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POLARIZATION OBSERVABLES AND HIGH
MOMENTA IN THE DEUTERON WAVE FUNCTION
M. Garçon
To cite this version:
M. Garçon. POLARIZATION OBSERVABLES AND HIGH MOMENTA IN THE DEUTERON WAVE FUNCTION. Journal de Physique Colloques, 1990, 51 (C6), pp.C6-61-C6-69.
�10.1051/jphyscol:1990605�. �jpa-00230868�
POLARIZATION OBSERVABLES AND HIGH MOMENTA IN THE DEUTERON WAVE FUNCTION
M. GARCON
Service d1Exp6rimentation en Physique NucleJaire, CEN Saclay, F-91191 Gif sur Yvette Cedex, France
Resume
-
Des experiences recentes de p o l a r i s a t i o n donnent un j o u r nouveau S l ' e t u d e de m u c t u r e du deuton. Des mesures de p o l a r i s a t i o n t e n s o r i e l l e en d i f f u s i o n e l a s t i q u e electron-deuton permettent pour l a premicre f o i s l a separation des f a c t e u r s de forme 61 e c t r i ques monopolai r e e t quadrupol a i re. La cassure de deutons p01 a r i ses, hadronique e t Electromagnetique, d e v r a i t conduire b i e n t B t S l a determination du r a p p o r t D/S en f o n c t i o n de l ' i m p u l s i o n i n t e r n e du deuton.A b s t r a c t
-
We w i l l review r e c e n t progress i n t h e measurements o f p o l a r i z a t i o n obser- vables, t h e i r t h e o r e t i c a l i n t e r p r e t a t i o n and t h e new i n s i g h t they give on t h e h i g h momentum behaviour o f the deuteron wave f u n c t i o n . New r e s u l t s i n e l a s t i c e l e c t r o n - deuteron s c a t t e r i n g a l l o w f o r t h e f i r s t time the separation o f t h e charge monopole and quadrupole e l e c t r i c form f a c t o r s o f t h e deuteron. P o l a r i z e d deuteron break-up, both hadronic and electromagnetic, should y i e l d i n t h e near f u t u r e the D/S r a t i o as a func- t i o n o f t h e deuteron i n t e r n a l momentum.I
-
INTRODUCTIONThe deuteron s t r u c t u r e i s r a t h e r w e l l known f o r r e l a t i v e distances between neutron and p r o t o n l a r g e r than 1 fm, t h a t i s f o r i n t e r n a l momenta smaller than 200 MeV/c. A d e s c r i p t i o n o f t h e deuteron i n terms o f two nucleons allows one t o study t h e nucleon-nucleon p o t e n t i a l i n a com- plementary way compared t o the i n f o r m a t i o n e x t r a c t e d from NN s c a t t e r i n g : one i S a1 so sensi
-
t i v e t o t h e o f f - s h e l l behaviour o f the p o t e n t i a l . I n f a c t , i n many instances, t h e two nucleon p i c t u r e o f the deuteron seems t o work up t o 500 !ieV/c o r above. S t i l l a t these h i g h momenta, o r s h o r t distances, our d e s c r i p t i o n o f t h e deuteron s t r u c t u r e i s n o t unique : one may add o t h e r degrees o f freedom, namely baryon resonances o r quarks, and n o t change considerably t h e d e s c r i p t i o n o f the observables. Furthermore, some non r e l a t i v i s t i c c a l c u l a t i o n s seem adequate t o s u r p r i s i n g l y h i g h momenta. I n r e l a t i v i s t i c c a l c u l a t i o n s , t h e choice o f the dynamics, as w e l l as t h e necessary approximations, are a l s o n o t unique. I n these conditions, only through p r e c i s e experiments, as we1 l as r e f i n e d and c o n s i s t e n t c a l c u l a t i o n s , can our knowledge pro- gress.
