EXPERIMENTAL ASPECTS OF THE NUCLEON WORKSHOP

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EXPERIMENTAL ASPECTS OF THE NUCLEON WORKSHOP

C. Lechanoine-Leluc

To cite this version:

C. Lechanoine-Leluc. EXPERIMENTAL ASPECTS OF THE NUCLEON WORKSHOP. Journal de

Physique Colloques, 1985, 46 (C2), pp.C2-399-C2-408. �10.1051/jphyscol:1985245�. �jpa-00224559�

JOURNAL DE PHYSIQUE

Colloque C2, supplement au n°2, Tome 46, fevrier 1985 page C2-399

EXPERIMENTAL ASPECTS OF THE NUCLEON-NUCLEON WORKSHOP

C. Lechanoine-Leluc

Department of Nuclear and Particle Physics, University of Geneva, Switzerland

Résumé.Une revue des résultats expérimentaux récents est faite dans les domaines suivants:

pp, diffusion élastique ird(t.„) et diffusion élastique nucleon-nucleon,en insistant tout particulièrement sur les problèmes existants. Différentes récentes analyses en déphasages sont discutées,ainsi que les difficultés rencontrées.

Abstract. A review of most recent experimental results in pp scattering and elastic Trd(t„n) and elastic nucleon-nucleon is made.Emphasis is put on controversial aspects. Problems related to most recent phase shift analyses are also discussed.

As most of the contributed papers are included in these proceedings, only some of the ideas suggested during the discussions will be presented. The physics with polarized deuterons is reviewed in separate papers by Drs.J. Arvieux and A.Boudard .The following topics will be treated:

PP SCATTERING

A new generation of pp experiments has been triggered due on the one hand to recent NN theoretical calculations (mainly potential models) and on the other hand to the construction of the new LEAR machine at CERN. KEK has also followed this trend with their own active program in pp as reported by N.Horikawa[l]. A Tokyo-KEK-Tsukuba group [2] has measured forward differential cross sections in pp and pd from which they deduce the real to imaginary ratio, p , of the forward pp elastic amplitudes. Their preliminary results for p(pp) are generally consistent with other available results . Comparison with theoretical models are difficult as no spin dependent effects were taken into account in the data fitting procedure and this has a quite strong influence on the results as shown by Lacombe et al.[3]. Another Tokyo-Tsukuba group [4] has measured pp reactions into two body final states; pp, nn, TT TT and k+k~ at 390, 490, 590, 690 and 780 MeV/c. In this latter channel, they have reported evidence for a resonant state, with mass 1935 ±15 MeV, T S 40 MeV and quantum number J = 2 , 1 = 0 or 1 . Fig. la) shows the measured do/dfi at a few energies and fig. lb) the integrated cross sections. One notices that at 490 MeV/c d o /dR has a symmetric shape and that the total cross section shows a enhancement with a statistical significance of more than 5 O . But this state should be distinguished from the S resonance, candidate for a baronium state, as it has not been confirmed in recent pp total cross section measurements[5],

A somewhat similar experiment is on the floor at LEAR (PS172) as reported by F.

Bradamante [6] . They have the following program: a) measurement of p also between 200 MeV/c and 600 MeV/c, b) study of 2 body final states but with a polarized target, which will allow to measure the polarization parameter,P, as well. In the meson channel,therefore a partial wave analysis will be feasible. For the elastic channel a polarimeter is also installed which will allow measurement of D and D . The energy range between 500 to 1800 MeV/c will be studied, c) the possibility of polarizing the p beam by scattering on Carbon at small angle, as is currently done for p beam, has also been investigated at 500 MeV/c. Another group (PS185) is measuring pp •* A A at threshold. Results are not yet available however.

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1985245

JOURNAL DE PHYSIQUE

c I00

-

a ⁷⁵

? 50

C ? so

u

25 25

cos e cos e

Fig.lb) Cross section for the reaction pp + K K-. References can be found in [4].

Fig.-la) Preliminary results for pp + K'K- differential cross section at 390 and 490 MeV.

