d e c a y m o d e s i n t o 3 p i o n s . F o r t h e o t h e r s l o p e s we take a(+ 0 0) = - 0.25 ± 0.02
[4]
a(+ + - ) = 0.097 ± 0 . 0 0 7 . T h e v a l u e of a(+ + -) i s o b t a i n e d b y c o m b i n i n g t h e v a l u e g i v e n in r e f . 4 w i t h m o r e r e ' c e n t r e s u l t s a(+ + - ) = (0.0955 ± 0.011)
[6]
a(+ + - ) = (0.102
[7]
and ±0.011)
* * * * *
60
References 1. P . B a s i l e , J . W . Cronin, B.Thevenet, R. Turlay, S. Zylberajch and A. Zylbersztejn. Phys. L e t t e r s 26B (1968) 542. 2. S.Weinberg, Phys. Rev. L e t t e r s 4 (1960) 87. 3. L.H. Brown and P. Singer, Phys. Rev. 133 (1964) B812. 4. G. H. Trilling, Intern. Conf. on Weak interactions, Argonne (1965),ANL Heport 7130. p. 115. 5. H.W.K. Hopkins, T . C . Bacon, F . R . E i s l e r , Phys. Rev. L e t t e r s 19 (1967) 185; B. M. K. Nefkens, A. Abashian, R . J . A b r a m s , D.W. Carpenter, G. P. F i s h e r , J. H. Smit, Phys. Rev. 157 (1967) 1233. 6. L. Moscoso, Th~se 3~me cycle, Orsay (1968). 7. S.Y. Fung, R. Goldberg, S. L. Meyer, R . J . Piano and A. Zinehenko, Intern. Conf. on High Energy Physics, Berkeley (1966).
EXPERIMENTAL
PHYSICS LETTERS
STUDY
OF
THE
28October 1968
DECAY
K L
~
~+~-~o
P. B A S I L E , J . W . CItONIN *, B. T H E V E N E T , It. T U I t L A Y , S. Z Y L B E I t A J C H a n d A. Z Y L B E I t S Z T E J N D~parternent de Physique des Particules El$rnentaires, CEN, Saclay, F r a n c e Received 7 September 1968
F r o m a sample of 2446 K~ -~ ~'+Tr-rt° decays the study of pion energy s p e c t r a according to the squared m a t r i x element IMI 2 Ceil + 2a0(2T o - T m a x ) M K / r n 2 ] where T O is the 7r° kinetic energy, is p r e s e n t e d . We find a0 = - 0.188 ± 0.020, this value is compared with the ]AII = ~ rule selection.
In a n e x p e r i m e n t to s t u d y t h e c h a r g e d d e c a y m o d e s of K L a t S a t u r n e [1] we h a v e s e l e c t e d 3043 c a n d i d a t e s f o r K~, ~ ~ + n - v o . T h e d e t a i l s of t h e e x p e r i m e n t a r e g i v e n i n r e f . 1. T h e s e e v e n t s were chosen from the total sample by the requirem e n t t h a t t h e r a n g e of e a c h s e c o n d a r y b e l e s s t h a n o r e q u a l to t h e r a n g e of a p i o n . T h e d e c a y m o d e s KLe3 and KL~3 are largely eliminated by these means. W i t h i n t h i s s a m p l e we h a v e m a d e a n u m b e r of c u t s . A f i r s t c l a s s of c u t s i s g e o m e t r i c : t h e two charged particles must come from a common vert e x , m u s t not s c a t t e r off t h e m a g n e t p o l e p i e c e s , a n d m u s t not b e ~ - ~ d e c a y s in f l i g h t . The kinematic cuts listed below are then made: 1 °) T h e m o m e n t u m of t h e c h a r g e d p i o n s in t h e l a b o r a t o r y m u s t b e l a r g e r t h a n 50 M e V / c . P i o n s w i t h l e s s m o m e n t u m do not p e n e t r a t e t h e f i r s t p l a t e of t h e r a n g e s p a r k c h a m b e r a n d g i v e i n s u f ficient range information. 2 °) T h e e f f e c t i v e m a s s of t h e d i p i o n m u s t b e l e s s t h a n 375 MeV. 3 °) T h e q u a n t i t y (P'o)2 m u s t b e in t h e i n t e r v a l b e t w e e n - 7 × 103 a n d +33 × 103 ( M e V / c ) 2. (PS) 2 i s t h e s q u a r e of t h e i n c i d e n t K L m o m e n t u m i n a s y s t e m w h e r e t h e l o n g i t u d i n a l m o m e n t u m of t h e two charged particles is zero. T h e d i s t r i b u t i o n of ( P ' ) 2 f o r a l l e v e n t s a n d o those selected by the geometric and range cuts a r e s h o w n i n f i g u r e l a . A f t e r a l l c u t s , 2446 e v e n t s r e m a i n w h i c h h a v e b e e n u s e d in t h e a n a l y s i s . A Monte-Carlo calculation showed that the a* P r e s e n t a d d r e s s : P a l m e r Physical Laboratory, Princeton University, Princeton, New J e r s e y . 58
