Nuclear Physics B (Proc. Suppl.) 25B (1992) 1-8 North-Holland

PROCEEDINGS SUPPLEMENTS

OPENING ADDRESS

attho

INTERNATIONAL CONFERENCE ON ELASTIC AND DIFFRACTIVE SCATFERING

(4th Blois Workshop) May 22-25, 1991, lsola d'Elba, Italy

Basarab NICOLESCU

Division de Physique Th6orique*, Institut de Physique Nucl~ire, 91406 Orsay Cedcx and LPTPE, Universit~ Pierre et Marie Curie, 4 Place Jussieu, 75252 Pads Cedex 05, France

Ladies and gentlemen, colleagues and friends,

The local organizing committee of this Conference asked

us, Tran Thanh Van and myself, to give the opening

address. Unfortunately, Tran Thanh Van could not come to

this Conference, so I have to assume this difficult task.

Why do I say that this task is difficult? Well simply because

the organizers asked us to provide not only a brief history

of the Blois Workshops but also a simple description, in a

non-specialized language, o f the physics arguments

underlying those workshops. All the difficulty lies in these

two words: "simple description".

I~. ~ me begin with the beginning.

1. BRIEF HISTORY OF THE BLOIS WORKSHOPS

Already in 1983-84, Tran Thanh Van and myself, we

began to discuss about organizing an international

workshop on "Elastic and Diffractive Scattering". Our main

motivation can be formulated in the form of an axiom:

"what is fundamental remains fundamental whvtever

happens". I mean that our domain in question is a

fundamental domain of strong interactions. You can say

that the above axiom is so trivial and obvious, that one can

wonder why we spent almost two years discussing about

the opportunity to organize such a workshop. The

explanation is very simple: the quoted axiom is in fact

extremely obscure.

First of all, our modern times are characterized by the

well known fact that everything that was considered in the

past as fundamental is considered now as senseless or

accidental: God, truth, life, man, universe. That is the

reason why philosophers speak so much about death: death

of God, death of ideologies, end of history. To that,

physicists add the possible death of the universe (for

example, by the desintegration of the proton). In some

sense, our world appears as being a groundless world.

You can of course point out that we are doing physics

not philosophy and therefore one can forget about these too

general considermions which have nothing to do with our

field of interest. You are right, in a sense which has to be

made precise. After all we have in physics fundamental

laws and principles, fundamental building blocks of matter,

fundamental theories and fundamental experimental results.

However, in our days, something is considered as really

"fundamental" if it is connected to a fashionable, dynamical

theory. This is the link with the previous general

considerations. In the 1980's the relation between our field

and the universally recognized theory of strong interactions

- Quantum Chromodynamics (QCD) - was not at all clear,

for physical reasons I will fry to explain latter.

So, in few words, before the 1st Blois Workshop our

f ield of interest , considered by some of us as

"fundamental", was non-fashionable. That was the reason

why our domain was in a sort of lethargy. Therefore we

had to confront two dangers. The first, a relatively minor

one, was to find sufficient money to organize the

workshop. The second, a major one, was the possibility of

*Unit6 de Recherche des Universit6 Pads 1 l e t Pads 6, Associ6e au CNRS

Elsevier Science Publishers B.V.

2 B. Nicolescu / Opening address

an unsuccessful Conference, which ~ould provide a strong

argument for not working further in this field of strong

interactions. We had to assume a terrible responsability.

However, Tran Thanh Van and myself, we kept being

confident in the truth of our axiom. Moreover, interesting

experimental results were already obtained at the CERN

S~pS collider and we knew that exciting new experiments

were planned both at the CERH S~pS and at the Tevatron

coUiders. We bet on the future.

However, the most important fact was the moral help

we got from several physicists we contacted all over the

world. These physicists who provided us the courage of

organizing our meeting are now, most of them, in the

Permanent Committee of our Blois Workshops.

To our nice surprise several important French scientific

organisms gave us a decent sum of money to organize the

workshop. A very important condition of the success of the

meeting was, of course, the practical organization of the

workshop by Rencontres de Moriond, whose efficiency is

weli known.

