PION DEUTERON REACTIONS AT INTERMEDIATE ENERGIES

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PION DEUTERON REACTIONS AT INTERMEDIATE ENERGIES

M. Locher

To cite this version:

M. Locher. PION DEUTERON REACTIONS AT INTERMEDIATE ENERGIES. Journal de

Physique Colloques, 1985, 46 (C2), pp.C2-319-C2-328. �10.1051/jphyscol:1985238�. �jpa-00224552�

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JOURNAL DE PHYSIQUE

Colloque C2, supplement au n°2, Tome *6, fevrier 1985 pageC2-319

PION DEUTERON REACTIONS AT INTERMEDIATE ENERGIES

M.P. Locher

SIN, Swiss Institute for Nuclear Research, CH-5234 Villigen, Switzerland

Résumé - L'état actuel de l'analyse des réactions pionique avec participation d'un deuton est passé en revue. En particulier sont discutées la diffusion élastique ird, la production ir en pp-dfr et les implications pour les résonances avec B=2.

A b s t r a c t - Recent t r e n d s i n t h e a n a l y s i s of p i o n i c d e u t e r o n r e - a c t i o n s a r e reviewed. In p a r t i c u l a r ird e l a s t i c s c a t t e r i n g , IT p r o - d u c t i o n i n pp-dTT and r e l a t e d t o p i c s a r e d i s c u s s e d , t o g e t h e r with i m p l i c a t i o n s f o r B=2 r e s o n a n c e s .

1. INTRODUCTION

In this note we review our present understanding of the reactions invol- ving a pion and a deuteron. We shall start with ird elastic scattering in order to illustrate and differentiate the sensitivities of the dynamics (Sec. 2 ) . Numerous recent theoretical and experimental acti- vities have concentrated on IT production and absorption channels. We shall therefore discuss (in Sec. 3) the elementary reaction pp-dir com- paring advanced calculations with experiment and commenting on direct phase shift and amplitude reconstruction. Similarly we shall report on some recent results on the continuum reaction pp-irNN. Since the deute- ron has baryon number two we shall briefly comment in Sec. 4 on the status of dibaryon resonances in reactions involving the pion.

2. PION DEUTERON ELASTIC SCATTERING

This reaction is helpful in clarifying some qualitative aspects of the underlying dynamics even if recent progress has been slow and an ex- perimental puzzle remains. For the gross features we first show a com- parison of the differential cross section /l to 4/ with theory (Fig. 1 ) . The theoretical curves are from the Lyon group / 5 / showing the results for an advanced Faddeev type multichannel scattering theory. Very simi- lar predictions were obtained by Rinat et al / 6 / and Blankleider and Afnan / 7 / . On the basis of Fig. 1 two conclusions can be drawn:

(i) the forward cone (0 < 70°) is described almost perfectly. This regime corresponds to the peripheral part of the interaction where the long range properties of the TTN amplitude and of the deuteron wave function are probed. In fact even the impulse approximation describes this part of the dynamics quite well, comp. ref. / 8 / , e.g.

(ii) For larger angles we probe the regime of large momentum transfers and small distances. Theory is systematically too high for T^ > 180 MeV which is true also for refs. /6,7/. Our understanding of the interme- diate and short range behaviour is therefore not perfect. The addition of heavy meson exchange by the Lyon group / 9 / does not improve the situation. Note, however, that the cross section is suppressed by two

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1985238

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C2-320 JOURNAL DE PHYSIQUE

t o t h r e e o r d e r s of magnitude i n t h i s r e g i o n of l a r g e a n g l e s ( F i g . 1).

The v e c t o r p o l a r i z a t i o n i T l l b e i n g a p u r e i n t e r f e r e n c e e f f e c t o f t h e t y p e I m AB* ( s e e

/lo/ a p p e n d i x ) i s a q u a n t i t y s e n s i t i v e t o d e t a i l s , i n p r i n c i p l e even i n t h e forward cone. Yet t h e e n e r g y dependence p r e d i c t e d /5,6,7/ i s q u i t e smooth. The new h i g h q u a l i - t y d a t a of Smith e t a 1 /11/ ( s e e F i g . 2 ) show l e s s s t r u c t u r e a t T, = 256 MeV t h a n p r e v i o u s l y r e p o r t e d . There i s , however, s t i l l a s y s t e m a t i c d i s c r e p a n c y between t h e c a l c u l a t e d iTll of / 5 , 6 / and e x p e r i m e n t , p a r t i c u l a r k y I n t h e t r a n s i t i o n r e g i o n o f