We w i l l s t a r t w i t h some d e f i n i t i o n s and n o t a t i o n s :
I n presence o f a t e n s o r i n t e r a c t i o n , t h e Schrodinger equation f o r t h e neutron-proton i s equiv- a l e n t t o a s y s t e m o f two c o u p l e d equations, the s o l u t i o n s o f which a r e u ( r ) and w ( r ) ( o r U,
and U,), t h e S and D components o f t h e d e u t e r o n w a v e - f u n c t i o n . This wave f u n c t i o n can be w r i t t e n , f o r a given s p i n s t a t e M :
pp -
ifnThe conjugate v a r i a b l e o f
f
=tp - tn
i s =-.
2 By a F o u r i e r t r a n s f o r m of yM, one d e f i n e s :
I n the momentum range of 200-500 MeV/c on which we w i l l concentrate, t h e S-wave component i s expected t o e x h i b i t a node (Fig. 1). A1 l cross-section measurements ( i n ed e l a s t i c as we1 l as deuteron break-up) w i l l be s e n s i t i v e mostly t o t h e dominating D-wave component. A d e t a i l e d knowledge o f t h e S-wave behaviour i s however o f the utmost importance : i t s node i s character- i s t i c o f the short-range r e p u l s i o n o f t h e M-N i n t e r a c t i o n , and i t s p r e c i s e behaviour c o u l d c o n t a i n i n f o r m a t i o n about non-nucleonic degrees o f freedom. Thus one has t o perform neasure- ments of p o l a r i z a t i o n observables t o separate t h e S and D-waves.
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1990605
COLLOQUE DE PHYSIQUE
Fig. 1
-
p ( p ) = u 2 ( p ) + w2(p)-
A(qi) = G$+ g o 2
66 + $ v & , $-
adapted from /l/The same reasonning a p p l i e s t o t h e electromagnetic form f a c t o r s , t h e deuteron being o f s p i n 1, i t s e l e c t r o m a g n e t i c s t r u c t u r e i s described by t h r e e form f a c t o r s : GC ( e l e c t r i c monopole, o r c h a r g e ) , GQ ( e l e c t r i c q u a d r u p o l e ) a n d Gb, ( m a g n e t i c d i o l e
.
Cross-section measurements i n2 2 2 2
e l a s t i c e-d s c a t t e r i n g determine C$, on one hand, and GC
+ Q
on the o t h e r hand (, = q /4m,
and q i s the 4-momentum t r a n s f e r ) . The measurement o f anoyher independent observable, depend- i n g upon p o l a r i z a t i o n , i s necessary t o f u r t h e r separate GC and G Whatever t h e model i n t e r - p r e t a t i o n o f these form f a c t o r s , t h i s separation i s fundamental T o completely determine the deuteron electromagnetic s t r u c t u r e . The observable which most conveniently a1 lows t h i s separa- t i o n i s :
which i s a measure o f t h e alignement o f the r e c o i l deuteron, t h a t i s a measure o f the probabi- l i t y o f t h e deuteron o f being i n s t a t e M = 0 as opposed t o s t a t e s M = 2 1, the q u a n t i z a t i o n a x i s being chosen along t h e deuteron d i r e c t i o n . A1 t e r n a t i v e l y
,
t h i s measurement can be done w i t h the use o f a tensor p o l a r i z e d t a r g e t .Whenever one can n e g l e c t t h e magnetic c o n t r i b u t i o n &forward angles and Gfi much s m a l l e r than G: and n 2 ~ $ ) , t 2 o depends o n l y on t h e r a t i o X =
2 19
:GC
W 1
Of p a r t i c u l a r i n t e r e s t i s t h e p o s i t i o n o f t h e node o f GC, determined by X + : tno =
- - .
~5
To g a i n more i n s i g h t i n t o t h e d e s c r i p t i o n o f t h e observables, and i n t o t h e l i n k between t h e electromagnetic form f a c t o r s and t h e momentum d i s t r i b u t i o n , i t i s u s e f u l t o consider t h e im- p u l s e approximation ( I A ) .
