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O N THE 1350 MeV

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Y PEAK PRODUCED IN " 'p INTERACTION

G . Bozóki, E. Fenyves, T. G ém esy , É. G om bosi, S. Krasznovszky a n d E. N agy

N. P. B ogachev, Yu. A. Budagov, V. B. V inogradov, A. G . Volodko, V. P. Dzhelepov, V. G . Ivanov, V. S. Kladnitsky, S. V. Klimenko, Yu. F. Lomakin, Yu. P. M erekov, I. Patofcka, V. B. Fliagin, P. V. Shlyapnikov

JOINT INSTITUTE FOR NUCLEAR RESEARCH, DUBNA

HUNGARIAN ACADEMY OF SCIENCES CENTRAL RESEARCH INSTITUTE FOR PHYSICS

B U D A P E S T

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2017

P r i n t e d i n t h e C e n t r a l R e s e a r c h I n s t i t u t e f o r P h y s i c s , B u d a p e s t K ia d ja a KFKI K ö n y v tá r - é s K ia d ó i O s z t á l y . O.V. F a r k a s I s t v á n n á Szakm ai l e k t o r : d r . F e n y v e s E r v i n . N y e lv i l e k t o r t S u r á n y i G yörgy P é ld á n y s z á m : 105 M unkaszám: KFKI 3894 B u d a p e s t, 1 9 6 8 . o k t ó b e r 9«

K é s z ü l t a KFKI h á z i s o k s z o r o s í t ó j á b a n . F . v . t G yenes Im re

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ON THE I35O MeV Ay PEAK PRODUCED IN тГр INTERACTION G .B o zó k i, E . F e n y v e s . T .G ém esy, É .G o m b o si, S .K r a s z n o v s z k y an d E.N agy

C e n t r a l R e s e a r c h I n s t i t u t e o f P h y s i c s , B u d a p e s t, H ungary N . P . B o g ach ev , T u .A .B udagov, V .В .V in o g ra d o v , A .G .V o lo d k o , V .P .D z h e le p o v , V .G .I v a n o v , V . S . K l a d n i t s k y , S .V .K lim e n k o , Y u .F .L o m a k in , Y u .P .M e re k o v , I . P a t o S k a , V . B . F l i a g i n , P .V , S h ly a p n ik o v

J o i n t I n s t i t u t e f o r N u c le a r R e s e a r c h , Dubna

SUMMARY

The e x i s t e n c e o f t h e Ay p e ak b e tw e e n 1300 a n d 1400 MeV was su p p o r t e d b y o u r m e a s u re m e n ts . The e x p l a n a t i o n o f t h i s p e a k by т е а п з o f t h e h y p o t h e t i c a l An / 1 6 8 0 MeV/ r e s o n a n c e c a n b e r e j e c t e d on a 97 % c o n f i d e n c e l e v e l .

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1

INTRODUCTION

I n s tu d y i n g t h e A p r o d u c t i o n i n i n t e r a c t i o n s o f n e g a t i v e p io n s w i t h p r o t o n s i n th e 0 . 5 m p ro p a n e cham ber o f th e JTNR a p e a k was o b s e r v e d

i n th e e f f e c t i v e m ass d i s t r i b u t i o n b e tw ee n 1300 and 140 0 MeV b o t h a t 7 -8 GeV [ 1 ] , a n d a t 4 GeV p r im a r y e n e r g i e s [2] / F i g . l a / . , The a u t h o r s c o n c lu d e d t h a t th e o r i g i n o f t h i s p e ak c o u ld be e x p l a i n e d by a 1 6 8 0 MeV An r e s o n a n c e d e c a y in g i n t o a A2y f i n a l s t a t e g iv i n g r i s e to t h e o b s e r v e d A and у p a r t i c l e s . B ecau se o f t h e low у r a y d e t e c t i o n e f f i c i e n c y i n e x p e r im e n ts

[ 1 ,2 ] i t w as n o t p o s s i b l e to i n v e s t i g a t e t h e A2y m ass d i s t r i b u t i o n i n o r d e r t o c h e c k th e e x i s t e n c e o f t h e An r e s o n a n c e d i r e c t l y .