Full line is a fit to the data using 4th order Legendre poly- nomials.

t20 MEASURPIENTS IN ELASTC a d SCATTERING

The new results presented at this conference did not resolve the disagreement between different t20 measurements. Two groups have measured t20

,

both b analyzing the deuteron scattered from an lD target in an 3 ~ e polarimeter using the reaction 'He (d, p) He. 4 An EElZ group [7] working at 2 SIN observed two pronounced peaks in the angular distribution at 134 MeV, which disappear at 125 and 151 MeV. ?he excitation function shows a pronounced structure at 150; , but not at 1.:~40 They observe t values which are predominantly positive. Their data are hard to explain with conventional tI?zoretical analyses. In contrast an Argonne Group

[a]

working at LAMPF has reported structureless excitation function at 144' with large negative t20 values, and no structure at 142 MeV in the angular distribution(see Fig.2a). cm Where they can be compared, the two data sets disagree in absolute value but one cannot clearly say that there are other systematic differences.At this conference the EXE group presented preli .nary measurements at 150' done with a new polarimeter detecting the scattered p fromTHe at 45' lab. Consistent results were found as shown in fig. un Zb).

Another group working at TRIUMF (Shin et al) [9] has reported preliminary results at 142 MeV at 3 angles, these are also negative as shown on fig. 2a). The error bars represent possible systematic errors at this preliminary stage of their analysis.

90 75 6 0 4 5 30 15 142 MeV

Fig. 2a) Angular distribution of tZ0 in lTd elastic scattering at T, = 142 MeV. Black dots are ETHZ work 171, open circles are from an Argonne group [ 8 ] and squares are preliminary results from Shin et al. [9] at TRIUMF.

- 0 . 2

- 110 120 130 140 150 I60 MeV T7r

Fig.2b) t excitation function at 8m.: =201500 for the elastic n d scattering. Black dots are from [ 7 ] , open circles are preliminary results from ETHZ obtained with a new polarimeter.

As stressed by W. Gruebler measurements should be repeated at 134 MeV or at 150; where the most pronounced structures were observed by the FXE group. A completely new technique will be used to measure tZ0 with a tensor polarized deuterium target both at SIN and TRIUMF in the course of the next year. One can hope that this will help clarify the situation. It would be prudent to wait for some clarification before drawing conclusions on narrow resonances.

During the last ten years, the activity in Nucleon-Nucleon experiments has been quite remarkable at Z G S , W F , S A T W E 11, SIN and TRIUMF, with each laboratory putting a different emphasis on pp or np experiments. This is closely related to the availability and quality of neutron beams. For instance at SIN no spin experiments have been done with the unpolarized neutron beam. At SATURNE 11, the highly polarized neutron beam will probably not be used until Summer 1985. Recent experiments are mostly oriented towards measurements of complex spin observables. Since completion of the experiments by the BASQUE group, TRIUMF's efforts have been oriented more towards the nd system and symmetry breaking experiments.

Let me first define the notation used in this review: all experimental quantities ,XabF

,

will have four indices ,abcd, corresponding to the spin orientation of scattered, recod, beam and target particles respectively.

Polarized neutron beams can be obtained by breaking-up polarized deuterons on a target (CH2), as has been done at SAWRNE 11, and as will be done at KEK in the near future. This is the best technique for the following reasons a) During the acceleration of the polarized deuterons, there are no depolarizing resonances to cross. This assures highly polarized deuterons (298% at SATLTRNE 11). b) Most of the deuteron vector polarization (2213 of the total polarization) is transferred to the neutrons/protons in the break-up. Only the D state component of the deuteron, which represents about 6%, low rs this polarization transfer.

Neutron beam polar'zations >58%, with an intensity of =10 n/sec on the experimental target

%

are expected with 10 d+/sec incident on the break-up target.

4

A serious drawback of this technique is that the maximum neutron energy is limited to half that of the deuteron (i.e.

