* S T I J.Ball, Ph.Cnesny, LCombet, J.M.Fontaine, R.Kunne, H.C.Lemaire', J.L.Sans,

Laboratoire National SATURNE, CNRS-IN2P3 and CEA/DSH, CE Saclay,

91191 Gif sur Yvette Cedex, France

2 J-Eystricky, C.D.Lac , F-Lehar, A- de Lesquen, H. de Hali,

F.Perrot-Kme, L. van ROSSU~,

DAPNIA, CE Saclay, 91191 Gif sur Yvette Cedex, France

4 5 P.BaCk3, Ph.Demierre, G.Gaillard , R-Hess, D.Rapin, Ph.Sormani ,

DPNC, University of Geneva, 24, quai Ernest-Ansermet, 1211 Geneva 4, Switzerland

J- P GOUdOUr , C.E.N.B., Domaine du Haut-Vigneau, 33170 Gradignan, France

R.Binz, A.Klett, E.Rtfssle, H.Schmitt,

Zacultg of Physics, Freiburg University, 7800 Freiburg im Br., Germany

6 LIS.3arabash, 2.3anout , B.A.Khachaturov, Yu.A.Usov, LNP - ZINR, Dubna, 101000 MOSCOW, P.O.Box 79, Russian Federation

D.Lopiano, H.Spinka,

ANL-HEP, 9700 South Cass Avenue, Argonne, Ill 60439, USA

Present address : 1) DAPNIA, CE Saclay, 91191 Gif sur Yvette, Cedex, France 2) Institut National des Telec3mmunications, 9, rue Charles Fourier,

3 ) College -%usseau, 16A, av. du ~ouchet~ 1209 Geneva, Switzerland 4) Schlumberger Ind., 87, rte de Grigny, 91130 Ris Orangis, France 5) Brainsoft Consulting S.A., Cusinand 46, 1285 Athenaz, Switzerland 6) Faculty of Nuclear Sciences and Physical Engineering, Czech Technical

91011 Evry, France

University, Brehova 7, 11519 Prague lr Czech Republic

* Work supported in part by the U.S. Department of Energy, Division of High Energy Physics, Contract W-31-109-ENG-38.

We present results of the rescattering observables Donon(np) and K,,,(np) measurements at eight energies between 0.80 and l.10 GeV. The SATURNE I1 poiarfied - beam of free neutrons obtained: from ,the break-up of polarizeU ' deuterons was scattered on the polarized Saclay frozen-spin proton target. Part of the data w a s

obtained with a CH2 target where only the polarization transfer &meter Komo was determined. The present results are the fkst existing measurements of these observables above 0.80 GN. They provide an important contribution to any future

theoretical or phenomenological analysis.

. . _ .

DISCLAIMER

This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsi- bility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Refer- ence herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, r a m - mendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.

*, .'- .I . - ..

We present measurements of the depolarization Donon and the polarization transfer parameter Konno in np elastic scattering at 0.80, 0.84, 0.86, 0.888 0.91, 0.94, 1-00 and 1.10 GeV. Results for these Wolfenstein parameters were obtained with the SATURNE I1 polarized beam of free quasi-monochromatic neutrons scattered

in the Saclay frozen spin proton target- The beam and target polarizations were oriented vertically., Recoil protons were rescattered in a-carbon analyzer. and the p-C asymmetry was measured. The single-scattering data from the experiment provided the analyzing power Aoono and spin correlation parameter Aoonn, which

were reported in refs[1,2,3]. All these data were taken simultaneously with the transmission measurement of the total cross section d.if f erence AnT( np) [ 41 . The experiment is part of a systematic study of the nucleon-nucleon system at SATURM: 11.

.. .

.

r .-

Throughout this paper we use the

notation of observables developed in nucleon-nucleon formalism and the four-spin

ref. (51 . 2. POLARIZKD BEBn AND !rARGFp

Polarized neutrons are produced by break-up of vector-polarized deuterons on a Be target. The production target was 20 cmthick and the neutron beam is defined

by a total of 8 meters of collimators inserted in the 17.5 m long neutron beam line(61. The neutron beam momentum spread of about 2 20 MeV is due to deuteron

absorption in the production target and to the F e d motion of the neutrons in the deuterons . The polarized deuteron beam with 2-3xJ.O" deuterons/burst produced - 6.10 neutrons/burst. The neutron beam intensity w a s monitored by a scintillation counter array inserted in the beam in front of the polarized target[4].

