This work was supported by the National Science Foundation Grant NSF PHY 81-14339 and by Indiana Universit

Clark, J.

D'Auria, J.

Dombsky, M.

Friesel, D.

Sheffer, G.

Singh, P.P.

Ward, T.E.

Yavin, A.

English

IUScholarWorks

MEASUREMENT OF TOTAL ( p , ~ )  CROSS SECTIONS THROUGH RESIDUAL ACTIVITY 
T.E.Ward, D. F r iese l ,  and P.P. Singh 
Indiana University Cyclotron F a c i l i t y ,  Bloomington, Indiana 47405 
J. D'Auria, M. Dombsky and G. Sheffer 
Department of Chemistry, Simon Fraser University, Burnaby 2, B.C. Canada 
J. Clark 
CNC-11, MS 824, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 
A. Yavin 
Department of Physics and Astronomy, Tel Aviv University, Tel Aviv, I s r a e l  
The (p,x-xu) reac t ion  on Bismuth was s tudied number a t  proton energies  of 200-220 MeV. These 
radiochemically using ac t iva t ion  techniques i n  the preliminary r e s u l t s  a re  l i s t e d  i n  Table I. The 
energy range of 120-800 MeV. These preliminary r e s u l t s  background l e v e l  f o r  secondary production of 211~t  was 
ind ica te  s u b s t a n t i a l  n- production of 1-15 pb per mass about 1-2 pb, f o r  2 0 9 ~ t  i t  was about 0.5-1.0 pb and f o r  
Table I. Preliminary Total Cross Sections f o r  Astat ine Production from 209~i  Target 
Cross Section ( ~ b ) ~  
Astat ine Isotope 
aThese da ta  were obtained only from res idua l  alpha emissions of At products; secondary 
contr ibut ions have not been subtracted yet. 
b ~ a t a  taken a t  TRIUMF or  LAMPF (800 MeV). 
*Data a t  these energies  and f o r  these isotopes a r e  s t i l l  under ana lys i s  and w i l l  be made 
avai lable .  
2 0 7 ~ t  i t  was about 0.1-0.5 ~ b .  The At products 
produced i n  the  (p,x-xn) r eac t ions  a t  these  energies  
a r e  3 t o  5 neutrons removed from the  doubly-coherent 
r e s idue ,  2 1 0 ~ t .  These r e s u l t s  a r e  q u a l i t a t i v e l y  i n  
agreement with recent  t h e o r e t i c a l l  9 and experimental2 
s t u d i e s  t h a t  inves t iga ted  the  energy dependence of 
t h e  (p,x-xn) t o t a l  r eac t ion  c ross  sec t ion  i n  terms of a 
cascade-isobar model1 o r  pion knockout model2. 
The prel iminary r e s u l t s  i n d i c a t e  t h a t  the  da ta  
below 200 MeV a r e  c r i t i c a l  s ince  they cover the  
threshold region. This experiment is approved a t  
TRIUMF (E189) and a t  W P F  (E679). The r e s u l t s  suggest 
t h a t  a multinucleon process is important i n  x' 
production, a s  ind ica ted  by a s t rong  dependence on 
the  nuclear  l e v e l  dens i ty  of par t ic le-hole  s t a t e s .  I n  
add i t ion ,  a t  energies  above 200-250 MeV, two nucleon 
models suggest t h a t  coherent production processes a r e  
being l imi ted  by the  increased momentum t r a n s f e r  and 
t h a t  quas i f r ee  processes a r e  beginning t o  dominate. 
1) D. Long, M. Sternheim and R. S i l b a r ,  "Simplified 
In t ranuc lea r  Cascade Approach t o  Inc lus ive  (p,x-xn) 
Reactions",  Phys. Rev. C ( i n  press) .  
2) J. Clark, P. Haustein,  T. Ruth, J. Hudis, A. 
Caret to ,  Jr., and W. Gibbs, "Measurements of 
Inc lus ive  x' Production with 200 MeV Protons: A 
Radiochemical Study of the  0 9 ~ i  (p, x') 210-~t 
Reactions,  " Phys. Rev. C ( i n  press) .  
A WO-NUCLEON MODEL FOR THE (p,x) REACTION 
J.S. Conte and R.D. Bent 
Indiana Univers i ty  Cyclotron F a c i l i t y ,  Bloomington, Indiana 47405 
M. Dillig 
I n s t i t u t e  f o r  Theoret ical  Physics,  Univers i ty  of Erlangen-Nurnberg, Erlangen, W. Germany 
Work on a two-nucleon model (TNM) computer program 
f o r  c a l c u l a t i n g  (p , x)  cross  sec t ions  and analyzing 
powers continued dur ing 1982. The ideas  of t h i s  model 
and prel iminary r e s u l t s  of ca lcu la t ions  have been 
repor ted previously. 1'3 
The goals  of t h i s  work a r e  t o  construct  a complete 
model t h a t  includes ,  t o  the  best  of our knowledge, a l l  
of the  main pieces  t h a t  a r e  thought t o  be important i n  
t h e  (p,x) process,  and t o  ca r ry  out the  ca lcu la t ions  
without u n j u s t i f i e d  numerical approximations. 
Concentrating on IUCF energies ,  i.e., from the  
pion production threshold up t o  about Tp = 200 MeV, we 
assume t h a t  the  dominant p iece  of the  r eac t ion  
mechanism involves  two nucleons, which allows proper 
momentum sha r ing  and considers  the  f a c t  t h a t  the  EN 
i n t e r a c t i o n  is f a i r l y  weak within  t h i s  energy domain 
(T, < 60 MeV). The one-nucleon con t r ibu t ion  w i l l  be 
added t o  the  two-nucleon term i n  the  plane-wave l i m i t  
f o r  the  outgoing pion ( t o  avoid double counting). 
I n i t i a l  s t a t e  i n t e r a c t i o n s  w i l l  be included v i a  a 
d i s t o r t e d  proton wave. Higher order  co r rec t ions  
r e s u l t i n g  from pion r e s c a t t e r i n g  w i l l  be included 
e i t h e r  i n  t h e  s p i r i t  of MJBA (using a x-nucleus o p t i c a l  
p o t e n t i a l )  o r  i n  a s impl i f i ed  isobar-doorway model by 
including sel f -energy cor rec t ions  f o r  the  in te rmed ia te  
isobar .  
The computer program is w r i t t e n  t o  maximize 
f l e x i b i l i t y  with r e spec t  t o  t h e  nuclear  s t r u c t u r e  and 
reac t ion  mechanism input  and t o  minimize t h e  execut ion 
time and core  s i z e  required. This w i l l  a l low f o r  a 
systemat ic  t e s t i n g  of the  physics involved i n  t h e  (p ,x)  
process,  which has not been poss ib le  so  f a r  wi th  o the r  
programs of t h i s  type now under development, 2, where 
execut ion times a r e  3-15 hours ( f o r  a 1 2 ~ ( p , x + ) 1 3 ~  


Measurement of Total (p,Pi) Cross Sections Through Residual Activity

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Measurement of Total (p,Pi) Cross Sections Through Residual Activity

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