angular dependence of the spin correlation parameter aoonn in np elastic scattering between 0.8 and...

Nuclear Physics A559 (1993) 511-525 North-Holland

NUCLEAR PHYSICS A

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, CNRS-IN2P3 and CFA / DSM, CE Saclay, 91191 Gif-sur-Yvette Cede.x, France

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*, Germany

L.S. Barabash, Z. Janout ‘, B.A. Khachaturov, 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, 128.5 Athenaz, 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

512 .I. Ball et al. / Angular dependence (III)

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 n,n), E = 0.8-1.1 GeV, measured spin correlation parameter. Polarized frozen-spin target.

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 produc- tion 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 collima- tor 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

E B = PB Aoono and E B = 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 micropro- cessor) 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-of- flight 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 I P, ) was independent of its direc- tion 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


Table 1 Results of the spin correlation parameter A,,,, for np elastic scattering at 0.80 GeV a

e C.rn. Exp. value e c.m. Exp. value

(deg.) (deg.)

28.8 0.093 - 0.156 f 0.067 32.3 0.116 - 0.083 + 0.026

36.0 0.143 - 0.077 f 0.017 39.8 0.174 -0.019 + 0.017

43.6 0.207 0.014 f 0.015 47.2 0.241 0.019 f 0.017 51.2 0.280 0.054 k 0.024

55.2 0.322 0.099 f 0.035 59.2 0.366 0.122 f 0.046

61.9 0.398 0.183 f 0.124

47.5 0.244 0.031 + 0.099 49.1 0.259 0.045 k 0.042

51.0 0.278 0.047 f 0.035 53.0 0.299 0.031 + 0.035 55.0 0.320 0.083 f 0.038 57.0 0.342 0.129 + 0.039 59.0 0.364 0.061 f 0.036

61.0 0.387 0.084 & 0.036 63.0 0.410 0.123 f 0.040

65.0 0.433 0.172 + 0.042 66.9 0.457 0.154 + 0.048 68.9 0.480 0.107 + 0.068 71.0 0.506 0.121 + 0.087 73.0 0.531 0.087 f 0.076 75.0 0.557 0.191 + 0.071 77.0 0.582 0.074 k 0.065 79.0 0.607 0.128 f 0.079 81.0 0.634 0.068 * 0.074 83.0 0.659 0.081 + 0.075 86.0 0.699 0.021 f 0.054 89.9 0.749 0.018 + 0.059 93.8 0.801 -0.119 * 0.071

98.3 0.895 0.107 + 0.272 102.3 0.910 -0.128 f 0.214 108.0 0.983 - 0.240 + 0.203 113.9 1.055 - 0.229 k 0.284 122.0 1.149 - 0.176 k 0.308

a Tkrn = 0.800 GeV, P ,ab = 1.464 GeV/c, total 37 points.


e c.m. Exp. value Exp. value

(deg.) &,c)2 A,,,

48.1 0.261 50.0 0.282 52.0 0.303 54.0 0.324 56.0 0.347 58.0 0.370 60.0 0.394 62.0 0.418 64.0 0.442 66.0 0.467 68.0 0.492 69.9 0.518 72.0 0.544 74.0 0.571 76.0 0.597 77.9 0.624

a Tki, = 0.840 GeV,

0.038 f 0.022 0.093 + 0.017 0.090 _+ 0.017 0.082 f 0.017 0.087 + 0.018 0.122 f 0.018 0.139 f 0.019 0.139 * 0.020 0.153 + 0.021 0.193 f 0.021 0.167 + 0.023 0.126 + 0.025 0.152 f 0.027 0.181 + 0.026 0.115 + 0.027 0.127 + 0.029

P,,, = 1.511 GeV/c, total

79.9 0.651 0.096 + 0.031 82.0 0.678 0.028 f 0.034 83.9 0.705 0.006 + 0.040 86.0 0.732 - 0.004 + 0.047 87.9 0.760 - 0.009 f 0.054 89.9 0.787 -0.170 * 0.073 92.5 0.832 -0.191 + 0.083

95.5 0.884 - 0.079 + 0.136 98.9 0.911 -0.193 + 0.105

103.1 0.966 -0.246 k 0.106 107.0 1.019 - 0.301 _+ 0.092 111.0 1.070 - 0.054 * 0.102 115.0 1.122 - 0.255 _+ 0.094 118.9 1.169 -0.159 * 0.101 125.4 1.247 0.005 + 0.098

- 31 points.