40° < 6 < 100° from s m a l l t o h i g h momentum

t r a n s f e r s . The d i s c r e p a n c y i s c o n s i s t e n t w i t h a 1 ~ 4 (2480) Argonne r e s o n a n c e c o n t r i - b u t i n g w i t h s u b s t a n t i a l upper c o u p l i n g

(L,=J+l) of t h e p i o n o r b i t a l a n g u l a r momen- tum /11/. Some s t r e n g t h f o r 1 ~ 2 (2200) lower c o u p l i n g i s a l s o r e q u i r e d i n /11/ b u t t h i s j u s t r e p r e s e n t s an a d j u s t m e n t of t h e l e a d i n g NA c o n t r i b u t i o n . G e n e r a l l y iTll i s not sen-

s i t i v e t o t h e Argonne r e s o n a n c e s , i f lower

140

M e V

20 F i g u r e 1

The d i f f e r e n t i a l c r o s s s e c t i o n s f o r ad-ad from t h e Lyon group /5/ com- p a r e d w i t h e x p e r i m e n t / L r 2 , 3 , 4 / .

F i g u r e 2

The v e c t o r p o l a r i z a t i o n i T l l ( % ) f o r ad-ad from Smith e t a 1 /11/. Measure- ments a r e compared t o p r e d i c t i o n s from t h e Lyon group /5/ (dashed l i n e s ) w i t h d i b a r y o n r e s o n a n c e s added ( s o l i d l i n e s ) by Smith e t a 1 /11/.

8, (degrees)

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c o u p l i n g happens t o be d o m i n a t i n g / 8 , 1 2 / . I n s u c h a c a s e t h e r e a r e no o s c i l l a t i o n s y e t t h e r e s o n a n c e s can b e p r e s e n t w i t h t h e i r f u l l s t r e n g t h . The t e n s o r p o l a r i z a t i o n t 2 0 i s b a s i c a l l y a l e s s s e n s i t i v e o b s e r v a b l e t h a n i T l l s i n c e i t s a l g e b r a i c s t r u c t u r e c o n s i s t s of a b s o l u t e s q u a r e s of h e l i c i t y a m p l i t u d e s /lo/. Yet a v i o l e n t s t r u c t u r e h a s been r e p o r t e d a t a n g l e s of 120° and 150° f o r T, = 134 MeV by Griiebler e t a l . /13/

d i s a p p e a r i n g r a p i d l y w i t h i n some 2 0 MeV. The e x c i t a t i o n c u r v e from a s i m i l a r e x p e r i m e n t by H o l t e t a l . /14/ i s f l a t f o r an i n t e r m e d i a t e a n g l e . The e x p e r i m e n t by G r u e b l e r i s f l a t t h e r e t o o , b u t t h e s i g n s o f t 2 0 a r e c o n f l i c t i n g . The c o r r e s p o n d i n g f i g u r e s have been shown r e p e a - t e d l y , s e e t h e r e v i e w s /15,16/. To r e s o l v e t h e c o n t r o v e r s y e x p e r i m e n t s a r e under way b o t h a t TRIUMF and SIN. Note t h a t on t h e t h e o r e t i c a l s i d e a s i m p l e admixture of a B r e i t Wigner r e s o n a n c e (of u n n a t u r a l p a r i t y , 1+, e.g.1 i s n o t l i k e l y t o r e p r o d u c e t h e o s c i l l a t i o n s o f t 2 0 u n l e s s some of t h e b i g g e r p a r t i a l waves a r e changed a s w e l l . Note a l s o t h a t a f i n e l y meshed s c a n around 134 M e V h a s n o t r e v e a l e d any s t r u c t u r e /17/

i n t h e h e a v i l y c o r r e l a t e d o b s e r v a b l e i T l l , comp. /18/. The c o n f i r m a t i o n of such a s t r o n g l y e n e r g y dependent e f f e c t f o r t 2 0 would t h e r e f o r e be a r e a l c h a l l e n g e t o t h e o r y . Although we a r e d e a l i n g h e r e w i t h h i g h momentum t r a n s f e r s such v i o l e n t e x c u r s i o n s a r e n o t l i k e l y t o o c c u r i n t h e framework o f c o n v e n t i o n a l one boson exchange dynamics.