The m ain p u r p o s e o f th e p r e s e n t e x p e r im e n t was t o r e p e a t t h e s e i n v e s t i g a t i o n s i n a l a r g e r cham ber h a v in g s i g n i f i c a n t l y g r e a t e r у r a y d e t e c t i o n o f f i c i e n c y .

EXPERIMENTAL

U s in g th e JINR 1 m p ro p a n e cham ber [3] i r r a d i a t e d by a 5» 1 GeV/c

i t* beam a b o u t 100 0 0 0 p i c t u r e s h a v e b e e n t a k e n . The p i c t u r e s w ere s c a n n e d tw ic e i n o r d e r to s e l e c t e v e n ts w i t h Л h y p e ro n s p r o d u c e d i n тт_ р - i n t e r a c t i o n s . The s e l e c t i o n c r i t e r i a u s e d w ere e s s e n t i a l l y i d e n t i c a l w i t h th o s e d e s c r i b e d i n r e f s [ 1 , 2 ] . *

The s e l e c t e d e v e n ts w e re m easu red on s e m ia u to m a tic d e v i c e s . v ° 's and y 's p a s s e d th r o u g h a g e o m e t r i c a l r e c o n s t r u c t i o n and k i n e m a t i c a l f i t p ro g ram [ 4 , 5 ] i n o r d e r t o i d e n t i f y A an d у p a r t i c l e s and t o r e j e c t p a r t i c l e s n o t b e lo n g in g t o th e e v e n t . A f t e r t h i s p r o c e d u r e we c l a s s i f i e d o u r e v e n t s a c c o r d in g t o th e num ber o f у r a y s a s s o c i a t e d w ith t h e A p a r t i c l e . S p e c i a l c a r e w as ta k e n t o r e c o g n i s e B r e m s s tr a h lu n g y ' s by com

p a r i n g t h e d i r e c t i o n o f t h e i r l i n e o f f l i g h t w ith t h a t o f o t h e r у r a y s b e in g s u p p o s e d to be p r im a r y o n e s .

The Лу i n v a r i a n t m ass d i s t r i b u t i o n i s shown i n F i g . l b . Only e v e n ts w i t h one o r tw o o b s e r v e d у r a y s w e re u s e d , a n d b o th p o s s i b l e com

b i n a t i o n s w e re ta k e n fro m th e l a t t e r t y p e . One can s e e a n e x c e l l e n t a g r e e m ent b e tw e e n F i g s . l a and l b ' , i . e . t h e p e a k i n t h e 1 3 0 0 -1 4 0 0 MeV mass

*The o n ly d i f f e r e n c e w a s, t h a t e v e n t s i n w h ic h а Л h y p e ro n was p ro d u c e d w ith o u t t h e a p p e a ra n c e o f a у r a y w ere a l s o m e a s u re d .

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i n t e r v a l was r e p r o d u c e d i n oxir e x p e r im e n t . F i g . 2 shows t h e p l o t o f t h e 2 y i n v a r i a n t m a sse s v s . th e Ayy i n v a r i a n t m a s s e s , w hich w e re c a l c u l a t e d u s i n g o n ly e v e n t s w ith two o b s e r v e d у r a y s . One can s e e on F i g . 2 t h e c o r r e s p o n d i n g p r o j e c t e d 2y and Луу mass d i s t r i b u t i o n s , a s w e l l . W hile t h e r e i s a c l e a r тг° p e a k i n t h e 2y m ass d i s t r i b u t i o n no e v e n t s can b é s e e n i n t h e n° r e g i o n .

U sin g t h e s e m ass p l o t s we w en t on c l a s s i f y i n g o u r e v e n t s / T a b l e I . / . E v e n ts w ith one у r a y h a v i n g Ay e f f e c t i v e m ass b e tw e e n 1300 and 1 4 0 0 MeV w e re d e n o te d b y ( Ay ) , a l l o t h e r e v e n ts w i t h one у r a y by Ay , e v e n t s w i t h two у r a y s , w here t h e r e i s a t l e a s t one Ay c o m b in a tio n w i t h a n e f f e c t i v e m ass i n t h e r e g i o n o f 1 3 0 0 -1 4 0 0 * b y (A y) у , an d a l l o t h e r e v e n t s w i t h two y 's by A2y , The n u m b ers o f e v e n t s i n c l u d e d i n T a b le I a r e c o r r e c t e d f o r t h e b a c k g r o u n d .