516 J. Ball et al. / Angular dependence (IIlj

Table 3

Results of the spin correlation parameter A,,,, for np elastic scattering at 0.86 GeV a

kg.,

Exp. value

&,c)2 A,,,,

e Cm. -t Exp. value

(deg.) (Gev/c)’ A DOII”

48.0 80.0 0.666

50.0 82.0 0.694

52.0 84.0 0.722

54.0 86.0 0.750

56.0 89.0 0.794

59.0 92.0 0.834

60.0 94.2 0.867

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 + 0.034

0.095 f 0.028

0.107 +_ 0.027

0.124 + 0.028

0.105 + 0.029

0.170 f 0.021

0.139 + 0.019

0.181 rt 0.031

0.142 + 0.031

0.172 + 0.033

0.210 + 0.034

0.194 + 0.036

0.108 f 0.038

0.155 f 0.037

0.096 f 0.039

0.096 + 0.040

0.113 * 0.040

0.037 + 0.043

0.032 + 0.042

- 0.019 + 0.043

- 0.139 + 0.032

- 0.154 + 0.048

- 0.160 f 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 + 0.171

- 0.193 f 0.105

- 0.276 k 0.106

-0.320 f 0.131

-0.366 + 0.125

-0.321 f 0.143

- 0.243 f 0.146

- 0.045 * 0.157

a Tki, = 0.860 GeV, P ,ab = 1.535 GeV/c, total 31 points.

different partial results are given. Measurements at the same angles were com- bined 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 of the spin correlation A,,,, for np elastic scattering around 0.8 GeV: this experiment

(full circle); 0.79 GeV, ref. [4] (open circle); 0.794 GeV, ref. [5] (plus).

J. Ball et al. / Angular dependence (iIll 517

Table 4

Results of the spin correlation parameter A,,,, for np elastic scattering at 0.88 GeV a

e c.m. Exp. value 0 c.m. Exp. value

(deg.1 (deg.1

28.9 0.103 - 0.157 f 0.053

31.1 0.119 - 0.143 + 0.035

33.1 0.134 - 0.133 * 0.026

35.0 0.149 - 0.078 + 0.022 37.0 0.166 - 0.058 + 0.020 39.0 0.184 - 0.035 + 0.020 41.0 0.202 - 0.026 * 0.021 43.0 0.221 - 0.003 f 0.023 45.0 0.242 0.101 + 0.023

47.0 0.262 0.046 f 0.023 49.0 0.284 0.070 f 0.025

50.9 0.305 0.083 * 0.029 52.9 0.328 0.129 + 0.036

54.9 0.351 0.113 f 0.045 56.7 0.374 0.098 + 0.072

47.9 0.272 0.063 + 0.022 49.1 0.285 0.056 + 0.017 50.0 0.296 0.120 + 0.025 51.0 0.306 0.093 t 0.016 52.0 0.317 0.105 & 0.024 52.9 0.328 0.137 + 0.018 54.0 0.341 0.123 + 0.023 55.0 0.352 0.121 f 0.020 56.0 0.364 0.143 It 0.019 56.9 0.375 0.145 * 0.019 58.0 0.388 0.159 i 0.018 59.0 0.401 0.222 f 0.025 60.0 0.412 0.190 + 0.019 60.9 0.424 0.147 + 0.024 62.0 0.438 0.183 rt 0.026 63.0 0.451 0.171 * 0.017 64.0 0.463 0.179 + 0.027

65.0 0.477 0.147 + 0.030 65.9 0.489 0.190 + 0.021 67.0 0.503 0.165 + 0.034 68.0 0.518 0.228 f 0.022 68.9 0.529 0.160 + 0.043 69.9 0.543 0.189 + 0.023 71.0 0.557 0.133 * 0.047 72.0 0.570 0.104 rt 0.024 73.1 0.585 0.110 * 0.040 73.9 0.597 0.129 _t 0.024 75.0 0.612 0.131 10.040 75.9 0.625 0.080 f 0.037 76.9 0.639 0.107 10.022 79.0 0.668 0.090 I 0.026 81.0 0.697 0.089 5 0.049 82.0 0.712 0.074 $ 0.037 83.0 0.724 0.086 f 0,052 83.9 0.739 0.047 + 0.046 84.9 0.753 - 0.021 10.022 85.9 0.768 - 0.092 + 0.055 87.5 0.791 -0.112 f 0.062 89.0 0.812 - 0.101 & 0.027 90.7 0.837 - 0.104 + 0.050 92.7 0.865 - 0.176 I 0.032 93.9 0.883 - 0.189 f 0.077

