This research was sponsored by the National Science Fooundation Grant NSF PHY-931478

Bacher, A.D.

Bowyer, S.M.

Bowyer, T.W.

Bugg, D.V.

Chang, S.

Franklin, W.

Liu, J.

Pitts, W.K.

Sowinski, J.

Stephenson, E.J.

Wells, S.P.

Wissink, S.W.

English

IUScholarWorks

NUCLEON-NUCLEON AND FEW-BODY STUDIES 
A MEASUREMENT OF THE SPIN TRANSFER OBSERVABLE DNN1 
FOR p+p ELASTIC SCATTERING AT T,=200 MeV 
S.M. Bowver, A.D. Bacher, T.W. Bowyer, S. Chang, W. Franklin, 
J.  Liu, J.  Sowinski, E.J. Stephenson, S.P. Wells, and S.W. Wissink 
I nd iana  Univers i ty  Cyc lo t ron  Facili ty,  B looming ton ,  I nd iana  47408  
W.K. Pitts 
Univers i ty  of Louisville,  Louisville,  K e n t u c k y  40292  
D.V. Bugg 
Q u e e n  M a r y  College, London ,  U K  
In most models of the nucleon-nucleon interaction, an important parameter, and one 
which appears explicitly in meson-exchange formulations, is the ?rNN coupling constant, 
9:. The strength of this coupling dictates much of the long-range behavior of the hadronic 
component of the N-N force, especially the tensor terms. Recent determinations of the 
values of both the neutral, gz (Ref. I) ,  and the charged, (Ref. 2), coupling constants, 
based primarily on the analysis of NN and ?rN scattering data, respectively, have been sig- 
nificantly smaller than values determined prior to 1987. These smaller coupling constants 
do not appear to agree with the value of required in meson-exchange models in order 
to yield the correct deuteron quadrupole moment and asymptotic D/S-state ratio.3 These 
inconsistencies motivated our collaboration to investigate the sensitivity of to high 
precision spin observable data that could be obtained at IUCF. We found that the normal- 
component spin transfer observable DNNl for p+p elastic scattering is very sensitive to g;, 
particularly over the angular range in which the NN scattering amplitude 6 crosses 
Over this angular range, the momentum transfer p ranges from 0.3-0.8 fm-l, which 
is sufficiently large that Coulomb effects are small, but sensitivity to multi-pion or heavy 
meson contributions is minimal. Of the existing DNNl data in the 150 MeV to 300 MeV 
energy range, none bracket the 6 crossover (which occurs near Blab x go), and all have 
relatively large st atistical errors and normalization uncert a i n t i e ~ . ~  -7 
Experiment E367 successfully completed data acquisition in August, 1993. DN N l  
measurements were made at 10 angles (elaa = 5.0°, 7.2", 8.4", 9.7", 11.8", 15.0°, 19.1°, 
24O, 30°, and 38") and total errors (statistical plus systematic) of 6DNNl = L-0.01 were 
achieved at all but the largest angle. Acquisition of the needed calibration data for the focal 
plane polarimeter, FPP, was also completed in August, 1994 (see article in this report). 
For E367, both outgoing protons from p+p elastic scattering were detected simul- 
taneously, and their energies were accurately measured. The forward-going proton was 
momentum analyzed in the K600 spectrometer focal plane, FP. The septum magnet8 was 
To K600 
Spectrometer 
FP and FPP 
Figure 1. Top view of experimental setup in 24" scattering chamber for E367. 
used for forward-angle measurements at 5O-18O. After passing through the FP, the po- 
larization of the forward-going proton was measured in the FPP. The recoil proton was 
detected in a Si/CsI detector telescope placed inside the 24" scattering chamber (see Fig. 1). 
The Si detector measured 4.0 cm wide x 6.0 cm high, and consisted of 7 horizontal strips 
which were ganged together to form three sections consisting of the top three strips, the 
middle strip, and the bottom three strips. Relative coincidence rates in the three sections 
provided a very accurate gauge of the vertical position of the beam spot on target. The 
500 pm thickness of the Si was sufficient to provide total energy information for protons 
from = 1 to 8 MeV. For protons of higher energy, a AE signal resulted from the Si. Sur- 
rounding the Si was a Faraday cage constructed mainly of aluminum with a front face 
consisting of 1.2 pm aluminized mylar. Behind the Si p-strip detector was a tapered CsI 
crystal, measuring 3.8 cm deep and 1.5 cm wide x 4.0 cm high on the front face. This 
crystal was optically glued to a 2" Burle 8575 PMT attached to a compact, water-cooled 
base built in-house. The CsI crystal was sufficiently thick to stop protons up to 100 MeV. 
The combination of these two detectors in series gave the recoil telescope a dynamic energy 
range of 4-100 MeV. 
We chose to use a solid (CH2), target in this experiment since the advantages over 
using a liquid hydrogen target far outweighed the disadvantages. Using a solid target (as 