1) El a s t i c e l e ~ t r o n ~ d e u t e r o n s c a t t e r i n g The d wave f u n c t i o n i s t e s t e d a t r e l a t i v e momentum
4
between t h e two nucleons.The e l e c t r i c form f a c t o r s have t h e f o l l o w i n g expression :
where f+S(q) i s t h e i s o s c a l a r combination o f t h e neutron and p r o t o n e l e c t r i c form f a c t o r s (GES
= GE,
+
GE,). I n t h e r a t i o X, and t h e r e f o r e i n t 2 0 , t h e dependence upon GE,
which i s n o t sor n
we1 l known, disappears. Even when going beyond the impulse approximation, a l l c a l c u l a t i o n s have shown t h a t t h e dependence o f t20 on GE, i s extremely small up t o 5 fm-l, i n c o n t r a s t w i t h t h e s t r u c t u r e f u n c t i o n s A and B ( B = A q ( 1 v)Gk).
3
Z)p(a,$p)n The n e u t r o n i s s p e c t a t o r and t h e r e a c t i o n i s e q u i v a l e n t t o a q u a s i - f r e e pp e l a s t i c s c a t t e r i n g . The wave f u n c t i o n
#
_----_ - _
i s t e s t e d a t momentum3
w i t h r e s p e c t t o t h e deuteron. - .
,' NN scatterins\'\.
c e n t e r o f mass(3
= 4/21:-
\0 'I The cross s e c t i o n i s p r o p o r t i o n a l t o t h e f r e e pp cross s e c t i o n ( w i t h an ambiguity on t h e passage from an o f f -
/
f s h e l l p r o t o n t o an on-she1 l one) and t o t h e p r o b a b i l i t y
I p t o f i n d a nucleon w i t h an i n t e r n a l momentum p.
.
The p o l a r i z a t i o n observables, s t i l l i n IA, a l l o w t e W( P9 s e p a r a t i o n o f U and W a t each value o f p. With z =
-
u ( p ) ' one g e t s :
Tensor analyzing power :
Vector a n a l y z i n g power : Ay =
3
PNN P O ( z ) ( 3 )PNN + Po(z)DNN P o l a r i z a t i o n o f t h e forward s c a t t e r e d p r o t o n : P =
1 + PO(z/PNN
l
' -
z i s the (p-dependent) p o l a r i z a t i o n o f the proton w i t h i n t h e pola- where P o ( z ) = , L , 2I '
r i z e d d e u t e r o n , PNN ;nd DDN a r e r e s p I c t i v e 1 y t h e p o l a r i z a t i o n and d e p o l a r i z a t i o n o f e l a s t i c p r p s c a t t e r i n g . Note t h e siml a r i t y between formulae ( 1 ) and (2).
The t h r e e observables a l l determine t h e r a t i o z ( p ) and are thus redundant w i t h i n IA. O f course r e s c a t t e r i n g c o r r e c t i o n s w i l l have t o be considered, b u t then t h e measurement o f a l l these observables should g i v e a reasonable handle on the v a r i o u s c o r r e c t i o n s . The disadvantage of d e a l i n g w i t h hadronic probes and w i t h a more complicated r e a c t i o n mechanism i s here counter- balanced by the f a c t t h a t one can measure many more observables, w i t h h i g h e r s t a t i s t i c a l pre- c i s i o n , than i n t h e case o f e l e c t r o n s c a t t e r i n g .
S i m i l a r expressions can be d e r i v e d i n t h e case of i n c l u s i v e break-up /2/ and o f e l e c t r o d i s i n - t e g r a t i o n /3/.
COLLOQUE DE PHYSIQUE
I 1 1
-
EXPERIMENTAL RESULTSTensor Polarization
t,,
( P a r i s , 8,. 7 0 " )
0
0 + N -
v - , -
1) P o l a r i z a t i o n measurements i n e l a s t i c e-d s c a t t e r i n g :
(D -
The tensor p o l a r i z a t i o n has been measured r e c e n t l y i n two experiments, one a t VEPP-3 (USSR) u s i n g a p o l a r i z e d atomic beam i n an i n t e r n a l storage c e l l /4/, and t h e o t h e r a t Bates (USA) u s i n g t h e d e t e c t o r AHEAD (A1 b e r t a High E f f i c i e n c y Analyzer f o r .Deuterons) t o determine t h e p o l a r i z a t i o n o f the r e c o i l deuteron /5/. The l a t e r i s reaching momentum t r a n s f e r s where one i s indeed s e n s i t i v e t o t h e t h e o r e t i c a l d e s c r i p t i o n o f the form f a c t o r s . A d e s c r i p t i o n o f t h i s experiment can be found i n /6/. The p r e l i m i n a r y r e s u l t s are displayed on Fig. 2, where the e r r o r s bars represent s t a t i s t i c a l and systematic e r r o r s added i n quadrature.
