DIMUON PRODUCTION IN HADRONIC INTERACTIONS

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DIMUON PRODUCTION IN HADRONIC INTERACTIONS

B. Cox

To cite this version:

B. Cox. DIMUON PRODUCTION IN HADRONIC INTERACTIONS. Journal de Physique Collo-

ques, 1982, 43 (C3), pp.C3-140-C3-145. �10.1051/jphyscol:1982332�. �jpa-00221885�

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JOURNAL DE PHYSIQUE

CoZZoque C 3 , suppZ6rnent au n o 12, Tome 43, de'cembre 1982 page c3-140

DIMUON PRODUCTION IN HADRONIC INTERACTIONS

B. Cox

Fermi National AcceZerator Laboratory, P.O. Box 500, Batavia, I2 60510, U.S.A.

I n t r o d u c t i o n

-

Experiments w h i c h measure t h e p r o d u c t i o n o f h i g h mass (M > 4 ~ e ~ / c ~ ) d i le p t o n p a i r s p r e s e n t o p p o r t u n i t i e s t o c o n f r o n t t h e c o n s t i t u e n t p i c t u r e o f hadrons w h i c h has e v o l v e d i n t h e l a s t decade. Comparison o f t h e d i l e p t o n d a t a w i t h t h e p r e d i c t i o n s o f t h e D r e l l - Y a n model' ( z e r o t h o r d e r QCD) and t h e Compton and

a n n i h i l a t i o n p r o c e s s e s 2 ( f i r s t o r d e r QcD) a1 low t h e q u a r k and g l u o n s t r u c t u r e o f t h e hadrons t o be determined. S t u d i e s o f t h e p r o d u c t i o n o f l e p t o n p a i r s i n pN c o l l i s i o n s p r o v i d e an o p p o r t u n i t y t o t e s t t h e D r e l l - Y a n and QCD p i c t u r e o f h a d r o n i c p r o d u c t i o n o f l e p t o n p a i r s u s i n g t h e n u c l e o n s t r u c t u r e f u n c t i o n s d e t e r m i n e d i n deep i n e l a s t i c l e p t o n s c a t t e r i n g e x p e r i m e n t s . Measurements o f h i g h mass l e p t o n p a i r p r o d u c t i o n i n TN i n t e r a c t i o n s make i t p o s s i b l e t o measure p i o n s t r u c t u r e f u n c t i o n s w h i c h cannot be determined i n deep i n e l a s t i c l e p t o n s c a t t e r i n g e x p e r i m e n t s . New d a t a have been p r e s e n t e d a t t h i s c o n f e r e n c e on t h e p r o d u c t i o n o f h i g h mass l e p t o n p a i r s i n b o t h j5N and a-N

interaction^.^^^^^

I n a d d i t i o n t o t h e new d a t a on t h e h i g h mass l e p t o n p a i r p r o d u c t i o n new d a t a have been r e p o r t e d a t t h i s c o n f e r e n c e on t h e p r o d u c t i o n o f J/$(3.1) i n PN and n-N

I n t h e same manner t h a t h i g h mass p a i r p r o d u c t i o n sheds 1 i g h t on h a d r o n i c q u a r k s t r u c t u r e f u n c t i o n s , t h e measurement o f d i r e c t J/$ p r o d u c t i o n has been used t o d e t e r m i n e g l u o n s t r u c t u r e f u n c t i o n s . F i n a l l y t h e o b s e r v a t i o n o f m u l t i p l e p r o d u c t i o n has been r e p o r t e d . ' The p r o d u c t i o n o f d i - $ e v e n t s may be an i n d i c a t i o n o f r a r e processes such as BB p r o d u c t i o n .