DISCUSSION OF THE RESULTS

I n th e f o l l o w i n g we com pare o u r r e s u l t s w i t h th e h y p o t h e s i s o f t h e e x i s t e n c e o f a An /1 6 8 0 MeV/ r e s o n a n c e s u g g e s t e d i n [ 1 , 2 ] . P o s s i b i l i t i e s f o r t h e e x p l a n a t i o n o f t h e a p p e a r a n c e o f t h e p e a k i n th e Ay mass d i s t r i b u t i o n b e tw e e n 13 0 0 and 1400 MeV b y means o f t h e Air , Лтттг and Ett

d e c a y o f w e ll known r e s o n a n c e s can b e r u l e d o u t , a s i t was shown i n r e f s .

[

1

,

2

,

6

].

The m ethod we a r e g o in g to a p p ly was e x p o s e d e s s e n t i a l l y i n r e f . [ 7 ] . The r a t i o o f t h e p r o b a b i l i t y f o r t h e p r o d u c t i o n o f a An e v e n t t o t h a t o f a (A y) у e v e n t i s g iv e n b y :

R = An c ' 2 [ р о„ + f i , a - e>*+ ^ , a - o 4]

2 e ' ( 1 - e ' ) [ P , 2e ( 1 - e ) + P 4e ( 1 - e ) 3 ] (Ay) у

/1/

w h ere e and e ' a r e t h e a v e r a g e у r a y d e t e c t i o n e f f i c i e n c i e s f o r у r a y s b e l o n g i n g o r n o t b e l o n g i n g to t h e p e a k , r e s p e c t i v e l y . Pq ^ , p a n d

р 2тг a r e th e r e l a t i v e p r o b a b i l i t i e s / n o r m a l i s e d t o u n i t y / o f th e p r o d u c t i o n o f 0 , 1 an d 2tt0 ,s a s s o c i a t e d w i t h a An r e s o n a n c e . A s e p a r a t e a n a l y s i s h a s shown t h a t e “ e ' , and we c an t a k e f o r b o th 0 , 2 0 .

I n o r d e r t o e s t i m a t e t h e v a l u e s o f

O TT I tt an d P„. 2 7Г we

assu m ed t h a t th e y a r e e q u a l t o t h e c o r r e s p o n d i n g v a l u e s o b t a i n e d f o r t h e

*We fo u n d o n ly o ne A2y e v e n t , w here b o t h Ay c o m b in a tio n s h a d an e f f e c t i v e mass b e tw e e n 1300 a n d 1400 MeV.

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p r o d u c t i o n o f tt° 's a s s o c i a t e d w i t h A° an d £° i n s t e a d o f An U sin g t h e e x p e r i m e n t a l d a t a fro m r e f . [8] we o b t a i n e d f o r

a n d 0 .5 5 , O .5O and 0 .1 5 , r e s p e c t i v e l y . I n s e r t i n g t h e s e v a l u e s i n t o E q . / l / we o b t a i n R = 0 , 6 4 . T a k in g t h i s R v a l u e and t h e e x p e r im e n t a ly o b ta i n e d num ber o f e v e n t s i n c l a s s e s (A y )y and An / s e e T a b le I / one c a n r u l e o u t th e h y p o t h e s i s w i t h a c o n f id e n c e l e v e l o f 97 %, a p p r o x im a tin g t h e a c t u a l d i s t r i b u t i o n by a G a u s s ia n o n e . I t c a n be shown t h a t t h i s r e s u l t i s n o t to o s e n s i t i v e f o r th e c h o is e o f t h e b a c k g ro u n d l e v e l . An i n c r e a s e o f t h e b a c k g ro u n d t o i t s h i g h e s t r e a s o n a b l e v a l u e , i . e . t h e d e c r e a s e o f t h e num ber o f (A y )у e v e n t s up t o 5 , l e a d s t o a r e s u l t e x c l u d i n g t h e f i r s t h y p o t h e s i s w ith a 92 % c o n f id e n c e l e v e l .