7

The deuteron beam polarization was flipped every burst of the accelerator by

achange of the RF transitions in the ion source. The polarization of the break-up

neutrons was determined by a dedicated experiment, as explained in refs C1 ,GI. The polarization of the neutrons is PB = 0.59, independent of energy. The polarization of the protons in the accelerated deuterons was also checked by the beam polarf- meter[7] .

Page 1

The proton polarized target (PFT) was 35 mm thick, 40 mm wide and 49 mm high [ 8 ] . The target material was pentanol, with a typical proton polarization of 85%. The target polarization was held in a magnetic field of - 0.33 T produced by a vertical superconducting holding coil. The target polarization was inverted every

few hours. The polarization direction was changed by a PPT repolarization at a different mfcrofrequency. Part of dataat 0.88 GeV was measured with a CH target at the same position at the PPT.

2

In order to monitor correctly measurements with two opposite target poiari-

zation directions, for part of the data-taking a polyethylene nCH2n target 3 to 10 mm thick was positioned downstream of the PPT and viewed by a dedicated scin- tillation counter. Particles scattered either of the PPT or of the CII target

produce independent triggers, but their tracks. are detected by the same MwpC's. The number of events from the CH2 target, is used to check the normalization of the data taken with opposite PPT polarizations.

2

The experimental set-up is described in ref.161. Outgoing particles are detected by a two-arm spectrometer which comprises single scintillation counters, counter hodoscopes, the neutron counter (NC) hodoscope with its VETO, an analyzing

magnet and eight multiwire proportional chambers.

The NC hodoscope[6,9] consists of 15 scintillating bars and measures a par-

ticle's position from the time difference between the signals from the two PN's

on either side of a bar, with a precision of 5 25 mm. Veto counters in front of

the neutron counter hodoscope distinguish between neutral and charged particles..

The recoil protons from the PET and from the additional CH target may be

rescattered in a carbon plate. The plate was 3 cm thickat small neutron scattering angles and 5 cm at large angles. The coordinates of rescattered protons are determined by hits in two MWPC's, behind the carbon plate. The rescattered events represent - 1% to 2% of the single scattering events. For this reason the res- cattering data have considerably larger statistical errors.

2

The triggers and fast electronics are described in ref.[6].

Page 2

Candidates for np events are determined and recognized by 2 d i f f e ren t pre- . t r iggers . The following pretr iggers are used :

1. Forward neutron, backward proton, np sca t t e r ing i n t he em! : pre trigger TND .

2. Forward neutron, backward proton, np s c a t t e r i n g i n t h e addi t iona l cH2 target : pretr igger MND.

The sum of pretriggers enters i n the NC logic , which determine charged or neut ra l NC events , and gives t h e Master Trigger. This trigger gives an event i n t e r rup t NIM signal t o t h e CAC module ibased on thk MOTOROLA 68000 microprocessor) and t o t h e on-line computer. The CAC module starts the acquis i t ion of MWPC*s, TDC's and t h e information of d i f fe ren t memory uni ts . Coincidences between the accepted master trigger signals and delayed pretriggers determine t h e f i n a l kind of trig- gers.

.

The data ana lys i s is described i n detail i n ref.163. The forward neutron momentum is determined by neutron time-of-flight between t h e PPT and t h e NC hodoscope. The wings i n t h e coplanarity d i s t r ibu t ion of the particles and t h e i r lef t - r ight angular cor re la t ion were used t o subtract the carbon and i n e l a s t i c background from t h e s ing le sca t t e r ing events. For events where t h e r e c o i l charged particle is rescattered i n t h e carbon block, t he off l i n e a n i y s i s applies all kinemat ic c u t s for single scat ter ing. Cuts on t h e posi t ion of the vertex of the r e c o i l particle i n the analyzer as w e l l as on the rescattering angle (required t o be larger than 4 O ) are added.

%nno 4. DETHZnINATIOH OF Donon

Thegeneral expression f o r t h e d i f f e r e n t i a l cross s e c t i o n o f e l a s t i c s c a t t e r i n g with polarized beam and polarized target is given i n ref.[5]. I n t h e present experiment t h e beamand target polar izat ions (P and P , respect ively) are oriented ver t ica l ly , The a f f e r e n c e between t h e first sca t t e r ing plane and t h e horizontal plane i s given by the azimuthal angle 9, which may reach f io at most. In t h i s case only t h e normal component of t h e recoil particle polar iza t ion (sph-index n ) provides non-zero observables and w a s measured i n t h e second sca t te r ing . Under