H i g h Mass Muon P a i r P r o d u c t i o n

-

The c o n f r o n t a t i o n o f D r e l l - Y a n and f i r s t o r d e r QCD w i t h t h e h i g h mass muon p a i r p r o d u c t i o n d a t a has had b o t h successes and f a i l u r e s t o date. The i n a b i l i t y o f t h e n a i v e D r e l l - Y a n model t o p r e d i c t t h e a b s o l u t e l e v e l o f t h e c r o s s s e c t i o n s f o r p p a i r p r o d u c t i o n has been q u a n t i f i e d as t h e ' K f a c t o r ' f o r aN and pN r e a c t i o n s . T h i s q u a n t i t y i s d e f i n e d as t h e r a t i o o f t h e measured c r o s s s e c t i o n t o t h e D r e l l - Y a n p r e d i c t i o n ( u s i n g some c h o i c e o f h a d r o n i c s t r u c t u r e f u n c t i o n s such as t h e CDHS n u c l e o n s t r u c t u r e f u n c t i o n s ) . The p r e l i m i n a r y new r e s u l t s (denoted by t h e a s t e r i s k s ) f r o m E-537 f o r K a r e shown i n T a b l e 1 a l o n g w i t h t h e r e s u l t s o f p r e v i o u s e x p e r i m e n t s .

d u

T a b l e 1 : E x p e r i m e n t a l K F a c t o r s (K =

-

dMdXF data/- dMdXF D r e l ^do 1 -Yan)

' ~ a b Beam/Ta r g e t K Exper iment

"

¹²⁵

_i

_N _2.25 _c_0.45 Fermi l a b E-537

I 5 0 pN 2.3 c 0.4 CERN NA3

39.5 T ~ N 2.6

+

^0.5 CERN BCE (Omega)

A 125 n N 2.5 C 0.5 Fermi l a b

150,200 nir-N 2.2 2 _0.3 _{CERN NA3}

150 T+N 2.4 i: 0.4 CERN NA3

150

TIP

2.4 2 0.4 CERN NA3

150,175 n p 2.8 CERN WAl l

150 PN 2.2

+-

0.4 CERN NA3

400 PN 1.7 F e r m i l a b E-288

400 PN 1.6

+

^0.3 Ferrni l a b E-439

21 15 (J?=63) PP 1.6 CERN R-209

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1982332

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B. Cox

The d a t a g i v e n i n f a b l e 1 f o r ITN r e a c t i o n a r e c o n s i s t e n t w i t h one a n o t h e r b u t t h e pN d a t a show t h r e e e x p e r i m e n t s w i t h K f a c t o r s o f a p p r o x i m a t e l y 1.6 t o 1.7 and one e x p e r i - ment, NA3 w i t h a n u c l e o n K f a c t o r o f 2.2. The new PN d a t a shown by E-537 i s t h e o n l y o t h e r e x p e r i m e n t b e s i d e s t h e NA3 experiment t o o b t a i n a K f a c t o r g r e a t e r t h a n 2 f o r t h e n u c l e o n o r a n t i n u c l e o n r e a c t i o n s . Other t h a n t h e problem w i t h t h e n u c l e o n K f a c t o r s t h e d a t a seem c o n s i s t e n t w i t h a K f a c t o r r e l a t i v e l y independent o f beam t y p e and i n g e n e r a l g r e a t e r t h a n two. No e x p e r i m e n t a l e v i d e n c e has y e t been p r e s e n t e d t h a t would suggest t h a t t h e K f a c t o r i s a f u n c t i o n o f any k i n e m a t i c v a r i a b l e .

- +

Using P r o t o n West e n r i c h e d a n t i p r o t o n beam ( o b t a i n e d f r o m

1

-t p r decays) F e r m i l a b Experiment E-537 r e c e n t l y completed t h e h i g h e s t s t a t i s t i c s measurement o f PN +

u+v-

t o d a t e .

I I I I I I I

8 125 GeV/c (€5371

10

r

^o150 GeVIc(NA3)

-

A 280GeV/c ( N A 3 ) 1

-

^-

C 0

- - -

0

V

.