Our feelings after the organization of the 1st Blois

workshop are perhaps best expressed in our foreword to

the Proceedings of the meeting: "Organizing in 1985 an

international workshop on elastic and diffractive scattering

was not an obvious idea. If this field is generally

recognized as being of fundamental importance for our

understanding of hadron interactions, it is only marginally

discussed in the major imemational conferences... We were

happy to see that the response of our community was

beyond our expectations. In fact, all individuals or groups

active in this field were present at our BIois meeting...The

future was much in prominence at the workshop,

stimulating a lot of excitement." We underlined here one

major condition of the success of our meeting: the response

of our community, which was beyond our expectations.

Last, but not the least, was the magical place of Chateau

de Blois.

We did not choose Blois in a random way. It was a

deliberate choice, based upon elaborate considerations.

First of all, we chose Chateau de Blois as a symbol of

the encounter between science and culture. C.P. Snow

introduced the famous expression "two cultures" of our

modern times: the humanistic culture and the scientific

culture, which never communicate between them. At our

modest scale, we wanted to show that this separation is

somewhat artificial.

At a perhaps more subconscious level, the Chateau de

Blois was somewhat like our own field: a magnificent

testimony of the past but empty, without life, good just for

guided tours. We made it full of life, having our sessions

inside the castle. A symbol of the life we expected in future

for our own field.

As you know very well, Chateau de Blois is a high

place not only of culture but also of the history of France.

We had our sessions in a nice room located on the 2nd

floor of Chateau de Blois. On the third floor occured a

tragic and important moment in the history of France: the

powerful rival of the king Henri llI, le duc de Guise, was

assassinated by 20 people paid by the king. This happened

in 1588, almost at the same time as in Italy, a young man,

25 years old, called Galileo Galilei, got the chair of

mathematics at the University of Pisa. It was of course

pleasant to think that four centuries later and one floor

down, we could solve rivalry problems not by murder or

killing but by more scientific objective methods.

The most important output of our Blois Workshop was

the collective proposal made by numerous participants to

transform the Blois meeting into a regular biennial event. In

fact, the Blois Workshop was really prolific: it generated

not one, but two series of Blois meetings. The first one is

our series of Blois Workshops which keep the name of

Blois, are organized all over the world and treat always the

same subject - Elastic and Diffractive Scattering. The

second one is known under the name "Rencontres de

Blois", parallel to the well-known "Rencontres de

Moriond". They are organized always in Blois and treat

various subjects in physics, astrophysics and biology. The

last meeting, in 1991, was a pluridisciplinary meeting on

origins of life.

Soon after the decision of transforming the Blois

meeting in a regular biennial event we formed the

Permanent Committee of our Blois Workshops. The

members of this committee are she following: Bernard

Auben (LAPP), Giorgio Belletini (Pisa), t Rodney L. Cool

(Rockefeller), Daniel Denegri (Saclay), Giorgio Giacomelli

(Bologna), Alan Krisch (Ann Arbor), Nicola N. Khuri

O. Nicolescu / Opening address 3

(Rockefeller), Andr6 Martin (CERN), Giorgio Matthiae

(Roma), Basarab Nicolescu (Orsay), Jay Orear (Comell),

John Peoples (Fermilab), Enrico Predazzi (Torino), J Tran

Thanh Van (Orasay), C.N. Yang (Stony Brook).

We can say that these physicists are the real fathers of

our Blois Workshops. The role of the Permanent

Committee is crucial in organizing the Blois Workshops

and I will describe it at the end of this section.

In pronouncing these names I feel a deep emotion

invading me when thinking of Rodney Cool, who is no

longer with us. Of course, I knew Rodney Cool as a

physicist longtime before he participated at the 1st Blois

Workshop. With big enthusiasm he accepted to be a

member of the Permanent Committee and to be the

chairman of the Program Committee ef the 2nd Blois

Workshop held in New York. I had the opportunity to

highly appreciate his human values. I think that Rodney

Cool will remain for all of us an exemplary case of man and

physicist.

For the further aspects of the history of the Blois

Workshops, I will insist more on experimental data

(number of participants, experimentalists, theorists etc.)

and on the evolution of our subject.

After the 1st Blois Workshop in 1985, three other

workshops were organized:

- 1987: 2nd Blois Workshop, New York, USA. Local

organizing committee: Konstantin Goulianos and Nicola

Khuri;

- 1989: 3rd Blois Workshop, Evanston, USA. Local

organizing committee: Martin Block, Roy Rubinstein,

Uday Sukhatme and Alan White;

- 1991: 4th Blois Workshop. lsola d'Elba, Italy. Local

organizing comittee: Stefano Belforte, France Cervelli,

Riccardo Paoletti, Cristina Vannini and Stefano Zuchelli.

