This work was supported by National Science Foundation Grants PHY 76-84033A01, PHY 78-22774, and Indiana Universit

Attard, A.C.

Devins, D.W.

Friesel, D.L.

Henderson, R.S.

Jones, W.P.

Officer, V.C.

Shute, G.G.

Spicer, B.M.

Svalbe, I.D.

English

IUScholarWorks

STUDIES OF KNOCK-OUT REACTIONS 
D.W. Devins, D.L. F r i e s e l ,  W.P. Jones, A.C. At ta rd ,  B.M. sp i ce r ,*  V.C. o f f i c e r , *  
G.G. ~ h u t e , *  I . D .  ~ v a l b e , *  and R.S. ~ e n d e r s o n *  
Of t h e  many poss ib l e  ways of s tudying the  o f f -  in termedia te  s t a t e s  involved very l i k e l y  a r e  not  
s h e l l  nucleon-nucleon i n t e r a c t i o n ,  t he  proton knock- g i an t  resonances. 4 
out ,  o r  (p,2p),  r eac t ion  provides one of t h e  most The next knock-out experiments were done t o  
s e n s i t i v e  t e s t s  of r eac t ion  f o r m l a t i o n s  which a r e  i n v e s t i g a t e  t h e  f a c t o r i z a t i o n  approximation used i n  
used a t  in termedia te  energies  t o  study nuclear  reac- t h e  DWIA. I n  t h i s  approximation it is  assumed t h a t  
t i o n  da ta .  I n  p a r t i c u l a r ,  t h e  Dis tor ted  Wave Impulse t he  proton-proton i n t e r a c t i o n  is no t  dependent on t h e  
Approximation (DWIA) has  achieved a measure of success momentum t r a n s f e r  of t h e  r eac t ion  so  t h a t  it may be 
i n  understanding both knock-out and i n e l a s t i c  proton fac tored  out  of t h e  t r a n s i t i o n  amplitude. This ap- 
s ca t t e r ing .  l) Severa l  f e a t u r e s  of t h e  DWIA need t o  proximation has been t e s t e d  f o r  t h e  knock-out of alpha 
be understood before  it can be used r e l i a b l y  t o  ex- c l u s t e r s  by a lpha  p a r t i c l e s  and found t o  be s a t i s f a c -  
t r a c t  spec t roscopic  information from in termedia te  tory .  5, But t h e  (a,2a)  r eac t ion  is  be l ieved t o  be 
energy r eac t ions  o r  t o  t e s t  var ious  phase-equivalent h ighly  su r f ace  l oca l i zed ;  i t  was not  c l e a r  t h e  same 
nucleon-nucleon p o t e n t i a l s :  a )  neglec t  of higher s a t i s f a c t o r y  r e s u l t  would be obtained using the  (p,2p) 
order r eac t ions ,  b)  f a c t o r i z a t i o n  of t h e  proton-proton r eac t ion .  We used t h e  4 0 ~ a  (p,  2p) 3 9 ~ *  (1s t  exc i t ed  
i n t e r a c t i o n ,  c )  replacement of t h e  nuclear  boundstate s t a t e ,  %+, 2.52 MeV) r eac t ion  f o r  t he  t e s t ,  and found 
overlap i n t e g r a l  wi th  a s ing l e -pa r t i c l e  wavefunction t h a t  f o r  a  momentum t r a n s f e r  of zero,  f a c t o r i z a t i o n  
generated from a Woods-Saxon we l l ,  and d) generat ion was q u i t e  s a t i s f a c t o r y .  6 
of t h e  d i s t o r t e d  waves by means of o p t i c a l  model po- The summed energy spec t r a  f o r  fou r  of t h e  
t e n t i a l s  determined by e l a s t i c  s c a t t e r i n g .  f i v e  momentum t r a n s f e r s  used i n  t h e  f a c t o r i z a t i o n  
Our f i r s t  experiments wi th  t h e  temporary telescope- t e s t s  a r e  shown i n  Figure 1. I n  each spectrum a 
spectrograph arrangement2) were done t a  examine t h e  ten  count b i a s  has  been added t o  each channel t o  
e f f e c t s  of neglec t ing  h igher  order  r eac t ions .  I n  t h e  enable background t o  be subt rac ted  on-line. The 
r eac t ion  1 2 ~ ( p  ,2p) l IB, t h e  second exci ted  s t a t e  (512- events p l o t t e d  a r e  those  which pass a proton window 
a t  4.44 MeV) should not  be seen,  i f  t h e  r eac t ion  pro- s e t  on t h e  te lescope  E vs. AE spectrum. The appro- 
ceeds purely by means of a  s i n g l e  s t e p  knock-out. I f  p r i a t e  r e c o i l  energy has been ca l cu l a t ed  f o r  each 
mul t ip le  s t e p  processes occur,  then t h i s  s t a t e  could event  and added on-l ine i n t o  t h e  summed energy. The 
be reached v i a  a v a r i e t y  of  in termedia te  s t e p s  in- FWHM f o r  t he se  s p e c t r a  vary from about 260 keV t o  300 
cluding i n e l a s t i c  e x c i t a t i o n  t o  low l y i n g  s t a t e s  by keV, most of t h i s  being the  consequence of energy l o s s  
