SPIN AND ELASTIC HADRON SCATTERING AT SUPERHIGH ENERGIES

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SPIN AND ELASTIC HADRON SCATTERING AT SUPERHIGH ENERGIES

S. Goloskokov, S. Kuleshov, O. Seljugin

To cite this version:

S. Goloskokov, S. Kuleshov, O. Seljugin. SPIN AND ELASTIC HADRON SCATTERING AT SUPERHIGH ENERGIES. Journal de Physique Colloques, 1985, 46 (C2), pp.C2-239-C2-241.

�10.1051/jphyscol:1985226�. �jpa-00224537�

JOURNAL DE PHYSIQUE

Colloque C2, supplément au n°2, Tome 46, février 1985 page C2-239

SPIN AND ELASTIC HADRON SCATTERING AT SUPERHIGH ENERGIES

S.V. Goloskokov, S.P. Kuleshov and O.V. Seljugin

Joint Institute for Nuclear Research; Laboratory of Theoretical Physics, Head Post Office, P.O. Box 79, Moscow, U.S.S.R.

RESUME : Nous considérons la possibilité de l'existence d'un mécanisme nouveau que nous appelons "le mécanisme de la dynamique du soin" et qui se manifeste dans les interactions fortes aux énergies asymptotiques. Nous avons montré que ce mécanisme est important dans le cas où les effets de spin dépendent peu de l'énergie. Nous ti- rons les conséquences expérimentales pour un modèle concret dans un large domaine d'énergie jusqu'à_ J"s = 40 TeV. Certaines ont été confirmées par les expériences du collisionneur pp au CERN.

ABSTRACT : We consider the possibility of existence of a new mechanism which we c a l l

"the mechanism of spin dynamics" and which reveals i t s e l f in strong interactions a t superhigh energies. This mechanism i s shown to be important in the case of slow ener- gy dependences of spin effects. I t s experimental consequences were derived in the concrete model framework for the wide range of energies up t o Js" = 40 TeV. Some of them were confirmed a t the CERN pp-collider.

At p r e s e n t some models a p p e a r i n which t h e s p i n e f f e c t s a t f i x e d t r a n s f e r momenta s l o w l y change w i t h growing energy / 1 , 2 / . I n t h i s c a s e , a s a r u l e , i s used t h e o r d i n a r y e i k o n a l r e p r e s e n t a t i o n f o r t h e r e g a r d of t h e hadron i n t e r a c t i o n a t s m a l l a n g l e s .

L e t us c o n s i d e r t h e s c a t t e r i n g of two n u c l e o n s i n t h e framework of t h e q u a s i p o t e n t i a l approach / 3 / . The e i k o n a l c h a r a c t e r of s m a l l - a n g l e s c a t t e r i n g means t h a t t h e p a r t i c l e s go n o t f a r from l i n e a r t r a - j e c t o r i e s . In t h i s c a s e t h e wave f u n c t i o n of t h e system s a t i s f i e s t h e s o l u t i o n i n t h e form of w i c k - d i s t o r t e d p l a n e wave.

T ^P (r)~e*-F ^P {r). ⁽¹⁾

Solving the quasipotential equation one can obtain the ordinary ei- konal representation for the scattering amplitude. However, it may be shown / 4 / that the approach (1) impose ontthe energy dependence of quasipotentials certain limits. The limits for the quasipotentials corresponding to Born's term of. scattering amplitudes

Then the spin-flip amplitude is rapidly decreasing with energy.

The slow-energy dependence of spin effects can be obtained only in the case of anomalous energy dependence of the quasipotential fi(.i,t), i.e. in case, when the latter has the growing as VF" term /5/

&($,*)--JFjiar.*) , *-»oo . That is contradiction with limits (2). In this case the obtained form of scattering amplitude, can be reduced to the eikonal representation for small /K£.*). As a result for the spin-non-flip and spin-flip amplitudes we have

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1985226

C2-240 JOURNAL DE PHYSIQUE

I n a s u p e r h i g h e n e r g y r e g i o n , where #/2-/($~)>>

t h e d o u b l e s p i n - f l i p c o n t r i b u t i o n t o

- . d e t e r m i n e t h e b e h a v i o u r o f s c a t t e r - i n g a m p l i t u d e s :

++,+t m ++.r

-

The new mechanism o f s t r o n g - i n t e r a c t i o n dynamics /6/ r e s u l t s i n a " s p i n " mechanism o f t h e t o t a l - c r o s s - s e c t i o n growth, r a p i d growth of d i f f e r e n t i a l c r o s s s e c t i o n s n e a r t h e d i f f r a c t i o n minimum-maximum r e g i o n and some o t h e r e f f e c t s / 5 / . On t h e b a s i s of o u r model p e r i p h e - r i c p a r t s of t h e e i k o n a l p h a s e s w e r e c a l c u l a t e d c o n d i t i o n e d by e f f e c t s o f t h e "meson c l o u d " of hadron, i n c l u d i n g t h e anomalous terms o f t h e s c a t t e r i n g a m p l i t u d e s which a l s o have a p e r i p h e r i c c h a r a c t e r / 7 / .

