EXPERIMENTAL POSSIBILITIES WITH UA-6

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EXPERIMENTAL POSSIBILITIES WITH UA-6

R. Cool

To cite this version:

R. Cool. EXPERIMENTAL POSSIBILITIES WITH UA-6. Journal de Physique Colloques, 1985, 46 (C2), pp.C2-737-C2-740. �10.1051/jphyscol:1985297�. �jpa-00224616�

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Colloque C2, supplément au n°2, Tome 46, février 1985 page C2-737

EXPERIMENTAL POSSIBILITIES WITH UA~6

R.L. Cool

Rockefeller University, NY 121-6399, U.S.A.

Résumé . Nous discutons certaines possibilités expérimentales avec un faisceau de protons polarisés au SPS et une cible gazeuse d'hydrogène polarisée.

Abstract . We discuss some experimental p o s s i b i l i t i e s a t the SPS with a polarized proton beam and a polarized hydrogen gas j e t t a r g e t .

To a s s e s s t h e adequacy of t h e design p a r a m e t e r s of an accelerator, a set of "typical" experiments is often worked out in some detail in a d v a n c e . T h u s t h e limitations and r e q u i r e m e n t s of the hypothetical machine can frequently be clarified. As it h a p p e n s , for one such set of t h e possible e x p e r i m e n t s , the details are r a t h e r readily available. While this set is only one of many which need to be examined, it may be of some i n t e r e s t to see if any conclusions can be drawn when the p a r a m e t e r s of the "canonical polari2ed beam" being discussed here are applied to i t .

I take t h e canonical p a r a m e t e r s to be 1 0l x p r o t o n s p e r b u n c h with

^ 70% polarization, t h r e e b u n c h e s of ^ 300 GeV being stored in a r i n g which p r e s e r v e s t h e i r polarization. The set of possible experiments to which I have r e f e r r e d above are those which constitute t h e CERN experiment UA-B, p r e s e n t l y installed at t h e S p p S . UA-6 p r o p o s e s to use t h e s t o r e d , unpolarized proton and antiproton beams in collision with e i t h e r an unpolarized or a polarized h y d r o g e n g a s jet t a r g e t [ 1 ] . For t h e p r e s e n t p u r p o s e , I t a k e the canonical polarized beam described above to be in collision with t h e polarized h y d r o g e n gas jet t a r g e t . A p r o t o t y p e of t h i s t a r g e t , designed by L. Dick and W. K u b i s h t a , has successfully given ^ 95% polarized h y d r o g e n atoms with a d e n s i t y of p =» 1 01 2 cm"

over a 1 cm length in t h e beam direction [ 2 ] . Improvements to this initial version

„ 3

could lead in the near future to p ~ 1 01 3 cm , Taking the l a t t e r , more optimistic d e n s i t y , the SppS luminosity would be 1 02 9 cm- sec . This t a r g e t h a s several valuable c h a r a c t e r i s t i c s : (1) p u r e h y d r o g e n ( t h u s no subtraction for Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1985297

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unpolarized constituents) ; ( 2 ) immunity to radiation damage; (3) comparatively small size; ( 4 ) the target polarization can be oriented in any chosen dixection with respect to that of the beam; and (5) target polarization may be rapidly reversed ( % l o 3 Hz.). Details are given in Ref. 2.

The apparatus of UA-6, Figure 1, has been designed to study the following inclusive reactions from an initial p + p , p + p 1. , or in this case, the p + + pl. state; y+X, y+y+X, e+ + e- + X , aO+x, a0 + a O + x , and A' (713) + X . In addition, the apparatus measures the elastic scattering and inclusive dif- fraction dissociation cross sections in the four momentum transfer range 0 . 0 0 1 < It 1 ^< 0.1 ( G ~ v / c ) 2. For this apparatus (Ref. 1) , estimates of rates have been made for some of the above reactions and are given in Table I .

p T ^{xT dN/dpT}

( GeV /c) (GeVIc day)-'

4 0.33 30

6 0.50 0.5

8 0.67 lo-2

T a b l e I b . p + p + y + X

It 1 ^{dN Id0}

( G ~ v / c ) ~ s r . day)-'

0.001 1.0 x10 3

0.01 3.0 x10 3

0'. 10 3.5 x 1 ~ 3

TableIc. p + p + p + p

F I G . 1 - A perspective view of the UA-6 apparatus in the SPS tunnel.

In addition, the rate for J/$ production would be about two per day while the rate for A0 + X production i s expected to be large.

The rates for inclusive a' and direct y production appear to limit data to pT 7 5 GeV/c, that is values of xT = pT/pTmax

'

The production of An-hyperons i s large. This i s a particularly interesting reaction since the polarization of the final state A' is readily

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determined.

A s expected, low t elastic rates are large and thus offer the possibility of high precision measurements to search for interference effects between the spin flip and coulomb amplitudes. While such effects are expected to be s m a l l , the experiment should be limited only by systematic e r r o r s .

References:

1. CERN Proposal SPSC /80-63, 1 9 August 1980; CERN Proposal SPSCl77-77, 28 August 1977.

2 . L . Dick e t al, Proceedings of the 1980 International Symposium, Lausanne ,

Birkhauser Verlag , Basel.