For t h e c l o s e l y r e l a t e d r e a c t i o n ad-anp o l d /19/ and new measurements of t h e c r o s s s e c t i o n and t h e v e c t o r p o l a r i z a t i o n i n t h e q u a s i e l a s t i c r e g i o n a r e a v a i l a b l e /20,21/. Agreement w i t h t h e o r y /20,22/ i n t h i s p e r i p h e r a l regime i s good. The break-up c h a n n e l i s i n p r i n c i p l e i n t e - r e s t i n g f o r a d i s c u s s i o n o f t h e b r o a d Argonne r e s o n a n c e s which s h o u l d have a s t r o n g c h a n n e l c o u p l i n g . However, a major e x p e r i m e n t a l and theo- r e t i c a l e f f o r t , i n p a r t i c u l a r f o r t h e s p i n o b s e r v a b l e s would be needed.

3. PION PRODUCTION AND ABSORPTION CHANNELS

A

remarkably r i c h and a l m o s t complete s e t of d a t a now e x i s t s f o r t h e s i m p l e s t

IT

p r o d u c t i o n c h a n n e l pp-tdn ( e q u i v a l e n t t o ~ d - t p p by t i m e r e v e r - s a l i n v a r i a n c e ) .

A

s i m i l a r e f f o r t h a s gone i n t o t h e o r e t i c a l c a l c u - l a t i o n s t r y i n g t o p r e d i c t t h i s r e a c t i o n from dynamic p r i n c i p l e s w i t h o u t u n j u s t i f i e d a p p r o x i m a t i o n s . The r e a c t i o n i s i n t h e h i g h momentum t r a n s - f e r regime even f o r forward a n g l e s s i n c e a p i o n h a s t o be c r e a t e d . We s h a l l t r y t o i l l u s t r a t e t h e d e g r e e t o which c o n v e n t i o n a l dynamics i s a b l e t o d e s c r i b e t h i s s e n s i t i v e r e a c t i o n . The d a t a , s e e t h e compi- l a t i o n s i n /26/ and /31/, a r e f a r more complete t h a n f o r a d e l a s t i c s c a t t e r i n g . I n p r i n c i p l e 11 o b s e r v a b l e s s u f f i c e t o d e t e r m i n e t h e s i x h e l i c i t y a m p l i t u d e s i n pp-da a p a r t from ( d i s c r e t e ) a m b i g u i t i e s /23,24/.

A t p r e s e n t 9 o b s e r v a b l e s (do/dQ,

A,,, AXXI

%y, Ax,,

A=,,

Aye,

A.

and itll) f o r 0 0 < 8 < 900 a r e a v a i l a b l e i n t h e r e s o n a n c e r e g l o n . T K ~ ~

c o u l d and s h o u l d b e supplemented by t 2 0 and t 2 1 r e . g .

The dynamical c a l c u l a t i o n s a r e o f two k i n d s : a ) The m u l t i c h a n n e l s c a t -

t e r i n g t h e o r i e s r e f e r r e d t o i n t h e e l a s t i c channel a l s o p r e d i c t pp-da,

s e e / 5 , 6 , 7 , 2 7 / , - b ) a l s o a v a i l a b l e a r e c a l c u l a t i o n s based on r e l a t i v i -

s t i c p e r t u r b a t i o n t h e o r y /23,26/ ( p i o n r e s c a t t e r i n g and s i n g l e n e u t r o n

exchange w i t h d i s t o r t i o n f a c t o r s a d d e d ) . I n b o t h c a s e s t h e two body

i n f o r m a t i o n (nN-aN, NN-NN, t h e dpn v e r t e x f u n c t i o n e t c . ) i s i n p u t .

T e c h n i c a l l y t h e two approaches a r e v e r y d i f f e r e n t . I n F i g . 3 we show

t h e d i f f e r e n t i a l c r o s s s e c t i o n s . Both t y p e s o f c a l c u l a t i o n d e s c r i b e t h e

s h a p e q u i t e w e l l and i n b o t h c a s e s t h e s i z e o f t h e c r o s s s e c t i o n i s

c o n t r o l l e d by t h e r a n g e p a r a m e t e r i n t h e aNN v e r t e x f u n c t i o n . I n r e f s

/ 5 , 6 / t h e p e r m i t t e d v a l u e s a r e r e s t r i c t e d by c h a n n e l c o u p l i n g and t h r e e

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C2-322 JOURNAL DE PHYSIQUE

0 0.5 1.0 cos ow

F i g u r e 3

D i f f e r e n t i a l c r o s s s e c t i o n s (CM) f o r pp+da compared t o e x p e r i m e n t . The t h i c k s o l i d l i n e s a r e ;he r e s u l t s o f Locher and S v a r c /26/. The t h i n l i n e s a r e f o r i n c r e a s e d t r i p l e t s t r e n g t h , s e e F i g . 4 . The dashed l i n e s a r e t h e r e s u l t s from R i n a t e t a l . /6/ m u l t i - p l i e d by 1 . 5 and i n t e r - p o l a t e d from a d j a c e n t e n e r g i e s where needed.