1200 MeV at SATURNE 11). Another technique to produce polarized neutron beams is to transfer the polarization from incident polarized protons to the "quasi-free" neutrons in a liquid deuterium target via the charge exchange reaction

Some spin traisfer parameters are rather high (~50%) at specific angles /energy. One disadvantage is that this technique requires an intense incident proton beam (pion factory type). Anothek remark has to be made about the possible neutron spin orientation; in general if one wants to obtain a beam with its polarization axis along a given direction, a complicated neutron sp;n precession system is needed. The only simple way is to start with proton polarizations normal to the scattering plane. Once the proton polarization has been precessed into the scattering plane, the three spin orientations are possible for- the neutrons, but with more or less strength depending on energy and angle , i.e. at 180° one eliminates the n component as Aoono = 0. Note that reversing the proton polarization does not reverse all the spin components of the polarized neutron beam. At TRIUMF 3se has been made of the large values of R

-

^K at golab (equiv lent

t OSSO 120:~

-

^170:~ ) to provide a 50-60%

transverse polarized neutron beam with 9.10 n/s.cm on target per 100 nA incident polarized proton. The other components (P and Kokso ) are both small (50.05) as illustrated in fig.

3a). The full and dashed lines are phase shift (PSA) predictions from Saclay Geneva[lO] and Arndt et a1 [ll] respectively. At LAMPF use of the

' FK

)( see fig 3b) was made which gives at 18% a ,40% beam polarization (K =-20, ~::8.70) 2nd more over with no other

o&o

spin components. Unfortunately its intensity 1s very low (few 10 n/s) which limits its utility. The second m a x i m in Kokk (265%) at c.m. angles 120' - 140° is more difficult to use. Large polarizations are produce8 along all three axes as illustrated in Fig 3 b) for the KoSko parameter and there is a substantial reduction in the neutron beam energy.

C2-402 JOURNAL DE PHYSIQUE

Fig. 3a) Phase shift predictions [lo] Fig. 3b) Phase shift predictions [lo]

[ll] for the maximum value of K in [ll] for Kokko parameter in npelas- osso

np elastic scattering. Kokso parameter tic scattering at 180'

,

for the 2nd for corresponding scattering angles maximum

[e

=1304.

%?

corresponding [= 160' ] is also plotted.

cm angles,K is also plotted.

osko

At W Fthe possibility of using Li instead of LD2 is being studied [lo], transfer parameter (Kokko) values as large as 50% have been measured at 800 MeV. But the background reactions are relatively high. A possibility would be to use the Li target in connection with a Medium Resolution Spectrometer.

Symmetry breaking experiments at TRIUMF

a) Data have been collected to check Time Reversal Invariance in pp scattering at 200 MeV by measuring the difference [Aooo - Aoono] (P-A). In order to achieve the required high precision an experimental set-up whlcg compares p p and p 12 C elastic scattering was used in order to avoid the need to make absolute determinations of the polarimeter analyzing power and beam polarization. The data collected permit a statistical precision in (P-A) of 2 0.0025 to be obtained. Evaluation of corrections for systematic effects is in progress. The final results should improve the existing limit at 200 MeV by a factor 3 [13].

b) An experiment to investigate Charge-Symmetry-Breaking (CSB) in elastic np scattering is underway at TRIUMF. Preliminary results using only a part of the final statistics have been presented [9]. The scattering matrix for the elastic scattering of two identical spin 1/2 particles has five complex amplitudes (a, b, c, d, e)

.

If Isospin Invariance is violated, the neutron and proton cannot be considered identical and a sixth amplitude f is necessary to describe the np system. Since f is expected to be small in magnitude, to investigate its properties it is clearly preferable to measure the interference b tween f and one of the non suppressed amplitudes rather than attempt to determine

I

^fl

5 .

