Phenomenology in Particle Physics

PHENOMENOLOGY IN

-

PART1

CLE

PHYSICS

197

1~

Phoceeding~ o

6

;the

Condaence.

Heed

at

t h e C&,ja&mid 1u-e

06

TechoLog y Mmch 2 5 and 2 6 , 1971

E d i t e d by : C.B. Ckiu. ,,. G.C. Fox A.S.G. Hey

Sponsaned by t h e DepatLtmevtt:

06

P h y b i c ~ , Ma;the.tnaXic4 and Ab&onomy, C&ech.

CONTENTS

PAGE

-

PREFACE

MAP

OF PHENOMENOLOGY WORLD

ABSTRACTS

Xi

1

.

WEAK

1 NTERACTlONS

...

S.B. Ttreiman, Phenomenology

od

Weak In;teha&n~

7

2 .

MULTTPARTI

C

LE PROCESSES

...

U . E .

Khue, Some Recent Expehimentd R e s u l 3 2

don

A , ,

A3,

Q

and

L

Meson6.

27

W.R.

Fnazeh, PhenamenoLogy

0 6

M

~

p

R u c ; t i o a . . . .

~

~

...

e

4 8

E . L .

Bmga,

Phenamenologid

A p p f i c a t i a n b

oh

Du& Mod

el^...

83

3 .

THE

QUARK

MOUEL

R . P .

Feynman, The Quanh Mod&

at

Low E n m g i u

...

224

4 . THE

A,

..

MESON

K .

W .

L a i , Recent

R~ALL!%

dtrorn Bubble Chamba Expm.i.men;ts on A,,

...

257

L

S.M.

~eattc

The

6'

Maaa Speahun i n

7

GeV/c

n'p

T n t a c t i o ~ .

...

322

S . Ozaki, The Double Vee MagnuXc SpeahomeAa: ExpehimeW S&p

and

Cwutent

R u

...

326

-+

M . Gettneh, Measmements

06

.the A; and

A2

Ma66

S p e m . .

...

358

J . L .

Rosneh, Theoketicd Remanb on .the A2 Muon

...

387

5.

PHASE

SHIFT ANALYSTS 1N TWO-BODY REACTlONS

ff

.

S . t ~ n e h , Pion-Nudeon S c a k . t d n g

:

Phane Skid& and E x p d m e w 2 .

...

4 2 0

R . E .

CILtlzoaky, Op;timized Alzaey&i.c

Data

A d y d A and A p p f i d o n

$0

to'p

Sc&&ng

...

444

6.

EXPERlMENTAL RESULTS 1 N

TWO-BODY

REACTIONS

8. Mughave,

A

Review

0 6

Some

Expm2nentu.t

RuuRtd on ffadhon-Deu;tc?hiwn

S U & n g

...

467

P.W.G.S.

LeiAh, Recent

RuuW on

n-p

-+

p O n

a;t

Sm&

Momentum

T h a a d m .

...

554

L .

Dick, Some New ExpcmimeMkde

R

u

m

utLth

PoRattized Tang&--1.

...

594

A.

Yukoaam, Some New ExpuiimenAde

R e n d 3 2

uLth Polmized Tange;ts--11..

...

6 7 2

7 . PHENOMENOLOGY

1N

TWO-BODY

REACTIONS

PREFACE

What is phenomenology? Reach n o t f o r your d i c t i o n a r y ; make no v a i n e f f o r t s t o pronounce i t ; w e w i l l come c l e a n and e x p l a i n a l l .

Science is noted f o r a competitive and h e l p f u l i n t e r a c t i o n between t h e o r i s t s and e x p e r i m e n t a l i s t s . Unfortunately i n almost a l l developing s c i e n c e s , t h e

moving hand of time d r i v e s a widening wedge between theory and experiment. Thus t h e o r i s t s a r e f u l l y occupied i n t h e mathematical and p h i l o s o p h i c a l i n t r i c a c i e s of their l a t e s t i d e a s . Again, e x p e r i m e n t a l i s t s

m u s t

concentrate o n t h e design of t h e i r apparatus t o i n s u r e they w i l l g e t t h e b e s t p o s s i b l e r e s u l t s c u r r e n t technology w i l l allow. Phenomenology s e e k s t o c l o s e t h e

----

between those once c l o s e f r i e n d s , theory ahd experiment, and s o r e s t o r e t h e i n t e r a c t i o n which i s b o t h v i t a l t o and c h a r a c t e r i s t i c of s c i e n c e . Although

a c l a s s i c a l concept, phenome~ology i s b e s t known i n its second-quantized form.

(Relevant (Relevant

Theory

1

Expts .)

(Theory) (Experiment)

The b a s i c t o o l of t h e phenomenologist i s , f i r s t , t h e c o n s t r u c t i o n of simple models t h a t embody important t h e o r e t i c a l i d e a s , and then, t h e c r i t i c a l

comparison of t h e s e models w i t h a l l r e l e v a n t experimental d a t a . It follows t h a t a phenomenologist must combine a broad understanding of theory w i t h a complete knowledge of c u r r e n t and f u t u r e f e a s i b l e experiments i n order t o allow him t o i n t e r a c t meaningf.ully w i t h b o t h major branches of a science. The impact of phenomenology i s f e l t i n both theory and experiment. Thus i t can p i n p o i n t unexpected experimental observations and s o d e l i n e a t e a r e a s where new t h e o r e t i c a l i d e a s a r e needed. F u r t h e r , i t can suggest t h e most u s e f u l experiments t o b e done t o test t h e l a t e s t t h e o r i e s . This i s e s p e c i a l l y important i n t h e s e b a r r e n days where funds a r e l i m i t e d , experiments t a k e many "physicist-years" t o complete,

and t h e o r i e s a r e multitudinous and complicated.

"FACE

main conference r e p o r t e d h e r e , and devoted t o physics a t i n t e r m e d i a t e energies (

; 5 GeV). This a r e a is p a r t i c u l a r l y s u i t a b l e f o r phenomenology a s t h e q u a l i t a t i v e f e a t u r e s have been w e l l explored and f u r t h e r progress demands d i f f i c u l t experiments w i t h h i g h s t a t i s t i c s . Phenomenology can i n d i c a t e , f o r i n s t a n c e , which of t h e some hundred (quasi) two body r e a c t i o n s w i l l b e most f r u i t f u l t o study. I n t h e following w e map some of t h e more a c t i v e f i e l d s of phenomenology i n d i c a t i n g where they have been covered i n e i t h e r t h e present volume, o u r companion workshop, o r elsewhere. The c o n t e n t s of t h e c u r r e n t

volume a r e summarized i n more d e t a i l i n t h e a b s t r a c t s of t h e i n v i t e d papers which h a v e been c o l l e c t e d t o g e t h e r i n pages x i t o

x v i .

We a r e indebted t o many people f o r making t h i s conference p o s s i b l e : Professor

R.B. Leighton f o r h i s generous sponsorship; Nancy Hopkins and James Black of t h e C a l t e c h Alumni O f f i c e f o r t h e i r e f f i c i e n t and c h e e r f u l o r g a n i z a t i o n ; t h e s e s s i o n chairmen, M. Gell-Mann, W. Selove, J . D . Bjorken, M . J . Moravcsik, J . D .

J a c k s o n , T . Ferbel, R.L. Walker and S.C. F r a u t s c h i , f o r t h e smooth running of t h e conference; Susan Berger f o r h e r d e l i g h t f u l cover; and our s e c r e t a r i e s f o r t h e i r c a r e f u l typing, w i t h an e s p e c i a l thank you t o C h r i s S t . C l a i r who a l s o drew

t h e amusing i l l u s t r a t i o n s . Alvin T o l l e s t r u p o r i g i n a l l y had t h e good i d e a of h o l d i n g a phenomenology conference: We a r e g r a t e f u l t o him and our colleagues

a t Caltech f o r t h e encouragement which has ~cade th e o r g a n i z a t i o n and e d i t i n g of t h i s con£ erence s o enjoyable.

E d i t o r s :

C.B. Chiu

G.C. Fox

MAP OF

PHENOMENOLOGY WORLD

In the following we indicate some of the main fields of phenomenology

and some typical references: These are listed on Page ix.