For t h e d a t a s e e t h e c o m p i l a t i o n s i n /26,31/.

body u n i t a r i t y , t h e a b s o l u t e p r e d i c t i o n s t h e n a r e s l i g h t l y t o o low. I n t h e r e l a t i - v i s t i c c a l c u l a t i o n /23,26/ t h e T N ampli- t u d e s have t o be e x t r a p o l a t e d o f f t h e mass- s h e l l s i n c e t h e r e s c a t t e r e d p i o n i s v i r t u a l . The e x t r a p o l a t i n g p r o c e d u r e which i s used h a s been cross-checked by demanding a s i m u l t a n e o u s d e s c r i p t i o n o f t h e t h r e e body p r o d u c t i o n pp-aNN, s e e /28,29/. Among t h e many s p i n o b s e r v a b l e s m e a s u r e d f o r pp-ad which a l l have been c a l c u l a t e d i n /6,26/

we show t h e r e s u l t s f o r

A=,

which a r e t y - p i c a l ( F i g . 4 ) . Q u a l i t a t i v e l y , t h e c a l c u -

l a t i o n s a g r e e w i t h t h e g e n e r a l t r e n d of t h e d a t a f o r b o t h t y p e s o f t h e o r y . I n r e f . / 2 6 / t h e r e m a i n i n g d i s c r e p a n c y i n A,, ( n o t e t h e f u l l r a n g e i s -1 <

A z Z (

1) h a s been t r a c e d back t o m i s s i n g s t r e n g t h i n t h e t r i - p l e t pp-waves. We c o n c l u d e t h a t t h e most complete c a l c u l a t i o n s t o t h i s d a t e d e s c r i b e t h e d i f f e r e n t i a l c r o s s s e c t i o n q u i t e w e l l b u t t h e f i n e r s p i n dependent p r o p e r t i e s o f t h e r e a c t i o n o n l y t o w i t h i n 1 0 % o f t h e f u l l r a n g e o f t h e r e l a t i v e o b s e r v a b l e s . No v i o l e n t e n e r g y dependence i s p r e d i c t e d by c o n v e n t i o n a l dynamics n o r i s it observed i n any o f t h e s p i n o b s e r v a b l e s measured s o f a r .

W e have mentioned t h a t t h e d a t a s e t i s a l - most complete and w i l l a l l o w f o r a d i r e c t i n v e r s i o n o f o b s e r v a b l e s i n t o h e l i c i t y a m p l i t u d e s a s a f u n c t i o n o f e n e r g y and a n g l e i n t h e n e a r f u t u r e /24/. The program h a s been s t a r t e d by r e c o n s t r u c t i n g t h e O0 and 90° a m p l i t u d e s by A p r i l e e t a l . /30/.

Meanwhile t h e t r a d i t i o n a l a n a l y s i s i n t e r m s

o f p a r t i a l waves h a s a l s o been a t t e m p t e d i n

a number o f p a p e r s . Such a p r o c e d u r e i s

p r e s e n t l y n o t p o s s i b l e w i t h o u t some ( t h e o -

r e t i c a l ) c o n s t r a i n t s . W a t a r i /33/ f l o a t s

a 1 t o a 1 0 ( s e e T a b l e I f o r n o t a t i o n ) and

Lyon p h a s e s f o r h i g h e r p a r t i a l waves. Bugg

e s s e n t i a l l y f l o a t s a 1 t o a 6 , and u s e s

v a r y i n g s t a b i l i s i n g c o n d i t i o n s i n r e f s .