mount of gg3 and Ke3 that can fall into the region of the geometric and kinematics cuts is less than 2% of the K ~3 sample. The M0nte-Carlo calculation of the expected distributions of the 3n events includes the geometric selection of the apparatus, the incident KL momentum spectrum, the counter trigger logic, multiple scattering and measurement errors, decays in flight, and in identical fashion all the cuts made for the real data. The Monte-Carlo then defines the relative efficiency as a function of position on the Dalitz plot, as well as other experimental distributions as modified by the apparatus. We have also evaluated the number of 3n events lost because of the misidentification of one of the pions as a lepton. In addition to the conditions on (p')2 and the effective mass we have found that the 3n events must satisfy the relations:
P±ni "-<110 MeV/c and I ,°±nI + *°±n21 < 140 MeV/c where P±niis the transverse component of a pion momentum. Further the two charged pions must each make an angle of less than 90o with the incident KL direction. Among the 17 000 identified leptonic decays observed we have found at most 125 events which could be in fact 3n decays. Figure Ib shows the tails of the (p,)2 distributions of events identified a s Kt~ 3 a n d Ke3. O n e c a n s e e t h a t a b o u t 60 K p 3 events from an excess above the Monte-Carlo c u r v e a n d a r e l i k e l y to b e 3n e v e n t s . In t h e a n a -
Volume 28B, n u m b e r 1
PHYSICS
28 October 1968
-•.N./phos
(Po) z DISTRIBUTIONS
Number
LETTERS
e spoce
of events
\ I
MONTEC A R L O nM~
>, o
I00C
MONTE CARLO K ~ rleO
0
-1o
-.1o
5
P~,V
dN (K~'ne'Ol
.c[ 0.5
n
N
\ ~
I
MONTECARLO
i
10
;
i
2g
I
40
30
T7° kinetic energy
I
S0
MeV
Fig. 2. /r ° s p e c t r u m / p h a s e space (2446 events). 50(
0
-20
-~0
'
()
'
~0
'
20
(,Po) 2WI 0-:3(MeV//c)
Fig. la. Distribution in (p~)2 of all experimental events. The continuous line is the expected distribution calculated by Monte-Carlo. The c r o s s hatched h i s t o g r a m r e p r e s e n t s the data which r e m a i n s a f t e r the cut Mef f < < 375 MeV and identification of the two charged pions by , 2 that we have range, mhe a r r o w indicates the cut in (Po) applied. lb. Detail of the tail of those events identified as Ktz 3 or Ke3. l y s i s w h i c h f o l l o w s we f i n d t h a t t h e l o s s of t h e s e e v e n t s d o e s not a l t e r o u r c o n c l u s i o n s . In fig. 2 we p r e s e n t t h e s p e c t r u m of k i n e t i c e n e r g y TTro of t h e n e u t r a l p i o n . T h e p o i n t s a r e o b t a i n e d b y d i v i d i n g t h e o b s e r v e d n u m b e r of e v e n t s i n e a c h b i n b y t h e n u m b e r e x p e c t e d on t h e b a s i s of a p u r e p h a s e s p a c e d i s t r i b u t i o n . W e h a v e f i t t e d o u r r e s u l t s to s e v e r a l m o d e l s w h i c h h a v e b e e n u s e d to p a r a m e t r i z e t h e d a t a . T h e s e f i t s a r e g i v e n in t a b l e 1. W e h a v e v e r i f i e d t h a t t h e a d d i t i o n of a c o r r e c t i o n to t a k e a c c o u n t of t h e l o s t K~3 e v e n t s d o e s not c h a n g e t h e a b o v e r e s u l t s . F o r e x a m p l e , w i t h t h e a d d i t i o n of t h e 125 c a n d i d a t e s f o r K~3 a m o n g Kt~ 3 a n d Ke3 e a c h w i t h a w e i g h t of 0.5, s i n c e o n l y
