The LHC marks perhaps a transitional phase into world-wide collaboration. Some 30% of the signatories to the two proton-proton experiments are from non-member states. There are 73 nationalities working in institutes in 54 countries. Of these the USA accounts for 507 people. Russia 362, Canada 60, India 42, Japan 38, China 34, Georgia 31, Belarus 28, Israel 22 and Bulgaria 22. All have different local resources, histories and possibilities. No single structure for cooperation agreements will suit all these. The political dimensions have developed both within countries and in supranational structures.
The European Committee for Future Accelerators (ECFA) has provided an important forum for developing proposals for new machines, whether at CERN or elsewhere. It has a brand-new counterpart in Asia (ACFA). The International Committee for Future accelerators (ICFA) provides a mechanism for cooperation between the directors of major accelerators world-wide. ICFA has blessed the formalisation of collaboration on the development of accelerator techniques for future linear electron-positron colliders: 23 laboratories in Asia, Russia, USA and CERN member states are involved. Comparison of LEP and the TeVatron shows that the reach in energy of the proton machine is higher, but that electron machines can grasp specific topics with great precision. The top-quark discovery [14] creates complementary virtues in proton-proton and electron-positron machines.To reach energies of 250 GeV or more in a reasonable length (say 20 km) accelerating fields over 10 MV/m are needed, and at a cost we can afford. Once this technical work has succeeded, it is more than likely that the strong support of laboratory directors in several major countries will be needed if such a project is to gain the required breadth of support across governments.
The alternatives to cooperation are atrophy, or at best external direction and delay. The OECD Megascience Forum has looked at Particle Physics, and has flirted with the idea of baskets of projects across a range of fields. (Reference [15] provides some background.) This might be attractive at a time of rapidly increasing wealth, but can run into the sand at times of stringency. The International Union of Pure and Applied Physics has argued strongly that science should not be the exclusive preserve of the wealthiest nations.
One of the products of Particle Physics most valued by governments is highly trained manpower. In the United Kingdom it is viewed in the following way. Students commence Ph D training at age 22 after four years of undergraduate training. They are financed for three years, and expected to complete their work promptly. Indeed the Universities are subject to penalties if students take more than four years. Compared with countries where the Ph D takes much longer, there are plenty of good applicants and when they finish their Ph D's their training is valued by employers. Working in a multi-national collaboration gives them leading-edge technical skills, project management skills, communication skills, team-working skills and self reliance. With Physics in its present stage of evolution, we have an excellent case for the number of research students to be increased.
Throughout the changes in Particle Physics since 1947, our techniques have always pursued the most advanced technology. We must conclude that international collaboration has proved a robust tool. It increases both the strength and the quality of the activity. Particle Physics has maintained its vigour, its scientific excellence, and its educational value. It has withstood rigorous scrutiny. We have every reason for confidence in the future, provided that we understand the changing environment in which our work takes place.
Figure 1: SPEAR magnetic detector. (a) schematic layout (b) a event of the type
;
. From the pattern of tracks, this was
jokingly called the `auto-signature' mode of the 
.
Figure 2: An event reconstructed in the ALEPH detector - main view is of the
event seen in the Time Projection Chamber, with the electromagnetic
calorimeter, hadron calorimeter and muon detectors in successive layers
around it. The vertex region, as reconstructed using
the vertex detector is shown on the right, with a 3mm flight path from
the interaction point to the Bs decay vertex.
See text for details of the event.
Figure 3: Trigger and Data Acquisition structure of the ATLAS experiment
being developed for the LHC
Figure 4: ZEUS (HERA) trigger rates as a function of luminosity. FLT - first
level trigger, SLT - second level trigger, TLT = third level, output to
tape.
Figure 5: Layout of the CMS detector as proposed for the LHC
Figure 6: A simulated event pictured in the central part of the ATLAS inner
detector. The inner layers are silicon tracking detectors with 80 
m
granularity. The outer layers are 4 mm diameter proportional drift tubes
(`straws') The event shown is at a luminosity of 
, and includes the production of a B0d meson decaying to 
,
with 
.