95.5 0.906 -0.150 & 0.126 99.1 0.958 -0.179 i 0.066

103.0 1.012 -0.319 i: 0.057 107.2 1.072 - 0.324 * 0.054 111.0 1.123 - 0.315 * 0.057 114.9 1.175 - 0.328 I 0.055 120.6 1.248 - 0.187 I 0.069

a T,, = 0.880 GeV, Ptab = 1.558 GeV/c, 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)


Exp. value Exp. value A GO”0

47.5 0.268 0.288 + 0.039 80.9 50.1 0.296 0.303 + 0.028 84.9 52.0 0.318 0.263 f 0.023 88.6 54.0 0.340 0.240 f 0.021 93.6 57.0 0.376 0.195 + 0.017 60.9 0.425 0.168 + 0.016 91.9 65.1 0.479 0.097 + 0.018 97.3 70.0 0.544 0.034 + 0.019 105.1 73.0 0.585 - 0.028 f 0.022 112.7 77.1 0.642 - 0.048 + 0.023 121.1

a Tkin = 0.880 Gev, Plab = 1.558 GeV/c, total 19 points.

0.695 -0.111 f 0.027 0.753 - 0.128 f 0.033 0.805 - 0.268 k 0.042 0.878 - 0.343 + 0.097

0.855 - 0.078 + 0.042 0.931 - 0.134 + 0.044 1.042 - 0.133 f 0.046 1.145 - 0.256 + 0.050 1.252 - 0.131 + 0.057

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


kg., &,cY Exp. value e C.ln. Exp. value A 00”” (deg.) &v,cY 00”” A

25.8 0.088 - 0.034 + 0.144 68.0 0.551 0.244 f 0.025 29.5 0.114 - 0.137 + 0.036 70.0 0.580 0.200 f 0.027 33.2 0.144 - 0.043 f 0.022 72.0 0.609 0.199 + 0.028 37.0 0.178 - 0.002 + 0.018 74.0 0.638 0.133 f 0.028 41.0 0.216 0.047 + 0.019 76.0 0.668 0.138 * 0.029 45.0 0.258 0.105 + 0.018 78.0 0.698 0.144 f 0.032 48.8 0.301 0.147 * 0.020 80.0 0.728 0.115 + 0.032 52.8 0.348 0.196 f 0.029 81.9 0.758 0.052 + 0.034 56.8 0.399 0.260 f 0.041 84.0 0.790 - 0.055 f 0.034 60.8 0.452 0.191 + 0.050 86.0 0.820 - 0.016 f 0.035

88.0 0.851 -0.155 + 0.038 48.0 0.292 0.163 f 0.020 90.0 0.882 - 0.182 + 0.038 50.0 0.315 0.126 + 0.017 92.6 0.921 - 0.192 + 0.034 52.0 0.338 0.161 + 0.017 54.0 0.363 0.169 zk 0.018 97.8 1.003 - 0.410 f 0.078 56.0 0.388 0.221 f 0.019 103.0 1.080 - 0.321 + 0.162 58.0 0.414 0.205 -I 0.020 105.7 1.122 - 0.392 f 0.068 60.0 0.440 0.215 + 0.020 111.1 1.199 - 0.333 f 0.157 62.0 0.467 0.257 + 0.021 112.9 1.225 - 0.342 + 0.074 64.0 0.495 0.215 + 0.022 115.0 1.256 - 0.399 f 0.126 66.0 0.523 0.224 + 0.023 119.0 1.311 - 0.328 f 0.155

121.5 1.345 - 0.234 f 0.070

a T,,, = 0.940 GeV, I’,,, = 1.628 GeV/c, total 41 points.



Exp. value Exp. value

20.7 0.060 -0.179 + 0.105 23.5 0.078 -0.129 + 0.037 26.4 0.098 - 0.065 k 0.024 29.7 0.123 0.015 + 0.021

32.8 0.150 0.088 + 0.021 36.0 0.179 0.098 f 0.021 39.1 0.211 0.127 f 0.023 42.2 0.243 0.181 f 0.032

45.6 0.281 0.247 f 0.087

48.0 0.310 0.141 + 0.025

50.0 0.335 0.143 + 0.023 52.0 0.361 0.155 + 0.022 54.0 0.386 0.199 f 0.023 56.0 0.413 0.219 f 0.023

58.0 0.441 0.249 f 0.024 60.0 0.468 0.192 k 0.025 62.0 0.498 0.215 f 0.027 64.0 0.527 0.253 f 0.027 66.0 0.556 0.158 f 0.029 67.9 0.586 0.193 + 0.032