It can be shown that the combination

(Aoono - A o o 0 = %(A+ - A +) = Re b*f

-

_{2 "P nP}

is one of the few simple experiments in the laboratory system. A bnitoba-Alberta-TRIUMF-Base1 group will complete an experiment of this type in 1984 for 480 MeV neutrons. A similar experiment at 200 MeV will also be done at IUCF. The procedure used is to determine the scattering asynnnetries for polarized neutrons incident on unpolarized protons (En(e)), and unpolarized neutrons on polarized protons (E (€I)), The difference in the measured asynnnetries enables the CSB effect AA = A -A to be determined P

oono ooon

The predicted effect is small (-0.004) and a precision in 4A of'0.001 is needed. To reduce systematic errors, AA is measured where the average analyzing power .A crosses through zero.

Apart from the nucleon spins, the measurements o f € and E are done under identical P

experimental conditions so that most systematic errors cancel when the difference is evaluated. The experiment is de igned to keep uncertainties in all individual corrections and systematic effects below the lo-' level in *A. A preliminary result, which included partial statistics and has not been corrected for some known systematic effects, gives a difference in the cross-over angle of 18 3p -

en;pl

= 0.24'

+

^0.11'. The error is purely statistical only.

This result excludes any gross discrepancy with present theoretical predictions.

Spin dependent parameters a) On the pp system

Below 800 MeV, precise and extensive measurements exist mainly from SIN and LAMF'F. At the Lausanne Conference (1980) of this series [14] the first direct amplitude reconstruction was presented at 578 MeV. For 8 between 34' and 90°, 15 linearily independent parameters

R"

["

'ymy

Konno' 'soso' 'soko' pssoy Koskoy Ms sn' Nossn' 'sokn' NRskn' Aoonn' .A ss7

'oaks'

A had been measured at exact y the same ang?e and energy with t e same beam an8 apparatus

[?!y

This direct reconstruction gave exactly the same amplitudes as a fixed energy PSA.

Since then, similar parameters have been measured at 4 other energies (448, 496, 515 and 540 MeV). Results are almost final and a similar amplitude reconstruction will be done [16].

This will allow a detailed study of P wave behaviour in this energy range where resonances have been predicted [17]. At LAMPF, complex spin parameters have been measured mainly at 597, 645, 699, 750 and 800 MeV. Data include correlation parameters Aoonn,

Aoosk' AoOkk) AoOSSf the spin transfer parameters K osso' Kokko' K ~ k s ' K~skoy Dsoso' 'soko' ~ o n p y D k o s o ' 'koko

dnd

polarization P. In constrast to what has been 8one at SIN, parameters lnvo vlng the rotatlon of the longitudinal spin component of the scattered proton by a magnet, such as D

koko' have been measured. Due to the fact that the data come from different experiments (even frcm different laboratories LAMPF,ZGS) and measured at different angles and energies, it has been preferable to introduce them in phase shift analyses ( except for the amplitude analysis at 9 0 2 [18]). Very interesting and unique work is done with the HRS ,which allows measurements ofL~omplex spin parameters down to very small angles (4cOm ), in the Coulomb interference region. This is of particular interest for probing the treatment of the electromagnetic interaction. A UCLA/MINNESOTA/LAMPF/KEK group [I91 [20] presented preliminary measurements of Aoonn at 647 and 800 MeV, and Aookk at 800 MeV.When final, data will extend down to 6 _cm

.

They used a KEK frozen spin target m t h a thin walled cryostat as well as thin polarized target. The new preliminary results on A and A are shown in fig. 4a) b) along with

oonn ookk

phase shift prediction [lo] [ll] [21] and previous similar data at larger angles [22] which are in good agreement. Similar small angle measurements of Aookk at 650 MeV and Aooks ,Aooss at 650 and 800 MeV are planned.

0 3

0 2

PRELlMlNARY

650 MeV

-.-.-

- - _---.',

^{800 MeV}

0 2 -

01-

Pig. 4a) Preliminary A in small angle pp elastic scatt%?Eg at 650 MeV [19]. The 2 curves are PSA pre- dictions the full one is from [lo], the dash-dotled is [2l]. The open triangles are from [22].

Fig. 4b) Preliminary .A kk results at 800 MeV in small ang?e pp elastic scattering [19]. The dash line is PSA prediction from [ll]. The crosses are from [221.

