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LAMPF NUCLEON-NUCLEON PROGRAM
O. van Dyck, M. Mcnaughton
To cite this version:
O. van Dyck, M. Mcnaughton. LAMPF NUCLEON-NUCLEON PROGRAM. Journal de Physique
Colloques, 1985, 46 (C2), pp.C2-417-C2-420. �10.1051/jphyscol:1985247�. �jpa-00224562�
JOURNAL DE PHYSIQUE
Colloque C2, supplement au n°2, Tome *6, fevrier 1985 page C2-417
LAMPF NUCLEON-NUCLEON PROGRAM
0. van Dyck and M.W. McNaughton
Los Alamos National Laboratory, Los Alamos, NM 87545, U.S.A.
Résume - Le programme Nucle'on-Nucléon réalise à LAMPF est résume'. Les efforts ont porte' sur les réactions p+p inelastiques pour l'étude des tranferts et des corrélations de spin. Nous espérons avoir une bonne couverture des corrélations de spin dans les réactions élastiques n+p en 1986. Les nouvelles installations prévues pour les expériences nucléon-nucléon et nucléon-noyau avec les faisceaux polarisés sont également présentées.
Abstract - NN a c t i v i t i e s at LAMPF are summarized. Measurements with p+p are now focusing on inelastic spin transfer and spin correlations. There should be good coverage of np spin correlations by 1986. Additional f a c i l i t i e s are outlined for polarized beam nucleon and nuclear physics.
Since our last summaries in 1981-82,*»2 the f a c i l i t i e s available at LAMPF have changed only a l i t t l e : (1) the BR channel was restored to a neutron beamline with a l i q u i d deuterium, source target, (2) another polarized target system has been assembled by a Japanese-American collaboration. The accelerator with a Lamb-shift polarized H" ion source delivers ~20nA average beam at 800 MeV {9% duty) or 7nA at lower energies down to 212 MeV (3% duty). The beam i s shared among three beamlines with f a i r l y complete precession equipment available. The beam current is generally adequate for proton experiments but i s marginal for production of the polarized neu-tron beam.
Table I l i s t s LAMPF NN experiment a c t i v i t i e s since -1981, covering experiments which have reported a c t i v i t y through publications, preprints, and LAMPF Progress Reports.3 The table is organized by number of particles observed and number of spins measured. Nucleon experiments with pion beams are discussed elsewhere.
In the pp channels, the t o t a l cross section experiments Aa, and Aa-r over 300-800 MeV are close t o completed analysis; prelimary results have Deen informally reported.3 The pp and pd parity measurements at 800 MeV are complete.
Results from many pp elastic scattering experiments from 500-800 MeV are p u b l i s h e d2'4'5 or available in preprint. Generally, there is a sufficient variety of measurements to overconstrain a phase s h i f t solution. The less-accessible in-plane spin rotation parameters as well as normal depolarization have been mea-sured in spin transfer experiments with error bars usually under 0.03. Other exper-iments focus on specialized features such as forward-angle Coulomb-nuclear interference.
There is one other pp reaction with a two-body f i n a l s t a t e , pp * dw, that has been well covered in cross section and analyzing power;" spin transfer to the deuteron has been sampled more sparsely.' In the l a t t e r experiment, a deuteron dissociator was placed in the center of the precession and analyzing magnet to give a unique signature of dissociation as the charged particle momentum is cut in half. The results are nearly ready for publication.
C2-418 JOURNAL DE PHYSIQUE
TABLE I
LAMPF NUCLEON-NUCLEON EXPERIMENT ACTIVITY 1981-84 Published, preprinted, or progress report since Jan. '81
Reaction p + p PP * PP pp • du+ PP * PX pp + NNir pd » pd np + np n p •• n p pp + NNir S.N.L = x,y D,K =• spin Measurement A C T A<J|_ Parity a ASS o,AN ANN»ALL ANN» ALL D1j
°U
AN °1j. AN A1j A1j o, AN a, AN AN N, AL L D1j a, A, D D1 j . AN A1jk o(8) a,AN AN,ANN AN DNN KNN ALL.ASS'ALS A1j ,z transfer F Beam Channels: B » BR Chan, No. BS04 E498 E792,... H563.760 E512 H385 H709 B517.518 E636.194 H392 H508 E637 B517 H790 H642 E336 B518 E708 H540 E635 H685 B56 H385 B65-66 B457 B590 B403 B770 E815 Comment also 4aj QF/F dissociator N,S,L, beams in progress F QF Wideband n QF QF and F F In progress 1985 1j = several A-f j- Free neutron beam QF = H = HRS (spectrometer) CM°(Lab°) 6-90 20-90 10-47 5-30 50-90 20-130 5-24 4-170 30-60 small (5-20) (5-25) (5-50) (30-60) small 60-180 14-75 70-170 20-90 20-90 168-177 40-160 = Initial : Quasi free E » EPB state Energies 300...800 300...800 800 500,650,800 500,650,800 800 650,800 500...800 500,..,800 500,800 550,..800 500,650,800 500...800 800 500,650,800 650,800 650,733,800 500,650,800 500,650,800 800 800 800 400-700 800 800 800 600,650,800 650,800 spin correlation (deuterium target) (External Proton Beam)
An i n t e n s i v e set o f measurements on s p i n t r a n s f e r i n pp -»• NNw has j u s t been f i n i s h e d ; t h i s experiment uses a two-arm d e t e c t i o n system. A recent p u b l i c a t i o n on cross s e c t i o n and a n a l y z i n g power a l s o used two coplanar arms. These two e x p e r i -ments present data as a f u n c t i o n of analyzed p r o t o n momentum i n several angular b i n s . A remarkable f e a t u r e of the momentum spectrum dN/dp i s the enhancement a t small i n v a r i a n t np e n e r g y , a f i n a l - s t a t e e f f e c t .
