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Angular dependence of the spin correlation parameter Aoonn in np elastic scattering between 0.8 and 1.1 GeV
NUCLEAR PHYSICS A
Nuclear Physics A559 (1993) 511-525 North-Holland
Angular dependence of the spin correlation parameter A OOnn in np elastic scattering between 0.8 and 1.1 GeV J. Ball, Ph. Chesny, M. Combet, J.M. Fontaine, C.D. Lac *, MC. Lemaire 2, J.L. Sans Laboratoire National SATURNE, France
CNRS-IN2P3 and CFA / DSM, CE Saclay, 91191 Gif-sur-Yvette Cede.x,
J. Bystricky, F. Lehar, A. de Lesquen, M. de Mali, F. Perrot-Kunne, L. van Rossum DAPNIA, CE Saclay, 9lf91
Gif-sur-Yrtette Cedex, France
P. Bach 3, Ph. Demierre, G. Gaillard 4, R. Hess, R. Kunne 5, D. Rapin, Ph. Sormani 6, B. Vuaridel DPNC, University of Geneva, 24 quai Ernest-Ansermet,
1211 Gene1.a 4, Switzerland
J.P. Goudour C.E.N.B.,
Domaine du Hart&Vigneau, 33170 Gradignan, France
R. Binz, A. Klett, E. Riissle, H. Schmitt Fizculty of Physics, Freiburg University, 7800 Freiburg im B&gal*,
L.S. Barabash, Z. Janout ‘, B.A. Khachaturov,
Germany
Yu.A. Usov
LNP-JINR, Dubna, P.O. Box 7% 101000 Moscow, Russian Federation
D. Lopiano, H. Spinka ANL-HEF,
9700 South Cass Acenue, Argonne, IL 60439, USA
Received 23 November 1992
Correspondence to: Dr. F. Lehar, DAPNIA/SPLN, CE Saclay, 91191 Gif-sur-Yvette Cedex, France. Present addresses: ’ lnstitut National des Telecommunications, 9 rue Charles Fourier 91011 Evry, France. 2 DAPNIA, CEN-Saclay, 91191 Gif-sur-Yvette, Cedex, France. s College Rousseau, 16A avenue de Bouchet, 1209 Geneva, Switzerland. 4 Schlumberger Ind., 87 route de Grigny, 91130 Ris Orangis, France. ’ LNS, CE Saclay, 91191 Gif-sur-Yvette, Cedex, France. ’ Brainsoft Consulting S.A., Cusinand 46, 128.5Athenaz, Switzerland. ’ Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University, Brehova 7, 11519 Prague 1, Czech Republic. 03759474/93/$06.00
Q 1993 - Elsevier Science Publishers B.V. All rights reserved
.I. Ball et al. / Angular dependence (III)
512 Abstract
We present a total of 323 data points of the spin correlation parameter A,,_(np) in a large angular interval at eight energies between 0.8 and 1.1 GeV. The SATURNE II polarized beam of free neutrons obtained from the break-up of polarized deuterons was scattered on the polarized Saclay frozen-spin proton target. The present data are the first existing results above 0.8 GeV. Key words: NUCLEAR REACTIONS ‘H (polarized correlation parameter. Polarized frozen-spin target.
n,n), E = 0.8-1.1 GeV, measured
spin
1. Introduction
The experiment is part of a systematic study of the nucleon-nucleon system in the energy range of SATURNE II. We present measurements of the spin correlation parameter A_,, at 0.80, 0.84, 0.86, 0.88, 0.91, 1.00, 1.08 and 1.10 GeV obtained with a polarized beam of free quasi-monochromatic neutrons scattered on the Saclay frozen-spin proton target. The beam and target polarizations were oriented vertically. In the same experiment were measured the analyzing power data presented in refs. [1,21, the depolarization Donon and the polarization transfer K onno, which will be reported in a forthcoming paper. All these data were taken simultaneously with the transmission measurement of the total cross-section difference Au-&p) [ref. 31. The results at 0.8 GeV are compared with the LAMPF data [41 and with the quasielastic scattering of neutrons in the accelerated polarized deuterons on the same target [51. Throughout this paper we use the nucleon-nucleon formalism and the four-spin notation developed in ref. [6].
2. Polarized
beam and target
Polarized neutrons are produced by break-up of vector-polarized deuterons on a 20 cm thick Be target. The vertically polarized neutron beam is defined by a total of 8 m of collimators inserted in the 17.5 m long neutron beam line. At the polarized target the beam spot was either 20 mm or 30 mm in diameter. The neutron beam has a momentum spread due to deuteron absorption in the production target and to the Fermi motion of neutrons in deuterons. The momentum spread is of the order of k 20 MeV. The polarized deuteron beam with (2-3) X 10” deuterons/ burst produces N 6 x 10’ neutrons/burst at the PPT with the collimator 30 mm in diameter. The neutron beam intensity was monitored by a scintillation counter array inserted in the beam in front of the polarized target [31. The deuteron beam polarization was flipped every burst of the accelerator by a change of the RF transitions in the ion source. The polarization of break-up neutrons was determined by a dedicated experiment measuring the asymmetries EB = PBAoonoand EB = P, A,_, [ref. 11. Using the known target polarization P, and assuming A.,,,,. = A...,, we obtain P, = 0.59, independent of the neutron
J. Ball et al. / Angular dependence (III)
513
beam energy [1,7]. At each energy the polarization of the protons in the accelerated deuterons was also checked by the beam polarimeter [8]. The PPT was 35 mm thick, 40 mm wide and 49 mm high [9]. The target material was pentanol, with a typical proton polarization of 85%. The target polarization is held in vertical magnetic field of - 0.33 T produced by a vertical superconducting holding coil. The target polarization was inverted every few hours.
3. Experimental
set-up and data analysis
The apparatus is designed for pp, np and pn elastic-scattering experiments in a large angular domain. The experimental set-up is described in ref. [7]. Outgoing particles are detected by a two-arm spectrometer which comprises single scintillation counters, counter hodoscopes, the neutron counter (NC) hodoscope with its VETO, analyzing magnet and eight multiwire proportional chambers. The NC hodoscope [7,10] consists of 15 scintillating bars and measures a particle position from the time difference between signals from the two PM’s on either side of a bar, with a precision of _t25 mm. Veto counters in front of the neutron-counter hodoscope distinguish between neutral and charged particles. The neutrons scattered at backward c.m. angles may be converted into charged particles in a carbon plate. These particles are subsequently detected in scintillation counters and their coordinates are determined by hits in two MWPC’s following the carbon plate. The NC hodoscope efficiency is - 15-20% whereas the efficiency for detecting np elastic scattering in the backward hemisphere by charge-exchange reactions on carbon is about 1.5%. For this reason the backward-scattering data have considerably larger errors. In order to monitor correctly measurements with two opposite target-polarization directions, a polyethylene “CH,” target 3-10 mm thick was positioned downstream from the PPT and viewed by a dedicated scintillation counter. Particles scattered either on the PPT or on the CH, target produce independent triggers, but their tracks are detected in the same MWPC’s. The number of events from the CH, target, is used to normalize the data taken with opposite PPT polarizations. The triggers and fast electronics are described in ref. [7]. Candidates for np events are determined and recognized by three different pretriggers. The following pretriggers are used: (1) Forward neutron, backward proton, np scattering in the PIT: pretrigger TND. (2) Forward neutron, backward proton, np scattering in the additional CH, target: pretrigger MND. (3) Forward proton, backward neutron from both targets: pretrigger TNG. The
514
.I.Ball et al. / Angular dependence (III)
backward neutrons are detected by CEX in carbon. Which of the targets is hit is determined in the OFF-LINE analysis. The sum of pretriggers enter in the NC logic, which determine charged or neutral NC events, and give the master trigger. This trigger gives an event interrupt NIM signal to the CAC module (based on the Motorola 68000 microprocessor) and to the on-line computer. The CAC module starts the acquisition of MWPC’s, TDC’s and the information of different memory units. Coincidences between the accepted master-trigger signals and delayed pretriggers determine the final kind of triggers. The data analysis is described in detail in ref. [7]. For all types of events the proton track was reconstructed from the hits in the MWPC’s. For the reconstruction of the neutron trajectory, the interaction vertex in the PPT is assumed to be the intercept of the track of the proton, measured in the conjugate arm, with the vertical plane containing the beam axis. The second point of the neutron trajectory is given either by the neutron position in the NC hodoscope (forward neutron) or by the intersection of the charged particle track from the np charge exchange in carbon with the center plane of the carbon converter. The forward particle momentum is determined by neutron or proton time-offlight between the PPT and the NC hodoscope (all events) and from the curvature of charged particles in the spectrometer magnet (TNG events).