C2-404 JOURNAL D E PHYSIQUE

Above 800 MeV, data are less abundant, except around 1 GeV. This justifies the extensive abundant work reported in this conference [23]. Differential cross section and analyzing powers have been measured between 600 to 1OOO MeV for lab scattering angles between 16' to 4

2 '

. A smooth energy dependence in the analyzing power at fixed scattering angle is reported as illustrated at 21' in fig. 5. The Saclay Nucleon-Nucleon group is also aiming to measure 10 spin observables at a few energies between 800 and 2800 MeV taking advantage of the high beam polarization (90 % below 940 MeV, 83% for higher energies). The parameters P, Aoom, Aookk' K K D D N N snk, Nosh have already been measured between 4 0 and m y a t ~ Z ~ ~ ' ~ E O ~ ? Z A , 1 W k d ?%'Me?. In t h s measurements target and

a cm

beam polarizations are along k or/and n direction. No measurement of parameters involving longitudinal polarization of the scattered proton is foreseen. A nice feature of the Saclay beam line is the transverse polarimeter which monitors any n or s components. Therefore for measurements with a longitudinally polarized beam, it was possible to determine the contribution coming from the pp analyzing power. Results on Aookk parameters have been presented [24] at these five energies. A good agreement with previous Argonne data [22] [25]

is found.

Fig. 5 Analyzing power at 21°

lab as a function of incident kinetic energy.

A series of eleven measurements of aQL between 0.52 and 2.8 GeV with a relative statistical precision of 2%5% at 2.8 GeV has also been reported. The structures below 800 MeV, first observed by Argonne, are now well confirmed. The Saclay data is in good agreement with the SIN results [26] at 0.52 GeV and with Argonne ZGS [27] and LAMPF [28] near that energy. The lRIUMF data [29]-are systematically larger ,but the energy behaviour is well reproduced.This illustrates the difficulty in controlling the systematic errors which come essentially from the beam and target polarizations and from the hydrogen content in the target. Above 800 MeV, the new Saclay data show no marked structures in their energy dependence at least up to 1.8 Gev. There is also no indication for a change of sign below 2.8 GeV. With a 1450 MeV accelerated deuteron beam incident on the NN beam line polarimeter, a simultaneous quasi-elastic scattering of n p and p p was observed[30]. The n-p analyzing power was directly obtained by multiplying the measured ratio of asymmetries ctp 1 cgp by the known p p analyzing power [30]. This method takes advantage of the fact that protons and neutrons coming from the break-up of polarized deuterons have the same polarization. The resulting systematic uncertainties of A (np) are essentially only those due to the

oono

uncertainty on A (pp).Results are in good agreement with the data from LAMPF obtained with oono

an unpolarized beam and polarized target ,thus conforming the LAMPF absolute normalization.

b) On the np system

The np system is not as well measured as the pp system. This is partly due to availability of good polarized neutron beams. Present and future plans at SATURNE I1 [23], LAMPF [12],TRIUMF [9] and SIN are listed in table I. At TRIUMF measurements of A. nn and aspmetry are planned for next year down to 210 MeV [9]. Figure 6 illustrates the pre8ictions

of .A nn at 210 MeV. The agreement between different PSA [lo] [ll] [32] is far from being satisyactory in contrast to what people generally believe. One sees also from Table 1 that most of the future planned experimental effort is above 600MeV, but it appears that more data below 600 MeV are still needed such as correlation parameters Aookk in order to assure a good PSA solution. There are also discrepancies among existing data which must be resolved. This will be discussed later in the paragraph concerning the status of the phase shift analyses.

SACLAY 0.8-

0.6

0.4 0.2

Aoonn'Aooss'Aookk

(1985-861

I

^F

/

2 0 ~ - 9 0 ~

1

550-1200 MeV

1

^PROPOSED

I

Aoosk'Aooks LAMPF

PO 40 60 80 100 120 140 160

8 c r n

A o o n n 210MeV -

-

-

-

Fig. 6 Predictions of Aoonn in np elastic scattering at 210 MeV.