I. Current Interactions

*

2

(a) Weak Interactions

-

Treiman

;

wolfenstein';

Lee and Wu

.

(b)

eN Scattering

-

~ i l m a n ~ ;

Daresbury

4

.

*

(c) vN Scattering

-

Treiman

;

Llewellyn Smith

5

.

11. Multiparticle Reactions

*

(a) General Properties

-

Frazer

;

Berger

6

.

*

(b

)

Inclusive Reactions

-

Frazer

;

Quigg

1

.

* . 6 (c)

Explicit Models (e.g., multiperipheral,

B5)

-

Berger

.

See also 111, IV(b) and V(b) (quasi two-body reactions).

111. Analysis and Interpretation of Production Experiments

*

*

1

(a)

Extraction of Resonance Properties

-

Kruse

;

A2 Session

;

Goldhaber

.

(b) nn

and KT Phase Shifts

-

Argonne

7

.

*

(c) Meson Spectroscopy

-

Feynman

;

Rosner

1

.

(a) to (c) are all covered by Reference

8.

IV. Analysis and Interpretation of Formation Experiments

*

*

(a) 2-body Phase-shif

ts

-

Steiner (nN)

;

Cvtkosky

(KN) ;

~oorhousel

(nN)

;

~oravcaik'

(KN,

NN);

(e);

Pfeil, Schwela

9

(YN)

1

(b) 3-body Phase-shifts

-

Cashmore

.

*

10

OF Pff

ENOMENOLOGY WORLD

MAP OF

PHENOMENOLOGY

WORLD

-

(Page

2)

V

.

High and Intermediate Energy Two-Body Reactions

(a) Applications of Duality and Finite Energy Sum Rules

*

(i) General Reviews

-

Schmid (Intermediate ~nergies); Jackson, 3

*

(ii) Dual Field Theory and Regge Cuts (Absorption)

-

Lovelace,

*

(iii) Veneziano Formulae

-

Berger

.

(iv) SU Constraints 1

3

-

Mandula et al.

.

₃

(v) Relations between Absorption Model and Duality

-

Harari

.

(b) Tests of High Energy Pole and Cut Models

*

1

(i) Experimental Emphasis

-

Part

6

; Diebold

.

*

(ii) General Reviews

-

.Jackson13; Fox (s-dependencex2, t-dependence ) ;

14 Barger, Phillips

(iii) Empirical Rules for Cuts and Line Reversal Relations

-

~hiu'.

(c) Further Topics

*

(i) Diffraction Scattering

-

orris on";

Gilman et a1.15; Fox

.

4

(ii) Photoproduction and Vector Dominance Model

-

~iebold'~ ; Daresbury

.

*

MAP

OF

Pff ENOMENOLOGY

WORLV

REFERENCES FOR

MAP

These are of course, only a representative collection: in particular,

w e refer, where possible, to reviews rather than the original phenomenology.

*

This conference: see Table of Contents.

1,

Proceedings of the Workshop on Particle Physics at Intermediate Energies,

edited by R. D. Field, preprint UCRL

-

20655 (1971)

2.

T. D. Lee and C. S.

Wu,

Ann. Rev. Nuc. Sci.

-

15 and

16

(1965 and 1966).

3.

Proceedings of the International Conference on Duality and Symmetry in

Hadron Physics (Tel-Aviv 1971).

4 .

Proceedings of 4th International Symposium on Electron and Photon Inter-

actions at High Energies, (~aresbury

Laboratory, Liverpool, 1969), edited by

D. W. Braben and R.

E. Rand.

5. C.

H. Llewellyn Smith, to be published in Physics Reports.

6 .

E. L. Berger

,

invited talk at the Irvine Conference, 1969; preprint

ANL/

HEP 6927 (1970).

7. Proceedings of the Conference onnn and

Kr

Interactions, edited by F.

Loef

f

ler and E. Malamud.?

'

(Argonne

preprint

,

1969).

8.

Experimental Meson Spectroscopy, edited by C. Baltay and A.

H. Rosenfeld.

(Columbia Univ. Press, 1970).

9.

Low Energy Hadron Interactions, Springer tracts in Modern Physics, Vol. 55

(1970)

.

10.

15th International Conference on High Energy Physics, Kiev, (1970).

11. G. Hehler and R. Strauss, Karlsruhe preprint (1970).

12.

High Energy Collisions, (Gordon and Breach, New York, 1970).

13. J.

D. Jackson, Rev. Mod. Phys.

42,

12 (1970).

14.

V. Barger and R. J. N. Phillips, Phenomenology of Total Cross Sections and

s

to be published in Nuclear Physics.

,

15. F.

Gilman, J. Pumplin,

A. Schwimmer and L. Stodolsky, Phys. Lett.

-9

31B

387 (1970).

ABSTRACTS

1. WEAK INTERACTIONS

S

.

B

.

TREDIAN

,

Phenomenology of Weak I n t e r a c t i o n s _{(Page 1)}

The following r e c e n t developments of s p e c i a l i n t e r e s t i n weak i n t e r a c t i o n s a r e reviewed: s t a t u s of t h e current-current p i c t u r e and t e s t s i n diagonal processes, e.g., v

+

e -+ v

+

e ; s p e c u l a t i o n s on t h e intermediate v e c t o r

boson; new l i m i t s on n e u t r a l c u r r e n t s ; a c r i s i s developing f o r t h e process

+ p - ; r e c e n t r e s u l t s on CP and T v i o l a t i o n ; t h e o r e t i c a l a n t i c i p a t i o n f o r i n e l a s t i c n e u t r i n o r e a c t i o n s .

2. MULTIPARTICLE PROCESSES

U.E. KRUSE, Some Recent Experimental Results f o r A,, A,, Q and L Mesons (Page 27)

J- J

After a b r i e f d e s c r i p t i o n of t h e methods of a n a l y s i s , some new r e s u l t s on t h e A1, Ag, Q and L mesons a r e p r sented. A s p i n p a r i t y a n a l y s i s of t h e 3a

_$

system i n t h e A1 region r e v e a l s 1 and

0-

components with both pn and En decays.

A preliminary a n a l y s i s of t h e A suggests s p i n 2- and a pn decay i n a d d i t i o n t o t h e dominant f n. The decay d i s h i b u t i o n of t h e A1, A and

Q shows approximate

t-channel h e l i c i t y conservation i n c o n t r a s t t o yp 4

sop

and

nN e l a s t i c , which

conserve h e l i c i t y i n t h e &channel.

W.R. FRAZER, Phenomenology of M u l t i p a r t i c l e Reactions (Page 48)

We discuss important q u a l i t a t i v e f e a t u r e s of m u l t i p a r t i c l e r e a c t i o n s .

A l l models must e x p l a i n t h e smallness of both t h e average t r a n s v e r s e momentum and t h e m u l t i p l i c i t y of produced p a r t i c l e s . The l o n g i t u d i n a l phase space p l o t s , introduced by Van Hove, allow a convenient summary of l o w m u l t i p l i c i t y events

.

Single p a r t i c l e d i s t r i b u t i o n s a r e t r e a t e d i n detail-these test t h e t h e o r e t i c a l i d e a s of s c a l i n g , l i m i t i n g d i s t r i b u t i o n , multiperipheralism and p i o n i z a t i o n . Most e x c i t i n g l y , t h e new diagrams, discovered by Mueller, suggest many new t h e o r e t i c a l and phenomenological developments.

E.L. BERGER, Phenomenological Applications of Dual Models (Page 8 3 )

Important a p p l i c a t i o n s of d u a l models t o a n a l y s i s of hadronic d a t a a r e reviewed. A d i s t i n c t i o n i s made between d e t a i l e d q u a n t i t a t i v e f i t s , i n which

sums of Veneziano-type functions a r e employed, and more q u a l i t a t i v e a p p l i c a t i o n s . Although q u a n t i t a t i v e f i t s have been generally unsuccessful, many valuable

q u a l i t a t i v e p r e d i c t i o n s can b e a b s t r a c t e d from t h e models. Four-point (B4) and five-point (B ) models a r e t r e a t e d thoroughly h e r e ; recent s t u d i e s with h ~ g h e r

5

order functions (B B8,

. . .

%)

a r e reviewed more b r i e f l y

.