The success of the previous meetings allow us to

predict the success of the present meeting.

Let us analyze first some experimental data.

One striking fact is the noticeable increase in the number

of participants as compared to the 1st Blois Workshop.

Another striking fact is the appearance of new names of

physicists who have become attracted by our Workshops

because of the evolution of the subject. This last fact is very

encouraging for the future of our Workshops.

60

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. . . . . . . . . . o . . . ° . B - " ' ° ~ ° ' " . . . . . " ~ ° ° " . L v OI

1985 I ~ 1989 1991 ~q~

FIGURE 1 Number of participants in terms of geographical regions.

In Fig.1 I show the number of participants in terms of

geographical regions. It is worthwhile to make two

remarks:

1) We can easily see the predominance of the "local"

physicists. This s a natural, but somewhat unpleasant

phenomenon and it has to be corrected. In other words we

need more money to pay travel or staying expenses for

physicists coming from countries located far from the

organizing counh-'y;

2) There is a quantum jump in the number of physicists

from Soviet Union: from O in 1985 to 13 in 1991. This

quantum jump corresponds to the only one increasing

function in Fig. 1. This is a good sign of changes in our

world and we hope ~hat everything will continue on this

line. It would be also desirable to have a bigger number of

participants, not only from URSS, but also from the

countries of Eastern Europe.

80 t number of p a ~ a n t s

0 , , " -'~ 1985 1987 1989 19911nww

FIGURE 2

The number of experimentalists vs the number of theorists

at the different Blois Workshops.

4 B. Xicolescu/Opening address

In Fig. 2, I show the number of experimentalists vs the

number of theorists at the different Blots Workshops. One

can also make two remarks:

1) There is a noticeable increase with time o f ~ e number

of experimentalists participating at our Workshops. This is

a very positive feature; 2) The mean value of the ratio experimentalists/theorists

over the last three Workshops is - 1.6, i.e. two times

bigger than that ar the 1st Blots Workshop. This is a

healthy value of the ratio.

Now, we have to understand the meaning of these

quantitative aspects through the qualitative changes which

already occured or will occur in our field.

Soon after the 1st Blots Workshop, Elliot Leader wrote

in the CERN Courtier: "...although asymptopia may be far

indeed, the path to it is not through a desert hut through a

flourishing region of exciting physics....". Such an

assertion could seem at that moment too optimistic. In fact

it was just realistic. I have in mind not only the many

interesting things which happened both in experiment and

theory in our field from 1985 till now but also the unique

possibility in the world to study at CERN both ~p and ~p

scattering at ultra-high energies. The name of this

wonderful machine is well-known: the Large Hadron

Collider (LHC).

In order to be alive, our Workshops have to adapt

themselves to the unavoidable changes occuring with time

in our field. In fact, they are nourished by these changes.

So, the highlight of the 2nd Blots Workshop held in the

New York was an exciting and extraordinary experimental

result obtained by the UA4 Collaboration at the CERN

S~pS collider~ It concerns the behaviour of the real part of

the pp amplitude at high energy. This result was a true

surprise for the majority of the physicists working in the

field of strong imeractions. If this experimental result is

really true, it would have extremely important

consequences both on theoretical and experimental level.

The emphasis of the 3rd Blois Workshop held in

Evanston was on a different aspect: theoretical progress in

our field. While confronting new and very important

experimental results obtained at the Tevatron, the meeting

centered more on theoretical problems. This fact was

reflected even by the slight but significant change of the title

of the Workshop: "Elastic and diffractive scattering - The

interface of soft and hard processes in QCD". In his closing

talk, Peter Landshoff underlined: "At this meeting there has

been much more emphasis on dynamics that there was at

Blots, and this is certainly a healthy development." This is

a capital remark. If we want to keep our field and our

Workshops alive we need to connect our venerable and

fundamental field of research with the modem theory of

strong interactions - QCD, i.e. with the dynamics

expressed in terms of quarks and gluons.

