We’ve been here before…

In April 1960, Prince Philip, husband of Queen Elizabeth II, piloted his Heron airplane to Geneva for an informal visit to CERN. Having toured the laboratory’s brand new “25 GeV” Proton Synchrotron (PS), he turned to his host, president of the CERN Council François de Rose, and struck at the heart of fundamental exploration: “What have you got in mind for the future? Having built this machine, what next?” he asked. De Rose replied that this was a big problem for the field: “We do not really know whether we are going to discover anything new by going beyond 25 GeV,” he said. Unbeknown to de Rose and everyone else at that time, the weak gauge bosons and other phenomena that would transform particle physics were lying not too far above the energy of the PS.

This is a story repeated in elementary particle physics, and which CERN Courier, celebrating its 60th anniversary this summer, offers a bite-sized glimpse of.

The first issue of the Courier was published in August 1959, just a few months before the PS switched on, at a time when accelerators were taking off. The PS was the first major European machine, quickly reaching an energy of 28 GeV, only to be surpassed the following year by Brookhaven’s Alternating Gradient Synchrotron. The March 1960 issue of the Courier described a meeting at CERN where 245 scientists from 28 countries had discussed “a dozen machines now being designed or constructed”. Even plasma-based acceleration techniques – including a “plasma betatron” at CERN – were on the table.

A time gone by

The picture is not so different today (see Granada symposium thinks big), though admittedly thinner on projects under construction. Some things remain eerily pertinent: swap “25 GeV” for “13 TeV” in de Rose’s response to Prince Philip, and his answer still stands with respect to what lies beyond the LHC’s energy. Other things are of a time gone by. The third issue of the Courier, in October 1959, proudly declared that “elementary particles number 32” (by 1966 that number had grown to more than 50 – see “Not so elementary”). Another early issue likened the 120 million Swiss Franc cost of the PS to “10 cigarettes for each of the 220 million inhabitants of CERN’s 12 Member States”.

The general situation of elementary particle physics back then, argued the August 1962 issue, could be likened to atomic physics in 1924 before the development of quantum mechanics. Summarising the 1962 ICHEP conference held at CERN, which attracted an impressive 450 physicists from 158 labs in 39 countries, the leader of the CERN theory division Léon Van Hove wrote: “The very fact that the variety of unexpected findings is so puzzling is a promise that new fundamental discoveries may well be in store at the end of a long process of elucidation.” Van Hove was right, and the 1960s brought the quark model and electroweak theory, laying a path to the Standard Model. Not that this paradigm shift is much apparent when flicking through issues of the Courier from the period; only hindsight can produce the neat logical history that most physics students learn.

Within a few years of PS operations, attention soon turned to a machine for the 1970s. A report on the 24th session of the CERN Council in the July 1963 issue noted ECFA’s recommendation that high priority be given to the construction in Europe of two projects: a pair of intersecting storage rings (ISR, which would become the world’s first hadron collider) and a new proton accelerator of a very high energy “probably around 300 GeV”, which would be 10 times the size of the PS (and eventually renamed the Super Proton Synchrotron, SPS). Mervyn Hine of the CERN directorate for applied physics outlined in the August 1964 issue how this so-called “Summit program” should be financed. He estimated the total annual cost (including that of the assumed national programmes) to be about 1100 million Swiss Francs by 1973, concluding that this was in step with a minimum growth for total European science. He wrote boldly: “The scientific case for Europe’s continuing forcefully in high-energy physics is overwhelming; the equipment needed is technically feasible; the scientific manpower needed will be available; the money is trivial. Only conservatism or timidity will stop it.”

The development of science

Similar sentiments exist now in view of a post-LHC collider. There is also nothing new, as the field grows ever larger in scale, in attacks on high-energy physics from outside. In an open letter published in the Courier in April 1964, nuclear physicist Alvin Weinberg argued that the field had become “remote” and that few other branches of science were “waiting breathlessly” for insights from high-energy physics without which they could not progress. Director-General Viki Weisskopf, writing in April 1965, concluded that the development of science had arrived at a critical stage: “We are facing today a situation where it is threatened that all this promising research will be slowed down by constrained financial support of high-energy physics.”