A c r i t i c a l a p p r a i s a l

6

'

i s given of evidence f o r and a g a i n s t predicted daughter s t a t e s ; i n p a r t i c u l a r , t h e p ' i s examined i n d e t a i l . Next, t h e important r o l e played i n dual models by dynamical zeroes i s described and s e v e r a l a p p l i c a t i o n s a r e suggested. Analyses

ABSTRACTS

of Dalitz plots for the annihilation process Fn -+ 3r are discussed. There

follows a section on

B

phenomenology. Concerning quantitativz applications,

it is shown that new

S

~

data on

C

-+ e r m P and KOp -+ K-IT p invalidate the

simple

B

approach of Chan, Raitio, Thomas and Tbrnqvist. New fits are

proposed! Evidence against Rosner-Harari rules from some

B

fits is disputed;

discrepancies are shown to lie rather in improper unitarizazion of the model.

Stressed is the importance of

B

as a qualitative tool for understanding

5

interference effects among competing channels in

2

+ 3 particle reactions. It

is demonstrated analytically that the model predicts asymptotic breaking of

line-reversal symmetq in related production processes (e.g., Kp -+

K

p and

Fp

-+

z*p

or rp +

KY

and

Ep

-+ VY* ). The magnitude of symmetry breaking

is directly proportional to the total. width of the produced resonance. Examined

closely is the possibility of using dual models to resolve the long-standing

question of resonance or kinematical interpretation of A

,

Q , and other

threshold enhancements.

A

simple counterexample is conshructed to demonstrate

the current dual models do not resolve this issue. The final section of the review concerns studies of inclusive reactions and of narrow resonances with

large values of mass and spin. Throughout the paper, specific experimental and _{- -} - -

theoretical investigations- are suggested in order to develop more-understanding

of the way duality and crossing-symmetry are manifest in hadronic data.

3. THE QUARK MODEL

R.P. FEYNMAN, The Quark Model at Low Energies (Page 224)

Matrix elements of vector and axial vector currents between one-hadron states are recalculated using a relativistic equation to represent the symmetric quark model of hadrons with harmonic interaction. Elements between states with large mass differences are too big compared to experiment, so a factor whose functional form involves one arbitrary constant is introduced to compensate for this. The vector elements are compared to experiments for photoelectric meson

production,

K

decay, and w -+ ry

.

Pseudo-scalar meson decay widths of hadrons

are calculate~3supposing the amplitude is proportional (with one new scale

constax~t) to the divergence of the axial current matrix elements. With only

these two constants, the slope of the Regge trajectories, and the masses of

the particles, more than 3/4 of the

75

calculated matrix elements agree with

their experimental values within

40%.

4.

THE A2 MESON

K.W.

LAI,

Recent Results from Bubble Chamber Experiments on A (Page 257) 2

Bubble chamber results on the

A

meson in different charge states and for

2

various decay modes are reviewed. Compared with the 7 GeV/c CERN r- counter experiment, recent experiments, with both counter and bubble chamber techniques,

have improved resolution but indicate "no-split" for the A We present a +

2 '

compilation of angular distributions and spin-density matrix elements for A-

2

**

production. Further it is shown that the decay branching ratios for A and*gor K

are in good agreement with S U assuming a single resonance for

A

and $or K

.

3

Finally, we stress the advantages of having 4n geometry, as in bhble chamber data,

for studying the

A

mass spectrum and decay distributions.

ABSTRACTS

K.W.J.

BARNBAM,

Interfering Resonance Model Fit to A2

Mass Spectrum (Page 294)

This contribution is in the form of two papers: (A) New data; (B) Fit

to all A2 data.

₊

₊

(A) A study of the A mass spectrum in a

q

interactions at 3.7 GeV/c

is presented. For a cut o$

-t' =

0.1

-P

2.0 GeV and on eliminating the

A*

we find that the three pion mass spectrum in the

:

A

region is fitted by the

dipole formula with a confidence level of 53% and a single Breit-Wigner formula

with a confidence level of 11%. Our result thus favors A2 splitting although

+

a single Breit-Wigner fit cannot be ruled out. We also report the A2 decay

branching fractions measured over all t' values. They are 0.78

f

0.05

,

0.15

It

0.04

,

0.06

+

0.03

,

and ~0.02

for

pn,

na,

6,

and n'a respectively,

in good agreement with other experiments.

(B) The A+*-,' three pion and missing mass spectra in the experiments

with the best sfatistics to date, have been fitted with a two-interfering

resonance model. Good fits are possible over a range of mass and width parameters

for both the asymmetric case (wide and narrow resonances with nearly degenerate

masses) and symmetric case (different mass values but approximately the same

widths).

Rather small changes in the relative amplitudes and phase of the two

resonances are found to be necessary to change from the split

A;

spectrum observed

by the

CERN Misstng Mass Spectrometer and

CERN

Boson Spectrometer experiments

to the uneplit A2 observed by Alston-Garnjost et al.

S

.M.

The f0 Mass Spectrum in

7

GeV/c

n+p

Interactions (Page 322)

We briefly report the f0 mass spectra and moments of the decay angular

+ +

distribution in the reaction a+p

+

a pa a- at

7

GeV/c. No significant fine

structure (e.g., splitting) is observed.

S. OZAKI, The Double Vee Magnetic Spectrometer: Experimental Setup and Current

Results (Page 326)

The current status of the Double Vee Spectrometer experiment at the AGS

is described. The experimental setup has both forward and recoil spectrometers.

These are now both working, but the present data comes from runs using only

the forward spectrometer. One of the two main reactions studied is:

(a) a-

+

p

+ KO

+

MM

(e.g.,

A ,

rO,

30)

at 8 GeV/c. Preliminary results indicate that da/dt for amp

+ KOLO

is somewhat

sharper than that for a-p

+ KOA

.

The other reaction is:

I

r ; BSTRACTS

+

M. GETTNER, Measurements of t h e A; and,A, Mass S p e c t r a (Page 358)

Observations of t h e mass d i s t r i b u t i o n of t h e A2 meson produced i n t h e r e a c t i o n IT^ + A2p a r e r e p o r t e d . The A 's were observed u s i n g a missing mass t e c h n i q u e . Measurements w e r made w i t h

3

and

7

G e V IT- a s

w e l l

as 5 GeV IT' beams.

$

F o r each beam s e t t i n g

( 5 , 5

,

and 7- GeV), more t h a n $7,000 A 2 ' s above

background were observed w i t h 0.20

I

t

1

0.29 (GeV)

.

The A peaks a r e w e l l d e s c r i b e d by a Breit-Wigner shape, whereas t h e d i p o l e mass formula does n o t f i t t h e d a t a .

J . L . ROSNER, T h e o r e t i c a l Remarks on t h e A2 Meson (Page 387)

The A2 is i n no way anomalous r e g a r d i n g i t s SU(3) p r o p e r t i e s o r production mechanism. Evidence r e g a r d i n g s u b s t r u c t u r e (or l a c k t h e r e o f ) i n t h e peak i s

d i s c u s s e d w i t h p a r t i c u l a r r e g a r d t o any f u r t h e r experiments t h a t may b e planned.

5 . PHASE SHIFT ANALYSIS I N TWO-BODY REACTIONS

H. STEINER, Pion-Nucleon S c a t t e r i n g : Phase S h i f t s and Experiments (Page 420) W e g i v e a b r i e f survey of new low energy ITN experiments and t h e s t a t u s of c u r r e n t phase s h i f t a n a l y s e s . It i s shown by Monte Carlo c a l c u l a t i o n s , t h a t

A and R measurements w i l l b e v e r y u s e f u l i n l i m i t i n g t h e number of a c c e p t a b l e p h a s e s h i f t s o l u t i o n s a t a given energy.

+

R.E. CUTKOSKY, Optimized A n a l y t i c Data Analysis and A p p l i c a t i o n t o K p S c a t t e r i n g (Page 444)

A new approach t o d a t a a n a l y s i s is d e s c r i b e d , which makes maximum u s e of g e n e r a l a n a l y t i c i t y p r o p e r t i e s t o e x t r a c t i n t e r e s t i n g physics from experimental d a t a . The a n a l y s i s i s a p p l i e d t o K + ~ s c a t t e r i n g , and p r e l i m i n a r y r e s u l t s a r e discussed--in p a r t i c u l a r , t h e s e n s i t i v i t y of t h e r e s u l t s t o t h e r e s i d u e s of t h e

A and C p o l e s .