opposed to an extended liquid target) allowed us to know our event origin very well. The 
excitation spectrum of 12C, simultaneously obtained in the focal plane, resulted in enough 
-0.2 
0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 
CM Angle 
Figure 2. E367 preliminary DNN1 data for p+p elastic scattering at T,=200 MeV. 
kinematic information to provide an absolute determination of the scattering angle. By 
comparing characteristics of 12C peaks and the 'H peak, we could constantly monitor 
beam and target properties with good sensitivity. The challenge of using a (CH2), target 
was in distinguishing p+p elastics from quasifree (p,2p) knockout. Since the minimum 
proton separation energy in 12C is 16 MeV, the combined energy resolution of our FP 
and our recoil telescope of <5 MeV was more than sufficient to distinguish the two events. 
Thicknesses of the (CH2), targets used in this experiment ranged from 1.4 mg/cm2 at 5.0" 
to 10 mg/cm2 at 38". 
During data collection, no hardware coincidence requirement was made between the 
FP and the recoil telescope, and the recoil telescope information, if any, was read out for 
every good event in the FP. In the replay software, a proton that fell within the hydrogen 
--- Bonn Potential 0-325 MeV 
---- Paris Potential 0-325 Mev 
- C200 175-225 MeV (611 993) 
--- Nijmegen I Potential 
Preliminary P+P DNN, Data 
- 
peak in the FP spectrum was tagged as a good p+p elastic event only if a second proton 
fired the recoil detector(s) in coincidence and deposited the correct amount of energy. 
For recoil protons above 8 MeV, timing and energy requirements had to be satisfied for 
both the Si and the CsI detectors. "Accidentals" were tagged as those events which also 
consisted of a proton within the hydrogen peak in the FP spectrum and had a second 
proton that deposited the proper amount of energy in the recoil detector(s), but for which 
the relative timing of the protons differed from "true" coincidences by one beam burst. 
FPP spin-sorted left-right spectra for both "reals" and "accidentals" were made for all 
three sections of the Si detector. This allowed us to optimize subtraction of accidentals, 
since at most angles a large majority of the recoil protons were incident on the center 
section, which consisted of a single strip. 
There are several systematic error checks available to us in the data. The 12C elastic 
peak was present on the focal plane from 5O to lgO, and for both the 12C elastic peak and 
the p+p peak, the induced polarization, P, and the analyzing power, A,, were measured. 
These two observables should be equal; and since they are sensitive to different possible 
sources of systematic error, their comparison is an import ant means of systematic error 
evaluation. We also simultaneously measured DN N l  for l2 C elastic scattering, which must 
be exactly 1. Careful evaluation of other possible systematic errors is presently underway. 
Preliminary results of our analysis up to this point are presented in Fig. 2. 
1. J.R. Bergervoet, P.C. van Campen, R.A. Klomp, J.L. de Kok, T.A. Rijken, V.G.J. 
Stoks, and J.J. de Swart, Phys. Rev. C 41, 1435 (1990). 
2. R.A. Arndt, 2. Li, L.D. Roper and R.L. Workman, Phys. Rev. Lett. 65, 157 (1990). 
3. R. Machleidt and F. Sammarruca, Phys. Rev. Lett. 66, 564 (1991). 
4. L. Wolfenstein, Ann. Rev. of Nucl. Sci. 6, 43 (1956). 
5. D.V. Bugg, et al., 5. Phys. G4, 1025 (1978). 
6. Kazuo Gotow, Frederick Lobkowicz, and Ernst Heer, Phys. Rev. 127, 2206 (1962). 
7. Y. Onel, R. Hausammann, E. Heer, R. Hess, C. Lechanoine-Leluc, W.R. Leo, and D. 
Rapin, Phys. Rev. D 40, 35 (1988). 
8. G.P.A. Berg, e t  al., IUCF Sci. and Tech. Rep., May 1992-April 1993. 
SPIN CORRELATION COEFFICIENTS IN j5$ ELASTIC SCATTERING AT 200 MeV 
W.A. Dezarn, J .  Doskow, J.G. Hardie, H.O. Meyer, R.E. Pollock, 
B. von Przewoski, T. Rinckel, and F. Sperisen 
Indiana Universi ty  and Indiana Universi ty  Cylotron Facility, 
Bloomington,  Indiana 474 0 8  
W. Haeberli, B. Lorentz, F. Rathmann, M.A. Ross, and T. Wise 
Universi ty  of Wiscons in-Madison,  Madison,  Wiscons in  53706 
P.V. Pancella 
W e s t e r n  Michigan Universi ty ,  Kalamazoo,  Michigan 49008 
An experiment to measure spin correlation coefficients in g$ elastic scattering with a 
stored, polarized beam on an internal, polarized target has been mounted in the A-region 


A Measurement of the Spin Transfer Observable D_NN' for p+p Elastic Scattering at T_p = 200MeV

https://scholarworks.iu.edu/dspace/bitstream/2022/497/1/iucf1993-1994_3-6.pdf

A Measurement of the Spin Transfer Observable D_NN' for p+p Elastic Scattering at T_p = 200MeV

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