Deciding where to build the next collider and getting international partners on board was also no easier in the past, if the SPS was any guide. The September 1970 issue wrote that the “present impasse in the 300 GeV project” is due to the difficulty of selecting a site and: “At the same time it is disturbing to the traditional unity of CERN that only half the Member States (Austria, Belgium, Federal Republic of Germany, France, Italy and Switzerland) have so far adopted a positive attitude towards the project.” That half-a-century later, the SPS, soon afterwards chosen to be built at CERN, would be feeding protons into a 27 km-circumference hadron collider with a centre-of-mass energy of 13 TeV was unthinkable.

A giant LEP for mankind

An editorial in the January/February 1990 issue of the Courier titled “Diary of a dramatic decade” summed up a crucial period that had the Large Electron Positron (LEP) collider at its centre: Back in 1980, it said, the US was the “mecca” of high-energy physics. “But at CERN, the vision of Carlo Rubbia, the invention of new beam ‘cooling’ techniques by Simon van der Meer, and bold decisions under the joint Director-Generalship of John Adams and Léon Van Hove had led to preparations for a totally new research assault – a high-energy proton–antiproton collider.” The 1983 discoveries of the W and Z bosons had, it continued, “nudged the centroid of particle physics towards Europe,” and, with LEP and also HERA at DESY operating, Europe was “casting off the final shackles of its war-torn past”.

Despite involving what at that time was Europe’s largest civil-engineering project, LEP didn’t appear to attract much public attention. It was planned to be built within a constant CERN budget, but there were doubts as to whether this was possible (see Lessons from LEP). The September 1983 issue reported on an ECFA statement noting that reductions in CERN’s budget had put is research programme under “severe stress”, impairing the lab’s ability to capitalise on its successful proton–antiproton programme. “The European Laboratories have demonstrated their capacity to lead the world in this field, but the downward trend of support both for CERN and in the Member States puts this at serious risk,” it concluded. At the same time, following a famous meeting in Lausanne, the ECFA report noted that proton–proton collision energies of the order of 20 TeV could be reached with superconducting magnets in the LEP tunnel and “recommends that this possibility be investigated”.

Physicists were surprisingly optimistic about the possibility of such a large hadron collider. In the October 1981 issue, Abdus Salam wrote: “In the next decade, one may envisage the possible installation of a pp̅ collider in the LEP tunnel and the construction of a supertevatron… But what will happen to the subject 25 years from now?” he asked. “Accelerators may become as extinct as dinosaurs unless our community takes heed now and invests efforts on new designs.” Almost 40 years later, the laser-based acceleration schemes that Salam wrote of, and others, such as muon colliders, are still being discussed.

Accelerator physicist Lee Teng, in an eight-page long report about the 11th International Conference on High Energy Accelerators in the September 1980 issue, pointed out that seven decades in energy had been mastered in 50 years of accelerator construction. Extrapolating to the 21st century, he envisaged “a 20 TeV proton synchrotron and 350 GeV electron–positron linear colliders”. On CERN’s 50th anniversary in September 2004, former Director-General Luciano Maiani predicted what the post-2020 future might look like, asserting that “a big circular tunnel, such as that required by a Very Large Hadron Collider, would have to go below Lake Geneva or below the Jura (or both). Either option would be simply too expensive to consider. This is why a 3–5 TeV Compact Linear Collider (CLIC) would be the project of choice for the CERN site.” It is the kind of decision that the current CERN management is weighing up today, 15 years later.

Driving success

This collider-centric view of 60 years of CERN Courier does little justice to the rest of the magazine’s coverage of fixed-target physics, neutrino physics, cosmology and astrophysics, detector and accelerator physics, computing, applications, and broader trends in the field. It is striking how much the field has advanced and specialised. Equally, it is heartening to find so many parallels with today. Some are sociological: in October 1995 a report on an ECFA study noted “much dissatisfaction” with long author lists and practical concerns about the size of the even bigger LHC-experiment collaborations over the horizon. Others are more strategic.

It is remarkable to read through back issues of the Courier from the mid-1970s to find predictions for the masses of the W and Z bosons that turned out to be correct to within 15%. This drove the success of the Spp̅S and LEP programmes and led naturally to the LHC – the collider to hunt down the final piece of the electroweak jigsaw, the “so-called Higgs mesons” as a 1977 issue of the Courier put it. Following the extraordinary episode that was the development and completion of the Standard Model, we find ourselves in a similar position as we were in the PS days regarding what lies over the energy frontier. Looking back at six decades of fundamental exploration as seen through the imperfect lens of this magazine, it would take a bold soul to claim that it isn’t worth a look.