In this connection, it is interesting to note that in their

Foreword to the Proceedings of the 3rd Blots Workshop,

Martin Block and Alan White used a very happy expression

- "Berlin Wall" - to characterize the separation between

perturbative and non-perturbative aspects of QCD. This

expression was in fact premonitory: the Workshop occured

in May 1989, and only few months after the real Wall of

Shame disappeared, vanished. Let us hope that the physical

"Berlin Wall" will disappear also in a not too far future.

I can not obviously predict what will be the highlight of

the present Workshop. We have to wait few days and see.

But I think that I can safely predict that there would be

several interesting surprises.

Let me close this section by indicating how we are

functioning.

First of all we have, as l already said, the Permanent

Committee of our Workshops. It has the very difficult task

to define the scientific orientation of the meetings in terms

of the general changes in high-energy strong interaction

physics. It also has the very difficult task of choosing

between different organisation proposals for every next

meeting. I must tell you that we always had more than two

countries wanting to organize the next meeting. This very

healthy fact shows the interest of our community for our

Workshops.

1995 is a special date: the 10th anniversary of the Blots

Workshop. Several colleagues and friends already

suggested us that it would be natural to celebrate this

anniversary by organizing the 6th Blots Workshop back in

France, perhaps even in Blots. Of course Tran Thanh Van

and myself we are open to this possibility. However, the

Permanent Comm!ttee has to take the final decision.

A very important role is played by the International

B. Nicolescu / Opening address 5

Advisory Committee, whose composition changes from

one meeting to the other. It has to define the specific

scientific orientation corresponding to the given moment of

time, it has to define the scientific structure of the meeting

and it has to solve the main.problems of the practical

organisation of the meeting.

Of course, the hard work is done by the members of the

Local Organizing Committee. I think that we have to

congratulate all of them. They devoted so much of their

time and energy to the success of our meetings. They have

to solve hundreds and hundreds o f problems of

organization both on scientific and practical level and

clearly they solved them always in a nice and efficient way.

In any case, we can say, using the words of Konstantin

Goulianos in his foreword to the Proceedings of the 2nd

Blois Workshop, that our Workshops provide".., a home

for scientific exchange and progress in this specialized field

of physics."I very much like this word "home" because it

crystallises precisely what we had in mind when we

organized the 1st BIois Workshop.

2. WHAT WE ARE TRYING TO UNDERSTAND ?

In fact I already made previously several suggestions

about physical challenges underlying our Workshops. Now

I will try to make the point more precise but still in a

nonspecialized language.

Very often people ask to particle physicists: "What are

you really doing?" In order to answer we have to forget

equations, theories, data and to use everyday language. My

own children put to me, of course, the same question. I use

to answer: "We try to reconstruct the universe". They think

that it is a joke. It is in fact only half-a-joke.

A famous quantum law ~ves us the connection between the

energy spread of a quantum event and the spread in time or

distance. If we want to penetrate in a smaller and smaller

region of space or of time, we have to increase the energy.

Higher and higher energy accelerators bring us, in some

sense, backwards in time, towards the early universe.

Looking in a smaller and smaller region of space and time

we are in fact nearer of the physics of the early universe.

Why do we think that this kind of physics is extremely

interesting? The gates of the quantum world open at a

staggering small distance : -10 "13 cm. The unification of

strong, electromagnetic and weak interactions takes place at

a fabulous energy: -1015 times greater than the energy

corresponding to the mass of the proton. This energy

corresponds to an infinitesimal distance: -10 .29 cm. If the

proton was as large as the sun, this scale of unification

would be that of a speck of dust. The unification of all

physical interactions takes place at an energy still more

fabulous: 1019 times the mass of the proton, which

corresponds to an even tinier distance. These simple

considerations can give you a flavour of what the word

"asymptopia" can mean. Of course, this kind of energies

will be never obtained in our human-made accelerators:

there are technical barriers of impossibility. The best

accelerator was probably the cosmic accelerator of the early

universe, were all secrets of physics were clearly exposed.

Unfortunately at that time physicists were not yet present

My previous answer is of course too general. One has

m say what is really specific to our field of physics - Elastic

and Diffractive Scattering. For that, l will use again an

analogy with the early universe.

We know that if we approach the "origin" in time of the

universe, t = 0, everything blows up. Universe blows up,

but also equations of physicists blow up. We can speak

about extremely tiny times, like say t -10 .35 sec. However

we are not allowed to speak about the "origin" t = 0: time

itself looses meaning in this limit.

