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

Bacher, A.D.

Bertozzi, W.

Blatt, S.L.

Donoghue, T.R.

Finn, J.M.

Foster, C.C.

Friesel, D.L.

Hausman, H.J.

Kovash, M.A.

Lourie, R.

Marchlenski, D.

Ulmer, P.

Wiggins, J.

English

IUScholarWorks

ELASTIC AND INELASTIC PKOTON SCATTEKING 
MEASUREMENTS OF S AND P-A USING THE 12~(p,p'y) REACTION AT 150 MEV 
M.A. Kovash, W. Bertozzi, J.M. Finn, R. Lourie, P. Ulmer, and J. Wiggins 
Massachusetts Institute of Technology, Laboratory for Nuclear Science, Cambridge, Massachusetts 02139 
S. L. Blat t , T. R. Donoghue, H. J. Hausman, and D. Marchlenski 
Ohio State University, Department of Physics, Columbus, Ohio 43210 
A.D. Bacher, C.C. Foster, and D.L. Friesel 
Indiana University Cyclotron Facility, Bloomington, Indiana 47405 
We have recently begun a study of the spin values of q from 200 to 400 MeV/c, where these 
excitation mechanism in the scattering of intermediate calculations show the tensor interaction to dominate. 
energy protons. The objectives of our initial In addition to providing a sensitive test of this 
measurements are a determination of the spin flip component of the nucleon-nucleon force, accurate 
probability (S) and the difference between the measurements of S in this high-q range may also provide 
polarization and analyzing power (P-A) for scattered a means for observing possible precursor effects toward 
protons exciting the 15.11 MeV (I+, T=l) state in 12c. a pion condensate in nuclei. 
These measurements were made using the 12~(p,p'y) The difference between the polarization and 
reaction at a bombarding energy of 150 MeV. This is analyzing power for inelastic scattering has been 
the first reported use of the gamma-ray coincidence little ~tudied.~ It results from an orthogonal 
technique to determine S and P-A at intermediate combination of spin flip amplitudes (P-A - a3 - at, 
energies. whereas S -- a3 + at, where a(O) - (au + at 
The 1+ state at 15 MeV in carbon is a good choice + a3 + a--), and is determined with the (p,p1y) 
for a first measurement of this kind primarily because reaction by a comparison of measured spin flip proba- 
the strong gamma-ray branching ratio to the ground bilities when the incident beam polarization is 
state (r  / r  = .88) allows an extraction of S and P-A rever~ed.~ Previous measurements of P-A for elastic 
yo 
with high accuracy. There also exist for this state scattering are of considerable interest because they 
high-q electron scattering results1 at 180' and cross directly determine time reversal noninvariant scattering 
sections and analyzing powers for intermediate energy amplitudes. Considerable experimental and theoretical 
proton scattering2 which have motivated previous work remains to be done to provide a similar level of 
theoretical treatments. Some polarization transfer understanding of the significance of P-A for inelastic 
measurements have also been made,3 although primarily scattering. 
at lower values of momentum transfer. In the present measurements the QDDM spectrograph 
Microscopic calculations within the DWBA have was used with a helical-wire position detector followed 
shown the spin flip probability to be most sensitive to by two (AE,E) scintillators in the standard 
the spindependent central and tensor components of the configuration. De-excitation gamma-rays were observed 
effective nucleon-nucleon interaction at this energy. at 90' to the reaction plane with a 10" diameter x 12" 
In the present experiment, S has been measured for four long NaI(T1) crystal suspended directly above the 
s c a t t e r i n g  chamber. A c a s t  lead s h i e l d  surrounded the  
d e t e c t o r ,  which was f u r t h e r  encased i n  a borated 
polyethylene sh ie ld .  Event t ime-of-fl ight wi th  r e spec t  
t o  the  pulse-se lected beam was used t o  lower the  f a s t  
neutron background. The e f f e c t s  of t he  high background 
r a t e s  were f u r t h e r  reduced wi th  p i l e -up  r e j e c t i o n  and 
ga in  s t a b i l i z a t i o n  c i r c u i t r y  s i m i l a r  t o  those  used f o r  
previous r a d i a t i v e  cap tu re  s t u d i e s  wi th  t h i s  d e t e c t o r O 6  
A l l  da t a  were recorded i n  event mode and s o r t e d  
on-line i n t o  histograms corresponding t o  coincident  and 
s i n g l e s  events.  Figure  1 shows two of these  s p e c t r a  a t  
q=200 MeV/c f o r  one sp in  o r i e n t a t i o n  of the  inc iden t  
beam. For these  da ta ,  i n  which f i n a l  s o r t i n g  c u t s  have 
not yet  been app l i ed ,  t he  t rue- to-accidenta l  
coincidence r a t i o  is approximately 10 t o  1. Because 
t h e  gamma-ray d e t e c t o r  remains f ixed  a s  q is va r i ed ,  
and the re fo re  the  p r o b a b i l i t y  f o r  a c c i d e n t a l  
coincidences  remains f ixed ,  t he  r e s u l t a n t  T:A r a t i o  a t  
any o the r  value  of q is determined only  by the  r a t i o  of 
peak t o  background i n  the  s i n g l e s  spectrum. This  f a c t  
enables  h ighly  r e l i a b l e  e x t r a c t i o n  of coincidence 
y i e l d s  out t o  l a r g e  values  of momentum t r a n s f e r  us ing 
the  ( p , p f y )  react ion.  Data f o r  t h i s  f i r s t  run a r e  
c u r r e n t l y  being analyzed, and w i l l  be presented a t  a 
l a t e r  time. 
Figure  1. On-line s p e c t r a  of 
i n e l a s t i c a l l y  s c a t t e r e d  protons  taken a t  
elab=220 wi th  a 150 MeV po la r i zed  ( sp in  
up) beam. The upper curve is  a s i n g l e s  
cl 
spectrum, the  bottom shows protons  i n  
coincidence wi th  any gamma ray i n  t h e  
out-of -plane NaI counter.  
CHANNELS 
1) J. Flanz e t  a l .  , Bull. Am. Phys. Sot. 23, 583 
(1978). 
4) T.A. Carey e t  a l . ,  Phys. Rev. Let t .  2, 266 
( 1982). 
2 )  J.R. Comfort e t  a l . ,  Phys. Rev. C 2, 2147 (1980); 5) R.N. Boyd e t  a l . ,  Phys. Rev. Le t t .  2, 955 (1972). 
Phys. Rev. C 24, 1834 (1981). 
6) M.A. Kovash, Ph.D. Thesis ,  Ohio S t a t e  Univers i ty ,  
3) J.M. Moss e t  a l . ,  IUCF S c i e n t i f i c  and Technical 1978 (unpublished).  
Report - 1980, p. 18. 


Measurements of S and P-A Using the 12-C(p,p'y) Reaction at 150 MeV

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Measurements of S and P-A Using the 12-C(p,p'y) Reaction at 150 MeV

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