CERN Courier – July-August 2019

CERNCOURIER

CERNCOURIER.COM

OPINION

INTERVIEW

CERN COURIER JULY/AUGUST 2019 39

When was the first LEP proposal

made, and by whom?

Discussions on how to organise a

“world accelerator” took place at a

pre-ICFA committee in New Orleans in

the early 1970s. The talks went on for a

long time, but nothing much came out

of them. In 1978 John Adams and Leon

Van Hove – the two CERN Director-

Generals (DGs) at the time – agreed to

build an electron–positron collider at

CERN. There was worldwide support,

but then there came competition

from the US, worried that they

might lose the edge in high-energy

physics. Formal discussions about a

Superconducting Supercollider (SSC)

had already begun. While it was open

to international contribution, Ronald

Reagan’s “join it or not” approach to

the SSC, and other reasons, put other

countries off the project.

Was there scientific consensus for

a collider four times bigger than

anything before it?

Yes. The W and Z bosons hadn’t yet

been discovered, but there were

already strong indications that they

were there. Measuring the electroweak

bosons in detail was the guiding force

for LEP. There was also the hunt for

the Higgs and the top quark, yet there

was no guidance on the masses of

these particles. LEP was proposed in

two phases, first to sit at the Z pole and

then the WW threshold. We made the

straight sections as long as possible so

we could increase the energy during

the LEP2 phase.

What about political consensus?

The first proposal for LEP was initially

refused by the CERN Council because

it had a 30 km circumference and cost

1.4 billion Swiss Francs. When I was

appointed DG in February 1979, they

asked me to sit down with both current

DGs and make a common proposal,

which we did. This was the proposal

Looking forward Herwig Schopper believes that the next

machine has to be a world facility.

Lessons from LEP

with the idea to make it 22 km in

circumference. At that time CERN had a

“basic” programme (which all Member

States had to pay for) and a “special”

programme whereby additional funds

were sought. The latter was how the

Intersecting Storage Rings (ISR) and

the Super Proton Synchrotron (SPS)

were built. But the cost of LEP made

some Member States hesitate because

they were worried that it would eat too

much into the resources of CERN and

national projects.

How was the situation resolved?

After long discussions, Council said:

yes, you build it, but do so within a

constant budget. It seemed like an

impossible task because the CERN

budget had peaked before I took over

and it was already in decline. I was

advised by some senior colleagues to

resign because it was not possible to

build LEP on a constant budget. So

we found another idea: make advance

payments and create debts. Council

said we can’t make debts with a

bank, so we raided the CERN pension

fund instead. They agreed happily

since I had to guarantee them 6%

interest, and as soon as LEP was built

we started to pay it back. With the

LHC, Carlo Rubbia had to do the same

(the only difference was that Council

said he could go to a bank). CERN is

still operating within essentially the

same constant budget today (apart

from compensation for inflation),

with the number of users having

more than doubled – a remarkable

achievement! To get LEP approved, I

also had to say to Council that CERN

would fund the machine and others

would fund the experiments. Before

LEP, it was usual for CERN to pay for

experiments. We also had to stop

several activities like the ISR and the

BEBC bubble chamber. So LEP changed

CERN completely.

How do LEP’s findings compare with

what was expected?

It was wonderful to see the W and

Z discovered at the SPS while LEP

was being built. Of course, we were

disappointed that the Higgs and the

top were not discovered. But, look,

these things just weren’t known then.

When I was at DESY, we spent 5 million

Deutsche Marks to increase the radio-

frequency power of the PETRA collider

because theorists had guaranteed

that the top quark would be lighter

than 25 GeV! At LEP2 it was completely

unknown what it would find.

What is LEP’s physics legacy?

These days, there is a climate where

everything that is not a peak is not

a discovery. People often say “not

much came out from LEP”. That is

The Large Electron Positron collider (LEP) changed particle physics, and CERN, forever.

Former Director-General Herwig Schopper describes what it took to make LEP happen.

S Hertzog/CERN-PHOTO-201906-169-

I was advised

by some senior

colleagues

to resign

because it was

not possible

to build LEP

on a constant

budget

CCJulAug19_Interview_v3.indd 39 27/06/2019 16:

Photo: Perry Nordeng

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