In strong interactions we have aiso a key-parameter,

called "momentum transfer", which characterizes the

transfer of momenta between colliding particles. By an

amusing coincidence the letter used for this key-parameter

is also 'T'. There is also something special about the regime

defined by t = 0 and high energy, which concerns our field

of interes) in some sense, the equations blow up towards

t=0. In fact, there is a kind of duality between small-t and

high-t regimes. At high-t the quarks, very close one to the

other, behave paradoxically like they were free, and allow

us to make clean computations, the corresponding

experimental events being rare ever, rs. On the contrary, at

small t, the strong interactions appear in their full splendor.

The experimental events are very abundant. There are also

crucial experimental and theoretical quantities ~ppearing

precisely at t = 0. There is only one annoying thing: uie~ is

a huge complexity of interactions in this regime, which

6 B. Nicolescu / Opening address

make theOretic',LI cnmputations extremely hard. It is very

fimpl¢ to understand the origin of this huge complexity: by

another paradoxical property, when two quarks are very far

one of each other, instead of separating and becoming free

(like everything in such a situation will do in ordinary life),

they are so attracted one by the other that they like to stay

together for ever, permanently confined in the hadron. In

order m realize their permanent community, the quarks will

do everything they can do in this aim and in such a way

they generate a huge complexity.

However, there is a difference with the impassable

barrier towards the origin of time of our universe. There is

an experimental proof that strong interactions do not blow

up at t = 0, when the scattering becomes "elastic": all the

experimental data concerning the strong interactions at t = 0

are finite quantities. The barrier between high-t and small-t

regimes is surely not impassable in Nature. Therefore, the

theory has to follow Nature and find out a way from the

present situation. In this important search, new theoretical

ideas are of course crucial, but also crucial are the expected

new experimental results to be obtained at the present

accelerators and the ones we hope to get at the planned new

accelerators, in order to guide our steps.

I hope that I have succeeded, even in an approximate

way, to give you a feeling about the beauty, the interest and

the importance of our field of physics. It is an exemplary

case of the encounter of tradition and modernity. However,

in order to make this encounter successful there is one

crucial interacting factor, new experimental data. Only then

our initial axiom will keep alive: "what is fundamental

remains fundamental whatever it happens".

3. FUTURE

We all know, from our ordinary life, that almost all our

predictions are wrong. Laymen, like the theoretical

physicists, are much safer in making ret~rodictions than

predictions. And even theorists, whose job is precisely to

make predictions, are relatively happy when they are

wrong, because this means that something really interesting

happens. So, I keep my predictions about what future

could bring to us for my physics t a i l I prefer to discuss

here just one point: the future experiments, in connection

with our Workshops. The reason is simple: without new

experimental data, panicle physics will become a branch of

metaphysics or a branch of mathematics.

We have the chance to expect in the near future new

interesting experimental results from the existing machines:

the CERN SppS and the Tevatron colliders. In fact, some

of them will be probably presented even at this meeting.

We also eagerly expect the realization o f experimental

projects at the future machines: UNK, RHIC, LHC and

SSC.

Let me underline just one fascinating possibility: that of

having both pp and pp options at LHC. at a cost

comparable or very ~lightly higher than that of having just

one option. Without any kind of chauvinism we have to

clearly state that the europeans will have here a unique

opportunity for a crucial experiment. This opportunity is

unique both in space and in time. In space, because

nowhere else in the world one can do such an experiment in

the multi-TeV region of energy and in time, because, at

least for the future century, one can not foresee such a

possibility from the technical and financial point of view.

Why do I say that this possibility is fascinating? It is, of

course, difficult to explain that in simple words. First of

all, let us note that we know, from various fields of physics

and even other sciences, that Nature seems to work by

keeping a very subtle balance between the respect of a

fundamental symmetry and a very small violation of this

symmetry. In its turn, the very small violation o f the

fundamental symmetry generates fundamental laws and

fundamental phenomena. Perhaps the most famous

example is given by the history of our own universe. The

very early universe was probably characterized by the

symmetry between matter and antimatter. An extremely

small violation of this symmetry, also compatible with the

known physical laws, was sufficient to lead rapidly to the

predominance of the matter over the antimatter. Finally,our

universe like it is now and also life could appear.

In a relatively similar way we can put the following

question: is the asymptotic symmetry of pp and pp

interactions accompanied by a violation of this symmetry ?

