This work was supported by the National Science Foundation Grants NSF PHY 78-22774 A03, NSF PHY 81-14339, and by Indiana Universit

Chang, C.C.

Ciangaru, G.

Cowley, A.A.

Hall, J.R.

Holmgren, H.D.

Mills, S.

Nadasen, A.

Roos, P.G.

Saber, M.K.

Singh, P.P.

English

IUScholarWorks (Indiana University)

Analyzing Power 1 Ep=200 MeV - 8= 20' n picture, although the collective excitation mechanism cannot be ruled out completely, especially for the spectra near the high energy end. The analyzing powers at backward angles measured in this experiment are vastly different from those obtained at Ep = 65 MeV. At Ep = 65 MeV, the analyzing powers at large angles are large, especially at low excitation. These large analyzing powers at low / excitation regions might be due to collective excitations. Calculations are now being carried out in which the plane wave impulse 'approximation (PWIA) expression for quasifree nucleon knockout is integrated over the / direction of the undetected outgoing nucleon. In the near future, distorted-wave impulse approximation calculations of the quasifree mechanism as well as collective excitation will also be performed. 1) J.R. Wu, C.C. Chang, and H.D. Holmgren, Phys. Rev. C 19, 698 (1979). -0 75 150 E (MeV) 2) B.A. Anderson et al., Phys. Rev. Lett. 46, 226 (1981). Fi ure 6 Analyzing powers for the reaction at eLu200 , 40' and 50' and Ep = 200 MeV. THE ROLE OF NUCLEON-NUCLEON INTERACTIONS IN PROTON-INDUCED REACTIONS ON 5 8 ~ i  AT 200 MEV C.C. Chang, G. Ciangaru, H.D. Holmgren, A. Nadasen, and P.G. Koos University of Maryland, College Park, Maryland 20742 A.A. Cowley and S. Mills Council for Scientific and Industrial Research, South Africa J.R. Hall, M.K. Saber, and P.P. Singh Indiana University Cyclotron Facility, Bloomington, Indiana 47405 As part of an effort to study the importance of component of the charged-particle coincidence yield is the quasifree nucleon-nucleon (QFNN) scattering as a associated with the emission of at least two fast dominant process in dissipating the incident proton protons. Furthermore, it was observed that the energy, a series of particle-particle coincidence secondary proton energy spectra at various angles, studies were previously carried out at Maryland using detected in coincidence with primary protons emitted at 100 MeV protons on 58~l.1 It was found that the major 15' with energies between 30 and 50 MeV, have the same shape and angular  dependence a s  the  s i n g l e s  proton energy s p e c t r a  obta ined by bombarding 5 4 ~ e  t a r g e t  with 61 MeV protons.  The s i m i l a r i t y  of the  coincidence secondary s p e c t r a  t o  the  s i n g l e s  (p ,p ' )  s p e c t r a  i n d i c a t e s  t h a t  t he  r e s u l t a n t  p a r t i c l e  (proton)  energy spectrum is  independent of whether an inc iden t  100 MeV proton t r a n s f e r s  60 MeV t o  t h e  t a r g e t  nucleus o r  whether a 60 MeV nucleon i s  inc iden t  on the  same t a r g e t  nucleus.  One simple way of expla ining the  s i m i l a r i t y  i s  t o  assume t h a t  t h e  inc iden t  100 MeV proton t r a n s f e r s  60 MeV t o  a t a r g e t  nucleon v i a  a q u a s i f r e e  nucleon- nucleon i n t e r a c t i o n .  The s t r u c k  nucleon wi th  60 MeV then proceeds t o  i n t e r a c t  with the  remainder of t he  nucleus i n  t h e  same manner a s  a 60 MeV inc iden t  proton. Although the  previous r e s u l t s  a t  100 MeV provide a c o n s i s t e n t  p i c t u r e  i n  agreement wi th  the  QFNN mechanism, more suppor t ive  evidence is needed. With t h i s  motive i n  mind, we have c a r r i e d  out  t he  same experiment a t  200 MeV. The advantage of the  p resen t  experiment over the  one a t  100 MeV i s  t h a t  coincidence secondary energy s p e c t r a  corresponding t o  t h r e e  energy s l i c e s  of t he  primary protons  de tec t ed  a t  forward angles  can be compared wi th  a v a i l a b l e  s i n g l e s  (p ,p ' )  s p e c t r a  a t  t h r e e  d i f f e r e n t  i n c i d e n t  energies .  These comparisons a l low us t o  examine no t  only t h e  shape and the  angular  dependence a t  one energy s l i c e ,  but  a l s o  the  r a t i o s  of y i e l d s  between d i f f e r e n t  energy s l i c e s .  I f  t h e  r a t i o s  agree  wi th  the  r a t i o s  of s i n g l e  measurements, we w i l l  have s t ronge r  support  f o r  t he  i n t e r p r e t a t i o n  made previously .  su r face  b a r r i e r  AE1-detector, a 1 mm s i l i c o n  s u r f a c e  b a r r i e r  AE2-detector, and a 3"x3"~5"  NaI(TR) E-detector.  The t h r e e  t e l e scopes  which were mounted i n  the  forward hemisphere u t i l i z e d  p l a s t i c  s c i n t i l l a t o r  a c t i v e  co l l ima to r s .  Pas t  e l e c t r o n i c s  were used throughout.  Coinci- dence requirements wi th  m u l t i p l i c i t y  6 > N > 2 amoug the  d e t e c t o r s  were made. Events c o n s i s t i n g  of up t o  18 energy s i g n a l s ,  6 TDC's, and 6 o r  12 tagging b i t s  were s e n t  t o  the  computer and the  event  was recorded on t ape  i n  the  l i s t  mode. Data were taken wi th  two of the  s i x  t e l e scopes  f ixed  a t  12' and 30°, whi le  t h e  o t h e r  fou r  t e l e scopes  were mounted on a l a r g e  movable p l a t e .  Two angular  s e t t i n g s  were made f o r  the  p l a t e  cover ing t h e  e n t i r e  angular  range from -20' t o  -160". Figure  1 shows a t y p i c a l  two-dimensional proton-proton coincidence spectrum. At p resen t ,  more than 30% of the  raw d a t a  have been processed. The d a t a  r ep lay  i s  cont inuing.  E2 (MeV) 100 Ep ' 2 0 0  MeV e, = -75O e2 = +30° With a l i m i t e d  amount of beam time a v a i l a b l e  f o r  dl , 0 , 8 , , , m 8 1 t h i s  low-yield coincidence experiment,  t h e  measurement 100 200 E, (MeV) was c a r r i e d  ou t  wi th  s i x  movable t r ip l e -coun te r  t e l e scopes  mounted i n  t h e  e q u a t o r i a l  plane of t h e  64" Figure  1. Proton-proton coincidence spectrum f o r  200 MeV po la r i zed  protons  on 58~i .  s c a t t e r i n g  chamber, us ing a 200 I4eV polar ized proton beam. Each t e l e scope  c o n s i s t s  of a 50 p o r  100 p 1 )  A.A. Cowley et a l . ,  Phys. Rev. L e t t .  45, 1930 (1980). 

The Role of Nucleon-Nucleon Interactions in Proton-Induced Reactions on 58-Ni at 200 MeV

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The Role of Nucleon-Nucleon Interactions in Proton-Induced Reactions on 58-Ni at 200 MeV

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