4. Results and discussion The general expression for the differential cross section of elastic scattering with polarized beam and polarized target is given in ref. [6]. For measurements with beam and target polarizations (P, and P,,respectively) oriented vertically, the general formula in ref. [61 reduces to
where v = (da/da) is the differential cross section, q is the angle between the reaction plane and the laboratory horizontal plane, A...., A_” and A...,, are measured observables. The beam polarization IP, )was independent of its direction whereas the absolute values of the target polarizations differ. The four measurements with different combinations of the beam and target polarizations allow the determination of the two analyzing powers and the spin correlation parameter A..,,,,. Only the A_” results are reported here. The results at nine energies are listed in tables l-9. Data from all runs at the same energy are in excellent agreement. This can be seen in ref. ill], where
J. Ball et al. / Angular dependence Table 1 Results of the spin correlation parameter A,,,,
28.8 32.3 36.0 39.8 43.6 47.2 51.2 55.2 59.2 61.9
0.093 0.116 0.143 0.174 0.207 0.241 0.280 0.322 0.366 0.398
- 0.156 - 0.083 - 0.077 -0.019 0.014 0.019 0.054 0.099 0.122 0.183
47.5 49.1 51.0 53.0 55.0 57.0 59.0 61.0 63.0
0.244 0.259 0.278 0.299 0.320 0.342 0.364 0.387 0.410
0.031 0.045 0.047 0.031 0.083 0.129 0.061 0.084 0.123
f + f + f f k f f f
0.067 0.026 0.017 0.017 0.015 0.017 0.024 0.035 0.046 0.124
+ 0.099 k 0.042 f 0.035 + 0.035 f 0.038 + 0.039 f 0.036 & 0.036 f 0.040
a Tkrn= 0.800 GeV, P ,ab = 1.464 GeV/c,
(deg.)
&,c)2
Exp. value A,,,
48.1 50.0 52.0 54.0 56.0 58.0 60.0 62.0 64.0 66.0 68.0 69.9 72.0 74.0 76.0 77.9
0.261 0.282 0.303 0.324 0.347 0.370 0.394 0.418 0.442 0.467 0.492 0.518 0.544 0.571 0.597 0.624
0.038 0.093 0.090 0.082 0.087 0.122 0.139 0.139 0.153 0.193 0.167 0.126 0.152 0.181 0.115 0.127
65.0 66.9 68.9 71.0 73.0 75.0 77.0 79.0 81.0 83.0 86.0 89.9 93.8
0.433 0.457 0.480 0.506 0.531 0.557 0.582 0.607 0.634 0.659 0.699 0.749 0.801
0.172 0.154 0.107 0.121 0.087 0.191 0.074 0.128 0.068 0.081 0.021 0.018 -0.119
+ + + + f + k f * + f + *
0.042 0.048 0.068 0.087 0.076 0.071 0.065 0.079 0.074 0.075 0.054 0.059 0.071
98.3 102.3 108.0 113.9 122.0
0.895 0.910 0.983 1.055 1.149
0.107 -0.128 - 0.240 - 0.229 - 0.176
+ f + k k
0.272 0.214 0.203 0.284 0.308
for np elastic scattering at 0.84 GeV a Exp. value
f 0.022 + 0.017 _+0.017 f 0.017 + 0.018 f 0.018 f 0.019 * 0.020 + 0.021 f 0.021 + 0.023 + 0.025 f 0.027 + 0.026 + 0.027 + 0.029
a Tki, = 0.840 GeV, P,,, = 1.511 GeV/c,
Exp. value
total 37 points.
Table 2 Results of the spin correlation parameter A,,,,
e c.m.
515
for np elastic scattering at 0.80 GeV a
e c.m. (deg.)
Exp. value
eC.rn. (deg.)
(III)
79.9 82.0 83.9 86.0 87.9 89.9 92.5
0.651 0.678 0.705 0.732 0.760 0.787 0.832
0.096 0.028 0.006 - 0.004 - 0.009 -0.170 -0.191
+ f + + f * +
95.5 98.9 103.1 107.0 111.0 115.0 118.9 125.4
0.884 0.911 0.966 1.019 1.070 1.122 1.169 1.247
- 0.079 -0.193 -0.246 - 0.301 - 0.054 - 0.255 -0.159 0.005
+ 0.136 + 0.105 k 0.106 _+0.092 * 0.102 _+0.094 * 0.101 + 0.098
total 31 points.
-
0.031 0.034 0.040 0.047 0.054 0.073 0.083
516
J. Ball et al. / Angular dependence (IIlj
Table 3 Results of the spin correlation
parameter
A,,,,
eCm. (deg.)
Exp. value kg.,
&,c)2
A,,,,
48.0 50.0 52.0 54.0 56.0 59.0 60.0 62.0 64.0 66.0 68.0 70.0 72.0 74.0 76.0 78.0
0.267 0.288 0.310 0.332 0.356 0.392 0.394 0.428 0.453 0.478 0.504 0.531 0.557 0.584 0.611 0.639
0.120 0.095 0.107 0.124 0.105 0.170 0.139 0.181 0.142 0.172 0.210 0.194 0.108 0.155 0.096 0.096
a Tki, = 0.860 GeV,
+ 0.034 f 0.028 +_0.027 + 0.028 + 0.029 f 0.021 + 0.019 rt 0.031 + 0.031 + 0.033 + 0.034 + 0.036 f 0.038 f 0.037 f 0.039 + 0.040
P ,ab = 1.535 GeV/c,
for np elastic
scattering
at 0.86 GeV a
-t (Gev/c)’
Exp. value A DOII”
80.0 82.0 84.0 86.0 89.0 92.0 94.2
0.666 0.694 0.722 0.750 0.794 0.834 0.867
-
0.113 0.037 0.032 0.019 0.139 0.154 0.160
* + + + + + f
0.040 0.043 0.042 0.043 0.032 0.048 0.052
95.4 98.9 101.0 107.1 111.0 115.0 118.9 123.0
0.883 0.911 0.962 1.044 1.096 1.148 1.197 1.246
-0.407 - 0.193 - 0.276 -0.320 -0.366 -0.321 - 0.243 - 0.045
+ f k f + f f *
0.171 0.105 0.106 0.131 0.125 0.143 0.146 0.157
total 31 points.
different partial results are given. Measurements at the same angles were combined and the final results here. The errors are statistical only. We estimate that an additional error due to uncontrolled instrumental effects is negligible for the
Fig. 1. Results
for np elastic scattering around 0.8 GeV: this experiment of the spin correlation A,,,, (full circle); 0.79 GeV, ref. [4] (open circle); 0.794 GeV, ref. [5] (plus).