Ue are now i n a p o s i t i o n t o perform f o r t h e f i r s t time a meaningful experimental s e p a r a t i o n o f t h e monopole and quadrupole form f a c t o r s o f t h e deuteron. The s e t o f 3 equations (A, B, t = f ( G
,
G,
GM) can e a s i l y be i n v e r t e d . F o r A and B, we use parametrizations ( p i o v i d e d gy S.~ 1 a F c h t g v ) of the w o r l d data, and we n e g l e t t e r r o r s ( t h e e r r o r s on GC and GQ come mostly from t h e tZ0 measurements). Since the equations are quadratic, t h e r e are i n general two s o l u t i o n s f o r
(GC,
Go);a c o n t i n u i t y requirement t o the values a t q = 0 i s s u f f i c i e n t t o s e l e c t-
t h e pro- -I 2 3 4 5 6
q ( f r n - l )
Fig. 2
-
eci e l a s t i c-
t,, ; empty c i r c l e s : N o v o s i ~ i r s k /7/ ; f u l l c i r c l e s : Bates-Argonne /8/ ; empty squares: Novosibirsk-Argonne /4/ ; f u l l squares: Bates-AHEAD /5/ ( p r e l i m i n a r y r e s u l t s ) ; see t e x t f o r t h e curves.-
p e r s o l u t i o n ; we a l s o assumed a c o n t i n u i t y o f t h e d e r i v a t i v e dGC/dq a t t h e p o i n t tZ0 =
- fi
where t h e two s o l u t i o n s cross each other. The r e s u l t s are i l l u s t r a t e d i n Fig. 3. Note t h a t GC i s determined w i t h i t s sign, so t h a t one can conclude, from our re1 im i n a r y r e s u l t s , t o t h e e x p e r i m e n t a l o b s e r v a t i o n o f t h e node o f GC a t 4.45
*
0.15 fin-!. GQ does n o t b r i n g any new i n f o r m a t i o n around 4 fm-' since i t i s completely determined by A.I
2) Exclusive hadronic break-up, dp + ppn (LNS experiment # 145) :
I I
The 2 GeV p o l a r i z e d deuteron bean) o f Saturne was sent on a l i q u i d hydrogen target. The f a s t forward p r o t o n was detected a t 18" i n t h e magnetic spectrometer SPES4 and i t s p o l a r i z a t i o n measured . w i t h t h e new p o l a r i m e t e r POMME /9/ l o c a t e d on t h e f o c a l plane. The slow p r o t o n was
-
Fig. 3
-
GC ; same p o i n t s as f i g u r e 2 ; t h e curve i s t o guide t h e eye.-
\
\
\
- , [\
/i I
detected i n coincidence i n a r e c o i l spectrometer c o n s i s t i n g o f 2 w i r e chambers and an a r r a y o f 7 A E and 28 E s c i n t i l l a t o r s ( s c a t t e r i n g angle 57 i4.2 deg., azimuth k 8 deg.)
.
I I I I
V
(3
I
- I
I O - ~
-to'3
0 %%.-. -. -
The p r e l i m i n a r y r e s u l t s o f t h e a n a l y z i n g powers A (Fig. 4) and Ay show s t r o n g d e v i a t i o n s from 'the I A as o f 150 fdeV/c. This can q u a l i t a t i v e l y 'ge accounted f o r by p r e l i m i n a r y c a l c u l a - t i o n s o f 0. Grebenyuk t a k i n g i n t o account r e s c a t t e r i n g o r FSI, i g n o r i n g i n t e r m e d i a t e pions o r d e l t a s (3N-only graphs). We a n t i c i p a t e t h a t the p r o t o n p o l a r i z a t i o n measurement w i l l h e l p f i x i n g the r e a c t i o n mechanism ( t h e s p i n - f l i p p r o b a b i l i t y i s p a r t i c u l a r l y s e n s i t i v e t o rescat- t e r i n g ) so t h a t u s e f u l i n f o r m a t i o n on t h e D/S r a t i o as a f u n c t i o n o f p can be extracted.
