MEASUREMENT OF n-p AND p-p ASYMMETRY WITH ACCELERATED POLARIZED DEUTERON BEAM

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MEASUREMENT OF n-p AND p-p ASYMMETRY WITH ACCELERATED POLARIZED DEUTERON

BEAM

J. Bystricky, J. Deregel, F. Lehar, A. de Lesquen, L. van Rossum, J .M.

Fontaine, F. Perrot, J. Arvieux, T. Hasegawa, C. Newsom, et al.

To cite this version:

J. Bystricky, J. Deregel, F. Lehar, A. de Lesquen, L. van Rossum, et al.. MEASUREMENT OF n-p

AND p-p ASYMMETRY WITH ACCELERATED POLARIZED DEUTERON BEAM. Journal de

Physique Colloques, 1985, 46 (C2), pp.C2-463-C2-466. �10.1051/jphyscol:1985256�. �jpa-00224571�

MEASUREMENT O F n - p AND p - p ASYMMETRY WITH ACCELERATED POLARIZED DEUTERON BEAM

J . Bystricky, J . Deregel, F. Lehar, A. de Lesquen, L. Van Rossum, J.M. Fontaine

+

, F. P e r r o t

+

. J . Arvieux

+ +

, T. Hasegawa

++

, C.R. Newsom

++

, H. Azaiez* and A. Penzo**

DPhPE, CEN-Saalay, France

+

DPhN/ME, CEH-Saclay, France

•^LNS, CEN-Saolay, France LAPP, Annecy, France

**INFN

J

Trieste, Italy

Abstract - The analyzing power for n-p e l a s t i c s c a t t e r i n g a t 725 MeV was de- termined by measuring the r a t i o of n-p to p-p analyzing powers with 1450 MeV polarized deuterons from SATURNE I I and using the p-p analyzing power as r e - ference. The nucleon p o l a r i z a t i o n in deuterons determined from the asymmetry 6

p p

agrees well with the value expected from d i r e c t measurement of the deute- ron beam vector p o l a r i z a t i o n .

We have determined the analyzing power for n-p e l a s t i c s c a t t e r i n g by measuring simul- taneously p-p and n-p s c a t t e r i n g with quasi-free neutrons and protons in the SATURNE I I polarized deuteron beam incident on the NN beam l i n e polarimeter. The analyzing power A

o o l i o

(n-p) i s obtained d i r e c t l y by multiplying t h e measured r a t i o e<L / 6 * by the known analyzing power A

Q O n 0

(p-p)• The method takes advantage of the f a c t t h a t protons and neutrons in polarized deuterons have the same p o l a r i z a t i o n s . The r e s u l - ting systematic u n c e r t a i n t i e s of A

o o n o

(n-p) a r e e s s e n t i a l l y only those due to t h e u n c e r t a i n t y on A (p-p) .

J

oono

r r

The measurements presented here were carried out with the 1450 MeV polarized deuteron beam and a r e compared with those obtained with the 725 MeV polarized proton beam.

F i r s t we have studied t h e counting r a t e s (Fig. 1) and asymmetries (Fig. 2) a s func- t i o n of A 9

r e c

= & - 9

CO

ni , • Here 8 i s the angular p o s i t i o n of the r e c o i l arm and 9

c o n

j

#

i s the conjugate angle for p-p e l a s t i c s c a t t e r i n g with respect to the forward arm p o s i t i o n a t 20.9° .

E l a s t i c p-p (n-p) s c a t t e r i n g of quasi free protons (neutrons) a r e shown in F i g . l b ( c ) . We observe p r a c t i c a l l y no difference in the width of t h e peaks corresponding to s c a t t e r i n g on hydrogen. The counting r a t e s from the carbon t a r g e t a r e e s s e n t i a l l y the same for free and quasi-free incident protons but the hydrogen effect for quasi-free protons i s only about 2/3 of t h a t for free proton beam. The r e l a t i v e r a t e s of hydro- gen and carbon events for quasi-free protons and quasi-free neutrons r e f l e c t t h e efficiency of 4 to 5 per cent of the neutron d e t e c t o r s .

The measured asymmetries for two opposite beam p o l a r i z a t i o n s a r e shown in F i g . 2 . The Figure shows also the asymmetries 6

p

n , 6fL, and £JL for s c a t t e r i n g on free t a r g e t protons, calculated from the normalized CH2 - C d i f f e r e n c e . In measurements

Résumé - Le pouvoir d'analyse pour l a diffusion n-p é l a s t i q u e à 725 MeV a été déterminé d ' a p r è s l a mesure du rapport des pouvoirs d'analyse n-p et p-p avec un faisceau de 1450 MeV de deutons p o l a r i s é s e x t r a i t de SATURNE I I et en u t i - l i s a n t l e pouvoir d'analyse p-p comme base. La p o l a r i s a t i o n des nucléons dans l e s deutons déterminée à p a r t i r de l ' a s y m é t r i e p-p e s t en bon accord avec l a valeur obtenue d ' a p r è s l a mesure d i r e c t e de l a p o l a r i s a t i o n v e c t o r i e l l e du

faisceau de deutons .