6. EXPERIMENTAL RESULTS I N TWO-BODY REACTIONS

B. MUSGRAVE, A Review of Some Experimental R e s u l t s on Hadron-Deuterium S c a t t e r i n g (Page 467)

The experimental t e c h n i q u e s used i n a n a l y z i n g deuterium bubble chamber

d a t a a r e c a r e f u l l y reviewed. These a r e u s u a l l y s u c c e s s f u l when t e s t e d v i a charge independence (symmetry) and hydrogen d a t a . However, h i g h e r s t a t i s t i c d a t a and a more uniform t r e a t m e n t of t h e c o r r e c t i o n s a r e needed f o r a r e a l l y q u a n t i t a t i v e assessment of deuterium e f f e c t s . F u r t h e r , we g i v e a b r i e f survey of t h e

ABSTRACTS

-

0

D.W.G.S. LEITH, Recent Results on IT p + p n

a t

Small Momentum Transfers _{(Page 554)}

This contribution i n i n t h e form of 3 papers: (A) Data; (B) Tests of Vector Dominance Model; (C) Tests of (Strong) Absorption Model.

-

(A) The r e s u l t s of a

w i r e

spark chamber experiment studying t h e r e a c t i o n

IT p + .rr+n'n a t 15 GeV/c a r e presented. The d i f f e r e n t i a l cross s e c t i o n , A-n

mass d i s t r i b u t i o n and density matrix elements have been de ermined from 10,000

5

n m events (M < 1.0 GeV) produced with -t < ,30 (GeV/c)

.

Both t h e deneity matrix elemen!: and t h e d f f e r e n t i a l cross s e c t i o n e x h i b i t s t r u c t u r e i n t h e

_i

f o w a r d d i r e c t i o n (-t < mIT)

.

(B)

We present a comparison of new d a t a on

np

-+ pOn a t 15 G e ~ / c with

polarized and unpolarized s i n g l e pion photoproduction data. P a r t i c u l a r emphasis

i s placed upon t h e behavior of t

₉

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 s and asymmetries i n t h e forward d i r e c t i o n (-t < mIT).

-

(C) The r e s u l t s of a w i r e spark chamber experiment studying t h e r e a c t i o n

IT p -t n'n-n a t 15 GeV/c a r e compared with t h e predictions of t h e absorptive

one pion exchange model. The r i c h s t r u c t u r e a t small values of momentum t r a n s f e r observed

i n

t h e d a t a i s w e l l described by t h e model.

L . D I C K , Some New Experimental Results with Polarized Targets-I (Page 594)

We present t h e f i n a l r e s u l t s of an experiment performed a t t h e CElW proton synchrgtron by a CERN-Orsay-Pisa collaboration. The proton p o l a r i z a t i o n i n n'p, K-p, pp and

pp

e l a s t i c s c a t t e r i n g has

been

measured at i n c i d e n t momenta of 6 , 10, 14, and 17.5 G e ~ / c , and i n t h e mmentum t r a n s f e r range

(

t

1

-

0.1 t o 2.7 (GeV/c)

.

A. YOKOSAWA, Some New Experimental Results with Polarized Targets--11 (Page 612)

+

We report new p o l a r i z a t i o n r e s u l t s f o r n\ and K p e l a s t i c s c a t t e r i n g a t l a r g e angles i n t h e intermediate energy region, and a l s o preliminary .rr-p

charge exchange p o l a r i z a t i o n measurements from CERN a t 5 and 8 GeV/c.

7. PHENOMENOLOGY I N TWO-BODY REACTIONS

C . SCHMID, Phenomenology a t Intermediate Energies (Page629)

The following t o p i c s a r e discussed. Regge f e a t u r e s a r e more e a s i l y and more c l e a r l y seen a t intermediate energies (shrinkage, p o l a r i z a t i o n s t r u c t u r e i n

ti.

The d i r e c t ( l o c a l ) confrontation of Regge and phase s h i f t amplitudes i n K p s c a t t e r i n g . The+partial wave analysis of t h e imaginary p a r t of t h e non-flip amplitude i n K-p e l a s t i c s c a t t e r i n g and t h e problem of t h e s t r e n g t h of

ABSTRACTS

C.

Lovelace, P r e s e n t and F u t u r e of Two-Body Phenomenology (Page 668)

We d i s c u s s t h e p r e s e n t s t a t e of s t r o n g i n t e r a c t i o n t h e o r y , e s p e c i a l l y Regge phenomenology, and l i k e l y d i r e c t i o n s f o r f u r t h e r p r o g r e s s . E l a s t i c p o l a r i z a t i o n experiments have s t r i k i n g l y confirmed exchange-degeneracy, and t h e r e f o r e pole-pole d u a l i t y . Its c o r o l l a r i e s have s t i l l n o t p e n e t r a t e d many t h e o r i s t s . Recent t h e o r e t i c a l i n v e s t i g a t i o n s have c a s t l i g h t on Regge c u t s and t h e Pomeron. The

NAL small-angle pp experiment

w i l l c r u c i a l l y t e s t t h e s e new i d e a s .

G.C. Fox, On t h e Importance of Being an Amplitude (Page 703)

We review c u r r e n t experimental knowledge on t h e momentum t r a n s f e r and s p i n dependence of t h e s c a t t e r i n g amplitudes a t h i g h energy. We consider two-body, q u a s i two-body, and m u l t i p a r t i c l e r e a c t i o n s . ( i ) The s m a l l -t d a t a f o r

n a t u r a l p a r i t y exchange i s shown t o b e i n c o n s i s t e n t w i t h a l l t h e c u r r e n t t h e o r i e s b u t c o n s i s t e n t w i t h s e v e r a l q u i t e p l e a s i n g e m p i r i c a l r u l e s . W e document t h o s e

d a l d t , P, R and A measurements which can extend and c l a r i f y t h e p r e s e n t s y s t e m a t i c s . ( i i ) n exchange d a t a a t v e r y s m a l l -t i s i n amazing agreement w i t h t h e poor man's

2

a b s o r p t i o n model which ssumes smooth e x t r a p o l a t i o n from t=m, t o t = O . A t l a r g e r -t = .6 (GeVlc)', p00 dcrldt f o r v e c t o r meson production shows s i m i l a r s y s t e m a t i c s t o t h e well-known n a t u r a l p a r i t y exchange CEX r e a c t i o n s . ( i i i ) We c o n s i d e r t h e behavior a t l a r g e -t > 1 ( G ~ V I C ) ~ of a l l two and q u q s i p - b o d y d a t a . I n photoproduction, t h e d a t a

1s

w e l l known t o s c a l e l i k e E i b e

.

A

s i m i l a r t-dependence i s observed f o r many h a d r o n i c r e a c t i o n s arouna 5 GeV/c. The energy dependence i s less w e l l s t u d i e d : t h e r e i s some s u g g e s t i o n t h a t i t

is more l i k e f o r p and A2 exchange. E x p l i c i t p a r t i a l wave a n a l y s i s of

dda/di

w i t h v a r i o u s phase assumptions i n d i c a t e s t h a t a l a r g e component of

s c a t t e r i n g i s a t s m a l l impact parameters. I n photoproduction, t h i s component t a k e s a u n i v e r s a l form which may r e f l e c t a new form of i n t e r a c t i o n p r e s e n t i n a l l p r o c e s s e s . ( i v ) We c r i t i c a l l y review quark model p r e d i c t i o n s f o r s i n g l e and double resonance production. Although t h e s e a r e q u i t e s u c c e s s f u l , t h e

d a t a seem t o d e v i a t e from t h e quark r e l a t i o n s , r a t h e r more than simple a b s o r p t i o n models p r e d i c t . This n e a r e q u a l i t y between quark and a b s o r p t i o n amplitudes

i m p l i e s one p a r t i c u l a r l y amazing r e s u l t . Thus a b s o r p t i o n c o r r e c t i o n s t o

one p i o n exchange g e n e r a t e s t h e Stodolsky-Sakurai d i s t r i b u t i o n f o r t h e n a t u r a l p a r i t y exchange component of A production. F u r t h e r w e show t h a t many f e a t u r e s of r e c e n t d u a l models based on t h e quark s u b s t r u c t u r e a r e i n q u a l i t a t i v e

PART

1 :

Weak IvLtenclc;tiou

(Although i t i s n o t w i d e l y known, t h e b e a u t i f u l p r i n c e s s ' l e g e n d a r y s e n s i t i v i t y n o t o n l y won h e r t h e hand of t h e handsome p r i n c e , b u t a l s o l a n d e d h e r a j o b a s p a r t of t h e d e t e c t i o n a p p a r a t u s a t one of o u r l e a d i n g l a b o r a t o r i e s . )

PHENOMENOLOGY

OF WEAK

1

NTERACT7ONS*

Jua

e p h

H

e&y LubancLtuGen

? ~ Z ~ Z C & U V ~

u V ? h m a y

Pkinc&an,

New

J m c y

0 8 5 4 0

*

Rueu-kch d p u m u n e d by

;the.

