11. London

“At the round earth’s imagined corners, blow
Your trumpets, Angels, and arise, arise.” – John Donne, Holy Sonnets.

Jim had already been professor at UCL for several months by the time he delivered his formal inaugural lecture at the Chemistry Theatre in Gower Street, with the Provost presiding. “Students of the University and others interested in the subject” were invited, “Admission free without ticket.” The lecture topic was ‘Advances in Elementary Particle Physics’.

With Patrick around 6 months old, the family moved to Epsom in the summer of 1961. Epsom lies about 15 miles southwest of the centre of London and at that time was an observably distinct town; since then the suburban sprawl of south London has absorbed many of the intervening gaps. The new home was on West Hill, the B280 : the road was busy at times, though likely much busier today. Just down the hill from the house was a pond, a village green where there would be games of cricket played, and a pub, unsurprisingly named ‘The Cricketers’. Further on lay Epsom Common, a large area of undeveloped land. One had the impression at the time that the place the family had moved to was semi-rural.

It was only a short walk along the east side of the common to a footbridge over a railway line. One Saturday morning, soon after the family’s arrival at Epsom, found Jim and the older son crossing the bridge just as a steam locomotive was approaching. This would have been a rarity by the time of the 1960s, most of the steam locomotives having been replaced by diesel units. The boy was concerned that waiting on the bridge for the locomotive to pass underneath might be dangerous – that the belching steam would be scalding. Jim explained briefly that this would not be so, and a cloud of steam enveloped the chuckling pair.

The centre of London had become a frantic place during the working week. Always too many people and always too much traffic. Jim remarked to Bill Woolcock that : “the number of collisions in a city increases as a square of the density of the population.” Though Jim occasionally would need to drive into London, he usually commuted from Epsom to London by train. His fellow commuters were mostly civil service or City types and nearly all wore a uniform of pin-striped suit and bowler hat. Jim usually wore grey trousers and tweed jacket.

Massey had returned to UCL in 1950. Jim’s old friend Bates had resumed at UCL in 1945, but in 1951 had returned to Queen’s, Belfast, where he also founded a Department of Applied Mathematics and Theoretical Physics. At UCL Jim immediately established the new ‘High Energy Physics Group’. There were six students at the outset; Woolcock and Spearman who had accompanied Jim from Cambridge, Geoff Oades and Lance Vick who had both just completed their bachelor degrees at UCL, John Kennedy and Pietro Menotti. Kennedy was a first year postgraduate student from Queen’s Belfast and Menotti was a visiting student on leave of absence from Pisa. Woolcock recalls that the six of them were all crammed into one rather small room.

The connection between Jim and Pisa was via Ernesto Corinaldesi. Corinaldesi, from Locri in Italy, had arrived as a research fellow in quantum mechanics at Manchester in 1949 and overlapped with Jim for a portion of that year. Obtaining his Ph.D. in 1951, he had then taken fellowships at Ottawa and Princeton prior to accepting an assistant professorship at DIAS in 1954. Perhaps his homeland was calling him, for he stayed in Dublin only a year and a half. He had obtained a lectureship at Pisa in 1957.

Jim was now a world-leading expert on elementary particle physics and immediately the group was very active. For the year 1960-61, the last year of his Ph.D., Bill Woolcock was working on three fronts. Following his successful work published in ‘Low Energy Pion Phenomena’, Jim had left him to his own devices for a while. In that time Bill came up with the idea of using an un-subtracted dispersion relation in order to calculate directly the pion-nucleon coupling constant. This led to calculation of reliable values for s- and p-wave scattering lengths and of the amplitudes of those waves. When Woolcock told Jim about this, he was immediately drawn into research with Jim, Spearman and Menotti on the use of partial-wave dispersion relations for the s-wave, where his work was used to improve the calculations. The four of them had their work published, in February 1961, in ‘Evidence for Pion-Pion Interactions from S-wave Pion-Nucleon Scattering’ (Nuovo Cimento 20, p.519).

Also that year Woolcock was required to write up his thesis, a tome which incorporated all his work from ‘Low Energy Pion Phenomena’ through to ‘Evidence for Pion-Pion Interactions from S-wave Pion-Nucleon Scattering’. The thesis was submitted in June, then, after a short break, he returned to assist Jim with the writing up of ‘S-wave Pion-Nucleon Scattering and Pion-Pion Interactions’ (Annals of Physics, 17, p.1) which was published in 1962. The paper refers back to ‘Low Energy Pion Phenomena’ and the s-wave phase shift work from ‘Low Energy Pion Scattering’ and uses Woolcock’s more accurate calculations.