J. Ball et al. / Angular dependence Table 4 Results of the spin correlation parameter A,,,, Exp. value
e c.m. 28.9 31.1 33.1 35.0 37.0 39.0 41.0 43.0 45.0 47.0 49.0 50.9 52.9 54.9 56.7
0.103 0.119 0.134 0.149 0.166 0.184 0.202 0.221 0.242 0.262 0.284 0.305 0.328 0.351 0.374
47.9 49.1 50.0 51.0 52.0 52.9 54.0 55.0 56.0 56.9 58.0 59.0 60.0 60.9 62.0 63.0 64.0
0.272 0.285 0.296 0.306 0.317 0.328 0.341 0.352 0.364 0.375 0.388 0.401 0.412 0.424 0.438 0.451 0.463
-
0.157 0.143 0.133 0.078 0.058 0.035 0.026 0.003 0.101 0.046 0.070 0.083 0.129 0.113 0.098
f + * + + + * f + f f * + f +
0.053 0.035 0.026 0.022 0.020 0.020 0.021 0.023 0.023 0.023 0.025 0.029 0.036 0.045 0.072
0.063 0.056 0.120 0.093 0.105 0.137 0.123 0.121 0.143 0.145 0.159 0.222 0.190 0.147 0.183 0.171 0.179
+ 0.022 + 0.017 + 0.025 t 0.016 & 0.024 + 0.018 + 0.023 f 0.020 It 0.019 * 0.019 i 0.018 f 0.025 + 0.019 + 0.024 rt 0.026 * 0.017 + 0.027
a T,, = 0.880 GeV, Ptab = 1.558 GeV/c,
for np elastic scattering at 0.88 GeV a 0c.m. (deg.1
(deg.1
517
(iIll
Exp. value
65.0 65.9 67.0 68.0 68.9 69.9 71.0 72.0 73.1 73.9 75.0 75.9 76.9 79.0 81.0 82.0 83.0 83.9 84.9 85.9 87.5 89.0 90.7 92.7 93.9
0.477 0.489 0.503 0.518 0.529 0.543 0.557 0.570 0.585 0.597 0.612 0.625 0.639 0.668 0.697 0.712 0.724 0.739 0.753 0.768 0.791 0.812 0.837 0.865 0.883
0.147 + 0.030 0.190 + 0.021 0.165 + 0.034 0.228 f 0.022 0.160 + 0.043 0.189 + 0.023 0.133 * 0.047 0.104 rt 0.024 0.110 * 0.040 0.129 _t 0.024 0.131 10.040 0.080 f 0.037 0.107 10.022 0.090 I 0.026 0.089 5 0.049 0.074 $ 0.037 0.086 f 0,052 0.047 + 0.046 - 0.021 10.022 - 0.092 + 0.055 -0.112 f 0.062 - 0.101 & 0.027 - 0.104 + 0.050 - 0.176 I 0.032 - 0.189 f 0.077
95.5 99.1 103.0 107.2 111.0 114.9 120.6
0.906 0.958 1.012 1.072 1.123 1.175 1.248
-0.150 -0.179 -0.319 - 0.324 - 0.315 - 0.328 - 0.187
& 0.126 i 0.066 i: 0.057 * 0.054 * 0.057 I 0.055 I 0.069
total 64 points.
present experiment. The uncertainties in the target polarization measurements are +3%. The systematic error due to the normalization on the event statistics with different signs of beam and target polarization to the same integrated beam intensity was considerably reduced using the additional CHZ target. ResuIts for A.,,, separately measured in three angular intervals smoothly connect in overlapping regions. The angular dependence of A..,, shows negative values below 50” c.m. at 0.8 GeV. The zero-crossing angle moves towards 40” at 1.1 GeV. Above this angle, in a large energy interval below 0.8 GeV, A,,, is positive with a maximum at 70°C
518
J. Ball et al. / Angular dependence (III)
Table 5 Results of the spin correlation parameter A,,,,
for np elastic scattering at 0.91 GeV a
Exp. value 47.5 50.1 52.0 54.0 57.0 60.9 65.1 70.0 73.0 77.1
0.268 0.296 0.318 0.340 0.376 0.425 0.479 0.544 0.585 0.642
0.288 0.303 0.263 0.240 0.195 0.168 0.097 0.034 - 0.028 - 0.048
+ + f f + + + + f +
Exp. value A GO”0
0.039 0.028 0.023 0.021 0.017 0.016 0.018 0.019 0.022 0.023
a Tkin= 0.880 Gev, Plab = 1.558 GeV/c,
80.9 84.9 88.6 93.6
0.695 0.753 0.805 0.878
-0.111 - 0.128 - 0.268 - 0.343
f f k +
0.027 0.033 0.042 0.097
91.9 97.3 105.1 112.7 121.1
0.855 0.931 1.042 1.145 1.252
-
+ + f + +
0.042 0.044 0.046 0.050 0.057
0.078 0.134 0.133 0.256 0.131
total 19 points.
c.m. and again crosses zero at 151” c.m. This shaped is observed even at 0.8 GeV as shown in fig. 1. At 0.84 GeV the forward maximum value increases, the data cross zero at 90” c.m. and reach a minimum at 120” c.m. A similar shape of the
Table 6 Results of the spin correlation parameter A,,,,
kg.,
&,cY
25.8 29.5 33.2 37.0 41.0 45.0 48.8 52.8 56.8 60.8
0.088 0.114 0.144 0.178 0.216 0.258 0.301 0.348 0.399 0.452
48.0 50.0 52.0 54.0 56.0 58.0 60.0 62.0 64.0 66.0
0.292 0.315 0.338 0.363 0.388 0.414 0.440 0.467 0.495 0.523
Exp. value A 00”” -
0.034 0.137 0.043 0.002 0.047 0.105 0.147 0.196 0.260 0.191
+ + f + + + * f f +
0.144 0.036 0.022 0.018 0.019 0.018 0.020 0.029 0.041 0.050
0.163 0.126 0.161 0.169 0.221 0.205 0.215 0.257 0.215 0.224
f 0.020 + 0.017 + 0.017 zk0.018 f 0.019 -I 0.020 + 0.020 + 0.021 + 0.022 + 0.023
a T,,, = 0.940 GeV, I’,,, = 1.628 GeV/c,
for np elastic scattering at 0.94 GeV a
e C.ln. (deg.)
&v,cY
68.0 70.0 72.0 74.0 76.0 78.0 80.0 81.9 84.0 86.0 88.0 90.0 92.6
0.551 0.580 0.609 0.638 0.668 0.698 0.728 0.758 0.790 0.820 0.851 0.882 0.921
0.244 0.200 0.199 0.133 0.138 0.144 0.115 0.052 - 0.055 - 0.016 -0.155 - 0.182 - 0.192
f f + f * f + + f f + + +
0.025 0.027 0.028 0.028 0.029 0.032 0.032 0.034 0.034 0.035 0.038 0.038 0.034
97.8 103.0 105.7 111.1 112.9 115.0 119.0 121.5
1.003 1.080 1.122 1.199 1.225 1.256 1.311 1.345
-
f + f f + f f f
0.078 0.162 0.068 0.157 0.074 0.126 0.155 0.070
total 41 points.
Exp. value A 00””
0.410 0.321 0.392 0.333 0.342 0.399 0.328 0.234
519
J. Ball et al. / Angular dependence (III) Table 7 Results of the spin correlation parameter A,,,,
for np elastic scattering at 1.00 GeV a Exp. value
Exp. value 20.7 23.5 26.4 29.7 32.8 36.0 39.1 42.2 45.6
0.060 0.078 0.098 0.123 0.150 0.179 0.211 0.243 0.281
-0.179 -0.129 - 0.065 0.015 0.088 0.098 0.127 0.181 0.247
+ + k + + f f f f
0.105 0.037 0.024 0.021 0.021 0.021 0.023 0.032 0.087
48.0 50.0 52.0 54.0 56.0 58.0 60.0 62.0 64.0 66.0 67.9
0.310 0.335 0.361 0.386 0.413 0.441 0.468 0.498 0.527 0.556 0.586
0.141 0.143 0.155 0.199 0.219 0.249 0.192 0.215 0.253 0.158 0.193
+ + + f f f k f f f +
0.025 0.023 0.022 0.023 0.023 0.024 0.025 0.027 0.027 0.029 0.032
a Tki,
= 1.00 GeV, P,,, = 1.697 GeV/c,
70.0 72.0 74.0 76.0 78.0 80.9 82.0 84.0 86.0 88.0 89.9
0.617 0.648 0.679 0.711 0.743 0.789 0.807 0.840 0.872 0.905 0.937
92.2 93.8 98.2 105.5 111.2 115.0 118.9 123.7 149.6
0.976 1.000 1.072 1.190 1.278 1.334 1.392 1.460 1.747
-
0.131 0.148 0.120 0.057 0.004 0.027 0.015 0.017 0.040 0.177 0.103
- 0.148 -0.153 - 0.181 -0.518 - 0.374 -0.276 - 0.307 -0.285 0.387
+ 0.037 + 0.035 + 0.035 f 0.036 + 0.039 f 0.029 + 0.043 f 0.046 _+0.050 f 0.056 + 0.063 f + f + + + + + f
0.072 0.158 0.162 0.100 0.132 0.115 0.128 0.119 0.369
total 40 points.
angular dependence, with more pronounced maxima and minima, can be observed up to 1.10 GeV. Our results at 1.10 GeV show that the A,,, values above 135” are again positive, but a sign change around 1.50”c.m. as found at smaller energies, is not seen. Our data can be compared with existing results only at 0.8 GeV, since no other measurements at higher energy exist. Fig. 1 shows a comparison of present results
Table 8 Results of the spin correlation parameter A,,,,
for np elastic scattering at 1.08 GeV a
0C.rn. (deg.)
&,cJ2
Exp. value A,,,,
I3C.rn. (deg.)