L)

^-

-0 e i '

%

I -

"

0 E -

- ^-

F -

z - 0.1

6 1 0.2 1 1 1 1 f

FIG. Ib

-

root

-

₀_e

-

_U

The s c a l i n g c r o s s s e c t i o n , ~ 3 da/dM, determined by t h e E-537 e x p e r i m e n t e r s i s shown i n F i g . l a a l o n g w i t h t h e h i g h e r energy NA3

FN

d a t a . The s o l i d l i n e i s 2.3 t i m e s t h e s i m p l e D r e l l - Y a n c a l c u l a t i o n o f t h i s c r o s s s e c t i o n o b t a i n e d by u s i n g t h e CDHS s t r u c t u r e

function^.^

F i g u r e l b shows new d a t a f r o m E-537 f o r IT-N -t ~"1.1- a l o n g w i t h o l d e r d a t a f r o m NA3 a t o t h e r e n e r g i e s . These f i g u r e s i n d i c a t e two o f t h e successes o f t h e s i m p l e D r e l l - Y a n model ( p r e d i c t i o n o f t h e shape o f ~ 3 do/dM and t h e s c a l i n g p r o p e r t y o f t h i s c r o s s s e c t i o n ) and one o f t h e f a i l u r e s ( i n a b i l i t y t o p r e d i c t t h e a b s o l u t e

l e v e l o f t h e c r o s s s e c t i o n ) .

A t h i r d success o f s i m p l e D r e l l - Y a n has been t h e p r e - d i c t i o n o f t h e shape o f t h e X F d i s t r i b u t i o n f o r dimuon p r o d u c t i o n . I n p a r t i c u l a r , as seen from t h e E-537 d a t a shown i n F i g . 2, shape o f t h e XF d i s t r i b u t i o n ( b u t once a g a i n , n o t t h e a b s o l u t e l e v e l ) i s w e l l p r e d i c t e d f o r PN -t ~ + V - X u s i n g t h e CDHS s t r u c t u r e f u n c t i o n s . T h i s r e a c t i o n ' t e s t s ' t h e D r e l l - Y a n p i c t u r e more c o m p l e t e l y t h a n t h e n-N d a t a shown i n t h e same f i g u r e s i n c e t h e

IT N dimuon d a t a as a f u n c t i o n o f X F must be used t o

e x t r a c t t h e p i o n s t r u c t u r e f u n c t i o n . I n t h e case o f t h e s PN r e a c t i o n t h e n u c l e o n s t r u c t u r e f u n c t i o n s can be

o b t a i n e d i n d e p e n d e n t l y f r o m deep i n e l a s t i c l e p t o n s c a t t e r i n g . The c u r v e s i n F i g . 2 a r e t h e n a i v e D r e l l - I a n p r e d i c t i o n u s i n g CDHS s t r u c t u r e f u n c t i o n s f o r t h e

-

pN r e a c t i o n and NA3 p i o n s t r u c t u r e f u n c t i o n s f o r t h e TI N d a t a . These p r e d i c t i o n s a r e m u l t i p l i e d by t h e E-537 K f a c t o r s g i v e n i n T a b l e 1. These d a t a i n d i c a t e t h a t t h e s t r u c t u r e f u n c t i o n s f o r t h e p and IT- a r e r o u g h l y

FIG. 2

-

m 125 GeV/c (E537) o 150 GeV/c ( N A 3

-

B N + ~ + K X

M > 4 G ~ V / C '

-

_XF>0

'.i'

- t -

'

^{l -}

.b

=

2 :

I

-

0.1

02 0.3 0.5 0.6

FIG. l a

-

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JOURNAL DE PHYSIQUE

c o n s i s t e n t w i t h CDHS and NA3 s t r u c t u r e f u n c t i o n s r e s p e c t i v e l y . The E-537 e x p e r i m e n t e r s have n o t y e t made an independent d e t e r m i n a t i o n o f s t r u c t u r e

-

f u n c t i o n s f r o m t h e i r d a t a .

f

F e r m i l a b e x p e r i m e n t E-326 has made t h e independent d e t e r m i n a t i o n o f t h e p i o n v a l e n c e s t r u c t u r e

f u n c t i o n as shown i n F i g . 3 u s i n g a p a r t o f t h e i r

1

225 GeV/c T-N d t t a . A f t e r c h e c k i n g t h a t t h e f a c - _E326

t o r i z a t i o n o f M do/dXldX2 i n t o a p r o d u c t o f PION STRUCTURE FUNCTION a f u n c t i o n o f X and a f u n c t i o n o f X i s v a l i d , t h e

