Quarks and Hadronic Structure

315 Pages·1977·6.096 MB·English

by  G. Morpurgo (auth.), G. Morpurgo (eds.)

QUARKS
AND
HADRONIC STRUCTURE
INTERNATIONAL PHYSICS WORKSHOP SERIES
Series Editor: A. Zichichi
European Physical Society
Geneva, Switzerland
Volume 1: QUARKS AND HADRONIC STRUCTURE
Edited by G. Morpurgo
QUARKS
AND
HADRONIC STRUCTURE
Edited by
G.Morpurgo
Istituto di Fisico dell'Universito
Genova, Italy
PLENUM PRESS· NEW YORK AND LONDON
Library of Congress Cataloging in Publication Data
Main entry under title:
Quarks and hadronic structure.
(International physics workshop series; v. 1)
In eludes index.
1. Quarks-Congresses. 2. Hadrons-Congresses. I. Morpurgo, Giacomo, 1927-
II. Ettore Majorana Centre for Scientific Culture.
QC793.5.Q252037 539.7'216 76-47490
ISBN 978-1-4684-0930-7 ISBN 978-1-4684-0928-4 (eBook)
DOl 10.1007/978-1-4684-0928-4
Proceedings of the International Workshop of the Ettore Majorana Center
for Scientific Culture held in Erice, Italy, September, 1975
© 1977 Plenum Press, New York
Softcover reprint of the hardcover 1 st edition 1977
A Division of Plenum Publishing Corporation
227 West 17th Street, New York, N.Y. 10011
All rights reserved
No part of this book may be reproduced, stored in a retrieval system,
in any form or by any means, electronic, mechanical, photocopying, microfilming,
recording, or otherwise, without written permission from the Publisher
Foreword
One of the activities of the Ettore Majorana Centre for
,Scientific Culture is the international advanced study courses on
scientific topics which are of particular relevance today. The
Centre is located in Erice, a mountain town in the province of
Trapani in Sicily. At present over seventy Schools of the Centre
are active, holding annual or biennial courses, so that about
forty courses are organized each year. To date some twenty thou
sand participants have attended the courses of the various Schools
of the Centre.
The International Physics Workshop Series has been established
to make the contents of the Workshops o'f great topical interest
available to those who were unable to attend them. The courses are
conducted on an advanced, post-doctoral level. This volume - the
proceedings of the session on "Quarks and Hadronic Structure" - is
the first of the Series.
In September 1975, thirty-three physicists from twenty-one
laboratories in nine countries met in Erice to attend the Workshop.
The countries represented were: Austria, France, Germany, India,
Italy, Poland, Switzerland, the United Kingdom, and the United
States of America. The purpose of this Workshop was to bring to
gether a group of theorists working on various aspects of the quark
structure of hadrons to discuss and critically evaluate the present
situation.
Professor Morpurgo was given the direction of the Workshop. I
would like to take this opportunity to thank him most warmly for
having accepted this responsibility and for the success of the Work
shop.
A. Zichichi
v
Preface
A glance at the table of contents and the names of the authors
will make it clear what this volume is about. There is no need
for further illustration -- all I could do is repeat the substance
of my introductory lecture, which was intended precisely to provide
a sort of annotated index.
The task of organ1z1ng the Workshop and editing this volume
was made easy by the cooperation of the lecturers. I am grate
ful for this to all of them. In particular, I thank warm~y
Professors R. H. Dalitz, H. Joos, and G. Moorhouse -- members of
the organizing committee of the Workshop -- for their invaluable
help in organizing the session and the details of its program.
I am also deeply indebted to Professor A. Zichichi, Director
of the Ettore Majorana Centre for Scientific Culture, for the es
sential support given during all the stages of the Workshop, from
the very beginning to the editing of these proceedings.
G. Morpurgo
Genoa, January 1977
vii
Contents
Open Problems in the Quark Model 1
G. Morpurgo
Electromagnetic Transitions of Nucleon Resonances,
Constituent Quark Theory, and the