8 T

-_

Page 3

these condition and assuming t h a t the first sca t te r ing plane is the horizqntal . plane, t h e general formula reduces to :

+ PC'(Ponoo + 'BKonno + 'TDonon + pBpTN~nnn )cos 'p213. .-.- . .-

where IC and Pc are t h e d i f f e ren t i a l c ross sect ion and analyzing power for tne second s c a t t e r i n g on t h e carbon analyzer, respectively. They depend on the angle of the second sca t t e r ing 8 and on t h e energy T2 of t h e r eco i l proton incident on t h e analyzer. The symbol u = (du/dQ) denotes t h e np d i f f e r e n t i a l cross section, fo r unpolarized beam and target and q2 is t h e angle between t h e normals of the first and t h e second scattering. The az imutha l angles 9 and q 2 8 f o r each recorded event, were taken i n t o account. The angular dependence of the observables A mno'

2

has been reported i n refs[l,2,3]. Assuming the generalized Pauli Amon and Aoonn principle ( i sosp in invariance) and time-reversal invariance t o hold as i n ref . 151 8

- - - . The result f o r POnOO, representing the - - Nonnn Aoono Aooon it follows Ponoo average over beam and ta rge t po lar f ia t ion , is obtained wi th r e l a t i v e l y large statistical errors and may be affected by a possible instrumental asymmetry which is not cancelled by beam or target-spin reversal . For t h i s reason w e fixed i n the

obtained - Aooon were used only as a check

- observables by the values of Aoono and

and Norum ana lys i s t h e Ponoo from refs[ l ,2] . The measured values of Ponoo of in te rna lcons is tencyof the measurements. W e have a l so fixed the sp in correlat ion

by tne accurately measured angular dependence of this observable from ref.[3]. The ( d 2 # q 2 ) dis t r ibu t ion i n t he second sca t te r ing w i t h mown ~ ~ ( 8 ~ ~ ~ ~ 1 (see ref.[6]), measured with d i f fe ren t combinations for the s igns P and P forms a redundant set which allows t o remove a major part of the instrumental asymmetries.

are obtained as "pure" observables, i.e. the The observables Donon corresponding asymmetries do not depend on o ther parameters,

Aoonn

E T'

and %nno

For t h e measurements wi th an unpolarized target, all terms containing PT i n survive. and Konno Eq.(l) drop out and only the observables AOOnO, Ponoo

Eq.(1) may be used t o determine the l i n e a r l y independent observables Donon and IConno by t h e maximum-likelihood method. As mentioned i n ref .[SI, i n the present

Page 4

analysis we have applied the momentum method, used with success and described by t h e Geneva University group [10,11]. This method, adapted t o our experiments, is '

t r ea t ed i n detail i n ref.[12]. Several test show t h a t the ~ u I a - l i k e l i h o o d m e t h o d and the momentum method give the same results.

5. RESULTS

One pa r t of the preliminary results of t h i s experiment is given i n ref.[l3]. The final results are l isted in Table 1. The statistical e r ro r s are dominant'and are given h the table. We estimate t h a t an addi t iona l error due t o uncontrolled instrumental effects is negl igible for t h e present experiment. The uncertainty i n t h e target polar izat ion measurements is f 3%, the e r r o r s in t h e p C analyzing power are of t h e same order. The systematic e r r o r due t o the normalization of the number of events obtained for opposite beam and target polar izat ions t o the same integrated beam in tens i ty , was considerably reduced by t h e use of t h e addi t iona l .. CH2 target. The angles given i n t h e table are t h e weighted averages over t h e corresponding angular bins .

Fig. 1 shows our results fo r Donon at 8 energies , IConoo data are given i n Fig. 2. The predict ion of the Saclay-Geneva phase s h i f t ana lys i s [14] are shown at 0.80 GeV i n both figures. The observable Donon reaches large values at all energies and angles. The observable Komo is small i n t h e measured angular range and mostly compatible wi th zero within errors.

6. CONCLUSIONS

The rescattering observables D (np) and Konno(np) were measured at eight energies between 0.80 and1.10 GeV u s i n g t h e SATURNE I1 v e r t i c a l l y polarized beam of free neutrons together wi th the Saclay frozen spin polarized proton target polarized i n the same direct ion.

onon

A t a l l energies and angles t h e measured &gular dependence of Donon(np) shows large values. The Kom0 data are mostly compatible w i t h zero.. Their values, i n general, s l i g h t l y increase at large angles.

Page 5'

-I- . ..