E-326 e x p e r i m e n i e r s have e x t r a c t e d t 8 e p i o n s t r u c -

X~ FIG. 3

1 . 0 1 ~ 0 . 1 0

-

t u r e f u n c t i o n V ( x i ) = ( 0 . 7 5 ~ . 2 ) K (I - X )

w h i c h i s c o n s i s T e n t w i t h p r e v i o u s NA3 measurement. A t t h e c u r r e n t s t a g e o f t h e i r a n a l y s i s , t h e y have used t h e p i o n sea q u a r k d i s t r i b u t i o n s o f NA3 r a t h e r t h a n i n d e p e n d e n t l y d e t e r m i n i n g t h e sea d i s t r i b u t i o n f r o m t h e i r d a t a .

The a n a l y s i s o f t h e dimuon c r o s s s e c t i o n s as a f u n c t i o n o f f i a n d XF t h a t have been r e p o r t e d above i n g e n e r a l depend o n l y on t h e s i m p l e D r e l l - Y a n p i c t u r e w i t h l i t t l e o r no need f o r r e c o u r s e t o h i g h e r o r d e r QCD. However, when t h e PT spectrum o f t h e dimuon i s analyzed, QCD e f f e c t s appear.

H i g h e r o r d e r processes i n a s such as g l u o n Compton s c a t t e r - i n g o r q u a r k - a n t i q u a r k a n n i h i l a t i o n c o n t r i b u t e and produce h i g h p ~ muon p a i r s . Two d i f f e r e n t t e c h n i q u e s have been used i n t h e c o n t r i b u t i o n s t o t h e conference t o a n a l y z e t h e

o f t h e dimuon system. E-537 has a n a l y z e d t h e shape o f t h e p ~ d i s t r i b u t i o n s o f t h e i r 125 GeV/c

p

and T- d a t a

(shown I n F i g . 4) by t h e A l t a r e l l i , P a r i s i , and P e t r o n z i o t e c h n i q u e . ' ' The nongaussian t a i l o f t h e pT d i s t r i b u t i o n

i s e x p l a i n e d i n t h i s t e c h n i q u e by t h e Compton and ^10-6

-

a n n i h i l a t i o n p r o c e s s e s . An i n t r i n s i c <k+ % 0.88 G ~ V / C ~

(which has been observed i n pN -+ p+p- i n t e r a c t i o n s ' ' ) , c o u n t i n g r u l e g l u o n s t r u c t u r e f u n c t i o n s and NA3 and CDHS

q u a r k s t r u c t u r e f u n c t i o n s have been used t o produce t h e I I I I I I

c u r v e s w h i c h a r e shown i n F i g . 4. However, t h i s t e c h n i q u e 0 1. 2.0 3.0 P,(GcV/c) FiG.4 r e q u i r e s t h e assumption t h a t t h e h a r d g l u o n processes a r e

t ? e o n l y c o n t r i b u t o r s t o t h e h i g h p ~ t a i l . I n f a c t , s o f t g l u o n processes may v e r y we1 1 c o n t r i b u t e and t h e <k2> w h i c h i s needed t o e x p l a i n t h e d a t a may be an o v e r e s t i m a t e . T

A second method can be used t o d e t e r m i n e t h e i n t r i n s i c kT o f t h e c o n s t i t u e n t s i f t h e S dependence o f <pf> i s assumed t o be due t o QCD processes. Then a l i n e a r e x t r a - p o l a t i o n o f <p:> ( b u t n o t n e c e s s a r i l y2<pT>)

t o S=O s h o u l d y i e l d an ' i n t r i n s i c ' <kT>. Î Î Î Î

F i g u r e 5 shows <p2> v s . S f o r s e v e r a l T-N + f i = 0.28

p+p- measurements? NA3 have f i t t e d t h e i r 2'5-<~:>= (0.62 +o,o~)+~o.oo2~+o.ooo~)~

t h r e e d a t a p o i n t s a t 150, 200 and 280 GeV/c

t o a l i n e a r form, <pf> = A+BS. They f i n d _2.0-

< P p = (0.76+0.07) + (0.0025+0.0002) S G ~ v / c ~ . I f a l l t h e d a t a i n t h e p l o t i n c l u d i n g t h e new , E-537 p o i n t a r e f i t , < p 2 > = (0.62k0.05) +