&cs
53.1 53.9 58.0 61.8 66.1
0.363 0.416 0.477 0.535 0.604
0.127 0.070 0.139 0.113 0.088
69.9 74.0 77.8 82.1 86.0
0.666 0.735 0.800 0.875 0.944
+ f + + +
0.040 0.037 0.039 0.048 0.070
a Tkin = 1.08 GeV, P lab= 1.788 GeV/c,
total 10 points.
Exp. value A 00”” 0.125 - 0.039 - 0.005 -0.173 - 0.091
k + f * +
0.063 0.072 0.082 0.091 0.104
J. Ball et al. / Angular dependence (III)
520
Table 9 Results of the spin correlation parameter A,,,, e E.rn. (deg.)
Exp. value
25.6 29.3 33.1 37.0 41.0 44.9 48.9 52.8 56.8 60.9
0.102 0.132 0.167 0.207 0.253 0.301 0.354 0.407 0.467 0.530
48.0 50.0 52.0 54.0 56.0 58.0 59.9
0.341 0.369 0.396 0.425 0.454 0.485 0.515
-
0.083 0.152 0.027 0.023 0.049 0.146 0.180 0.169 0.231 0.078
f 0.071 + 0.029 + 0.022 f 0.020 * 0.022 f 0.022 f 0.023 + 0.033 + 0.047 IL-0.068
0.095 0.135 0.150 0.166 0.224 0.187 0.202
+ f f + f + +
0.031 0.030 0.029 0.031 0.035 0.038 0.044
a Tkin = 1.10 GeV, P ,ab = 1.810 GeV/c,
for np elastic scattering at 1.10 GeV a eCm. (deg.)
Exp. value
62.0 64.9 68.8 72.0 75.0 79.0 82.0 83.9
0.548 0.594 0.659 0.714 0.766 0.836 0.890 0.924
0.184 0.160 0.136 0.053 - 0.068 - 0.214 - 0.265 -0.216
+ 0.048 rf:0.041 f 0.052 + 0.092 f 0.072 f 0.088 f 0.163 + 0.163
91.9 97.1 105.0 113.0 120.8 126.5 137.1 142.9
1.068 1.160 1.301 1.437 1.561 1.645 1.791 1.858
-0.155 - 0.247 - 0.329 - 0.252 - 0.142 0.206 0.397 0.636
+ + f + + f k f
0.174 0.081 0.078 0.075 0.086 0.207 0.287 0.336
total 33 points.
at 0.8 GeV with the LAMPF results at 0.79 GeV [ref. 41 and with the SATURNE II quasielastic np scattering data [5] at 0.794 GeV. 5. Conclusions The spin correlation parameter A,,, (np) has been measured at nine energies between 0.80 and 1.1 GeV using the SATURNE II polarized beam of free
_0,3_
0.84 GeV
C+-~(deg) Fig. 2. Spin correlation parameter A,,,
(np) at 0.84 GeV.
J. Ball et al. / Angular dependence (III)
I
I
I
I
I
I
I
I
I
I
II
II
521
11
a3
Aoonn
0.2-
0.86 GeV
I
0.1 O--o.l-0.2-0.3 SATURNE
-0.4I
-‘“O
I
I
30
I
II I
I
60
I
I
Ill
90 eCM(deg)
I
i
’ i20
Fig. 3. Spin correlation parameter A,,,,
I
I
I
I
150
I
I
180
(np) at 0.86 GeV.
neutrons in conjunction with the Saclay frozen-spin polarized proton target. At all energies high statistics for A..., (np) could be obtained below 90” c.m. where the scattered neutrons are detected with a neutron-counter hodoscope. For angles above 90” c.m., where neutrons are converted into protons by charge exchange in a carbon block, the experimental errors are larger. At energies above 0.84 GeV the measured angular dependence of A,,,,.” (np) shows well-pronounced structures. Most interesting is a dip between 110” and 120 c.m., which does not exist below 0.8 GeV.
0.3 Aoonn
0.2
n-p
0.88
GeV
0.1 I O___---
-O.l-
-0.40
’ ’ 30 ’ ’ ’ 60’ ’ ’ 90’ 1 1 120 1 1 1 150 1 1 1180 6~~ Meg)
Fig. 4. Spin correlation parameter A,,,
hp) at 0.88 GeV.
522
J. Ball et al. / Angular deference
(III)
0.2 0.1
0
Fig. 5. Spin correlation parameter A,,,
(np) at 0.91 GeV.
The present results represent an important contribution to the np -+ np data base. They will contribute to the extension of the phase-shift analysis towards higher energies and to a direct reconstruction of the np elastic-scattering matrix.
We acknowledge J. Arvieux, R. Beurtey, P.A. Chamouard, A. Fleury, M. Havlicek, E. Heer, T. Kirk, J.M. Laget, N.A. Rusakovich, J. Saudinos, Ts. Vylov
-0.3-0.4 -
I I I I I I I I I 30
60
90 BCM(de9)
Fig. 6. Spin correlation parameter A,,,
(np) at 0.94 GeV.
.i. Bail et al. / Angular dependence @IJj
523
@CM(deg) Fig, 7. Spin correlation parameter A,,,,
(np) at 1.00 GeV.
and A. Yokosawa for support of this work. Discussions with J. Deregcl, J. Franz, Yu.M. Kazarinov, J.M. Lagniei, C. Lechanoine-Leluc, G. Milleret and Y. Terrien have solved several problems. The exploitation of the polarized target owes a lot to 6. Guillier, Ph. Marlet and J. ~omm~jat. We thank T. Lambert, E. Perrin, J. Poupard and J.P. Richeux for their efficient help in preparation of the experiment,
Fig. 8. Spin correlation parameter A,,,
(npf at 1.08 GeV.
J.Balletal./ Angular dependence(III)
524
06 05 04
*oonn n-p 1.1 GeV
t 0.3t 0.2 0.1 0 _--! -0.1 -0.2
44
9 I 1 +
t I1itt
-_ _-*!_-___
_I---____
+
-0.3 -0.4I
Fig. 9. Spin correlation
parameter
A,,,
(np) at 1.10 GeV.
Finally we express our gratitude to F. Haroutel, which organized stays of all visiting participants. This work was partly supported by the Swiss National Science Foundation and by the US Department of Energy Contract No. W-31-109-ENG-38.