U.S.

Akumic Etz~ttgy Cummdaiatz utzdm CumhuCk

AT(30-11-4159.

S.B.

TRElMAN

: WEAK INTERACTIONS

Most of o u r p r e s e n t i d e a s about t h e s t r u c t u r e of weak i n t e r a c t i o n s have

been a b s t r a c t e d from t h e l i m i t e d phenomenology o f low e n e r g y decay p r o c e s s e s .

Each s u c h p r o c e s s s u p p l i e s a t b e s t a few p i e c e s of i n f o r m a t i o n : t h e decay

r a t e and p e r h a p s s e v e r a l s p e c t r u m and p o l a r i z a t i o n p a r a m e t e r s . The w i d e r

p r o s p e c t s t h a t would b e a f f o r d e d by s t u d y of weak i n t e r a c t i o n e f f e c t s i n

c o l l i s i o n r e a c t i o n s seems t o b e f o r e c l o s e d f o r weak n o n l e p t o n i c phenomena.

But h i g h energy n e u t r i n o p h y s i c s , which h a s a l r e a d y y i e l d e d i m p o r t a n t r e s u l t s ,

i s f u l l of promise f o r t h e e a r l y f u t u r e and h a s a t t r a c t e d a g r e a t d e a l of

a t t e n t i o n l a t e l y . N e v e r t h e l e s s , t h e low e n e r g y p r o c e s s e s c o n t i n u e t o produce

new i n s i g h t s and o c c a s i o n a l i n t i m a t i o n s t h a t t h e s t a n d a r d phenomenology may

b e f a r from complete.

There i s no need h e r e f o r a s y s t e m a t i c review o f t h e whole of weak i n t e r -

a c t i o n p h y s i c s . I w i l l i n s t e a d r u n t h r o u g h a s u b s e t of r e c e n t developments

t h a t seem t o b e of s p e c i a l i n t e r e s t . L e t me b e g i n by reminding you t h a t on

t h e p r e s e n t day p i c t u r e one u s u a l l y imagines t h a t a l l c l a s s e s of weak i n t e r -

a c t i o n s

--

n o n l e p t o n i c , s e m i l e p t o n i c , and p u r e l e p t o n i c

--

a r i s e from t h e e f f e c t i v e s e l f i n t e r a c t i o n of charged V , A c u r r e n t s composed of l e p t o n i c and

h a d r o n i c p a r t s . T h i s p i c t u r e r a t h e r d i r e c t l y summarizes what we r e a d o f f from

o b s e r v a t i o n s on muon decay and on v a r i o u s s e m i l e p t o n i c p r o c e s s e s ; b u t owing t o

t h e c o m p l e x i t i e s o f hadron p h y s i c s i t g o e s beyond d i r e c t e v i d e n c e s o f a r a s t h e

n o n l e p t o n i c i n t e r a c t i o n s a r e concerned. Indeed, w i t h o u t t h e i n t r o d u c t i o n of

n e u t r a l c u r r e n t s o r o t h e r s p e c u l a t i v e i n p u t s , one h a s t h e f a m i l i a r problem

I

h e r e of a c c o u n t i n g f o r t h e e m p i r i c a l s u c c e s s of t h e A I = r u l e . The s u b j e c t

h a s been e n d l e s s l y d i s c u s s e d , w i t h o u t d e c i s i v e outcome, and I s h a l l n o t review

i t f u r t h e r . Equally s p e c u l a t i v e , s t i l l , i s t h e q u e s t i o n whether t h e weak

S.B. TRElMAN

: WEAK

INTERACTIONS

For p u r e l y l e p t o n i c p r o c e s s e s t h e c u r r e n t x c u r r e n t p i c t u r e , a t l e a s t on

a s t r a i g h t f o r w a r d and p e r h a p s n a i v e i n t e r p r e t a t i o n , p r o v i d e s a s h a r p p r e d i c t i o n

c o n c e r n i n g

&c)(~e)

i n t e r a c t i o n s : namely, t h a t t h e s e have t h e

same s t r u c t u r e and s t r e n g t h a s t h e

(gel

9 ~ )

i n t e r a c t i o n r e s p o n s i b l e f o r muon

decay. It h a s been t h e r e f o r e a m a t t e r of p r e s s i n g i n t e r e s t f o r some time t o

test f o r t h e e x i s t e n c e of t h e s e i n t e r a c t i o n s , s a y through s e a r c h f o r t h e

e l a s t i c s c a t t e r i n g p r o c e s s

we+%&

@

.

The s i t u a t i o n i s made even more

i n t e r e s t i n g by t h e s p e c u l a t i o n s of Gell-Mann, Goldberger, K r o l l , and Low, 1

who s u g g e s t t h a t h i g h e r o r d e r weak i n t e r a c t i o n e f f e c t s f o r s u c h "diagonal"

p r o c e s s e s can l e a d t o an e f f e c t i v e c o u p l i n g s t r e n g t h which d i f f e r s from t h a t

d e s c r i b i n g muon decay. There have been s e v e r a l developments on t h e s e m a t t e r s

i n t h e p a s t y e a r . An upper l i m i t on

&-e

s c a t t e r i n g h a s been e x t r a c t e d by

s t e i n e r 2 from t h e d a t a on e l e c t r o n p r o d u c t i o n o b t a i n e d i n t h e 1963-64 CERN

n e u t r i n o s p a r k chamber e x p e r i m e n t . E l e c t r o n t y p e n e u t r i n o s i n t h e beam

a r i s e from decay and have a s p e c t r u m c h a t peaks a t u 1 Gev. Some 30

eg

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

9 4 9

6 + ~

were s e e n . A t

most one e v e n t was compatible w i t h

%*e+beg4.e

.

T h i s sets a n upper l i m i t

s

4 0 6 t h e o r y ("theory" h e r e r e f e r s t o t h e s t a n d a r d e x p e c t a t i o n ) , Nore

13

r e c e n t l y , Reines and GurrJ have r e p o r t e d n e g a t i v e r e s u l t s i n a s e a r c h f o r

c. e

t h e r e a c t i o n .

&e+&+e

induced by a n t i n e u t r i n o s from t h e Savannah R i v e r

r e a c t o r . They l o o k i n s c i n t i l l a t o r m a t e r i a l f o r r e a c t o r - a s s o c i a t e d e l e c t r o n

p u l s e s c o r r e s p o n d i n g t o e l e c t r o n s i n t h e energy range 3.8-5 Mev. The

e x p e r i m e n t a l upper l i m i t i s e x p r e s s e d by

<

4

@e

t h e o r y *

Another p e r e n n i a l concern o f weak i n t e r a c t i o n p h y s i c s h a s t o do w i t h t h e

h y p o t h e t i c a l i n t e r m e d i a t e v e c t o r b o s o n s , W

.

When Yukawa i n t r o d u c e d t h e p i o n s

as m e d i a t o r s of t h e n u c l e a r f o r c e , h e c o u l d i n f e r from t h e known r a n g e o f t h e

S . B .