p r o t o n s p i n transfer.'' The t h r u s t o f t h i s program has been t o develop a model o f t h e deuteron w i t h nucleon i n p u t amplitudes; t h e s p i n measurements a r e e s s e n t i a l t o proceed beyond a simple Glauber p i c t u r e . Reports a r e i n press.
The np e l a s t i c measurements are l e s s complete. An e a r l y np experimentl1 a t LAMPF was i n i t i a l - s t a t e normal-di r e c t i o n s p i n c o r r e l a t i o n ; t h i s experiment was done w i t h a broadband neutron beam p o l a r i z e d by p r o d u c t i o n a t 20°. Only r e n t l y has
a
reasonably complete angular cross-section measurement been published;@ o t h e r s p i n measurements13 t e n d t o be l i m i t e d i n angular coverage. However, an extensive pro- gram o f i n i t i a l - s t a t e i n - p l a n e s p i n - c o r r e l a t i o n measurements i s un erway even though
rt
t h e a v a i l a b l e f l u x o f p o l a r i z e d neutrons i s l i m i t e d t o about 10 /s on t a r g e t . As p i n - d i f f e r e n c e t o t a l cross s e c t i o n measurement may f o l l o w perhaps i n two years. Other f r e e - n e u t r o n measurements are l i k e l y t o w a i t u n t i l a more i n t e n s e p o l a r i z e d neutron beam i s a v a i l a b l e .
Proton s c a t t e r i n g on q u a s i f r e e neutrons i n deuterium has been used as a supplement t o np s c a t t e r i n g w i t h f r e e neutron beams, p a r t i c u l a r l y t o extend t h e angular range t o small CM angle Quasifreelfree-deuterium/hydrogen comparisons a r e made by using t h e pp reaction)' and by o v e r l a p p i n g f r e e np data. L i m i t s t o t h e v a l i d i t y o f t h e q u a s i f r e e s u b s t i t u t e a r e n o t c l e a r l y established.
A plan15 has been sketched o u t f o r f a c i l i t y development over t h e next few years which would have b e n e f i t s f o r both t h e NN and nucleon-nucleus programs. A key element i s improvement o f t h e BR channel neutron beam. A f a c t o r o f 10-100 i n c r e a s e i n i n t e n s i t y w i l l be achieved, h o p e f u l l y i n 1987, probably by i n s t a l l a t i o n o f a more i n t e n s e p o l a r i z e d i o n source, o r p o s s i b l y by incremental improvements t o t h e e x i s t - i n g source and BR channel. A 100-ns beam buncher w i l l be i n s t a l l e d w i t h t h e new source o r perhaps b e f o r e then t o enable neutron energy measurements by t i m e o f f l i g h t . Even w i t h present beam i n t e n s i t i e s , t h e buncher would p e r m i t a d d i t i o n a l v a l u a b l e measurements such as np s p i n - d i f f e r e n c e t o t a l cross sections. A medium-resolution spectrometer (MRS),
AE
-
1 MeV, w i l l be b u i l t i n t h e External Pro- t o n area. T h i s spectrometer w i t h f o c a l - p l a n e p o l a r i m e t r y w i l l enable f u r t h e r NN small-angle measurements and w i l l be t h e p r i n c i p a l equipment i n a program i n few-body physics. The MRS w i l l have a non-magnetic p i v o t t o f a c i l i t a t e mounting of a new, large-volume p o l a r i z e d t a r g e t ; t h e t a r g e t system i s intended t o permit frozen-spin H o r D o p e r a t i o n w i t h any o r i e n t a t i o n . The primary beam l i n e might e v e n t u a l l y be equipped w i t h a 1 it h i u m t a r g e t c e l l which c o u l d d e l i v e r monoenergetic p o l a r i z e d neutrons on t h e spectrometer t a r g e t . These changes would p e r m i t broad ev- o l u t i o n o f t h e nucleon-beam physics program a t LAMPF.References
1. VAN
DYCK,
O., LAMPF Nucleon-Nucleon F a c i l i t i e s-
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3. Los A1 amos N a t i o n a l Laboratory r e p o r t s Progress a t LAMPF, LA-10070-PR (1983), LA-9709-PR (1982), LA-9256-PR (Dec. 1981), LA-8944-PR (June 1981).
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JOURNAL DE PHYSIQUE8. BONNER, B. E,, e t a l , i b i d , V, 11, p. 183.
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