-

_P^1.5

^-

(0.0028+0.0002) S i s o b l a i ned. T h i s second

f i t i s shown i n F i j . 5. F i g u r e 6 shows a ^II'N -+a+&-x

s i m i l a r p l o t o f <pT> VS. S p r e p a r e d f o r A

n

rsce)

pN + u+p-. The p r o t o n d a t a when f i t w i t h FN*U+U-x n E 537

<pf> = A+BS y i e l d s <pf> = (0.59+0.19) + 05- E537 o NA3

(0.0013+0.0002)S. The s l o p e i s l e s s t h a n NAS

+

CIP

t h a t observed i n F i g . 5, b u t t h e i n t e r c e p t

1

^I I I 9

which we a r e d e f i n i n g t o be i n t r i n s i c kT ¹⁰⁰ ²⁰⁰S ( G ~ V ~ I ³³⁰ ⁴⁰⁰ ⁵⁰⁰ ⁶⁰⁰

-

FIG. 5

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B. Cox C3- 1 43

where OA, UC, and o0 a r e t h e a n n i h i l a t i o n , C o m p t o n , and D r e l l - Y a n c r o s s s e c t i o n s r e s p e c t i v e l y . K i s t h e K f a c t o r p r e v i o u s l y d e f i n e d and L i s a c o r r e c t i v e m u l t i p l i e r wh'ch i s used t o p a r a m e t e r i z e t h e d i s c r e p a n c y between t h e p r e d i c t e d and observed

5

As can be seen f r o m F i g . 7,the c a l c u l a t i o n ( f o r ~ = 1 , ~ = 1 . 8 ) o f t h e s l o p e *pf>

vs. S f a l l s f a r s h o r t o f t h e observed s l o p e a t d i f f e r e n t masses. F o r as = 0.3, L/K = 1.52A0.13 and L/K i s i n c r e a s i n g w i t h M.

I 1

i s a p p r o x i m a t e l y t h e same f o r t h e ⁶ ^/

p r o t o n and p i o n d a t a . (The t h r e e J i 7 . 0 2 2

E-288 d a t a p o i n t s have been lowered

'-

³

^-

s l i g h t l y t o account f o r t h e f a c t ^<^P^,^!^>^. (0.59~0.10)+l0.0013t0.0002)S

t h a t they a r e XF=O d a t a . The ^{4 -} average o f a l l e v e n t s a t X F > 0

i s expected by t h e A1 t a r e 1 1 i ^%^.\y^{3 -} model t o have a 15% l o w e r <p2> t h a n t h e X F =-0 d a t a . ) I n T

z -

_A_{2 -}

a d d i t i o n t h e p N d a t a (see F i g . 5)

$

^a0 ^OMEGACFS

from E-537 and NA3 whi l e n o t o f _I

- +

CFS (CORRECTEOI

t h e q u a l i t y o f t h e IT-N d a t a seem a ~ 2 0 9 (ISRI

t o be s i m i l a r t o t h e p i o n measurements e x c e p t t h a t t h e <p!> f o r

S ( G ~ v ' )

4 b 0 8 b 0

I&

¹⁶⁰⁰ 2 b 9 0 2 4 b 0 2%00 3 2 0 0 3 6 0 9 4 0 ~ 0

t h e

p

d a t a i s s l i g h t l y l o w e r a t ^F ^U

a g i v e n energy. P a r t o f t h e

The NA3 e x p e r i m e n t e r s have a l s o d i s p l a y e d <pT> as a f u n c t i o n o f 2

A ,

y , and mass a t each o f t h e i r t h r e e e n e r g i e s . As seen i n F i g . 8a, b, c t h e r e a r e s t r o n g v a r i a t i o n s o f <p+ w i t h each o f t h e s e v a r i a b l e s and i n g e n e r a l t h e s t r e n g t h o f t h e v a r i a t i o n

i n c r e a s e s w i t h energy. E x p l a n a t i o n o f t h i s d a t a by quantum chromodynamics w i l l be a c h a l l e n g e f o r t h e f u t ~ t r e .