TRETMAN : WEAK ZNTERACTIONS

l e s s w e l l s p e c i f i e d by i t s e n t h u s i a s t s . R e c a l l t h a t i f g i s t h e d i m e n s i o n l e s s

c o u p l i n g c o n s t a n t t h a t c h a r a c t e r i z e s t h e i n t e r a c t i o n of t h e boson f i e l d w i t h

t h e l e p t o n and hadron c u r r e n t s , t h e n

It h a s o f t e n seemed t o p e o p l e t h a t a " n a t u r a l " v a l u e f o r g might correspond

t o

$&

n

ek;&

.

A more s p e c i f i c v e r s i o n of t h i s a s s o c i a t i o n of weak

and e l e c t r o m a g n e t i c c o u p l i n g c o n s t a n t s h a s r e c e n t l y been s u g g e s t e d by

S c h e c h t e r and Uedu; and i n d e p e n d e n t l y , T. D. Lee. I n L e e ' s n o t a t i o n , t h e

i d e a i s t o d e f i n e "charge" o p e r a t o r s K a c c o r d i n g t o i

where J weak h e r e i s t h e t o t a l l e p t o n p l u s hadron c u r r e n t ; and t o d e f i n e

an equcii-time commutator. With Q t h e u s u a l e l e c t r o m a g n e t i c charge o p e r a t o r ,

d e f i n e a l s o

z

Q-K3

*

I n t h e u s u a l q u a r k model f o r t h e hadron p a r t of t h e c u r r e n t one now f i n d s t h e

equal-time commutation r e l a t i o n s

With r e s p e c t t o K-spin one s e e s t h a t t h e e l e c t r o m a g n e t i c c h a r g e h a s a K = l and

a K=O p a r t , whereas t h e weak c u r r e n t i s p u r e K = l . It i s proposed now t h a t

S.

B.

TRETMAN

:

WEAK 1NTERACTlONS

t h a t

8=

e / a 6 >

hence

MW

= 37.29 Gev! I f t h i s i s a n y t h i n g l i k e r i g h t , t h e s e a r c h f o r W p a r t i c l e s i s n o t going t o b e e a s y .

I mentioned e a r l i e r t h e s p e c u l a t i v e p o s s i b i l i t y t h a t t h e weak n o n l e p t o n i c

i n t e r a c t i o n s might i n v o l v e t h e c o u p l i n g s of n e u t r a l hadron c u r r e n t s . The

q u e s t i o n a l s o a r i s e s f o r p u r e l y l e p t o n i c i n t e r a c t i o n s whether n e u t r a l l e p t o n

c u r r e n t s couple among t h e m s e l v e s ; o r f o r s e m i l e p t o n i c i n t e r a c t i o n s , w h e t h e r

t h e r e are c o u p l i n g s of n e u t r a l l e p t o n and n e u t r a l hadron c u r r e n t s . The l a t t e r

might g i v e rise t o p r o c e s s e s of t h e s o r t

Y+

l d r o n

+

P+

hadbe

Upper l i m i t s d e r i v e d from t h e CERN HLBC n e u t r i n o e x p e r i m e n t s have been

5

r e p o r t e d d u r i n g t h e p a s t y e a r f o r two s u c h p r o c e s s e s ; namely,

( I ' v e t a k e n t h e l i b e r t y t o d e s c r i b e t h e s e a s upper l i m i t s ) . Concerning

6

n e u t r a l c u r r e n t s i n p u r e l y l e p t o n i c p r o c e s s e s , A l b r i g h t h a s n o t i c e d t h a t t h e

CERN n e u t r i n o d a t a u s e d t o s e t a l i m i t on e l a s t i c

4--e

s c a t t e r i n g a l s o p r o v i d e s

a l i m i t on t h e r e a c t i o n

Y ;

+

&'.

He f i n d s

c$&)se-)

4

0.40

qheory

r ' P

("theory" h e r e r e f e r s t o s t a n d a r d V-A c o u p l i n g w i t h s t a n d a r d s t r e n g t h ) .

Another n e g a t i v e r e s u l t , t h i s one c o r r e s p o n d i n g t o t h e r e a c t i o n

V+X'+*V

,

-

6

S.B.

TRETMAN

:

WEAK 1NTERACTlONS

To b e s u r e , any o f t h e s e p r o c e s s e s , i f found, would n o t have t o be

i n t e r p r e t e d a s e v i d e n c e of n e u t r a l c u r r e n t c o u p l i n g s . One c o u l d imagine

t h a t t h e y a r i s e i n s t e a d from second o r d e r e f f e c t s i n c o n v e n t i o n a l weak

d.

-

i n t e r a c t i o n s , a s i l l u s t r a t e d i n t h e diagram f o r t h e example of

K+&+*v:

Formally one e x p e c t s such second o r d e r e f f e c t s t o b e "doubly" weak, b u t i t ' s

n o t c l e a r what t h i s means: n a i v e p e r t u r b a t i o n c a l c u l a t i o n s l e a d t y p i c a l l y

t o d i v e r g e n t i n t e g r a l s . I f e v i d e n c e f o r p r o c e s s e s of t h e t y p e under d i s c u s s i o n

i s some day f o u n d , one w i l l b e g i n t o make d i s t i n c t i o n s among a l t e r n a t i v e

i n t e r p r e t a t i o n s on t h e b a s i s of spectrum s t r u c t u r e ; e . g . , a c c o r d i n g t o w h e t h e r

t h e l e p t o n p a i r seem t o c o u p l e l o c a l l y t o t h e h a d r o n s . But t h e s e p o i n t s need

h a r d l y b e p r e s s e d a t t h e moment.

Of g r e a t e r i n t e r e s t j u s t now i s t h e s t i l l unseen p r o c e s s

T h i s i s a n o t h e r example o f a r e a c t i o n t h a t might a r i s e from h y p o t h e t i c a l

n e u t r a l l e p t o n c o u p l i n g s , o r from h i g h e r o r d e r weak e f f e c t s . But t h e r e i s

a l s o a n o t h e r mechanism, one whose o p e r a t i o n would seem t o be i n d u b i t a b l e :

t h e sequence KL 0

3

two r e a l o r v i r t u a l photons+#*p

-

+

.

On t h i s l a t t e r

mechanism, a rough e s t i m a t e would s u g g e s t t h a t 8

h e n c e

f&*pj

- 8

b r a n c h i n g r a t i o = 2 x 1 0

.

S ,

B.

TREIMAM

:

WEAK I m E R A C T I O M S

I n any c a s e , i f CP v i o l a t i n g e f f e c t s can b e i g n o r e d , one g e t s a lower bound

on t h e r a t e by t a k i n g t h e

\+y

a m p l i t u d e t o b e p u r e l y a b s o r p t i v e . It can t h e n

be e x p r e s s e d , a n t h e b a s i s of u n i t a r i t y c o n s i d e r a t i o n s , a s a sum of con-

t r i b u t i o n s coming from p u r e l y on-mass-shell i n t e r m e d i a t e s t a t e s . To l o w e s t

r e l e v a n t o r d e r i n t h e f i n e s t r u c t u r e c o n s t a n t only t h e 2K

s,

and ~ f s t a t e s

need be c o n s i d e r e d . I f t h e l a t t e r two c h a n n e l s a r e t o t a l l y i g n o r e d ( P a i s

c a l l s t h i s "naive u n i t a r i t y " ) one t h e n f i n d s

9

L e t us now r e i n s t a t e t h e c h a n n e l , c o n t i n u i n g f o r a w h i l e l o n g e r t o i g n o r e

t h e 3 @ s t a t e . Then one needs t o know t h e a m p l i t u d e s f o r K L + a and

1 R d 4 ~

-

The l a t t e r can b e e s t i m a t e d w i t h r e l i a b i l i t y i n s t a n d a r d e l e c t r o d y n a m i c s ;

t h e o n l y unknown element i s t h e e l e c t r o m a g n e t i c form f a c t o r of t h e p i o n ,

which i s however p r o b a b l y s a f e l y approximated in the! meson dominance

model. A s f o r t h e p r o c e s s h a s n o t y e t been s e e n and t h e bound

-4

(B.R. 4 4 x 10 ) s e t s a l i m i t on t h e modulus of t h e a m p l i t u d e . A l t o g e t h e r ,

on t h e s c a l e r e p r e s e n t e d by "naive" u n i t a r i t y , t h e n e t

%#

c o n t r i b u t i o n i s

u n i m p o r t a n t . F i n a l l y , l e t us r e i n s t a t e t h e c h a n n e l . It h a s two e f f e c t s .