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1985256

C2-464 JOURNAL DE PHYSIQUE

w i t h i n c i d e n t p r o t o n beam, one e x p e c t s E t o be a c o n s t a n t throughout t h e e n t i r e width of t h e hydrogen peak. T h i s i s i n fag! observed w i t h i n e r r o r s (Fig. 2a) . ^The

d a t a fir b o t h q u a s i - f r e e i n c i d e n t p r o t o n s and n e u t r o n s a r e c o n s i s t e n t w i t h in- dependence on A0 o n l y a t Aerec >

⁰

, whereas a t Aerec <

⁰

, €gp i s s t r o n g l y decreasing. For e t d e c t h e s t a t i s t i c a l e r r o r s i n t h i s r e g i o n a r e l a r g e and do n o t a l l o w t o draw any c o n c l u s i o n .

F i g .

1

- Counting r a t e s from CH2 and

C

t a r g e t f o r + and - beam p o l a r i z a t i o n s t a t e a s a f u n c t i o n of t h e backward arm p o s i t i o n . AQreC

=

0 i s t h e c o n j u g a t e p o s i t i o n f o r e l a s t i c p-p s c a t t e r i n g . The forward arm i s a t 20.9' l a b .

a ) p r o t o n beam

b) and c) d e u t e r o n beam

a ) and b) two charged p a r t i c l e s d e t e c t e d

c ) forward n e u t r o n and backward charged p a r t i c l e

Fig. 2a,b,c - Asymmetries c a l c u l a t e d from t h e d a t a shown i n F i g u r e s l a , l b and l c , r e s p e c t i v e l y .

The d i f f e r e n t behaviour of tpp and ed a t AQreC < ^{0 could} be due t o c o n t r i b u t i o n s t o t h e hydrogen e f f e c t from r e a c t i o n s o!Rers t h a n p-p e l a s t i c s c a t t e r i n g (e.g. pp - d T + ) . The r e s u l t s of t h e measurements w i t h d e u t e r o n beam of 1450 MeV a t t h r e e d i f f e r e n t forward a n g l e s w i t h t h e r e c o i l p r o t o n s a t Aerec

= 0

a r e g i v e n

i n

T a b l e 1.

The column 6 g i v e s t h e measured r a t i o €ip ^/ tip . Using a t e a c h a n g l e t h e known

( o b t a i n e d w i t h u n p o l a r i z e d neutron beam and p o l a r i z e d proton t a r g e t ) . Our r e s u l t s a g r e e w e l l w i t h t h e LAMPF measurements and con£

i r m

t h e i r a b s o l u t e n o r m a l i z a t i o n .

R o m t h e measured asmmetries ed and t h e h o r n a n a l y z i n g power Aoono (p-p) ,we caleu- PP

Table

1

- R e s u l t s f o r t h e r a t i o E : ~ / L p d and f o r t h e a n a l y z i n g power Aoo,(n-p) .

The l a s t column shows t h e beam nucleon po!arization deduced from t h e s e measurements.

0.6

'lab.

d eg .

16.1

18*4

20.9

I I I I I l l 1

725 MeV

-

THIS EXP.

0 LAMPF 1980

-

^{P S A}

-

-

-

-

-

I l l I I I I I .

Fig. 3 - R e s u l t s f o r t h e a n a l y z i n g powers of 725 MeV e l a s t i c n-p s c a t t e r i n g a t t h r e e a n g l e s . Also shown a r e t h e

LAMPF

d a t a a t t h e same energy and t h e Saclay-Geneva phase s h i f t a n a l y s i s p r e d i c t i o n s f o r

Aoono

(n-p) and

A

oono (P-P)

•

l a t e t h e beam nucleon p o l a r i z a t i o n PB i n t h e p o l a r i z e d deuteron beam given in t h e l a s t column of Table 1.

Or

'CM

deg .

37.6

42*9

48.4

The weighted a v e r a g e (PB

=

0.5773

k

0.0017) can be compared t o t h e v a l u e expected from t h e independent measurement of t h e d e u t e r o n v e c t o r p o l a r i z a t i o n Pd

=

0.651 + ^0.009

Aoono P-P 0.5293

+ ^0.0012

0.5345

f

0.0014 0.5232

+ ^0.0019

6

"P

0.1999

+ ^0.0038

0.1859

* ^0.0041

0.1715

+ ^0.0050

*-P

0.3462 2 0.0137 0.3208

f

0.0157 0.2988

+ ^0.0193

ed PP

0.3056

+ ^0.0012

0.3097

* ^0.0012

0.3002

+ ^0.0015

P~

0.5774

+ ^0.0026

0.5794

* ^0.0029

0.5738

+ ^0.0036

+ d

PP

0.6541

+ ^0.0259

0.6003

f

0.0293 0.5713

+ ^0.0367

C2-466

JOURNAL

DE PHYSIQUE

( s t a t i s t i c s ) f 0.027 ( s y s t e m a t i c s ) . b e f o r e i n j e c t i o n

.

Assuming a D wave c o n t r i b u t i o n of 0.064 f 0.006 and no F e m i momentum c u t i n t h e d e u t e r o n wave f u n c t i o n one p r e d i c t s a nucleon p o l a r i z a t i o n of

0.589

t 0.027 i n e x c e l l e n t agreement w l t h our v a l u e of PB

.

The r e s u l t

i s

c o n s i s t e n t w i t h no d e p o l a r i z a t i o n during d e u t e r o n a c c e l e r a t i o n . The agreement checks o u r assumpion t h a t t h e same analyzing power Aoono(p-p) d e s c r i b e s t h e asymmetry f o r e l e s t i c s c a t t e r i n g of f r e e p r o t o n s and of p r o t o n s i n deuterons.

The p r e s e n t experiment a l s o y i e l d s " i n c l u s i v e " asymmetries w i t h o n l y one charged o r n e u t r a l p a r t i c l e d e t e c t e d .