A

v

t t

t

Y d i f f e r e n c e i n s l o p e o f t h e S dependence may be due t o t h e d i f f e r e n t S dependence o f v a l e n c e -

v a l e n c e q u a r k i n t e r a c t i o n s (which d o m i n a t e 3 - pN and IT-N r e a c t i o n s ) and valence-sea q u a r k

i n t e r a c t i o n s (which dominate pN i n t e r a c t i o n s ) .

The o b s e r v a t i o n o f s i m i l a r i n t e r c e p t s o f t h e s e

"

⁰^2-

two p l o t s suggests s i m i l a r i n t r i n s i c kT f o r m x

v a l e n c e and sea quarks i n p r o t o n s and p i o n s . The NA3 e x p e r i m e n t e r s have a t t e m p t e d t o p r e d i c t t h e s l o p e o f t h e i r IT-N d a t a ( ~ i g . 5 ) due t o t h e a n n i h i l a t i o n and Compton processes. The

I 1 I I

t -

I -

+

_-s=.3

--__----

C

---

^{u s =}^.2

expected <p:> i s g i v e n by ¹

,

^L

-

4 5 6 7 8

M ( G ~ v / c ' )

FIG.7

-

(6)

JOURNAL DE PHYSIQUE

P r o d u c t i o n o f t h e J/$ Resonance

-

T h r e e new c o n t r i b u t i o n s o n t h e p r o d u c t i o n o f J/$

resonance have been r e p o r t e d a t t h i s c o n f e r e n c e by t h e E-537, N A and WAll ~ ~ a e x p e r i m e n t e r s . E-537 has s t u d i e d t h e a n t i p r o t o n p r o d u c t i o n o f J/$ a t 125 GeV/c and

i n p a r t i c u l a r emphasized t h e comparison o f t h e s e c r o s s s e c t i o n s w i t h T-N p r o d u c t i o n o f J/$ a t t h e same energy. The r a t i o o f t o t a l c r o s s s e c t i o n s (a-/a = 0.88+0.05) shown i n F i g . 9a r e q u i r e s a l a r g e g l u o n f u s i o n c o n t r i b u t i o n t o JY$ F r o d u c t i o n a c c o r d i n g t o t h e g l u o n / q u a r k f u s i o n model o f Barger, e t a ] . , l 2 t o equal i z e t h e

p

^and

a- c r o s s s e c t i o n s . The r a t i o a /a- shown i n F i g . 9b i n d i c a t e s t h a t g l u o n f u s i o n i s t h e most i m p o r t a n t c o n t r i b u t i o n P t o P J/$ p r o d u c t i o n i n n u c l e o n - n u c l e o n i n t e r a c t i o n s a t h i g h e n e r g i e s , and i s needed t o e x p l a i n t h e energy dependence o f t h e a /a- r a t i o . The d o t t e d c u r v e i n F i g . 9b i s t h e p r e d i c t i o n o f t h e

x

p r o d u c t i o n mode7

8f

C a r l s o n and Suaya13 i n which t h e J / + ' s a r e produced t h r o u g h an i n t e r m e d i a t e P wave

s t a t e .