The results for both observables were measured for the first time above 0.8 G ~ V . They represent an important contribution to the np .) np data base, They will be used for a Wect reconstruction of np scatteringamplitudes, will iinFrove the existing PSA solutions and will. contribute to the extension of the O S towards

higher energies,

We acknowledge support for this work from J-Arvieux, R.Beurtey, P-A-Chamouard,

Discussions with J-Dereel, J.M-Lagniel, C-Ledhanoine-Leluc, G-Mlleret and Y.Terrien have solved several problems. The exploitation of the polarized target

. A.Fleury, M.Havlicek, E.Heerr 'JoH.mgetr N~A-RLlSakoviCh~ J-Saudinos and Ts.Vylov.

owes a lotto G.Guillier, Ph.Marletand J.Hommejat- we thank T.Lambert, E-Perrin, J.Poupard and J.P.Richeux for their efficient help in preparation of the experi- ,.

ment. Finallyr we express our gratitude to F-Haroutel, who organized the stay of all visitors. This work was partly supported by the Swiss National. Science Fciun- dation and by the US Department of Energy Contract No. W-31-109-ENG-38.

I. J.Ball, Ph-Chesny, M.Combet, J.H.Fontaine, R.Kunne, H.CiLeaaire, J.L.SanS, J-Bystricky, C.D.Lac, F-Lehar, A. de Lesquen,'H. de Mali,

F.Perrot-Kunne, L. van ~ossuin, P.Bach, Ph.Demierre, ~ . ~ a i u a r u , . . R-Hess, D-Rapin, Ph.Sord, J.P.Goudour, R.Binz, A-Klett, E.R'dssle,

H.Schmitt, L-S.Earabash, Z.Janout, B.A.Khachaturov, Yu.A.Usov,

D.Lopiano, H-Spinka, submitted to Nucl.Phys. B

2. J.Ball, Ph-Chesny, M.Combet, 3.H.Fontaine, C.D.Lac, J.L.Sans,

J.Bystricky, F.Lehar, A. de Lesquen, H. de Mali, F.Perrot-Kunne,

L. van Rossum, A.Ahmidouch, P.Bach, Ph.Demierre, G-Gaillard, R.HeSs, R.Kunne, D.Raph, Ph.Sonaani, J.P.Goudour, R.Blnz, A.Klett, E.Rijssle.,

H.Schmitt, D-Lopiano, H.Spinka, submitted to NucLPhys, B.

3. J-Ball, Ph-Chesny, ILCombet, J-H.Fontahe, C.D.Lac, J.L-Sans,

J.Bystricky, F.Lehar, A, de Lesquen, H. de Mali, F.Perrot-Kunne,

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E. R&sle, H Schmitt , L. S .Barabash , 2 . Janout , B. A.Khachaturov, Yu.A.Usov, D.Lopiano, H,Spinka, submitted to Nucl.Phys, B,

4. J.M.Fontaine, F. Oerrot-Kunne, J. Bystricky, 3, Deregel, F.Lehar,

A. de Lesquen, M, de Mali, L. van Rossum, J. Ball, Ph. Chesny,

C.D. Lac0 J.L. Sans, J.P. GoudoUr, P, Bach, G. Gaillard, R. Hess,

R. Kunne, D. Rapin, Ph- S o m i , 2. Binz, A. Klett, R, Peschina, E. Rijssle, H. Schmitt, Nucl.Phys. 8358 (1991) 297

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6. J.Bal1, Ph-Chesny, M.Combet, J.M.Fontahe, R-Kunne, J.L.SanS,

J-Bystricky, F.Lehar, A. de Lesquen, H. de Mali, F.Perrot-Kunne,

L. Van ROSSU, P-BaCh, Ph.Demierre, G . G a i l l X d , R.Hess, Z.F.JanOUt,

D.Rapin, Ph-Sormani, B.Vuaride1, J.PIGoudour, R.Binz, A.Klett,

E-Rb'ssle, H-Schmitt, L.S.Sarabash, ZJanout, V.A.Kalinnikov,

YU.M.KazarinOV, B,A.Khachaturov, V.N.Matafonov, I.L.Pisarev,

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' .