The dashed line is the Paris potential model 1311, the full dotted dash-dotted and open circles are PSA predictions from [10],[11], 2 solutions from D. Bugg [9].

Dnono

1

Dsoso'Dkoso'Dsoko'Dkoko Konno'Kosso'Kokso Kokko'Konno Aookk'Aooss'Aoosk Aoann

DOL. AOL

Konno.K ,,sS,,. Kokso.KOSkO,KOkkO

~ n o n o ~ ~ s o s o ~ ~ k o s o ~ D s O k O ~ ~ k O k O TRIUMF

Table I Summary of np experiments at Saclay,LAMPF,SIN and TRIUMF. In the 2nd column, F and QF stand for free and quasi free scattering.

iF F QF F

QF F F F F QF

SIN

Aoonn' A (1985)

Dsokos Dsoso3 Dnono, A (1984)

Phase shift analyses

--

Two recent analyses were discussed. Hoshizaki's latest work [21], including preliminary

20'-90' 110°-1600 75'-170' 25'-60' 160~-180~

180' 8 0 ~ - 1 6 0 ~ 7 0 ~ - 1 7 0 ~

5 0 ~ - 1 8 0 ~ 7 ~ ~ - 1 0 0 ~

F 60'-160~

TYPE OF EXPERIMENT

small angle results on Aoonn at 800 MeV from LAMPF [19] and A ~ L inelastic from Argonne [22], was presented by A. Masaike [20]. J. Bystricky [33] reported on the Saclay-geneva phase shift analysis but also made a comparison with other recent analyses, pointing out a few problems.

210,325,425.500 MeV

QF

800 MeV

395,465,565.66s MeV 500,800 MeV 800 MeV 500,800 MeV 500,650.800 !,:eV

650.800 HeV

650,800 MeV 800 MeV

BEING ANALYZED

RUNNING

PROPOSEU

3 0 '- 90'

STATUS ANGLES

580 MeV

EXPERIMENT ENERGIES

C2-406 JOURNAL DE PHYSIQUE

One needs as input not only complex spin elastic parameters but also spin independent quantities such as do /dR,total cross-sections and also some information on the inelasticities via the reaction cross-sections. Between 10 to 800 MeV and around 1000240 MeV the overall number of data points in pp and np is about the same (26100), but their distribution is very different: d o /dQ represents 70% in np, 39% in pp, while spin observables(except P) represent only 6% in np compared to 32% in pp. Bystricky also illustrated in the distribution of existing pp complex spin parameters that 1) around 200 MeV, data are quite rare and have rather large error bars (1C-15%) and 2) between 800 and 1000 MeV almost no measurements exist, which makes it difficult to do energy dependent analysis in this region. SATURNE I1 results will help solve this difficulty. The np data base is not as complete,more measurements are needed in the whole energy range: below 600 MeV correlation parameters A (see TRIUMF proposal) Aookk

,

and above 600 MeV the proposed programs at LAMPF and

will

improve the situation.

As important, are conflicting results such as the np total cross section, which one might think to have been settled a long time ago. Fig. 7 shows the np q o t a s a function of kinetic energy T. The black dots are the M F 1982 data [34] which disagree with previous measurements between 200 and 600 MeV. The solid and dotted lines are the Saclay-Geneva [lo]

and Arndt [ll] fits respectively, both of these analyses could very easily describe the data in ref [34]. At the Heidelberg Conference last August, a Freibourg group working at SIN presented data (shown as black squares) in perfect agreement with those of Ref [ 3 4 ] . ^Another example of controversial data in the np system exists between precise measurements of A

ooon [35] and Aoono [36] at 425 MeV and around 490 MeV. Relative differences as big as 30% are seen for c.m. scattering angles around 100' as illustrated in Bystricky7s talk 1331. It is very important to clarify this point as each laboratory might be tempted to use their own measured asymmetry values for further determination of the spin dependent parameters, thereby

.:;

opagating discrepancies artificially

.

^{The TRIUMF} proposal to measure Aoonn and asyetry L'lould be able to resolve this point.