References
[l] J. Ball, Ph. Chesny, M. Combet, J.M. Fontaine, R. Kunne, M.C. Lemaire, J.L. Sam, J. Bystricky, CD. Lac, F. Lehar, A. de Lesquen, M. de Mali, F. Perrot-Kunne, L. van Rossum, P. Bach, Ph. Demierre, G. Gaillard, R. Hess, D. Rapin, Ph. Sormani, J.P. Goudour, R. Binz, A. Klett, E. Rossle, H. Schmitt, L.S. Barabash, Z. Janout, B.A. Khachaturov and Yu.A. Usov, Nucl. Phys. A559 (1993) 477 121 J. Ball, Ph. Chesny, M. Combet, J.M. Fontaine, CD. Lac, J.L. Sans, J. Bystricky, F. Lehar, A. de Lesquen, M. de Mali, F. Perrot-Kunne, L. van Rossum, A. Ahmidouch, P. Bach, Ph. Demierre, G. Gaillard, R. Hess, R. Kunne, D. Rapin, Ph. Sormani, J.P. Goudour, R. Binz, A. Klett, R. Rossle, H. Schmitt, D. Lopiano and H. Spinka, Nucl. Phys. A559 (1993) 489 [3] J.M. Fontaine, F. Perrot-Kunne, J. Bystricky, J. Derigel, F. Lehar, A. de Lesquen, M. de Mali, L. van Rossum, J. Ball, Ph. Chewy, CD. Lac, J.L. Sans, J.P. Goudour, P. Bach, G. Gaillard, R. Hess, R. Kunne, D. Rapin, Ph. Sormani, R. Binz, A. Klett, R. Peschina, E. Rossle and H. Schmitt, Nucl. Phys. B358 (1991) 297
J. Ball et al. / Angular dependence (III)
525
[4] S. Nath, G. Glass, J.C. Hiebert, J.A. Holt, A.B. Kenefick, L.C. Northcliffe, D.P. Grosnick, D. Lopiano, Y. Ohashi, T. Shima, H.M. Spinka, R. Stanek. T.S. Bhatia, J.J. Jarmer, P.J. Riley, S. Sen. J.A. Faucett, G. Kyle, R.H. Jeppesen and G.E. Tripard, Phys. Rev. D39 (1989) 3520 151 A. de Lesquen, F. Lehar, L. van Rossum, P. Chaumette, J. Deregel, J. Fabre, J.M. Fontaine, F. Perrot, P. Bach, R. Hess, Ph. Sormani, J. Ball, C.D. Lac, D. Adams, J. Bystricky, V. Ghazikhanian and C.A. Whitten, Nucl. Phys. B304 (1988) 673 [6] J. Bystricky, F. Lehar and P. Winternitz, J. de Phys. 39 (1978) 1 [7] J. Ball, Ph. Chesny, M. Combet, J.M. Fontaine, R. Kunne, J.L. Sans, J. Bystricky, F. Lehar, A. de Lesquen, M. de Mali, F. Perrot-Kunne, L. van Rossum, P. Bach, Ph. Demierre, G. Gaillard, R. Hess, Z.F. Janout, D. Rapin, Ph. Sormani, B. Vuaridel, J.P. Goudour, R. Binz, A. Klett, E. Rossle, H. Schmitt, L.S. Barabash, Z. Janout. V.A. Kalinnikov, Yu.M. Kazarinov, B.A. Khachaturov, V.N. Matafonov, I.L. Pisarev, A.A. Popov, Yu.A. Usov, M. Beddo, D. Grosnick, T. Kasprzyk, D. Lopiano and H. Spinka, Nucl. Instr. Meth. A327 (1993) 308 [8] J. Bystricky, J. Deregel, F. Lehar, A. de Lesquen, L. van Rossum, J.M. Fontaine, F. Perrot, C.A. Whitten, T. Hasegawa, C.R. Newsom, W.R. Leo, Y. Onel, S. Dalla Torre-Colautti, A. Penzo, H. Azaiez and A. Michalowicz, Nucl. Instr. Meth. A239 (1985) 131 [9] R. Bernard, P. Chaumette, P. Chesny, J. Deregel, R. Duthil, J. Fabre. C. Lesmond, G. Seite, J. Ball, T.O. Niinikoski and M. Rieubland, Nucl. Instr. Meth. A249 (1986) 176 [lo] A. Ahmidouch, P. Bach, R. Hess, R. Kunne, C. Lechanoine-Lcluc, Ch. Mascarini. D. Rapin, J. Arvieux, R. Bertini, H. Catz, J.C. Faivre, F. Perrot-Kunne, F. Bradamante, A. Martin, Nucl. Instr. Meth. A326 (1993) 538 [ll] J. Ball, Ph.D. Thesis, Faculty of Science, University of Paris, Orsay, No. 2132
Nuclear Physics A559 (1993) 511-525 North-Holland
Angular dependence of the spin correlation parameter A OOnn in np elastic scattering between 0.8 and 1.1 GeV J. Ball, Ph. Chesny, M. Combet, J.M. Fontaine, C.D. Lac *, MC. Lemaire 2, J.L. Sans Laboratoire National SATURNE, France
CNRS-IN2P3 and CFA / DSM, CE Saclay, 91191 Gif-sur-Yvette Cede.x,
J. Bystricky, F. Lehar, A. de Lesquen, M. de Mali, F. Perrot-Kunne, L. van Rossum DAPNIA, CE Saclay, 9lf91
Gif-sur-Yrtette Cedex, France
P. Bach 3, Ph. Demierre, G. Gaillard 4, R. Hess, R. Kunne 5, D. Rapin, Ph. Sormani 6, B. Vuaridel DPNC, University of Geneva, 24 quai Ernest-Ansermet,
1211 Gene1.a 4, Switzerland
J.P. Goudour C.E.N.B.,
Domaine du Hart&Vigneau, 33170 Gradignan, France
R. Binz, A. Klett, E. Riissle, H. Schmitt Fizculty of Physics, Freiburg University, 7800 Freiburg im B&gal*,
L.S. Barabash, Z. Janout ‘, B.A. Khachaturov,
Germany
Yu.A. Usov
LNP-JINR, Dubna, P.O. Box 7% 101000 Moscow, Russian Federation
D. Lopiano, H. Spinka ANL-HEF,
9700 South Cass Acenue, Argonne, IL 60439, USA
Received 23 November 1992
Correspondence to: Dr. F. Lehar, DAPNIA/SPLN, CE Saclay, 91191 Gif-sur-Yvette Cedex, France. Present addresses: ’ lnstitut National des Telecommunications, 9 rue Charles Fourier 91011 Evry, France. 2 DAPNIA, CEN-Saclay, 91191 Gif-sur-Yvette, Cedex, France. s College Rousseau, 16A avenue de Bouchet, 1209 Geneva, Switzerland. 4 Schlumberger Ind., 87 route de Grigny, 91130 Ris Orangis, France. ’ LNS, CE Saclay, 91191 Gif-sur-Yvette, Cedex, France. ’ Brainsoft Consulting S.A., Cusinand 46, 128.5Athenaz, Switzerland. ’ Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University, Brehova 7, 11519 Prague 1, Czech Republic. 03759474/93/$06.00
Q 1993 - Elsevier Science Publishers B.V. All rights reserved
.I. Ball et al. / Angular dependence (III)
512 Abstract
We present a total of 323 data points of the spin correlation parameter A,,_(np) in a large angular interval at eight energies between 0.8 and 1.1 GeV. The SATURNE II polarized beam of free neutrons obtained from the break-up of polarized deuterons was scattered on the polarized Saclay frozen-spin proton target. The present data are the first existing results above 0.8 GeV. Key words: NUCLEAR REACTIONS ‘H (polarized correlation parameter. Polarized frozen-spin target.
n,n), E = 0.8-1.1 GeV, measured
spin
1. Introduction
The experiment is part of a systematic study of the nucleon-nucleon system in the energy range of SATURNE II. We present measurements of the spin correlation parameter A_,, at 0.80, 0.84, 0.86, 0.88, 0.91, 1.00, 1.08 and 1.10 GeV obtained with a polarized beam of free quasi-monochromatic neutrons scattered on the Saclay frozen-spin proton target. The beam and target polarizations were oriented vertically. In the same experiment were measured the analyzing power data presented in refs. [1,21, the depolarization Donon and the polarization transfer K onno, which will be reported in a forthcoming paper. All these data were taken simultaneously with the transmission measurement of the total cross-section difference Au-&p) [ref. 31. The results at 0.8 GeV are compared with the LAMPF data [41 and with the quasielastic scattering of neutrons in the accelerated polarized deuterons on the same target [51. Throughout this paper we use the nucleon-nucleon formalism and the four-spin notation developed in ref. [6].
2. Polarized
beam and target
Polarized neutrons are produced by break-up of vector-polarized deuterons on a 20 cm thick Be target. The vertically polarized neutron beam is defined by a total of 8 m of collimators inserted in the 17.5 m long neutron beam line. At the polarized target the beam spot was either 20 mm or 30 mm in diameter. The neutron beam has a momentum spread due to deuteron absorption in the production target and to the Fermi motion of neutrons in deuterons. The momentum spread is of the order of k 20 MeV. The polarized deuteron beam with (2-3) X 10” deuterons/ burst produces N 6 x 10’ neutrons/burst at the PPT with the collimator 30 mm in diameter. The neutron beam intensity was monitored by a scintillation counter array inserted in the beam in front of the polarized target [31. The deuteron beam polarization was flipped every burst of the accelerator by a change of the RF transitions in the ion source. The polarization of break-up neutrons was determined by a dedicated experiment measuring the asymmetries EB = PBAoonoand EB = P, A,_, [ref. 11. Using the known target polarization P, and assuming A.,,,,. = A...,, we obtain P, = 0.59, independent of the neutron
J. Ball et al. / Angular dependence (III)
513
beam energy [1,7]. At each energy the polarization of the protons in the accelerated deuterons was also checked by the beam polarimeter [8]. The PPT was 35 mm thick, 40 mm wide and 49 mm high [9]. The target material was pentanol, with a typical proton polarization of 85%. The target polarization is held in vertical magnetic field of - 0.33 T produced by a vertical superconducting holding coil. The target polarization was inverted every few hours.