t h e  inc ident  o r  e x i t i n g  protons o r  i n e l a s t i c  s c a t t e r -  e f f e c t s  i n  t he  t a r g e t  (4 mg/cm2). Severa l  of t h e  
i ng  t o  one o r  more g i an t  resonances. A t  50 MeV t h i s  p a r t i a l l y  resolved peaks i n  t h e  region  of 5 MeV can 
s t a t e  i s  q u i t e  s t rong ly  exc i t ed  i n  t h e  (p,2p) reac- be i d e n t i f i e d  a s  p a r t s  of t h e  fragmented ld512 hole  
t i ~ n . ~ )  ~u r ' r e su l t s  a t  100 MeV i n d i c a t e  t h a t  mu l t i p l e  by comparison t o  (d,  3 ~ e )  t r a n s f e r  r eac t ion  r e s u l t s  on 
s t e p  processes ,  whi le  they do occur,  a r e  much l e s s  t h e  same t a r g e t .  Also v i s i b l e  i n  t h e  109 MeV/c spec- 
important than a t  t h e  lower energy and t h a t  t h e  trum a r e  s eve ra l  p a r t i a l l y  resolved peaks a t  higher 
e x c i t a t i o n ,  near  14 MeV. No s t a t e s  had been reported 
above 9 MeV i n  lower energy (d,3He) t r a n s f e r  experi-  
ments. 7, A 76 MeV deuteron beam is ava i l ab l e  from 
IUCF; we speculated a higher inc ident  energy could be 
more e f f e c t i v e  i n  producing higher exc i t a t i ons .  We 
were ab l e  t o  use d i r e c t o r ' s  d i s c re t i ona ry  time t o  
make a prel iminary run8) using 4 0 ~ a  (d, )He) 3 9 ~ ,  and 
l a t e r  we received beam time through t h e  normal Pro- 
gram Advisory Committee procedure f o r  a more d e t a i l e d  
study.  9 1 
The ( d , 3 ~ e )  da t a  were taken with t he  spectro-  
graph. A composite spectrum covering t h r e e  spectro-  
graph s e t t i n g s  a t  a 60 s c a t t e r i n g  angle is  shown i n  
Figure 2. There a r e  no s t rong  s t a t e s  a t t r i b u t a b l e  
t o  3 9 ~  above about 9 MeV. We were a b l e  t o  confirm 
t h a t  t h e  v i s i b l e  ld512 s t a t e s  account f o r  only about 
70% of t h e  ld512 hold s t r eng th .  ~ a l c u l a t i o n s " )  
i nd i ca t e  t h i s  s t r eng th  should extend above 9 MeV. 
We bel ieve  we a r e  see ing  i t  i n  t h e  (p,2p) da ta .  We 
th ink  these  s t a t e s  a r e  not  seen i n  t h e  proton t r a n s f e r  
r eac t ions  because ind iv idua l ly  they can have a very 
small  spectroscopic f a c t o r ,  about .02. When t h i s  
number is used wi th  a DWBA ca l cu l a t i on  f o r  s t a t e s  
having 14 MeV e x c i t a t i o n  energy, a c ros s  s ec t ion  is 
ca l cu l a t ed  which is not  s i g n i f i c a n t l y  h igher  than 
t h e  measured background. The only background i n  t h e  
(p,2p) summed energy spectrum a t  109 M ~ V / C  has t o  come 
from the  low energy t a i l  of t h e  presumably fragmented 
1s and l p  hole  s t a t e s .  But a t  t h i s  high va lue  of 
momentum t r a n s f e r  t h e  c ros s  s ec t ions  f o r  R=O and R = l  
s t a t e s  should be very small  compared t o  t h e i r  va lues  
a t  small  momentum t r a n s f e r .  On t h e  o t h e r  hand, the  
RR2 s t a t e s  ( t h e  suspected ld5/2  s t a t e s )  would be  near  
t he  peak of t h e i r  c ros s  s ec t ions  and would thus stand 
ou t  above the background. 
*univers i ty  of  Melbourne, Aus t r a l i a  
1) G.  Jacob and Th. A . J .  Maris, Rev. Mod. Phys. 45, 
6 (1973). 
2) D.L. F r i e s e l ,  e t  a l . ,  IUCF I n t e r n a l  Report 77-1. 
3) H.G. Pugh, e t  a l . ,  Phys. Rev. 155, 1054 (1967). 
4) D.W. Devins, e t  a l . ,  accepted f o r  publ ica t ion  by 
Aust ra l ian  Journal  of Physics. 
5) N.S. Chant, e t  a l . ,  Phys. Rev. C x ,  8 (1978). 
6) P.G. Roos, e t  a l . ,  Phys. Rev. Le t t .  40, 1439 (1978). 
7) D. Doll ,  e t  a l . ,  Nucl. Phys. A263, 210 (1976); 
J . C .  Hieber t ,  e t  a l . ,  Phys. Rev. 154, 
8) D.L. F r i e s e l ,  e t  a l . ,  Bull.  Am. Phys. Soc. 23, 
539 (1978). 
9) D.L. F r i e s e l ,  e t  a l . ,  Bull .  Am. Phys. Soc. 24, 
52 (1979). 
10) G . J .  Wagner, e t  a l . ,  Phys. L e t t .  E, 413 (1975). 
0 
R.. 
0 
X .  
- 
20 10 0 20 
E x  E x  
Figure 2. 
4 0 ~ a  (d ,  3 ~ e ) 3 9 ~  
Ed=76.4 MeV 
LO 1'5.10 30.10 45.10 60.10 
CHRNNEL ( X  101 I 
Figure 2 .  


Studies of Knock-Out Reactions

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Studies of Knock-Out Reactions

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