Melosh-Gilman-Kugler-Meshkov
Parametrization • • • • • • • • • • • • • • . . •• 25
R. G. Moorhouse
The Spectrum of Baryonic States • • • • • • • • . • • • • •• 39
R. H. Dalitz
Null Plane Field Theory and Composite Models 73
J. S. Bell and H. Ruegg
Current and Constituent Quarks: Theory and
Practice 93
A. J. G. Hey
Current Quarks and Constituent-Classification
Quarks: Some Questions and Ideas •• • • • . • •• 137
F. E. Close
SU(6)-Strong Breaking: Structure Functions and
Small Momentum Transfer Properties of
the Nucleon • . • • • 167
A. Le Yaouanc, L. Oliver, o. Pene, and
J. C. Raynal
Relativistic Motion of Composite Systems with
Nonrelativistic Internal Dynamics 195
G. Morpurgo
Dynamics of the Meson Spectrum • • • • • • • • • . • • • •• 203
H. Joos
ix
x CONTENTS
Relativistic Quark Equations 225
R. G. Moorhouse
On the Formulation of Relativistic Hadron Couplings • • • • • 239
A. N. Mitra
Quark Dynamics in the SLAC Bag Model 249
R. C. Giles
Descriptions of Hadronic Structure 281
Y. Nambu
Appendix: Summaries of Seminars 293
. . . . ..
Participants 309
. . . . . . .
Index ••••• , , 311
OPEN PROBLEMS IN THE QUARK MODEL
G. Morpurgo
Istituto di Fisica dell'Universita - Genova
Istituto Nazionale di Fisica Nucleare - Sezione di Genova
1. Introduction
After ten years from the formulation of the realistic
quark model there is little doubt that the model has provided
a considerable insight in the hadron physics; but it is equal
ly sure that a large number of conceptual and practical ques
tions remains open.
Probably most of these questions might be answered rather
easily if we could meet the free quark and measure its proper
ties; its mass, its charge, its magnetic moment etc. But,
be~
cause this has not been so far the case (and, maybe, it will
never be the case) we continue to be confronted with a strange
and difficult situation,in some respects a paradoxical one:
quarks are not seen but many things go as if they existed.
Indeed there is now little doubt that, unless the free
quark is discovered, a satisfactory way out from this situation
will require some radically new idea; an idea which, of course,
will have to take into account the new spectroscopy being devel
oped in these days after the discovery of the J (3.1) and of
the f'(3.7) about which we shall hear more in this meeting.
Let me remark, incidentally, that this spectroscopy appears to
2 G.MORPURGO -
show already, as a subproduct, the usefulness of the non relativ
istic concepts; also if we do not still know if the objects
which are bound are charmed quarks, coloured quarks or perhaps
heavy leptons interacting through some medium strong interac
tion 1)
Meanwhile it seems appropriate to clarify as much as pos
sible the present status of the quark model so as to recognize
clearly its successes, its limitations and its difficulties.
This has been the motivation for this meeting; in these intro
ductory remarks, I confine myself to list a number of questions
which are going to be dealt in the talks and discussions which
follow. I may take the opportunity to express my personal point
of view on these questions but the main purpose of these short
remarks will be to give a logical order to the set of questions
which are going to be debated. The order by which I shall pro
ceed will be from the more clear or simple questions to those
which are less understood. Let me start with the classifica
tion of the states in the quark model.
2. Classification-of the states
a) Mesonic. Here I refer to the talk by A.P. French 2) at the
recent EPS Conference in Palermo. It is certainly very pleasant
that in addition to the 3-g(1680) meson a new h(2020) meson
with spin 4 and parity + has been established independently by
two groups, corresponding to an excitation of the L= 3 family.
It is however unpleasant that the problems with the 1+, 0+ fami~
ly all remain open. Only an optimist can, at the moment, see
clear evidence for these mesons. One should continue to keep
this point in mind.
b) Baryonic. I am not in the best position for analyzing the