-
3) I n c l u s i v e hadronic break-up dp + pX, o r dA + pX :
3 6 4 4.4 4.8
q(frn-11
I I I I I
T h i s r e a c t i o n was s t u d i e d w i t h t h e 7.3 GeV p o l a r i z e d d beam a t Dubna by the ALPHA c o l l a b o r a t - i o n and w i t h t h e 2.1 GeV beam a t Saturne (Lids experiment $202). The cross s e c t i o n s were found t o e x h i b i t a shoulder around p = 350 MeV/c f o r both i n c i d e n t energies and f o r many d i f f e r e n t t a r g e t s . Ploreover the tensor analyzing power TZ0 was shown t o be independent on energy and t a r g e t nature /2/. Therefore i t was assumed t h a t t h e observables were a d i r e c t r e f l e x i o n o f t h e deuteron s t r u c t u r e . Since the data c o u l d n o t be explained by a formula o f type ( 2 ) w i t h any conventional 2-nucleon deuteron wave f u n c t i o n , one had t o add ( w i t h i n t h e IA) a 6 quark component t o t h e deuteron. One then obtained an S-wave momentum d i s t r i b u t i o n w i t h o u t a node.
COLLOQUE DE PHYSIQUE
F i g . 4
-
2 GeV/c.
( f o r m u l a
F i g . 5
-
f r o m I A .
- - c - -
l -
I.A. 1.6 QeV/c1 :
.G-
2.0 QeV/c , II
k (GeV/c)
Ayy f o r Or, + ppn a t 2 GeV ; f a s t p r o t o n angle 18", momenta 1.6 GeV/c, Dashed curves t o guide t h e eye. ( P r e l i m i n a r y ) . F u l l c u r v e f r o m impulse (1) and P a r i s d-wave f u n c t i o n ) .
- v . .
k
(GeVlc 1
d
+
12C + p+
X a t 9 GeV/c (ep=OO) /10/. K p o l a r i z a t i o n t r a n s f e r c o e f f i cl. 8 GeV/c and a p p r o x i m a t i o n
. i e n t . Curves
However, one should n o t r e l y on I A t o draw such conclusions. F i r s t i t i s c l e a r now t h a t an S wave f u n c t i o n w i t h o u t a node i s incompatible w i t h t h e new Bates data i n ed s c a t t e r i n g /5/.
Also some c a l c u l a t i o n s /2,11/ o f r e s c a t t e r i n g and f i n a l s t a t e i n t e r a c t i o n s w i t h o n l y 3-nucleon graphs were performed t o e x p l a i n e x i s t i n g data b u t have had l i m i t e d success i n doing so. An- o t h e r one /12/, i n c l u d i n g i n t e r m e d i a t e pions and i n e l a s t i c elementary NN cross-sections, i s a b l e t o reproduce the main f e a t u r e s o f t h e Dubna data, t h a t i s t h e enhancement i n t h e cross- s e c t i o n a t 350 MeV/c and t h e r e l a t i v e l y shallow minimum o f T2 (as i l l u s t r a t e d i n Fig.5).
I t would be i n t e r e s t i n g t o check whether t h a t same c a l c u l a t i o n aqso e x p l a i n s t h e Saturne data and thus r e s o l v e t h e puzzle o f the u n i v e r s a l behaviour r e f e r r e d t o hereabove.
I V
-
MODEL INTERPRETATIONS OF GC and t,,As demonstrated above, t h e new Bates-AHEAD data a l l o w a separation o f the two e l e c t r i c form f a c t o r s o f t h e deuteron. Any model o r theory o f the deuteron s t r u c t u r e and i t s electromagnetic c u r r e n t should describe e q u a l l y we17 a l l t h r e e form f a c t o r s , o r e q u i v a l e n t l y A, 8, and t,9.