one half can be true I~3 events, one finds a 0 = = - 0 . 1 8 0 + 0.020, a s h i f t w e l l w i t h i n t h e e r r o r . T h e v a l u e g i v e n f o r a 0 i s to b e c o m p a r e d w i t h e x i s t i n g m e a s u r e m e n t s [4- 5]. T h e k n o w l e d g e of o n l y t h e K L d i r e c t i o n a n d t h e m o m e n t a of t h e two c h a r g e d p a r t i c l e s d o e s not p e r m i t a u n i q u e s o l u t i o n f o r t h e e n e r g y of t h e charged pions in the K L rest system. The geome t r y of t h e a p p a r a t u s f a v o r s d e c a y s f o r w h i c h t h e d i f f e r e n c e b e t w e e n t h e two p o s s i b l e s o l u t i o n s i s s m a l l . In 80% of t h e e v e n t s t h e d i f f e r e n c e b e t w e e n t h e two s o l u t i o n s i n t h e e n e r g y of a c h a r g e d p i o n i s l e s s t h a t 10 M e V . In a l l t h e a n a l y s i s t h a t f o l l o w s we h a v e s u c c e s sively considered the following cases: 1) E * i i - e n e r g y of c h a r g e d p i o n s f o r s o l u t i o n w i t h t h e l o w e r m o m e n t u m K L. 2) E ' i S - e n e r g y of c h a r g e d p i o n s f o r t h e s o l u t i o n w i t h t h e h i g h e r m o m e n t u m K L. 3) E * i - m e a n of t h e two a b o v e s o l u t i o n s . If w e d e v e l o p l i n e a r l y t h e ~± s p e c t r a a s ddTTr± N _ I 1 + 2 a + ( 2 T ~ ± - T m a x ) ~ 2 1 x phase space we find t h e r e s u l t s g i v e n in t a b l e 2. O n e s e e s in t a b l e 2 t h a t t h e c h a r g e d s l o p e s a r e s e n s i t i v e to t h e c h o s e n s o l u t i o n . T h i s e f f e c t a p p e a r s to b e m o s t s e n s i t i v e to t h e e v e n t s a t low m o m e n t u m . If we r e m o v e t h e f i r s t two p o i n t s we f i n d f o r t h e averaged solution: a + = 0.077 ± 0 . 0 0 4 a- = 0.078 ± 0.004 T h e s e v a l u e s a r e in a g r e e m e n t f r o m t h e r e l a t i o n In01 = 2 aft=.
with those obtained 59
Volume 28B, number 1
PHYSICS
LETTERS
28 October 1968
Table 1. F o r m of matrix element 1.
Value of p a r a m e t e r
Linear: [2]
1 + olTyO/MK 1 + 2ao(2T~.O2.
Tmax)MK/m2
Quadratic
1 + OlTrfO/MK + ~ (TriO/MK) 2 3.
X2/degrees of freedom
(7-resonance: [3]
ol
= -6.12 ~=0.40
ao
= -0.188 :L 0.020
0.56
OL
= -6.00 ± 0.5
fl
= -8.6 ± 4.5
0.64
M0- = (380 + 416)MeV _
0.68
F(~ = (150 ~ 17)MeV Table 2.
w i t h t h e s e v a l u e s w e find t h e r a t i o s :
a +
a-
Lower solution
0.077 ~ 0.010
0.070 ± 0.009
Upper solution
0.080 ~ 0.008
0.078 ± 0.006
Mean solution
0.085 :~ 0.006
0.072 e 0.003
- a ( + - 0) / 2a(+ + - ) = 0.97 ± 0.13 and a(+-
W e h a v e a l s o l o o k e d a t t h e a s y m m e t r y in t h e Dalitz plot. A statistically significant asymmetry w o u l d i n d i c a t e a v i o l a t i o n of CP. W e find:
0) / a ( +
0 0)
= 0.76 ± 0 . 1 0 .
T h e f i r s t r a t i o i s c o m p a t i b l e w i t h t h e I Al[ = ½ r u l e ; t h e s e c o n d r a t i o d i s a g r e e s , but we s h o u l d e m p h a s i z e t h a t f u r t h e r m e a s u r e m e n t s on a(+ 0 0) a r e n e c e s s a r y [4] b e f o r e a f i r m c o n c l u sion can be drawn.
R = I NF~+>E~- -_ NEv+
[4]
a(+ + - ) = 0.097 ± 0 . 0 0 7 . T h e v a l u e of a(+ + -) i s o b t a i n e d b y c o m b i n i n g t h e v a l u e g i v e n in r e f . 4 w i t h m o r e r e ' c e n t r e s u l t s a(+ + - ) = (0.0955 ± 0.011)
[6]
a(+ + - ) = (0.102
[7]
and ±0.011)
* * * * *
60
References 1. P . B a s i l e , J . W . Cronin, B.Thevenet, R. Turlay, S. Zylberajch and A. Zylbersztejn. Phys. L e t t e r s 26B (1968) 542. 2. S.Weinberg, Phys. Rev. L e t t e r s 4 (1960) 87. 3. L.H. Brown and P. Singer, Phys. Rev. 133 (1964) B812. 4. G. H. Trilling, Intern. Conf. on Weak interactions, Argonne (1965),ANL Heport 7130. p. 115. 5. H.W.K. Hopkins, T . C . Bacon, F . R . E i s l e r , Phys. Rev. L e t t e r s 19 (1967) 185; B. M. K. Nefkens, A. Abashian, R . J . A b r a m s , D.W. Carpenter, G. P. F i s h e r , J. H. Smit, Phys. Rev. 157 (1967) 1233. 6. L. Moscoso, Th~se 3~me cycle, Orsay (1968). 7. S.Y. Fung, R. Goldberg, S. L. Meyer, R . J . Piano and A. Zinehenko, Intern. Conf. on High Energy Physics, Berkeley (1966).