A.A.Popotr, Yu-A-Usov, LEeddo, D.Grosxdck, T-mprzyk, D.Lopiano,

H-Sphka, Nucl.Instrum.Methods, in print

7. J.Bystricky, J-Deregel, F.Lehar, A. de Lesquen, Lo vari 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.Instrum.Hethods, Bi?is. (1985) 131

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t -' . . . . I

_ . 9. A.Ahmidouch, ?.Bach, R.HeSS, R.Kme, C-Lechanoine-Leluc, Ch.Hascarini,

D-Rapin, J-Arvieux, R-Bertini, H.Catz, J-C-Fdvre, F.Perrot-Kunne,

F-Bradamante, A.Martin, Nucl.Instrum.Methods, in print

10. D-Besset, P M Thesis, Universite de Genbve, Geneva 1975

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and D.W.Werren, Nucl.1nstrum.Methods a (1979) 515

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Page 8

_- - ..

. .. . . I . ...

: .- . . . I _

.. -. . .-. . . . 1. . _ ... -- . - ..? 4 ; .,. . . . . . . ., ... . - . and t3e polarization ;:&: - :'.: TABLE 1 Results of the depolarization Donon

transfer parameter KOma in np elastic scattering at 0.80, ..__ .. - . . 1 -

*. .. ~ 0.84, 0.86r 0.88, 0.91tr 0.94r 1.OOand 1.10 GeV. - -

. - . I

. .

:.

. I . " .. . , ' . .. -. n-.. .

. .. .. -...a .* . - . . . . . . ,, - .. .. ., . . . . .

Page 9

FIGURE CAPTIOHS

I

I

i n : . . 7i.. ... Fig. 1 Angular dependence of the depolarization parameter Donon ..,., . np elastic scattering at 0 . 8 0 ~ 0.84~ 0.86. 0.88r 0.91~ 0.94,. 1.00 and 1.10 GeV. The hashed line at 0.80 GeV represents 'the _.- prediction of the saclay-Geneva phase shift analysis[14].

- ,

Pig. 2 Angular dependence of the polarization transfer parameter Kom0 in np elastic scattering at 0.80, 0.84, 0.86, 0 . 8 8 ~ 0.91, O-W, 1.00 and 1-10 GeV. .The dashed-line at 0.80 GeV represents the '

". z..:. - - prediction of the Sac-y-Geneva phase shift ana~ysis[~]. . ' _.' . L .. -. - - C'. ., ' 1 .. . - ; ; .y - . I ::. .. .. . - . .. -

Page 10

T a b l a i .., ' .. . . _.. .

Tkin = 0.80 GeV Plab = 1.463 GeV/c

Angle -t

CM deg. (G€?V/C)~ Donon

48.2 0.251 0.801 f 0.146 0.108 f 0.221 64.1 0.423 1.113 f 0.157 0.281 f 0.215

= 0.84 GeV Plab = 1.511 Gev/c Tkin

Angle -t

CM deg. ( G ~ V / C ) ~ Donon

~

51.9 0.302 0.662 2 0,103 -0.021 f 0.111 58-7 0-379 0.834 f 0.105 0.011 f 0.118 65.6 0-463 0.886 f 0.117 0.329 f 0-135 76.7 0.608 0-581 f 0.146 0.033 f 0.167

Angle -t 2

CM deg. (GeV/c) Donon

-I_-- - 53.0 0.322 0.675 f 0.129 -0.079 f 0.146 61.7 0.425 0.921 f 0.128 -0.029 k 0.146 76.3 0-580 0.785 ? 0.118 0.186 f 0.135

..

Page 11

. .

Table 1 - a n t .

= 1.558 *V/c plab . Tkin = 0.88 G e V ,

'onon Angle -t CM deg. ( G ~ V / C ) ~

49.5 0.289 0.619 f 0.067 0-042 f 0.089 55.8 0.362 0.994 t 0.070 0.120 f 0.078 60.8 0.423 0.810 t 0.058 0.084 f 0.065 77.1 0.642 0.909 f 0.046 0.139 f 0.050

= 1.593 G e V / c plab Tkin = 0.91 G e V ,

=0Ilon Angle -t CM deg. ( G e V / c ) 2

= 1.628 G e V / c %ab

= 0.94 G e V , Tkin

Donon Angle -t CM deg. ( G e V / c ) 2

KOllIIO

47.6 0.288 0.996 f 0.094 -0.CS4 F: 0.123 53.8 0.362 0.996 f 0.104 0.210 f 0-125 58.8 0.426 0.693 f 0.099 0.077 f 0.115 72.9 0.623 0.727 f 0.083 0.240 f 0.096 --------------- --

Page 12

.,

Table 1 - Cont. = 1.697 GeV/c ?lab Tgin = 1-00 GeV

Angle -t 2

CM deg. ( GeV/c) 'onon '

.-