Through t h e sequence

vs,

w++

i t makes a d i r e c t c o n t r i b u t i o n t o t h e

a b s o r p t i v e

%+?

a m p l i t u d e . The q u a n t i t a t i v e s i t u a t i o n h e r e i s made u n c e r t a i n

b e c a u s e t h e p r o c e s s cannot. b e t r e a t e d w i t h t h e o r e ~ i c a l r e l i a b i l i t y and

Y

i s n o t y e t a c c e s s i b l e t o e x p e r i m e n t a l s t u d y . In a d d i t i o n t h e c o n t r i b u t i o n

of t h e

;\l(

s t a t e t o t h e a b s o r p t i v e

%+p

a m p l i t u d e i s now made u n c e r t a i n b e c a u s e t h e

X

s t a t e g i v e s r i s e t o an a b s o r p t i v e p a r t f o r %9#. t h r o u g h t h e

u n i t a r i t y sequence

%*P,

And a g a i n t h e p r o c e s s

a+a

cannot b e

S.B.

T R E T M A N

:

W E A K T N T E R A C T T O N S

D e s p i t e a l l of t h e s e q u a l i f i c a t i o n s on t h e n a i v e u n i t a r i t y bound,

e s t i m a t e s made by M a r t i n , deRafae1, and Smith s u g g e s t th&L i t cannot e a s i l y

b e reduced by more t h a n about 20%. lo I n advance o f t h e e x p e r i m e n t a l r e s u l t s

t h a t I w i l l p r e s e n t l y m e n t i o n , most p h y s i c i s t s would p r o b a b l y have r e g a r d e d

t h i s bound as a s a f e b e t t i n g p r o p o s i t i o n ; and p e r h a p s some o f them s t i l l do.

But t h e Berkeley group, C l a r k e t . a l . ,I1 have e a r n e s t l y looked f o r

"

'

3

"

e v e n t s ; and a t l e a s t f o r t h e r u n s where KL decay t a k e s p l a c e i n vacuum

,

t h e y do n o t f i n d any. The upper l i m i t , a t t h e 90% c o n f i d e n c e l e v e l , i s

I n s o f a r a s t h i s s i t u a t i o n i s s u s t a i n e d , t h e r e a r e t h e makings h e r e of a f i r s t

c l a s s c r i s i s .

There i s one more remark t o b e made. I n t h e above d i s c u s s i o n CP

i n v a r i a n c e h a s been assumed, s o t h a t i t i s decay i n t o t h e

3s

s t a t e of two

0

muons t h a t i s i n q u e s t i o n . Of c o u r s e t h e

%

p a r t i c l e i s i n f a c t known t o be

v e r y n e a r l y p u r e w i t h r e s p e c t t o CP. L e t us i g n o r e t h e s m a l l CP i m p u r i t y

and ignore a l s o t h e 2X c~~cbniieis

-'-

-

which t h i s opens up f o r

5

decay. But l e t us a l l o w f o r t h e p o s s i b i l i t y of s u b s t a n t i a l CP v i o l a t i o n i n t h e e l e c t r o m a g n e t i c

i n t e r a c t i o n s of h a d r o n s , s o t h a t we may comtemplate t h e CP v i o l a t i n g decay o f

+

5

i n t o t h e 3 ~ 0 s t a t e ( s p i n - p a r i t y 0 ) of t h e muons. W e s i m i l a r l y a l l o w f o r CP v i o l a t i n g

v#

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

f o r KL+y('% ) decay can r e c e i v e c o n t r i b u t i o n s only from t h e

a

and

+

+

i n t e r m e d i a t e 0 s t a t e s

--

t h r e e p i o n s cannot form a 0 s t a t e . For t h i s same r e a s o n t h e a m p l i t u d e f o r %S~(O') h a s n o a b s o r p t i v e p a r t t o l e a d i n g e l e c t r o -

m a g n e t i c o r d e r . L e t u s f o r a moment i g n o r e t h e d c o n t r i b u t i o n t o t h e

a b s o r p t i v e

~t')r

('g

) a m p l i t u d e , We t h e n g e t a r e l i a b l e lower ( u n i t a r i t y )

S.B.

TRETMAN :

W E A K

7NTERACTlONS

t u r n i n g t h i s a r o u n d , we g e t a n upper bound on t h e CP v i o l a t i n g

%+a#

r a t e i n terms of t h e

~~99

) r a t e . But t h e Berkeley r e s u l t s set an

upper bound on t h e l a t t e r ; and we h e r e b y l e a r n t h a t 1 2

On t h e b a s i s o f t h e k i n d s of c o n s i d e r a t i o n s d i s c u s s e d e a r l i e r , i t i s found

t h a t t h e c o n t r i b u t i o n can b e n e g l e c t e d w i t h f a i r r e l i a b i l i t y and t h a t

t h e above r e s u l t i s s e c u r e t o w i t h i n about 20%, s o l o n g a s t h e Berkeley

r e s u l t s a r e s u s t a i n e d . These c o n s i d e r a t i o n s o f c o u r s e do n o t h i n g t o

r e s o l v e t h e " c r i s i s " f o r

\.)*

(

$

) decay, b u t t h e y have an i n t e r e s t of

S.B.

TRETMAN

:

WEAK TNTERACTIONS

CP VIOLATION

Seven y e a r s a f t e r t h e i n i t i a l d i s c o v e r y of CP breakdown i t i s s t i l l

t h e c a s e t h a t t h e r e a s o n a b l y w e l l e s t a b l i s h e d e v i d e n c e s o f t h i s breakdown

a r e c o n f i n e d s o l e l y t o t h e n e u t r a l K meson system, where one h a s d e t e c t e d t h e

CP f o r b i d d e n decays

%*R'x-

and ? m e a n d h a s observed t h e CP f o r b i d d e n

e

asymmetry between

%+I$$

and

%+a*,*$

( anF) .). T h i s l a t t e r e f f e c t

d e m o n s t r a t e s d i r e c t l y t h a t t h e

%

s t a t e i s impure w i t h r e s p e c t t o CP,

w h a t e v e r may b e t h e fundamental o r i g i n of t h e i m p u r i t y . One gloomy p o s s i b i l i t y ,

as you know, i s t h a t t h e o r i g i n l i e s i n superweak, o r o t h e r k i n d s of e x t r a -

v a g a n t i n t e r a c t i o n s which f o r a l l p r a c t i c a l p u r p o s e s can r e v e a l themselves

o n l y through t h e g e n e r a t i o n o f CP i m p u r i t i e s i n

%

and K On t h i s p i c t u r e

S "

n o t h i n g o f t h e symmetry v i o l a t i o n would show up ( a t f o r e s e e a b l e l e v e l s of

p r e c i s i o n ) o u t s i d e t h e n e u t r a l kaon system; and even t h e r e , no a d d i t i o n a l

on-mass-shell v i o l a t i o n s of t h e symmetry would be s e e n . I n p a r t i c u l a r , f o r

t h e

KL3m

decays one would have

'lm+$-s6

.

and a r g t . t a < k d * r = 43.2 -+_ 0 . 4 ~ . Thanks t o r e c e n t p r e c i s i o n d e t e r m i n a t i o n s of

OL-3

t h e p h a s e of

₉

-

i s now w e l l determined on t h e b a s i s of KS-KL i n t e r f e r e n c e e f f e c t s i n vacuum

1 3 o

decay t o e g - : a c c o r d i n g t o Aronson, e t . a l .

% _ =

4 5 . 2 2 4 . 0 . The

0 p h a s e of

%

i s l e s s w e l l determined. A r e c e n t r e p o r t 1 4 g i v e s

ge

= 5 1 & 30

.