I n t h i s model we have o b t a i n e d a q u a n t i t a t i v e d e s c r i p t i o n o f t h e d i f Z e r e n t i a l c r o s s - s e c t i o n a t 4 . 5 G ~ V G S * ⁶² GeV and

14 G e V / 3 , 9 / . The o b t a i n e d

+ u c r o s s i n g p r e d i c t i o n s f o r F P s c a t - t e r i n g a r e i n agreement w i t h e x p e r i m e n t /lo/.

We emphasize t h a t t h e p o l a r i z a t i o n behaviour a t

100 GeV is mainly d e t e r m i n e d by t h e anomalous term of t h e q u a s i p o t e n t i a l .

Fig. 1. Comparison of dynamical- -model p r e d i c t i o n s f o r p o l a r i z a - t i o n w i t h e x p e r i m e n t .

F i g . 2 . Our p r e d i c t i o n s :

w i t h and- - -

w i t h o u t " s p i n " mecha*

nism; - - - - -Amaldi

Note t h a t t h e s i g n o f p o l a r i z a t i o n o f t h e d i f f r a c t i o n minimum is r e l a t e d w i t h t h e s i g n o f ReT,,,.. . The r e a l p a r t of TI..,, C t

o b t a i n e d i n t h e model changes sign a t

- ^{400 GeV /I6 .}

^a r e s u l t , t h e model p r e d i c t s a r a p i d change o f p o l a r i z a t i o n a t d ⁼ 28 G e V

( f i g . 1 ) . A t t h e s e e n e r g i e s t h e p o l a r i z a t i o n h a s a weak energy depen- dence and becomes p o s i t i v e n e a r t h e d i f f r a c t i o n minimum.

The model r e s u l t s f o r q.+

a r e shown i n f i g . 2. The main c o n t - r i b h t i i o n t o t h e &.* growth a t m $ 100 GeV i s due t o t h e s t a n d a r d mechanism d e t e r m i n e d by t h e e f f e c t i v e - r a d i u s growth. A s ~ + s a t h e

" s p i n " mechanism c o n t r i b u t i o n i s a main c o n t r i b u t i o n t o Got and l e - a d s t q a r a p i d grows' of t h e d i f f e r e n t i a l c r o s s s e c t i o n a t

1 G e V < l * \ * 1 . 4 G ~ v ~ . A s a r e s u l t

o n t h i s r e g i o n a t CERN PP - c o l l i d e r e n e r g i e s i n c r e a s e s by a n o r d e r o f magnitude /9,10/, s e e F i g . 3 and F i g . 4 .

Thus we c o n c l u d e t h a t t h e f i r s t m a n i f e s t a t i o n o f t h e new " s p i n "

mechanism i s s t r o n q - i n t e r a c t i o n dynamics i s p r o b a b l y found. A f i n a l

F i g . 4 . The r o l e o f s p i n mechanism i n d d / d t

o u r p r e d i c t i o n s a t d?? =2; 1 0 and 40 TeV

---- - p r e d i c t i o n s Bour- r e l y C . a.0. /11/ a t g = 2 and 40 TeV.

F i g . 3. P r e d i c t i o n s o f o u r models a t

..rJ\ =540 GeV: -.- - - w i t h and w i t h - o u t " s p i n " mechanism ( g e o m e t r i c a l s c a l - i n g ) . p r e d i c t i o n a t 9 =I TeV.

c o n c l u d i o n a b o u t t h e e x i s t e n c e o f t h i s mechanism may b e drawn a t f u - t u r e a c c e l e r a t o r s on t h e b a s i s o f t h e p o l a r i z a t i o n e x p e r i m e n t s , mea- surement of t h e e n e r g y dependence o f d i f f e r e n t i a l c r o s s s e c t i o n s n e a r

l t l - 0 . 5

1 ~ e ~ 2 .

R e f e r e n c e s

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Purnplin J., Kane G.L. Phys.Rev., v. D11, ( 1 9 7 5 ) , p. 1133.

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Goloskokov S.V., P e p l i a k o v V . G . , Yad.Phys., v . 38, ( 1 9 8 3 ) , p. 1335.

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9 . Goloskokov S.V., J I N R E2-83-313, Dubna, 1983.

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11. B o u r r e l y C. e t a l . P r e p r i n t TH 3587 - CERN.