3. Experimental
set-up and data analysis
The apparatus is designed for pp, np and pn elastic-scattering experiments in a large angular domain. The experimental set-up is described in ref. [7]. Outgoing particles are detected by a two-arm spectrometer which comprises single scintillation counters, counter hodoscopes, the neutron counter (NC) hodoscope with its VETO, analyzing magnet and eight multiwire proportional chambers. The NC hodoscope [7,10] consists of 15 scintillating bars and measures a particle position from the time difference between signals from the two PM’s on either side of a bar, with a precision of _t25 mm. Veto counters in front of the neutron-counter hodoscope distinguish between neutral and charged particles. The neutrons scattered at backward c.m. angles may be converted into charged particles in a carbon plate. These particles are subsequently detected in scintillation counters and their coordinates are determined by hits in two MWPC’s following the carbon plate. The NC hodoscope efficiency is - 15-20% whereas the efficiency for detecting np elastic scattering in the backward hemisphere by charge-exchange reactions on carbon is about 1.5%. For this reason the backward-scattering data have considerably larger errors. In order to monitor correctly measurements with two opposite target-polarization directions, a polyethylene “CH,” target 3-10 mm thick was positioned downstream from the PPT and viewed by a dedicated scintillation counter. Particles scattered either on the PPT or on the CH, target produce independent triggers, but their tracks are detected in the same MWPC’s. The number of events from the CH, target, is used to normalize the data taken with opposite PPT polarizations. The triggers and fast electronics are described in ref. [7]. Candidates for np events are determined and recognized by three different pretriggers. The following pretriggers are used: (1) Forward neutron, backward proton, np scattering in the PIT: pretrigger TND. (2) Forward neutron, backward proton, np scattering in the additional CH, target: pretrigger MND. (3) Forward proton, backward neutron from both targets: pretrigger TNG. The
514
.I.Ball et al. / Angular dependence (III)
backward neutrons are detected by CEX in carbon. Which of the targets is hit is determined in the OFF-LINE analysis. The sum of pretriggers enter in the NC logic, which determine charged or neutral NC events, and give the master trigger. This trigger gives an event interrupt NIM signal to the CAC module (based on the Motorola 68000 microprocessor) and to the on-line computer. The CAC module starts the acquisition of MWPC’s, TDC’s and the information of different memory units. Coincidences between the accepted master-trigger signals and delayed pretriggers determine the final kind of triggers. The data analysis is described in detail in ref. [7]. For all types of events the proton track was reconstructed from the hits in the MWPC’s. For the reconstruction of the neutron trajectory, the interaction vertex in the PPT is assumed to be the intercept of the track of the proton, measured in the conjugate arm, with the vertical plane containing the beam axis. The second point of the neutron trajectory is given either by the neutron position in the NC hodoscope (forward neutron) or by the intersection of the charged particle track from the np charge exchange in carbon with the center plane of the carbon converter. The forward particle momentum is determined by neutron or proton time-offlight between the PPT and the NC hodoscope (all events) and from the curvature of charged particles in the spectrometer magnet (TNG events).
4. Results and discussion The general expression for the differential cross section of elastic scattering with polarized beam and polarized target is given in ref. [6]. For measurements with beam and target polarizations (P, and P,,respectively) oriented vertically, the general formula in ref. [61 reduces to
where v = (da/da) is the differential cross section, q is the angle between the reaction plane and the laboratory horizontal plane, A...., A_” and A...,, are measured observables. The beam polarization IP, )was independent of its direction whereas the absolute values of the target polarizations differ. The four measurements with different combinations of the beam and target polarizations allow the determination of the two analyzing powers and the spin correlation parameter A..,,,,. Only the A_” results are reported here. The results at nine energies are listed in tables l-9. Data from all runs at the same energy are in excellent agreement. This can be seen in ref. ill], where
J. Ball et al. / Angular dependence Table 1 Results of the spin correlation parameter A,,,,
28.8 32.3 36.0 39.8 43.6 47.2 51.2 55.2 59.2 61.9
0.093 0.116 0.143 0.174 0.207 0.241 0.280 0.322 0.366 0.398
- 0.156 - 0.083 - 0.077 -0.019 0.014 0.019 0.054 0.099 0.122 0.183
47.5 49.1 51.0 53.0 55.0 57.0 59.0 61.0 63.0
0.244 0.259 0.278 0.299 0.320 0.342 0.364 0.387 0.410
0.031 0.045 0.047 0.031 0.083 0.129 0.061 0.084 0.123
f + f + f f k f f f
0.067 0.026 0.017 0.017 0.015 0.017 0.024 0.035 0.046 0.124
+ 0.099 k 0.042 f 0.035 + 0.035 f 0.038 + 0.039 f 0.036 & 0.036 f 0.040
a Tkrn= 0.800 GeV, P ,ab = 1.464 GeV/c,
(deg.)
&,c)2
Exp. value A,,,
48.1 50.0 52.0 54.0 56.0 58.0 60.0 62.0 64.0 66.0 68.0 69.9 72.0 74.0 76.0 77.9
0.261 0.282 0.303 0.324 0.347 0.370 0.394 0.418 0.442 0.467 0.492 0.518 0.544 0.571 0.597 0.624
0.038 0.093 0.090 0.082 0.087 0.122 0.139 0.139 0.153 0.193 0.167 0.126 0.152 0.181 0.115 0.127
65.0 66.9 68.9 71.0 73.0 75.0 77.0 79.0 81.0 83.0 86.0 89.9 93.8
0.433 0.457 0.480 0.506 0.531 0.557 0.582 0.607 0.634 0.659 0.699 0.749 0.801
0.172 0.154 0.107 0.121 0.087 0.191 0.074 0.128 0.068 0.081 0.021 0.018 -0.119
+ + + + f + k f * + f + *
0.042 0.048 0.068 0.087 0.076 0.071 0.065 0.079 0.074 0.075 0.054 0.059 0.071
98.3 102.3 108.0 113.9 122.0
0.895 0.910 0.983 1.055 1.149
0.107 -0.128 - 0.240 - 0.229 - 0.176
+ f + k k
0.272 0.214 0.203 0.284 0.308
for np elastic scattering at 0.84 GeV a Exp. value
f 0.022 + 0.017 _+0.017 f 0.017 + 0.018 f 0.018 f 0.019 * 0.020 + 0.021 f 0.021 + 0.023 + 0.025 f 0.027 + 0.026 + 0.027 + 0.029
a Tki, = 0.840 GeV, P,,, = 1.511 GeV/c,
Exp. value
total 37 points.
Table 2 Results of the spin correlation parameter A,,,,
e c.m.
515
for np elastic scattering at 0.80 GeV a
e c.m. (deg.)
Exp. value
eC.rn. (deg.)
(III)
79.9 82.0 83.9 86.0 87.9 89.9 92.5
0.651 0.678 0.705 0.732 0.760 0.787 0.832
0.096 0.028 0.006 - 0.004 - 0.009 -0.170 -0.191
+ f + + f * +
95.5 98.9 103.1 107.0 111.0 115.0 118.9 125.4
0.884 0.911 0.966 1.019 1.070 1.122 1.169 1.247
- 0.079 -0.193 -0.246 - 0.301 - 0.054 - 0.255 -0.159 0.005
+ 0.136 + 0.105 k 0.106 _+0.092 * 0.102 _+0.094 * 0.101 + 0.098
total 31 points.
-
0.031 0.034 0.040 0.047 0.054 0.073 0.083
516
J. Ball et al. / Angular dependence (IIlj
Table 3 Results of the spin correlation
parameter
A,,,,
eCm. (deg.)
Exp. value kg.,
&,c)2
A,,,,
48.0 50.0 52.0 54.0 56.0 59.0 60.0 62.0 64.0 66.0 68.0 70.0 72.0 74.0 76.0 78.0
0.267 0.288 0.310 0.332 0.356 0.392 0.394 0.428 0.453 0.478 0.504 0.531 0.557 0.584 0.611 0.639
0.120 0.095 0.107 0.124 0.105 0.170 0.139 0.181 0.142 0.172 0.210 0.194 0.108 0.155 0.096 0.096
a Tki, = 0.860 GeV,
+ 0.034 f 0.028 +_0.027 + 0.028 + 0.029 f 0.021 + 0.019 rt 0.031 + 0.031 + 0.033 + 0.034 + 0.036 f 0.038 f 0.037 f 0.039 + 0.040
P ,ab = 1.535 GeV/c,
for np elastic
scattering
at 0.86 GeV a
-t (Gev/c)’
Exp. value A DOII”
80.0 82.0 84.0 86.0 89.0 92.0 94.2
0.666 0.694 0.722 0.750 0.794 0.834 0.867
-
0.113 0.037 0.032 0.019 0.139 0.154 0.160
* + + + + + f
0.040 0.043 0.042 0.043 0.032 0.048 0.052
95.4 98.9 101.0 107.1 111.0 115.0 118.9 123.0
0.883 0.911 0.962 1.044 1.096 1.148 1.197 1.246
-0.407 - 0.193 - 0.276 -0.320 -0.366 -0.321 - 0.243 - 0.045
+ f k f + f f *
0.171 0.105 0.106 0.131 0.125 0.143 0.146 0.157
total 31 points.
different partial results are given. Measurements at the same angles were combined and the final results here. The errors are statistical only. We estimate that an additional error due to uncontrolled instrumental effects is negligible for the
Fig. 1. Results
for np elastic scattering around 0.8 GeV: this experiment of the spin correlation A,,,, (full circle); 0.79 GeV, ref. [4] (open circle); 0.794 GeV, ref. [5] (plus).