T h e o r e t i c i a n s w i l l f i n d i t more u s e f u l t o compare t h e i r c a l c u l a t i o n s d i r e c t l y t o t h e i n d i v i - dual form f a c t o r s , thus g a i n i n g more p h y s i c a l i n s i g h t . We w i l l i l l u s t r a t e t h e s i g n i f i c a n c e o f t h e new Bates data on
k , ,
b u t one should bear i n mind t h a t i n most instances, t h e magnetic form f a c t o r /13/ i s a l s o very s e n s i t i v e t o t h e d e t a i l o f the dynamics and o f t h e deuteron s t r u c t u r e .When i n c l u d i n g meson-exchange c u r r e n t s (MEC) and some re1 a t i v i s t i c c o r r e c t i o n s , t h e non- r e 1 a- t i v i s t i c NN c a l c u l a t i o n s o f t h e form f a c t o r s y i e l d very s i m i l a r p r e d i c t i o n s f o r tZ0, f o r most r e a l i s t i c p o t e n t i a l s . One would need a t z o < 0.1 a t 5 fm-l t o d i s c r i m i n a t e between P a r i s and Argonne p o t e n t i a l s , f o r example. One exception i s t h e " f u l l " Bonn p o t e n t i a l /14/, f o r which however a r i g o u r o u s treatment o f t h e energy dependence i s needed /15/.
I n s p i t e o f 20 years o f a c t i v e work, t h e i s o s c a l a r MEC are s t i l l uncertain. Recently, a reeva- l u a t i o n o f MEC (pny and way graphs) was performed i n a r e l a t i v i s t i c approach c o n s i s t e n t w i t h NN dynamics ( w i t h i n OBE model ) /16/. The p ~ y c o n t r i b u t i o n was found s i g n i f i c a n t l y s m a l l e r than i n previous n o n - r e l a t i v i s t i c c a l c u l a t i o n s and the way term was proven t o be important. The r e s u l t f o r t2, a r e i n agreement w i t h our p r e l i m i n a r y data.
Other r e l a t i v i s t i c c a l c u l a t i o n s /17/, which d i f f e r by some choices i n the NN dynamics ( l i g h t - f r o n t form vs i n s t a n t form) and by various approximations, g i v e a reasonable d e s c r i p t i o n of t h e form f a c t o r s , which l e d some authors t o conclude t h a t t h e r e was no need t o consider MEC. A f u l l y c o n s i s t e n t approach o f MEC w i t h i n r e l a t i v i s t i c models i s needed before a d e f i n i t e con- c l u s i o n can be drawn on t h i s respect.
AA components i n the wave f u n c t i o n have been considered i n coupled channel c a l c u l a t i o n s . I n a boundary c o n d i t i o n model /18/, t2, i s n o t very s e n s i t i v e t o t h e balance between d i f f e r e n t AA channels, b u t our data favours, w i t h i n t h i s model, the s m a l l e s t " r a d i u s o f asymptotic f r e e - dom", o r bag r a d i u s . I n another model /19/ w i t h a s m a l l e r amount o f AA s t a t e i n t h e deuteron (0.36 % compared t o 2 % f o r t h e previous one) t h e e f f e c t o f i s o b a r s on t h e observable t2, i s n e g l i g i b l e up t o q = 6 fm-l.
One c l e a r i m p l i c a t i o n o f t h e observation o f t h e node o f
GC
i s t h a t "naive" quark models, where one adds by hand" a 6q component t o t h e deuteron /20/ do n o t work, since they would imply t h a t t remains l a r g e and n e g a t i v e as shown i n Fig. 2. On t h e o t h e r hand c a l c u l a t i o n s w i t h Quark t f u s t e r Models /21/ o r a H y b r i d Quark-Hadron model /22/ show t h e same behaviour f o r t as conventional NN c a l c u l a t i o n s , so t h a t quark degrees o f freedom (which i n some cases can6;
expressed as a 2 t o 3 % p r o b a b i l i t y o f a 6q c o n f i g u r a t i o n i n t h e deuteron) would have l i t t l e e f f e c t s on the observables.