/25,31,32/. F i g . 5 shows t h e Argand p l o t s

f o r a2 ( t h e dominant 1 ~ 2 w a v e ) , f o r a. and

a6 (of medium s i z e ) from t h e f i t s by Bugg

/31,32/ t o g e t h e r w i t h t h e t h e o r e t i c a l p r e -

d i c t i o n of /26/. Argand d i a g r a m s f o r t h e

Watari s o l u t i o n s a r e n o t r e a d i l y comparable

s i n c e a f l o a t i n g phase c o n v e n t i o n f o r c i n g

a2 t o b e r e a l a t a 1 1 e n e r g i e s i s used. H i s

s o l u t i o n s a r e c e r t a i n l y d i f f e r e n t from

Bugg's, comp. T a b l e I. I t i s o b v i o u s t h a t

t h e f i t s a r e n o t y e t s t a b l e b u t t h e r e i s

hope t h a t t h e s i t u a t i o n w i l l improve when

t e n s o r p o l a r i z a t i o n s and s p i n t r a n s f e r ob-

s e r v a b l e ~ w i l l be measured.

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Mad

Azz -0.4

Mad

Azz 1 -

F i g u r e 4

The s p i n c o r r e l a t i o n p a r a m e t e r

A,,

f o r 6 6 - d ~ v e r s u s exper-

iment. Thick s o l i d l i n e s r e f . / 2 6 / , dashed l i n e s /6/.

The t h i n s o l i d l i n e s a r e f o r i n c r e a s e d pp t r i p l e t s t r e n g t h i n o r d e r t o f i t

A,,

and

Ayy

a t 800 MeV /26/.

A

r e c e n t a n a l y s i s of t h e t h r e e body r e a c t i o n pp-aNN h a s been g i v e n i n /29/. The Deck model (one p i o n exchange) w e l l d e s c r i b e s t h e c r o s s s e c - t i o n f o r t h e d i f f e r e n t c h a r g e c h a n n e l s ( F i g . 6 ) e x c e p t f o r a d e v i a t i o n n e a r p~

=

1 . 5 GeV/c. T h i s d i s c r e p a n c y a l s o shows i n t h e i n e l a s t i c l o n g i t u d i n a l c r o s s s e c t i o n d i f f e r e n c e ~ o i n e l which i s dominated by t h e pp-TNN c h a n n e l and s e n s i t i v e t o s p i n t r i p l e t pp c o n t r i b u t i o n s . The d i f - f e r e n c e can be e x p l a i n e d by adding a 3 ~ 3 ( 2 2 3 0 ) r e s o n a n c e w i t h r=120 t o 150 MeV. For p o l a r i z e d d i f f e r e n t i a l c r o s s s e c t i o n s a n a l y s e d a l o n g s i m i l a r l i n e s , s e e /35/. U l t i m a t e l y , a comprehensive a n a l y s i s i n c l u d i n g more complete s p i n i n f o r m a t i o n i n t h i s and o t h e r c h a n n e l s w i l l d e c i d e about t h e c o r r e c t n e s s o f such a p i c t u r e .

4 . DIBARYONS

To a h i g h d e g r e e t h e i n t e r e s t i n ~d r e a c t i o n s o v e r t h e l a s t y e a r s was s t i r r e d by t h e problem of d i b a r y o n r e s o n a n c e s . Numerous s t a t e s i n t h e B=2 s e c t o r have been p r e d i c t e d on t h e b a s i s of bag models / 3 6 , 3 7 / . However, most o f them a r e e x p e c t e d t o be v e r y broad and hence d i f f i c u l t t o o b s e r v e , p a r t i c u l a r l y s i n c e t h e c o u p l i n g t o d e u t e r o n c h a n n e l s i s presumably v e r y s u p p r e s s e d due t o poor o v e r l a p w i t h s i x q u a r k s t a t e s /38/. On t h e o t h e r hand, some of t h e s e s t a t e s might be t r u l y e x o t i c

(hidden d o l o r ) and narrow T < 2 0 MeV ( w i t h no c o u p l i n g t o N N , e . g . 1 .