Another important source of the discrepancies comes from the different treatment of inelasticities.krhi1 pp inelastic cross-sections are well measured the situation is not as good for np.For example ,data for the channnel u(np+ np?)is scarce even though it is the most dominant. It would be extremely useful to do such measurements between400-1000 MeV.Another source of disagreement is due to the fact that in some analyses inelasticities for high partial waves are imposed from a theory. But theoretical predictions [38] [31] are not in good agreement[39].

LAMPF 1982 0 PPA 1973 0 TRIUMF 1981 0 RHEL 1966 A HARVARD 1966 n DUBNA 1955 -

rnb - S ^{A Others} FREISURG 1984

4 I

Fig. 7 Total cross section as a function of kinetic energy T.

References are to be found in [35].

It is not too surprising that PSA analyses starting from somewhat different data bases, theoretical input, are not in total agreement. For 1=1 phase shifts above 500 MeV the four recent analy es [l 1, [ll], [21], [32], are not in agreement even for such 1 rge contributing phases as 'So

A0.

^{Ffg. 8} shows the Argand diagrams for 'D2 and F3. The study of

9

anti-clockwise turning of Fg needs precise data up to 1OOO MeV. One can only hope that when all the results from the current experiments at SIN, SATURNE I1 and W Fare available, a good agreement for 1=1 phase shifts will be reached up to 1OOO MeV. The I = 0 phase shifts show larger discrepancies even at lower energies 1331. This is a reflection of the lack of data.Wolfenstein parameters have been measured more frequently than spin correlations.The inelasticities are very badly known :no measurement of free np haL and bat exist, moreover the amount of inelasticity one should put in the 1=0 phases above 500 MeV is not yet resolved either.

Fig. 8a) Argand diagram for 1 ~ 2 phase shift. Fig. 8b) Argand diagram for The symbols are as follows:

Full line [lo], dash-dotted [ll] open squares 3 ~ 3 phase shift. Symbols are [32], stars [ 2 1 ] . The four solutions [L,H,V,S] the same as in the Fig. 8a).

at 1 GeV are from [lo].

Conclusions

The Gp domain is developping rather fast in the theory as well as in the experimental domain.The coming years will bring new and precise data. Review of the elastic nd system has been made by M.Locher[OO]. The clarification between different t,, results is necessary before drawing any conclusions on possible resonances. The np scitering is not adequately determined.More data are needed in the whole energy range.An overdetexmination is necessary in view of possible systematics errors.Below 600 MeV, spin correlation parameters are needed, Aoon~ but also Aookk 'hookQ ,Aoo ,

3

^{k.Above 500} MeV spin transfer parameters K onno ,KoS which requlre hlgh intense po arlze beam are required.Measurements with free neutrons of AU and

0 L

Aat and total inelastic cross section u (np-+np?r ) would bring important knowledge on inelasticities. Very few measurements have been performed at m l l angles.It is important to study the np system as extensively as it has been done for the pp system.0ne should avoid to repeat the situation which occured for pp scattering few years ago:it was believed by some people that the pp system was well known,so that a rather moderate priority was assigned to further experimental program.But when in 1980 LAMF'F results on Dno

3

^D . sogo 'Dsok~ became available ,changes in phase shift predictions as big as 5 standart evlatlons were observed!

(i.e Dsoko changes from 0.2 to -0.2 ). The pp system is in a better situation.Very interesting and unique small angle correlation parameters are studied at W F . As SIN and LAMPF have worked mainly above 400 MeV

,

the pp data around 200 MeV are rather scarse and have large statistical errors.From these 2 laboratories a lot of data are still being analyzed and should help clarifying the situation. One can then hope for a better agreement between different pp PSA above 500 MeV. Above 800 MeV a very detailed program is being done at SATURNE II.One can hope for KEK results with polarized beam and target in a near future.