J. Ball et al. / Angular dependence Table 4 Results of the spin correlation parameter A,,,, Exp. value
e c.m. 28.9 31.1 33.1 35.0 37.0 39.0 41.0 43.0 45.0 47.0 49.0 50.9 52.9 54.9 56.7
0.103 0.119 0.134 0.149 0.166 0.184 0.202 0.221 0.242 0.262 0.284 0.305 0.328 0.351 0.374
47.9 49.1 50.0 51.0 52.0 52.9 54.0 55.0 56.0 56.9 58.0 59.0 60.0 60.9 62.0 63.0 64.0
0.272 0.285 0.296 0.306 0.317 0.328 0.341 0.352 0.364 0.375 0.388 0.401 0.412 0.424 0.438 0.451 0.463
-
0.157 0.143 0.133 0.078 0.058 0.035 0.026 0.003 0.101 0.046 0.070 0.083 0.129 0.113 0.098
f + * + + + * f + f f * + f +
0.053 0.035 0.026 0.022 0.020 0.020 0.021 0.023 0.023 0.023 0.025 0.029 0.036 0.045 0.072
0.063 0.056 0.120 0.093 0.105 0.137 0.123 0.121 0.143 0.145 0.159 0.222 0.190 0.147 0.183 0.171 0.179
+ 0.022 + 0.017 + 0.025 t 0.016 & 0.024 + 0.018 + 0.023 f 0.020 It 0.019 * 0.019 i 0.018 f 0.025 + 0.019 + 0.024 rt 0.026 * 0.017 + 0.027
a T,, = 0.880 GeV, Ptab = 1.558 GeV/c,
for np elastic scattering at 0.88 GeV a 0c.m. (deg.1
(deg.1
517
(iIll
Exp. value
65.0 65.9 67.0 68.0 68.9 69.9 71.0 72.0 73.1 73.9 75.0 75.9 76.9 79.0 81.0 82.0 83.0 83.9 84.9 85.9 87.5 89.0 90.7 92.7 93.9
0.477 0.489 0.503 0.518 0.529 0.543 0.557 0.570 0.585 0.597 0.612 0.625 0.639 0.668 0.697 0.712 0.724 0.739 0.753 0.768 0.791 0.812 0.837 0.865 0.883
0.147 + 0.030 0.190 + 0.021 0.165 + 0.034 0.228 f 0.022 0.160 + 0.043 0.189 + 0.023 0.133 * 0.047 0.104 rt 0.024 0.110 * 0.040 0.129 _t 0.024 0.131 10.040 0.080 f 0.037 0.107 10.022 0.090 I 0.026 0.089 5 0.049 0.074 $ 0.037 0.086 f 0,052 0.047 + 0.046 - 0.021 10.022 - 0.092 + 0.055 -0.112 f 0.062 - 0.101 & 0.027 - 0.104 + 0.050 - 0.176 I 0.032 - 0.189 f 0.077
95.5 99.1 103.0 107.2 111.0 114.9 120.6
0.906 0.958 1.012 1.072 1.123 1.175 1.248
-0.150 -0.179 -0.319 - 0.324 - 0.315 - 0.328 - 0.187
& 0.126 i 0.066 i: 0.057 * 0.054 * 0.057 I 0.055 I 0.069
total 64 points.
present experiment. The uncertainties in the target polarization measurements are +3%. The systematic error due to the normalization on the event statistics with different signs of beam and target polarization to the same integrated beam intensity was considerably reduced using the additional CHZ target. ResuIts for A.,,, separately measured in three angular intervals smoothly connect in overlapping regions. The angular dependence of A..,, shows negative values below 50” c.m. at 0.8 GeV. The zero-crossing angle moves towards 40” at 1.1 GeV. Above this angle, in a large energy interval below 0.8 GeV, A,,, is positive with a maximum at 70°C
518
J. Ball et al. / Angular dependence (III)
Table 5 Results of the spin correlation parameter A,,,,
for np elastic scattering at 0.91 GeV a
Exp. value 47.5 50.1 52.0 54.0 57.0 60.9 65.1 70.0 73.0 77.1
0.268 0.296 0.318 0.340 0.376 0.425 0.479 0.544 0.585 0.642
0.288 0.303 0.263 0.240 0.195 0.168 0.097 0.034 - 0.028 - 0.048
+ + f f + + + + f +
Exp. value A GO”0
0.039 0.028 0.023 0.021 0.017 0.016 0.018 0.019 0.022 0.023
a Tkin= 0.880 Gev, Plab = 1.558 GeV/c,
80.9 84.9 88.6 93.6
0.695 0.753 0.805 0.878
-0.111 - 0.128 - 0.268 - 0.343
f f k +
0.027 0.033 0.042 0.097
91.9 97.3 105.1 112.7 121.1
0.855 0.931 1.042 1.145 1.252
-
+ + f + +
0.042 0.044 0.046 0.050 0.057
0.078 0.134 0.133 0.256 0.131
total 19 points.
c.m. and again crosses zero at 151” c.m. This shaped is observed even at 0.8 GeV as shown in fig. 1. At 0.84 GeV the forward maximum value increases, the data cross zero at 90” c.m. and reach a minimum at 120” c.m. A similar shape of the
Table 6 Results of the spin correlation parameter A,,,,
kg.,
&,cY
25.8 29.5 33.2 37.0 41.0 45.0 48.8 52.8 56.8 60.8
0.088 0.114 0.144 0.178 0.216 0.258 0.301 0.348 0.399 0.452
48.0 50.0 52.0 54.0 56.0 58.0 60.0 62.0 64.0 66.0
0.292 0.315 0.338 0.363 0.388 0.414 0.440 0.467 0.495 0.523
Exp. value A 00”” -
0.034 0.137 0.043 0.002 0.047 0.105 0.147 0.196 0.260 0.191
+ + f + + + * f f +
0.144 0.036 0.022 0.018 0.019 0.018 0.020 0.029 0.041 0.050
0.163 0.126 0.161 0.169 0.221 0.205 0.215 0.257 0.215 0.224
f 0.020 + 0.017 + 0.017 zk0.018 f 0.019 -I 0.020 + 0.020 + 0.021 + 0.022 + 0.023
a T,,, = 0.940 GeV, I’,,, = 1.628 GeV/c,
for np elastic scattering at 0.94 GeV a
e C.ln. (deg.)
&v,cY
68.0 70.0 72.0 74.0 76.0 78.0 80.0 81.9 84.0 86.0 88.0 90.0 92.6
0.551 0.580 0.609 0.638 0.668 0.698 0.728 0.758 0.790 0.820 0.851 0.882 0.921
0.244 0.200 0.199 0.133 0.138 0.144 0.115 0.052 - 0.055 - 0.016 -0.155 - 0.182 - 0.192
f f + f * f + + f f + + +
0.025 0.027 0.028 0.028 0.029 0.032 0.032 0.034 0.034 0.035 0.038 0.038 0.034
97.8 103.0 105.7 111.1 112.9 115.0 119.0 121.5
1.003 1.080 1.122 1.199 1.225 1.256 1.311 1.345
-
f + f f + f f f
0.078 0.162 0.068 0.157 0.074 0.126 0.155 0.070
total 41 points.