The asymmetry between pp and pp interactions would lead

to tremendous experimental and theoretical consequences.

At LHC we have a unique chance to study this problem. In

fact, we should win in both cases: either symmetry or

B. Nicolesca / Opening address 7

antisymmetry. Solving this problem of symmetry or

antisymmetry at a finite, multi-TeV region of energy, a

problem impossible to be solved by theory in its present

stage, will lead to a major progress for our understanding

of strong interaction physics.

Of course many of us present here dreamt or dream

about this fascinating possibility of having both pp and ~p

options in the multi-TeV region of energies. I begun myself

to dream about this possibility in 1972-1973. In 1976-1977

when I spent a long stay in Berkeley, we had the chance to

have as neighbours Bruno Autin and his family. Naturally

we begun to speak about this possibility. Several years

passed and from my discussions with the specialists of

accelerators I became more and more convinced that this

possibility is in fact realistic. Let me quote the conclusions

of Bruno Autin's talk at the 1st Blois Workshop in 1985:

"One of the highlights of this workshop devoted to elastic

and diffractive scattering is the interest of pursuing the

comparison between pp and ~p collisions...Another point

which is worth emphasizing is the great activity in the field

of stochastic cooling. Its use for either proton or antiproton

beams may open new realms to basic parameters like

luminosity or beam lifetime of any future machine."

Retroactively, these words sound prophetic. In our days,

the dream is very near to become reality. The specialized

talks at the recent Aachen Workshop on LHC are very

encouraging in this direction. Our community emphasizes

more and more the need for having both pp and ~p at LHC.

Let us hope that the physicists who will take the final

decision will recognize the fundamental character for the

future of strong interactions of having both ~p and pp at

LHC.

I do not know if the organizers chose Isola d'Elba for

symbolic reasons or just for practical reasons. In any case,

it is difficult to resist to think about one emperor who had

once a huge empire and who saw himself suddenly ruling

over just one island. One year later he went back to Paris in

triumph. I leave open to you all the many possible symbolic

interpretations of these facts.

I very much hope that this Conference will be an

extremely successful one, a milestone in the way of Blois

Workshops.

In the name of the Permanent Committee of Blois

Workshops, I would like to thank f'nst those who, by their

sponsorship, made this Workshop possible: The islimto

Nazionale di Fisica Nucleate (INFN), the Italian Physical

Society (SIF), the European Physical Society (EPS), the

University of Pisa and the University of Bologna. We are

really honoured that otir Conference is sponsored by such

prestigious institutions.

I would like to thank also very warmely the

International Advisory Committee and the Local Organizing

Committee, who did a hard and efficient work both on

scientific and practical level.

I thank also the members of the secretariat - Susanna

Antichi, Monica Fagioli, Adriana Guerrieri and Paola

Z a i o n e - who spent, I am sure, much energy for the

organization of this Conference. In fact, their work will

continue in the next days and even after the Conference

when, together with the members of the Local Organizing

Committee, they will take care of the important task of

editing our Proceedings.

Let me finally thank all of you who participate at this

Conference. You are in fact those who, by your active

presence, bring life to our Blois Workshops.

REFERENCES

1. Proceedings of the I st Blois Workshop on Elastic and

Diffractive Scattering, Chiteau de Blois, France, 3-6

June 1985, edited by B. Nicolescu and J. Tran Thanh

Van, Editions Fronti~res, 1986.

2. Proceedings of the 2nd Blois Workshop on Elastic and

Diffractive Scattering, New York, USA, 15-18

October 1987, edited by K. Goulianos, Editions

Fmnti~res, 1988.

3. Proceedings of the 3rd Blois Workshop on Elastic and

Diffractive Scattering - The Interface of Soft and Hard

Processes in QCD, Evanston, USA, 2-6 May 1989,

edited by M.M. Block and A.R. White, Nuclear

Physics B (Proc. Suppl.) 12 (1990).

8 B. Nicolescu / Opening address

4. Proceedings of the ECFA Large Hadron Coilider

Workshop, Aachen, Federal Republic of Germany, 4-

9 October 1990, vols. IoIlI, edited by G. Jarlskog and

D. Rein, CERN 90-10/ECFA 90-133, 3 December

1990. See, in particular the talks given by D. Denegri,

E. Leader and G. Matthiae.