CONCLUSION

The e x i s t e n c e o f th o Ay p e a k b e tw e e n 1300 and 1400 MeV was su p p o r t e d by o u r m e a s u re m e n ts . A d e t a i l e d a n a l y s i s o f o u r e x p e r i m e n t a l r e s u l t s showed t h a t t h e e x p l a n a t i o n o f t h i s p e a k b y m eans o f t h e h y p o t h e t i c a l An /1 6 8 0 MeV/ re s o n a n c e c a n be r e j e c t e d on a 97 % c o n f id e n c e l e v e l .

We h a v e t o e m p h a s iz e , h o w e v e r, t h a t t h e r e i s a p o s s i b i l i t y f o r e x p l a i n i n g t h e Ay p e a k by a Y * • • r e s o n a n c e s t a t e / S = 1 , 1 = 0 / .d e c a y i n g i n t o A an d у , a s i t was a l r e a d y m e n tio n e d i n r e f s . ( 1 , 6 ] .

The p o s s i b l e e x i s t e n c e o f .a s i n g l e t o f t h i s t y p e was c o n s i d e r e d t h e o r e t i c a l l y i n r e f s . [ 9 ,1 0 ] .

U n f o r t u n a t e l y t h e s t a t i s t i c a l m a t e r i a l p r e s e n t e d i n t h i s p a p e r d o e s n o t a llo w t o ch eck t h i s h y p o t h e s i s . The a u t h o r s i n t e n d t o a n a l y s e t h i s p ro b le m b a s e d on a much l a r g e r e x p e r i m e n t a l m a t e r i a l i n a f o r th c o m in g p a p e r .

T a b le I

Type o f e v e n ts Number o f e v e n ts

(Ay) 10 / 1 2 /

Ay 94

(Ay) у 7 / 5 /

A2y 22

An 0

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ч -

а / Taken fro m r e f . C23; b / Our e x p e r im e n t / a l l e v e n t s / ; с / E v e n ts fro m F i g . l b , d / E v e n ts fro m F i g . l b b e lo n g in g to

•where o n ly e v e n ts w ith t h e Л2y c lp .s's.

l y r a y w ere u s e d ;

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F ig « 2 . The y y v s . Луу e f f e c t i v e m ass p l o t w i t h t h e c o r r e s p o n d in g p r o j e c t e d d i s t r i b u t i o n s

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~ 6 ^-

REFERENCES

[1] Van Y un-T chan e t a l . P r e p r i n t JINR P -1 6 1 5 . / 1 9 6 4 /

P r о с . X I I . I n t e r n . C o n f . on H ig h E n e rg y P h y s i c s , Dubna V o l. I . 615 / 1 9 6 4 /

[2 ] B .P . B an n ik e t a l . P r e p r i n t JINR E -2858 / 1 9 6 6 / E .G . B u b elev e t a l . P h y s ic s L e t t e r s 24В. 24 6 /1 9 6 7 / [3] A.V. Bogomolov e t a l . P r i b .T e c h n .E k s p . 1 , 61 / 1 9 6 4 / {4] N.A. B u z d a v in a e t a l . P r e p r i n t JINR 2095 / 1 9 6 5 /

C5] Z.M. Iv a n c e n k o e t a l . P r e p r i n t JINR P -2 3 9 9 / 1 9 6 5 / [6] B .V . F l y a g i n e t a l . P r e p r i n t JINR P l- 3 3 5 1 / 1 9 6 7 / [7 ] E . Nagy P r e p r i n t JINR 1 -3 6 8 3 /1 9 6 8 /

[Ö] I . O hba, T. K a b a y a sh i S u p p l. o f t h e P r o g r e s s o f T h e o r. P h y s ic s 41 an d 42 /1 9 6 7 /

[9] M. G e ll-M an n , Y. Neeman' The E i g h t f o l d W ay., p . 4 3 . N .Y . A m sterdam , / 1 9 6 4 /

[10] I . S c h w in g e r P h y s . R e v . L e t t . 1 2 , 237 / 1 9 6 3 /

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