2.0 x,>o

k

1.6 E537 Q 0.6

b'

\

X N A 3 0.8

S ( G ~ V ~ )

CERN e x p e r i m e n t WAll has a t t e m p t e d t o d e t e r m i n e t h e g l u o n s t r u c t u r e f u n c t i o n . o f t h e p i o n by a n a l y z i n g J/$ p r o d u c t i o n i n t h e i r 190 GeV/c n- data. I n p e r f o r m i n g t h i s a n a l y s i s t h e y a l l o w e d f o r a 30.5% p r o d u c t i o n o f J / $ by t h e d i r e c t p r o d u c t i o n o f a

x

s t a t e w h i c h subsequent decays i n t o a J/$ p l u s a photon. T h i s c o r r e c t e d X d i s t r i - b u t i o n w h i c h i s shown i n F i g . 10 was f i t by v a r y i n g t h e i n p u t n- and n u c l e o n s t r u c t u r e f u n c t i o n t o t h e g l u o n f u s i o n model f o r J/$ p r o d u c t i o n . The r e s u l t s o b t a i n e d f o r t h e p i o n and n u c l e o n g l u o n s t r u c t u r e f u n c t i o n s a r e gT(X1) - - % ( I - x l ) 1.9'0.3 and N 2 (X ) =

( T - x ~ ) ~ . ? N e g l i g i b l e changes i n t h e p i o n exponent t a k e p l a c e when t h e CDHS para- m e t e r i z a t i o n i s used f o r t h e n u c l e o n .

The f i n a l new c o n t r i b u t i o n t o t h e c o n f e r e n c e was t h e r e p o r t o f NA3 o f t h e d e t e c t i o n o f d i - $ p r o d u c t i o n i n t h e i r 150 GeV/c and 280 GeV/c

T-N d a t a . Out o f a sample o f 1,359,000 $ e v e n t s ¹ ^I

accumulated a t t h e two e n e r g i e s , a t o t a l o f 13

W A l l

events w i t h two J / $ ' s have been found (6 a t 150 Gev/c n-N -+ J/$+x

and 7 a t 280 GeV/c). T h i s y i e l d corresponds t o a r a t i o ( a f t e r c o r r e c t i o n f o r t h e

u+

- b r a n c h i n g

r a t i o ) o f a$)/a$ = ( 3 . 0 ~ 1 .O) x and c r o s s 0 s e c t i o n s , cn$$ =

18i8

p i c o b a r n s a t 150 GeV/c,

30+10 p i c o b a r n s a t 280 GeV/c. The acceptances used

2

t o a r r i v e a t t h e s e c r o s s s e c t i o n s were c a l c u l a t e d u s i n g e i t h e r an u n c o r r e l a t e d $$ p r o d u c t i o n o r a model w h i c h assumes t h a t t h e $ ' s a r e decay p r o d u c t s w o f B mesons. The e r r o r i n t h e c r o s s s e c t i o n s

i n c l u d e s t h e u n c e r t a i n t y i n t h i s acceptance due t o t h e u n c e r t a i n t y i n t h e p r o d u c t i o n process.

.05

(7)

The s t r o n g i n d i c a t i o n as seen i n t h e mass s p e c t r u m o f t h e d i - $ I s shown i n F i g . I l a i s t h a t t h e

$ I s a r e c o r r e l a t e d . The c u r v e shown i n t h i s f i g u r e i s t h e p r e d i c t i o n f o r u n c o r r e l a t e d d i - $ I s . I t peaks c o n s i d e r a b l y

b e l o w t h e average mass o f t h e o b s e r v e d d i - $ e v e n t s . (The c r o s s h a t c h e d squares a r e t h e 150 GeV/c d a t a . ) A second e v i d e n c e f o r a c o r r e l a t i o n between t h e t w o

$ ' s i s t h e p ~ spectrum o f t h e d i - $ system shown i n F i g . I l b . The u n c o r r e l a t e d $ model p r e - d i c t i o n peaks somewhat h i g h e r t h a n t h e observed e v e n t s . The e x p e r i m e n t e r s have made no s t a t e - ment a t t h i s t i m e about t h e p r o d u c t i o n mechanism f o r t h e d i - $ I s because o f t h e l i m i t e d

s t a t i s t i c s .