Broad s t a t e s (l?>120 MeV), l i k e t h e Argonne c a n d i d a t e s i n pp s c a t t e r i n g ,

a r e presumably p r e s e n t i n ad r e a c t i o n s . I n Sec. 2 and 3 we have shown

s o l u t i o n s which a r e c o n s i s t e n t w i t h c o n t r i b u t i o n s from 3 ~ 3 ( 2 2 3 0 ) and

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C2-324 JOURNAL D E PHYSIQUE

P$iRTI&L pp STATE BUGG BUGG WATARI LYON BLANK- L-S

WAVE AND L, I1 I11 LEIDER

The partial waves a1 to a6 for pp+dn corresponding to the fits /31,32, 33/ and the calculations /5,7,26/, respectively. (Upper figure real part, lower figure imaginary part). Conventions and (phase rotated) values for Watari /33/ as in Bugg /25/. The numbers for Lyon /5/ and Blankleider /7/ are from table 4 in /34/. For the conversion of Locher and &arc (L6) /26/ see Fig. 5 caption.

l ~ ~ ( 2 4 8 0 ) . Note, however, that resonance loops driven by the NA inter- mediake state must be considered as trivial background (mostly in the 1~~ wave). Moreover, these broad states are certainly describable both in the eonventional language involving colorless (heavy) meson exchange or in hybrid models /39,40/ where the interior is described by bag mo- dels and quarks (unfortunately the predictive power of these models is quite limited since the relation to the underlying QCD lagrangian is very loose). As far as the deuteron itself is concerned there are des- criptions for scattering at high momentum transfers /41,42/ which re- quire genuine 6-quark admixtures in the wave function. In all this, however, there is always the danger of identifying deficiencies of con- ventional descriptions with exotic dynamics.

A more direct evidence for exotic dynamics would be the discovery of truly narrow structures (r<10 to 20 MeV) in the B=2 sector. Unfortu- nately, several finely meshed searches were not successful. See the 900 excitation function for ad+pp and the analysing power Ayo(180) in

$d+p(pn) /43/ or the scan of np total cross sections between 50 and

800 MeV /44/. Some positive indications exist as well: we have men-

tioned the possibility of a narrow structure in t20 for nd elastic

scattering (and some difficulties of interpretation). Narrow structures

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F i g u r e 5

Argand p l o t s f o r t h e p a r t i a l waves a,, a2

S

and a6 f o r pp+dv (no-

t a t i o n a s i n t a b l e I ) . The c u r v e s marked I1 _and 111 a r e t h e f i t s by Bugg /31/ and / 3 2 / , r e s p e c t - i v e l y , u s i n g h i s normal- i z a t i o n . ( H i s f i t r e f . /25/ i s n o t shown) . ^The

c o n v e r s i o n of t h e t h e o - r e t i c a l p r e d i c t i o ; ~ f o r

@J of Locher and Svarc /26/ (marked LS) i n t o t h e p a r t i a l waves TJ

( o r a i ) of Bu g i s g i v e n by + J= (N/n) T3 where N

=

-87~2s1/2/ (mp1l2k1/2) p and k a r e t h e cm mo- menta o f p r o t o n and p i o n , r e s p e c t i v e l y . The Born t e r m s i n /26/ a r e r e a l and t h e minus s i g n above h a s been chosen t o make I m a 2 > 0 , s i m i l a r t o Bugg. Within t h i s con- v e n t i o n a c o n s t a n t over- a l l phase f a c t o r i n t h e f i t s c o u l d s t i l l be a d j u s t e d . The e n e r g i e s a r e marked i n t h e s e n s e of t h e a r r o w s , by c r o s s e s f o r Bugg (Tp=451, 493, 533, 578, 650, 700, 750, 800 MeV) and by d o t s f o r Locher and .&arc

(Tp=400, 451, 510, 578, 647, 799 MeV), r e s p e c t i v e l y .

i n t h e i n v a r i a n t np mass have been r e p o r t e d f o r dp+p(np) and f o r dp-pnna /45,46/. Some o f t h e s e measurements a r e i n c o n f l i c t w i t h /47/.

S i g n a l s have a l s o been s e e n i n p 3 ~ e - t . d ~ / 4 8 / . F i n a l l y t h e i n v a r i a n t pp

mass i n y d - ( p p ) n - might have some narrow s t r u c t u r e /49/. A l l t h e s e

e x p e r i m e n t s need c o n f i r m a t i o n . E s t a b l i s h i n g a narrow r e s o n a n c e i n t h e

B=2 system would be t r u l y e x c i t i n g and d e s e r v e s a c o n c e r t e d e f f o r t .

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C2-326 JOURNAL DE PHYSIQUE

F i g u r e 6

T o t a l c r o s s s e c t i o n f o r pp+rNN from t h e Deck model c a l c u l a t i o n /29/ compared t o e x p e r i m e n t .

Acknowledgement - I am g r a t e f u l t o A l f r e d & a r c f o r numerous d i s - c u s s i o n s and h e l p i n t h e p r e p a r a t i o n of t h e f i g u r e s .

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