70.0 0.617 0.131 + 0.037 72.0 0.648 0.148 + 0.035 74.0 0.679 0.120 + 0.035 76.0 0.711 0.057 f 0.036 78.0 0.743 - 0.004 + 0.039 80.9 0.789 - 0.027 f 0.029 82.0 0.807 0.015 + 0.043 84.0 0.840 - 0.017 f 0.046 86.0 0.872 - 0.040 _+ 0.050 88.0 0.905 - 0.177 f 0.056 89.9 0.937 - 0.103 + 0.063

92.2 0.976 - 0.148 f 0.072 93.8 1.000 -0.153 + 0.158 98.2 1.072 - 0.181 f 0.162

105.5 1.190 -0.518 + 0.100 111.2 1.278 - 0.374 + 0.132 115.0 1.334 -0.276 + 0.115 118.9 1.392 - 0.307 + 0.128 123.7 1.460 -0.285 + 0.119 149.6 1.747 0.387 f 0.369

a Tki, = 1.00 GeV, P,,, = 1.697 GeV/c, 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


0 C.rn. Exp. value &,cJ2 A,,,,

I3 C.rn. Exp. value (deg.) (deg.) &cs 00”” A

53.1 0.363 0.127 + 0.040 69.9 0.666 0.125 k 0.063 53.9 0.416 0.070 f 0.037 74.0 0.735 - 0.039 + 0.072 58.0 0.477 0.139 + 0.039 77.8 0.800 - 0.005 f 0.082

61.8 0.535 0.113 + 0.048 82.1 0.875 -0.173 * 0.091 66.1 0.604 0.088 + 0.070 86.0 0.944 - 0.091 + 0.104

a Tkin = 1.08 GeV, P lab = 1.788 GeV/c, total 10 points.



e E.rn. Exp. value e Cm. Exp. value

(deg.) (deg.)

25.6 0.102 - 0.083 f 0.071 29.3 0.132 - 0.152 + 0.029 33.1 0.167 - 0.027 + 0.022 37.0 0.207 - 0.023 f 0.020 41.0 0.253 0.049 * 0.022 44.9 0.301 0.146 f 0.022 48.9 0.354 0.180 f 0.023 52.8 0.407 0.169 + 0.033 56.8 0.467 0.231 + 0.047 60.9 0.530 0.078 IL- 0.068

48.0 0.341 0.095 + 0.031 50.0 0.369 0.135 f 0.030 52.0 0.396 0.150 f 0.029 54.0 0.425 0.166 + 0.031 56.0 0.454 0.224 f 0.035 58.0 0.485 0.187 + 0.038 59.9 0.515 0.202 + 0.044

62.0 0.548 0.184 + 0.048 64.9 0.594 0.160 rf: 0.041 68.8 0.659 0.136 f 0.052 72.0 0.714 0.053 + 0.092 75.0 0.766 - 0.068 f 0.072 79.0 0.836 - 0.214 f 0.088 82.0 0.890 - 0.265 f 0.163 83.9 0.924 -0.216 + 0.163

91.9 1.068 -0.155 + 0.174 97.1 1.160 - 0.247 + 0.081

105.0 1.301 - 0.329 f 0.078 113.0 1.437 - 0.252 + 0.075 120.8 1.561 - 0.142 + 0.086 126.5 1.645 0.206 f 0.207 137.1 1.791 0.397 k 0.287 142.9 1.858 0.636 f 0.336

a Tkin = 1.10 GeV, P ,ab = 1.810 GeV/c, 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.


I I I I I I I I I I II II 11 I

a3 Aoonn

0.2-

0.1 -

O--

-o.l-

-0.2-

-0.3 -

-0.4-

0.86 GeV

SATURNE II

I I I I I I I I Ill I i I I I I I I

-‘“O 30 60 90 ’ i20 150 180 eCM(deg)

Fig. 3. Spin correlation parameter A,,,, (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

0.2

0.1 I

O___---

-O.l-

-0.40 ’ ’ 30 ’ ’ ’ 60 ’ ’ ’ 90 ’ 1 1 120 1 1 1 150 1 1 1 180

6~~ Meg)

Fig. 4. Spin correlation parameter A,,, hp) at 0.88 GeV.

Aoonn

n-p 0.88 GeV

522 J. Ball et al. / Angular deference (III)

0.2

0.1

0


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)


.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.


06

*oonn 05 n-p

04

t

1.1 GeV

0.3t

0.2

0.1

!

0 _---

-0.1

-0.2

-0.3

-0.4 I

4 + 4 9 _-*!_-___

I 1 -_

+ 1 _I---____

I it t t 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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[ll] J. Ball, Ph.D. Thesis, Faculty of Science, University of Paris, Orsay, No. 2132

angular dependence of the spin correlation parameter aoonn in np elastic scattering between 0.8 and...

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