ANALYZING POWER MEASUREMENTS FOR p-p ELASTIC SCATTERING AT HIGH-P⊥2

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ANALYZING POWER MEASUREMENTS FOR p-p ELASTIC SCATTERING AT HIGH-P ⊥ 2

R. Raymond, K. Brown, R. Bruni, P. Cameron, D. Crabb, R. Cummings, F.

Khiari, A. Krisch, A. Lin, K. Terwilliger, et al.

To cite this version:

R. Raymond, K. Brown, R. Bruni, P. Cameron, D. Crabb, et al.. ANALYZING POWER MEASURE-

MENTS FOR p-p ELASTIC SCATTERING AT HIGH-P ⊥ 2. Journal de Physique Colloques, 1985,

46 (C2), pp.C2-303-C2-305. �10.1051/jphyscol:1985236�. �jpa-00224550�

JOURNAL DE PHYSIQUE

Colloque C2, supplement au n°2, Tome 46, fevrier 1985 page C2-303

ANALYZING POWER MEASUREMENTS FOR p - p ELASTIC SCATTERING AT H I G H - P± 2

R . S . Raymond. K.A. Brown, R . J . B r u n i , P . R . Cameron, D.G. C r a b b , R . L . Cummings, F . Z . K h i a r i , A.D. K r i s c h , A.M.T. L i n , K.M. T e r w i l l i g e r , G.T. Danby⁺,

Y.Y. L e e+, L.G. Ratner"1", J . R . 0 ' F a l l o n+ +, D.C. P e a s l e e * , T . S . B h a t i a * * , G. G l a s s * * and L . C . N o r t h c l i f f e * *

Randall Laboratory of Physics, The University of Michigan, Ann Arbor, Michigan 48109, U.S.A.

^Accelerator Department, Brookhaven National Laboratory, Upton, New York 11973, U.S.A.

++Office of Advanced Studies and Department of Physics, University of Notre Dame, Notre Dame, Indiana 46556, U.S.A.

Department of Physics, University of Maryland, College Park, Maryland 20742, U.S.A.

**'Department of Physics, Texas A & M University, College Station, Texas 77843, U.S.A.

Résumé - Au Laboratoire National de Brookhaven (AGS), la mesure de la puis- sance d'analyse d'une diffusion élastique p-p de 28 GeV/c a été effectuée à Pj_2 = 5,95 et 6,56 (GeV/c)' en u t i l i s a n t une cible de protons polarisée et un faisceau de protons non-polarisë. Les résultats montrent que la puissance d'analyse, A, augmente rapidement avec Pj_ .

A b s t r a c t - The analyzing power i n 28 GeV/c p r o t o n - p r o t o n e l a s t i c s c a t t e r i n g was measured a t P i2 = 5.95 and 6.56 (GeV/c)2 using a p o l a r i z e d proton t a r g e t and an unpolarized proton beam a t the Brookhaven National Laboratory AGS.

Results i n d i c a t e t h a t the analyzing power, A, i s r i s i n g s h a r p l y w i t h P^2.

Previous measurements1 of the analyzing power, A, f o r p r o t o n - p r o t o n e l a s t i c s c a t t e r i n g suggested a r i s e w i t h t r a n s v e r s e momentum above P^2 = 3.5 (GeV/c)2. Such a r i s e was c o n t r a r y t o t h e o r e t i c a l e x p e c t a t i o n s , so t o c l a r i f y the s i t u a t i o n , we made f u r t h e r measurements at P ,2 = 5.95 (GeV/c)2, the maximum 9 ^ of the e a r l i e r measurements, and at Pj_2 = 6.56 (GeV/c)2.

Measurements were made using an unpolarized 28 GeV/c proton beam from the Brookhaven A l t e r n a t i n g Gradient Synchrotron, AGS, i n c i d e n t upon the U n i v e r s i t y of Michigan p o l a r i z e d proton t a r g e t . The t a r g e t c o n s i s t s of t a r g e t m a t e r i a l cooled t o 0.5°K by an evaporation r e f r i g e r a t o r , i n a 2.5 T magnetic f i e l d . P o l a r i z i n g t r a n s i t i o n s are driven by a 70 GHz microwave system and the p o l a r i z a t i o n of the f r e e protons i s measured w i t h a 107 MHz NMR system. A high beam i n t e n s i t y ,

t y p i c a l l y 5 x 101 0 protons per p u l s e , was made p o s s i b l e by using i r r a d i a t e d ammonia as the t a r g e t material and by using a 3He - **He mixture as the c i r c u l a t i n g f l u i d i n the r e f r i g e r a t o r . The p o l a r i z a t i o n of the t a r g e t hydrogen p r o t o n , P j , was

t y p i c a l l y 45% w i t h beam and 60% w i t h o u t beam.

E l a s t i c proton events were detected i n a double-arm forward-backward s p e c t r o - meter, shown i n F i g . 1 , c o n s i s t i n g of s i x magnets and a s i x - f o l d eight-channel s c i n t i l l a t i o n - c o u n t e r hodoscope. The Px 2 - acceptance f o r these measurements was about 1 ( G e V / c )2.

The analyzing power, f o l l o w i n g the Basel convention f o r our l a y o u t , i s defined as

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1985236

JOURNAL DE PHYSIQUE

Figure 1. Layout o f Experiment

F i g u r e 2. Analyzing Power f o r Proton-Proton E l a s t i c S c a t t e r i n g as a Function o f Pl*

where N ( f ) and N(+) are t h e number o f events w i t h t a r g e t p o l a r i z a t i o n d i r e c t i o n up and down, r e s p e c t i v e l y . Accidental coincidences between t h e forward and backward arms were measured continuously and s u b t r a c t e d from t h e raw number o f events. An e s t i m a t e o f t h e non-hydrogenous and n o n - e l a s t i c background events was obtained by s u b s t i t u t i n g T e f l o n beads f o r t h e normal ammonia beads. The r e s u l t i n g background events were presumed t o have an analyzing power o f zero and were t r e a t e d as a d i l u t i o n o f t h e proton-proton e l a s t i c analyzing power. The f i n a l values o f A we r e :

The value a t pL2 = 5.95 (GeV/c)* c o n t a i n s t h e data from our e a r l i e r runl. These new values are p l o t t e d i n Fig. 2 along w i t h e a r l i e r measurements from t h e AGS1, 2 and CERN~. The sharp r i s e i s not, as f a r as we know, described by any theory.

Planning i s now i n progress f o r more measurements i n order t o reduce t h e

s t a t i s t i c a l u n c e r t a i n t y o f t h e 6.56 (GeV/c)2 p o i n t and a l s o t o o b t a i n data a t even h i g h e r P12.

This research was supported by a g r a n t from t h e U.S. Department o f Energy.

REFERENCES

1. D.C. Peaslee e t al., Phys. Rev. L e t t . 51, 2359 (1983).

2. P.H. Hansen e t al., Phys. Rev. L e t t .

5 c

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.,