F i n a l l y i t i s a l s o c l e a r t h a t p e r t u r b a t i v e QCD, which p r e d i c t s a
-
J? a t very h i g h q, i s s t i l l f a r (we a1 r e a d y knew i t from t h e observation o f a d i f f r a c t i v e minimum i n /13/) and t h a t no simple p r e s c r i p t i o n as t o how t h e t r a n s i t i o n t o t h e p e r t u r b a t i v e regime s e t s i n can even be guessed /23/.5
-
COIJCLUSIONSThe new tZ9 data i n ed s c a t t e r i n g , though s t i l l p r e l i m i n a r y , shows unambiguously t h e existence o f a node i n t h e charge form f a c t o r o f t h e deuteron. We have discussed t h e main aspects o f t h e
C6-68 COLLOQUE DE PHYSIQUE
comparison o f these data w i t h v a r i o u s c l asses o f model S. More p r e c i s e comparisons w i t h speci- f i c models remain t o be done when t h e f i n a l data w i l l be a v a i l a b l e .
More t,, data c o u l d be obtained i n t h e n e x t few years, b u t t e c h n i c a l progress i n t h i s f i e l d , though spectacular, i s always t o o slow i n regard o f t h e t h e o r e t i c a l i n t e r e s t . For a q u a n t i t a - t i v e comparison o f t h e d i f f e r e n t experimental approaches t o t h i s measurement, t h e reader i s r e f e r r e d t o r e f ./6/.
High energy p o l a r i z e d deuteron hadronic break-up i s promising t o e x t r a c t , as a f u n c t i o n o f i n t e r n a l momentum, t h e r a t i o o f D over S components o f t h e wave f u n c t i o n . The complications which a r i s e from t h e hadronic i n t e r a c t i o n a r e n o t mastered a t t h e present, b u t t h e o r e t i c a l c a l c u l a t i o n s are i n progress and t h e i n c r e a s i n g number o f p01 a r i z a t i o n observabl es being meas- u r e d should c o n s t r a i n them.
The n e x t experimental achievement t o be expected i n t h i s f i e l d i s t h e measurement o f t h e ten- s o r analyzing power i n d(e,elp)n r e a c t i o n . Since already, t h e r e i s a good confidence t h a t t h e momentum d i s t r i b u t i o n p ( p ) up t o 500 MeV/c was r i g h t l y e x t r a c t e d from c r o s s - s e c t i o n measure- ments /24/ w i t h t h e o r e t i c a l c o r r e c t i o n n o t exceeding 50% /25/, t h e t e n s o r a n a l y z i n g power should g i v e almost unambiguously t h e D/S r a t i o .
I w i l l f i n i s h w i t h a s p e c i a l acknowledgement t o a l l my colleagues :
"t,," c o l l a b o r a t i o n a t Bates (A1 berta, CALTECH, IUCF, MIT, Saclay, Syracuse, Worcester) : L. Antonuk, J. Arvieux, D. Beck, E. Beise, A. Boudard, E.B. Cairns, J.M. Cameron (spokes person), G. Dodson, K. Dow, M. Farkhondeh, H.W. F i e l d i n g , J. Flanz, M. G a r ~ o n (sp.), R. Goloskie, S. ~ l i b r i t e n , J. Jourdan, S. Kowalski, C. Lapointe, W.J. McDonald, B. Ni, D. Pham, R. Redwine, N Rodning, G. Roy, M.E. Schulze, P.A. Souders, J. Soukup, I. The ( t h e s i s ) W. Turchinetz (sp.), G. van den Steinhoven, J. Wagner, C.F. Williamson, K. Wilson, S. Wood and W. Z i e g l e r .
"Cassure du deuton" c o l l a b o r a t i o n a t SATURNE (LNPI-Gatchina, Sac1 ay, CRIP-Budapest, W i l l iam &
Mary college, V i r g i n i a ) :
S.L. B e l o s t o t s k y (sp.), H.C. Bhang, M. Boivin, B. Bonin, A. Boudard (sp.), J. Ero, Z. Fodor, M. Gar~on, L. Kudine, P. Koncz, R. Lombard, B. Mayer, V.N. N i k u l i n , C.F. P e r d r i s a t , V. Punjabi, Z. Seres, Y. Terrien, E. Tomasi-Gustafsson, J. Yonnet and M. Youn ( t h e s i s ) . REFERENCES
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