C2-408 JOURNAL DE PHYSIQUE

References

[ 11 N. Horikawa invited talk to the Intermediate Energy Workshop

[ 21 T. Takeda et al., Contributed paper to the V I I ~ ~ European Symposium on Antiproton Interactions ,Durham ,UK, July 84

[ 31 M. Lacombe et al Phys. Lett. 124 B (1983 443

[ 61 K. Nakamura, contributed paper to the YIIt' European Symposium on Antiproton Interactions Durham, UK, July 84

[ 51 K.Nakamura et al., Phys.rev. D29(1984)349 A.Clough et al., to be published in Phys.Lett

[ 61 F, Bradamante, invited talk to the Intermediate En rgy Workshop and C.I.Beard et al.

,

contributed paper to the YIIt6 European Symposium on Antiproton Interactions

,

Durham, UK ,July 84 [ 71 W. Gruebler et al., Phys. Rev. Lett. 49 (1982) 444 [ 81 E. Ungricht et al., Phys. Rev. Lett. 52 (1984) 333

[ 91 L.G. Greeniaus, invited talk to the Intermediate Energy Workshop [lo] J. Bystricky et al., Saclay Report DPWE 79-12, revised in February 84 [Ll] R.A. Arndt et al., Phys. Rev. D 28 (1983) 97

[I23 0. V a n Dyck, invited talk to the Intermediate Energy Workshop [13] J. Bystricky et al., Journal de Physique 45 (1984) 207

[14] R. Hess, in High Energy Physics with polarized beam and polarized targets

~irkhguser Verlag, Basel, 1981 p. 519-521

[15] E.Aprile et al., Phys. Rev. D 28(1983)21, and Phys. Rev.D 27(1983)260 [16] R. Hess, invited talk to the Intermediate Energy Workshop

[17] E. Lomon, Phys. Rev. D 26 (1980) 576 [18] C.L.Hollas et al., Phys. Lett. 143B(1984) 343

[19] G. Pauletta

,

contributed talk to the Intermediate Energy Workshop [20] A.Masaike

,

invited talk to this conference.

[21] N. Hoshizaki invited talk in High Energy Physics Problems in Dubna June 1984 [22] M.W. &Naughton et al., Phys. Rev. C 25 (1982) 2107

and I.P. Auer et al., Phys. Rev. Lett. 51 (1983) 1411 [23j F. Lehar, invrted talk at the Intermediate Energy Workshop [24] A. De.ksquen, invited talk at the Intermediate Energy Workshop [25] I.P. Auer et al., Phys. Rev. Lett. 41 (1978) 1436

[26] E. Aprile-Giboni et al., to be published in Nuclear Physics A.

[27] I.P. Auer et al., Phys. Lett. 67 B (1977) 113 [28] I.P. Auer et al., Phys. Rev. D 29 (1984) 2435 [29] J.P. Stanley et al., Nucl. Phys. A 403 (1983) 525

[30] F. Perrot, contributed talk to the Intermediate Energy Workshop [31] M. Lacombe et al., Phys. Rev. C21 (1980) 861 and J. Cote et al.,

Nucl. Phys. A379 (1982) 349

[32] D. Dubois et al., Nucl. Phys. A377 (1982) 554

[33] J. Bystricky, contributed talk to the Intermediate Energy Workshop

[34] P.W. Lisowski et al,

,

Phys. Rev. Lett. 49 (1982) 225 [numerical values taken from Arndt's data base SAID program]

[ 351 J. Bystricky , F. Lehar

.

Nucleon-Nucleon data Fachinf ormationszentum Karlsruhe Nr 11.1 Part I and I1 (1978) Nr 11-2 and 11-3 (1981) editors H.Behrens and G.Ebe1 [36] See ref N-39 in ref [35].

[37] A.S. Clough et al., Phys. Rev. C 21 (1980) 988 [38] i.e. A.M. Green et al., J. Phys. G5 (1979) 503 [39] R.R.Silbar ,invited talk to this conference.

[40] M.Locher, invited talk to this conference.

[41] M.W.MrNaughton et al., Polariz. Phenom. in Nucl. Phys.(~~~ Int Symposium, Santa-Fe,NM (1980) ) AIP Conf. Proc. no 69 (1981).