The above r e s u l t s , e s p e c i a l l y t h a t f o r

(P+-,

a r e c e r t a i n l y compatible w i t h t h e superweak c l a s s o f t h e o r i e s . A s f o r t h e moduli of t h e

'Z

p a r a m e t e r s , t h e

s i t u a t i o n f o r

n*asl

decay h a s been s t a b l e from t h e beginning: t h e p r e s e n t

-3

w o r l d a v e r a g e i s

/$-I

= 1 * 9 2 ? 0 * 0 5 x 10 . _For

\To,\

_{t h e s i t u a t i o n i s s t i l l}

p r o b l e m a t i c . I n s e v e r a l e x p e r i m e n t s one f i n d s r e s u l t s c o m p a t i b l e w i t h

; i n s e v e r a l o t h e r s one f i n d s t h a t i s n o t i c e a b l y b i g g e r t h a n

S.B. TRElMAN : WEAK INTERACTTONS

two of t h e most r e c e n t p u b l i s h e d r e s u l t s . C h o l l e t e t . a l . 1 4 9 i n a CERN

-3

e x p e r i m e n t , f i n d = 3 . 3

2

0.6 x 10 Barmin, e t . a l . 1 5 , a t DUBNA, f i n d = 2 . 0 2 f 0 . 2 3 x

I n c o n t r a s t t o t h e superweak a l t e r n a t i v e , i t may b e t h a t CP v i o l a t i o n r e s i d e s i n c o n v e n t i o n a l n o n l e p e o n i c and p e r h a p s s e m i l e p t o n i c i n t e r a c t i o n s .

The s e a r c h f o r e f f e c t s i n weak p r o c e s s e s o u t s i d e t h e n e u t r a l K meson s y s t e m

h a s s o f a r y i e l d e d o n l y n e g a t i v e r e s u l t s . This i s d i s c o u r a g i n g b u t n o t

n e c e s s a r i l y s u r p r i s i n g i f t h e s c a l e i s "milliweak", a s would be s u g g e s t e d

on t h i s p i c t u r e from t h e n e u t r a l K p a r a m e t e r s . I w i l l b r i e f l y mention h e r e

o n l y a few r e c e n t r e s u l t s , which a r e b e g i n n i n g t o approach t h e milkiweak

l e v e l o f p r e c i s i o n . P i r o u e and h i s c o l l a b o r a t o r s 1 6 have c o l l e c t e d d a t a on

6 8

+ +

-

* ID.--=

1 . 6 x 1 0 K

+ll

fl fl and an e q u a l number of

K+%*

'

K

decays. To t h e f r a c t i o n of a p e r c e n t a c c u r a c y which such l a r g e s t a t i s t i c s i m p l i e s , t h e y f i n d no

=+

-

s i g n i f i c a n t d i f f e r e n c e s between K and K i n any r e g i o n of t h e D a l i t z p l o t .

A s one measure of t h i s t h e y compare t h e u s u a l odd p i o n s l o p e p a r a m e t e r s and

+ -

+

*

f i n d

b=

(q-a

) / ( @ + a

) = -0.0070

2

0.0053.

A new bound on t i m e r e v e r s a l v i o l a t i o n i n n u c l e a r decay h a s been

o b t a i n e d i n t h e p a s t y e a r i n an experiment of remarkable p r e c i s i o n c a r r i e d

o u t by C a l a p r i c e e t . a l . 1 7 . They look f o r t h e T v i o l a t i n g c o r r e l a t i o n

3 . , 9 ₁₉

J (

hgpy

) i n

p

decay f ram p o l a r i z e d Ne : ~ e l F" 3

+

eC

+

!$ The

c o e f f i c i e n t of t h i s c o r r e l a t i o n term measures t h e imaginary p a r t of i n t e r f e r e n c e

between t h e v e c t o r and a x i a l m a t r i x e l e m e n t s . They a r e r e l a t i v e l y r e a l i n t h e

absence o f T v i o l a t i o n -- a p a r t from e l e c t r o m a g n e t i c e f f e c t s . The l a t t e r can

b e r e l i a b l y computed and p r o v e t o b e n e g l i g i b l e a t p r e s e n t l e v e l s of e x p e r i -

m e n t a l a c c u r a c y . The e x p e r i m e n t a l upper l i m i t on phase d i f f e r e n c e between

C

t h e v e c t o r and a x i a l v e c t o r c o e f f i c i e n t s i s found t o be 0 . 3

.

A

similar h i g h s t a t i s t i c s s t u d y of muon p o l a r i z a t i o n e f f e c t s i n K + YIR decay

k p

S.B.

TRElMAN

:

WEAK 1NTERACTIONS

6

a n a l y z e d a b o u t a f o u r t h of some 3 x 10 e v e n t s . The components of muon

p o l a r i z a t i o n i n t h e p l a n e of decay p r o v i d e I n f o r m a t i o n on t h e r e a l p a r t

o f t h e c e l e b r a t e d p a r a m e t e r . The component normal t o t h e p l a n e measures

f

1 m

f

,

which a g a i n ought t o v a n i s h i n t h e absence o f T v i o l a t i o n . No i n d i c a t i o n of T v i o l a t i o n h a s y e t been d e t e c t e d h e r e .

The most e x p e r i m e n t a l l y p r o d u c t i v e p o s s i b i l i t y f o r symmetry v i o l a t i o n

would b e t h a t C and T i n v a r i a n c e a r e s u b s t a n t i a l l y v i o l a t e d i n t h e ( p a r i t y 1 8

c o n s e r v i n g ) e l e c t r o m a g n e t i c i n t e r a c t i o n s o f h a d r o n s

.

Two p o s i t i v e

i n d i c a t i o n s were r e p o r t e d some t i m e ago. W. Lee and c ~ l l a b o r a t o r s ~ ~ l o o k e d

+

-

f o r

I

,x

asymmetries i n t h e

$illo

decay mode of mesons produced i n t h e

-

3"

r e a c t i o n ~ f 4 f l ~ '

.

They r e p o r t e d a 1 . 5

2

0 . 5 % asymmetry f o r A = [N(E+FE-)

-

N (E-<E+)] 2 N . An i n t e r p r e t a t i v e d i f f i c u l t y h e r e a r i s e s from p o s s i b l e

i n t e r f e r e n c e produced by t h e s m a l l 3T continuum background under t h e

7

peak.

The experiment h a s s i n c e been r e p e a t e d a t t h e PPA and t h e r e s u l t s a r e

p r e s e n t l y b e i n g a n a l y z e d . Some t i m e ago a l s o , B a r t l e t t and Goulianos and

t h e i r c o l l a b o r a t o r s 2 0 s t u d i e d t h e r e a c t i o n fj#

_P

+d+f

a t s e v e r a l e n e r g i e s and made a d e t a i l e d b a l a n c e comparison w i t h t h e i n v e r s e r e a c t i o n t t d * ~ s t u d i e d

by o t h e r s . They found a 2 112 s t a n d a r d d e v i a t i o n d i f f e r e n c e i n t h e a n g u l a r

d i s t r i b u t i o n s f o r t h e e v e n t s i n t h e e n e r g y b i n around t h e N

+

N*(1236)

t h r e s h o l d . This experiment t o o h a s r e c e n t l y been r e p e a t e d a t t h e PPA and

t h e r e s u l t ' s a r e now b e i n g a n a l y z e d .

I n t h e meantime some new e v i d e n c e h a s been r e p o r t e d f o r what c o u l d b e

a v e r y s u b s t a n t i a l breakdown o f d e t a i l e d b a l a n c e i n e l e c t r o m a g n e t i c p r o c e s s e s .

C

Berardo e t . a1. 21 have measured 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 f o r

~ ~ + Y I ) L

,

a t center-of-mass e n e r g i e s 1337 Mev and 1245 Mev. I n f o r m a t i o n on t h e i n v e r s e

r e a c t i o n , o b t a i n e d e l s e w h e r e , h a s t o b e e x t r a c t e d , u n f o r t u n a t e l y , from

measurement of p h o t o d e u t e r o n c o l l i s i o n s . T h i s i n v o l v e s p r o b l e m a t i c d e u t e r o n

S.

B.

TREIMAN

:

WEAK INTERACTTONS

b a l a n c e i n f a c t works o u t w e l l f o r t h e h i g h e r e n e r g y c a s e (1337 Mev)

.

On

t h e o t h e r hand a t 1245 Mev, n e a r t h e N* r e g i o n , t h e d i s c r e p a n c y between

f o r w a r d and i n v e r s e r e a c t i o n s seems t o be s u b s t a n t i a l . F o r

@

)

90' t h e

B"rr

fpS*j(

d i f f e r e n t i a l c r o s s s e c t i o n i s s y s t e m a t i c a l l y s m a l l e r , by about 30%!