C o n c l u s i o n

-

H a d r o n i c p r o d u c t i o n o f dimuons, b o t h c o n t i n u u m and resonance, c o n t i n u e s t o be a r i c h s o u r c e o f i n f o r m a t i o n a b o u t t h e c o n s t i t u e n t s o f hadrons and t h e i r i n t e r a c t i o n s . I n p a r t i c u l a r w i t h t h e p r e s e n t s t a t e o f t h e c o n t i n u u m h i g h mass d a t a , quantum chromodynamics i s b e g i n n i n g t o be c o n f r o n t e d w i t h a w i d e v a r i e t y o f e f f e c t s t h a t t h e t h e o r y must e x p l a i n . The f i r s t successes o f low o r d e r QCD must now be f o lowed w i t h h i g h e r o r d e r c a l c u l a t i o n s i n o r d e r t o e x p l a i n t h e K f a c t o r and

h

<p > b e h a v i o r as a f u n c t i o n o f t h e v a r i o u s k i n e t i c q u a n t i t i e s . The resonance d a t a o n t h e o t h e r h a n d , w h i l e n o t h a v i n g as c o m p l e t e t h e o r e t i c a l framework f o r i n t e r - T

p r e t a t i o n , i s b e g i n n i n g t o y i e l d i n f o r m a t i o n about t h e g l u o n c o m p o s i t i o n o f t h e hadrons.

I n t h e f u t u r e we can a n t i c i p a t e b o t h new e x p e r i m e n t s and new a n a l y s e s and perhaps new u n d e r s t a n d i n g s o f t h e s e fundamental p r o c e s s e s .

REFERENCES

1 . DRELL, S.D., and YAN, T.M., Phys. Rev. L e t t e r s

3,

316 (1970).

2. HALIEN, F., and SCOTT, D.H., Phys. Rev.,

DE

(1978), 3778.

3. ANASSONTZIS, E., e t a l . , E-537 C o l l a b o r a t i o n , p a p e r 665, XXI I n t . Conf. o n H i g h Energy P h y s i c s , P a r i s , France, 1 9 8 2 / ~ e r m i l a b P r e p r i n t , ~ o n f - 8 2 / 5 0 - ~ ~ ~ , 7530.537.

4. BADIER, J . , e t a ) . , NA3 C o l l a b o r a t i o n , Paper 350, X X I I n t . Conf. on H i g h Energy P h y s i c s , P a r i s , France, 1982/Ecole P o l y t e c h n i q u e P r e p r i n t LPNE/X 82/02.

5. STICKLAND, D.P., e t al., E-326 C o l l a b o r a t i o n , paper 169, XXI I n t . Conf. o n H i g h Energy P h y s i c s , P a r i s , France, 1982.

6. ANASSONTZIS, E., e t a l . , E-537 C o l l a b o r a t i o n , paper 656, XXI I n t . Conf. on H i g h Energy P h y s i c s , P a r i s , France, 1 9 8 2 / f e r m i l a b P r e p r i n t

,

C o n f - 8 2 / 4 9 - ~ ~ ~ , 7550.537.

7. PIETRZKY, B . , e t a l . , WAll C o l l a b o r a t i o n , paper 625, X X I I n t . Conf. on H i g h Energy P h y s i c s , P a r i s , France, 1982.

8. BADIER, J . , NA3 C o l l a b o r a t i o n , paper 535, XXI I n t . Conf. on H i g h Energy P h y s i c s , P a r i s , France, 1982/CERN P r e p r i n t , C E R N - ~ ~ / 8 2 - 6 7 .

9. DE GROOT, J.G.H., e t a l . , CDHS C o l l a b o r a t i o n , Phys. L e t t e r s

828,

456 (1979).

10. ALTARELLI, e t a l . , P h y s i c s L e t t e r s ,

z,

356 (1978).

1 1 . [ T O , A.S., e t a l . , Phys. Rev.

9,

604 (1981).

12. BARGER, V . , e t a l . , Z e i t s c h r i f t f u r P h y s i k C , 6, 169 ( 1 9 8 0 ) . 13. CARLSON, C.E., and SUAYA, R., Phys. Rev.

2,

7 6 0 (1978).