Exp. value A 00””
0.410 0.321 0.392 0.333 0.342 0.399 0.328 0.234
519
J. Ball et al. / Angular dependence (III) Table 7 Results of the spin correlation parameter A,,,,
for np elastic scattering at 1.00 GeV a Exp. value
Exp. value 20.7 23.5 26.4 29.7 32.8 36.0 39.1 42.2 45.6
0.060 0.078 0.098 0.123 0.150 0.179 0.211 0.243 0.281
-0.179 -0.129 - 0.065 0.015 0.088 0.098 0.127 0.181 0.247
+ + k + + f f f f
0.105 0.037 0.024 0.021 0.021 0.021 0.023 0.032 0.087
48.0 50.0 52.0 54.0 56.0 58.0 60.0 62.0 64.0 66.0 67.9
0.310 0.335 0.361 0.386 0.413 0.441 0.468 0.498 0.527 0.556 0.586
0.141 0.143 0.155 0.199 0.219 0.249 0.192 0.215 0.253 0.158 0.193
+ + + f f f k f f f +
0.025 0.023 0.022 0.023 0.023 0.024 0.025 0.027 0.027 0.029 0.032
a Tki,
= 1.00 GeV, P,,, = 1.697 GeV/c,
70.0 72.0 74.0 76.0 78.0 80.9 82.0 84.0 86.0 88.0 89.9
0.617 0.648 0.679 0.711 0.743 0.789 0.807 0.840 0.872 0.905 0.937
92.2 93.8 98.2 105.5 111.2 115.0 118.9 123.7 149.6
0.976 1.000 1.072 1.190 1.278 1.334 1.392 1.460 1.747
-
0.131 0.148 0.120 0.057 0.004 0.027 0.015 0.017 0.040 0.177 0.103
- 0.148 -0.153 - 0.181 -0.518 - 0.374 -0.276 - 0.307 -0.285 0.387
+ 0.037 + 0.035 + 0.035 f 0.036 + 0.039 f 0.029 + 0.043 f 0.046 _+0.050 f 0.056 + 0.063 f + f + + + + + f
0.072 0.158 0.162 0.100 0.132 0.115 0.128 0.119 0.369
total 40 points.
angular dependence, with more pronounced maxima and minima, can be observed up to 1.10 GeV. Our results at 1.10 GeV show that the A,,, values above 135” are again positive, but a sign change around 1.50”c.m. as found at smaller energies, is not seen. Our data can be compared with existing results only at 0.8 GeV, since no other measurements at higher energy exist. Fig. 1 shows a comparison of present results
Table 8 Results of the spin correlation parameter A,,,,
for np elastic scattering at 1.08 GeV a
0C.rn. (deg.)
&,cJ2
Exp. value A,,,,
I3C.rn. (deg.)
&cs
53.1 53.9 58.0 61.8 66.1
0.363 0.416 0.477 0.535 0.604
0.127 0.070 0.139 0.113 0.088
69.9 74.0 77.8 82.1 86.0
0.666 0.735 0.800 0.875 0.944
+ f + + +
0.040 0.037 0.039 0.048 0.070
a Tkin = 1.08 GeV, P lab= 1.788 GeV/c,
total 10 points.
Exp. value A 00”” 0.125 - 0.039 - 0.005 -0.173 - 0.091
k + f * +
0.063 0.072 0.082 0.091 0.104
J. Ball et al. / Angular dependence (III)
520
Table 9 Results of the spin correlation parameter A,,,, e E.rn. (deg.)
Exp. value
25.6 29.3 33.1 37.0 41.0 44.9 48.9 52.8 56.8 60.9
0.102 0.132 0.167 0.207 0.253 0.301 0.354 0.407 0.467 0.530
48.0 50.0 52.0 54.0 56.0 58.0 59.9
0.341 0.369 0.396 0.425 0.454 0.485 0.515
-
0.083 0.152 0.027 0.023 0.049 0.146 0.180 0.169 0.231 0.078
f 0.071 + 0.029 + 0.022 f 0.020 * 0.022 f 0.022 f 0.023 + 0.033 + 0.047 IL-0.068
0.095 0.135 0.150 0.166 0.224 0.187 0.202
+ f f + f + +
0.031 0.030 0.029 0.031 0.035 0.038 0.044
a Tkin = 1.10 GeV, P ,ab = 1.810 GeV/c,
for np elastic scattering at 1.10 GeV a eCm. (deg.)
Exp. value
62.0 64.9 68.8 72.0 75.0 79.0 82.0 83.9
0.548 0.594 0.659 0.714 0.766 0.836 0.890 0.924
0.184 0.160 0.136 0.053 - 0.068 - 0.214 - 0.265 -0.216
+ 0.048 rf:0.041 f 0.052 + 0.092 f 0.072 f 0.088 f 0.163 + 0.163
91.9 97.1 105.0 113.0 120.8 126.5 137.1 142.9
1.068 1.160 1.301 1.437 1.561 1.645 1.791 1.858
-0.155 - 0.247 - 0.329 - 0.252 - 0.142 0.206 0.397 0.636
+ + f + + f k f
0.174 0.081 0.078 0.075 0.086 0.207 0.287 0.336
total 33 points.
at 0.8 GeV with the LAMPF results at 0.79 GeV [ref. 41 and with the SATURNE II quasielastic np scattering data [5] at 0.794 GeV. 5. Conclusions The spin correlation parameter A,,, (np) has been measured at nine energies between 0.80 and 1.1 GeV using the SATURNE II polarized beam of free
_0,3_
0.84 GeV
C+-~(deg) Fig. 2. Spin correlation parameter A,,,
(np) at 0.84 GeV.
J. Ball et al. / Angular dependence (III)
I
I
I
I
I
I
I
I
I
I
II
II
521
11
a3
Aoonn
0.2-
0.86 GeV
I
0.1 O--o.l-0.2-0.3 SATURNE
-0.4I
-‘“O
I
I
30
I
II I
I
60
I
I
Ill
90 eCM(deg)
I
i
’ i20
Fig. 3. Spin correlation parameter A,,,,
I
I
I
I
150
I
I
180
(np) at 0.86 GeV.
neutrons in conjunction with the Saclay frozen-spin polarized proton target. At all energies high statistics for A..., (np) could be obtained below 90” c.m. where the scattered neutrons are detected with a neutron-counter hodoscope. For angles above 90” c.m., where neutrons are converted into protons by charge exchange in a carbon block, the experimental errors are larger. At energies above 0.84 GeV the measured angular dependence of A,,,,.” (np) shows well-pronounced structures. Most interesting is a dip between 110” and 120 c.m., which does not exist below 0.8 GeV.
0.3 Aoonn
0.2
n-p
0.88
GeV
0.1 I O___---
-O.l-
-0.40
’ ’ 30 ’ ’ ’ 60’ ’ ’ 90’ 1 1 120 1 1 1 150 1 1 1180 6~~ Meg)
Fig. 4. Spin correlation parameter A,,,
hp) at 0.88 GeV.
522
J. Ball et al. / Angular deference
(III)
0.2 0.1
0
Fig. 5. Spin correlation parameter A,,,
(np) at 0.91 GeV.
The present results represent an important contribution to the np -+ np data base. They will contribute to the extension of the phase-shift analysis towards higher energies and to a direct reconstruction of the np elastic-scattering matrix.
We acknowledge J. Arvieux, R. Beurtey, P.A. Chamouard, A. Fleury, M. Havlicek, E. Heer, T. Kirk, J.M. Laget, N.A. Rusakovich, J. Saudinos, Ts. Vylov
-0.3-0.4 -
I I I I I I I I I 30
60
90 BCM(de9)
Fig. 6. Spin correlation parameter A,,,
(np) at 0.94 GeV.
.i. Bail et al. / Angular dependence @IJj
523
@CM(deg) Fig, 7. Spin correlation parameter A,,,,
(np) at 1.00 GeV.
and A. Yokosawa for support of this work. Discussions with J. Deregcl, J. Franz, Yu.M. Kazarinov, J.M. Lagniei, C. Lechanoine-Leluc, G. Milleret and Y. Terrien have solved several problems. The exploitation of the polarized target owes a lot to 6. Guillier, Ph. Marlet and J. ~omm~jat. We thank T. Lambert, E. Perrin, J. Poupard and J.P. Richeux for their efficient help in preparation of the experiment,
Fig. 8. Spin correlation parameter A,,,
(npf at 1.08 GeV.
J.Balletal./ Angular dependence(III)
524
06 05 04
*oonn n-p 1.1 GeV
t 0.3t 0.2 0.1 0 _--! -0.1 -0.2
44
9 I 1 +
t I1itt
-_ _-*!_-___
_I---____
+
-0.3 -0.4I
Fig. 9. Spin correlation
parameter
A,,,
(np) at 1.10 GeV.
Finally we express our gratitude to F. Haroutel, which organized stays of all visiting participants. This work was partly supported by the Swiss National Science Foundation and by the US Department of Energy Contract No. W-31-109-ENG-38.
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