The work for ‘Evidence for Pion-Pion Interactions from S-wave Pion-Nucleon Scattering’ and ‘S-wave Pion-Nucleon Scattering and Pion-Pion Interactions’ was also summarised in ‘Low-Energy Pion-Nucleon Scattering and Pion-Pion Interactions’ (Proceedings of 1961 Aix-en-Provence Conference on Elementary Particles, p.351) by Jim, Menotti, Spearman and Woolcock.

After assisting Jim with ‘S-wave Pion-Nucleon Scattering and Pion-Pion Interactions’, Bill Woolcock had to return to Brisbane in August 1961, due to an illness in the family (he took up a lecturing position at Queensland University). There had been no time to prepare the work on fixed-momentum dispersion relations (in which he had discovered that one could use an un-subtracted dispersion relation) for publication. Jim knew that this work was too important to be left lying in a thesis and took on the job of writing it up himself, for which Bill says “I am forever grateful.” Jim reviewed the high-energy behaviour of the scattering amplitudes, its consequences for the number of subtractions required and also reviewed the convergence problems, showing where Bill’s calculations could be trusted and where they became unreliable (the rates of convergence are of basic importance for the prediction of low-energy pion-nucleon phase shifts by dispersion relations – Jim later said : “Convergence difficulties arise in various practical problems in pion-nucleon analysis, and it is unwise to ignore them.”

Their paper, ‘Determination of Pion-Nucleon Parameters and Phase Shifts by Dispersion Relations’ (Rev. Mod. Phys. 35, p.737), published in 1963, became one of the most quoted papers in pion-nucleon physics. The paper became a Citation Classic, being cited over 330 times between 1963 and 1985. In ‘Current Contents : Physical, Chemical and Earth Sciences’, 26, no.7 (from 17th February 1986), Bill wrote : “The paper brought together in a comprehensive way the theoretical and practical aspects of fixed momentum transfer dispersion relations for the pion-nucleon system. It gave precise numerical values of the parameters and low-energy phase shifts, quantities that are needed for many other investigations. That is no doubt why the paper was so often cited.”

David Spearman had also completed his thesis. He returned to Ireland to get married, then went to America for a year as a postdoctoral researcher before returning to a lectureship at Durham. Later he moved back to Ireland again, taking a professorship at Trinity College, Dublin. After the departure of Woolcock and Spearman a new Ph.D. student arrived, Andrew Lea. Jim also took responsibility for supervising David Atkinson, a Cambridge student.

Meantime Jim had been involved in parallel work with the other half of the group, Menotti, Oades and Vick. The 1962 publication ‘Pion-Nucleon Scattering and Pion-Pion Interactions’ (Phys. Rev. 128, p.1881) improves upon the methods Jim had developed with Spearman in ‘Low Energy Pion Scattering’ (Annals of Physics, 12, p.172) and discusses how the results could be regarded as a fairly good physical proof of the Mandelstam representation. There is a considerable contribution by Claud Lovelace concerning discrepancies.

In early 1962 Jim was again in Russia, first in Leningrad and then Moscow. ‘Moscow News’ from 24th March carried a photograph of Jim delivering a lecture at the University (Jim shared a page with a piece by the Chargé d’Affaires of the Iraqi Republic in the Soviet Union, titled “Freedom Day in Iraq” which celebrated the third anniversary of Iraq’s withdrawal from the Baghdad Pact). From Jim’s visit to Moscow there is also a photograph of Pomeranchuk lecturing at the Steklov Institute, Jim sitting at the front beside N.N. Bogoliubov.

Yuzik Pomeranchuk had in 1935 joined a new centre of theoretical physics in Kharkov led by Lev Landau and became a close friend and collaborator of Landau’s (Landau had earlier spent some years at the University Institute of Theoretical Physics in Copenhagen and had been inspired to set up a similar centre in the Soviet Union). By May 1943 Pomeranchuk was working in what later became the Kurchatov Institute in Moscow on the first Soviet nuclear reactor, which culminated in the completion of a reactor in 1946. In the 1950s, after being obliged by Stalin to spend a year in the atomic weapons centre at Arzamas-16, his work focused on quantum field theory and using dispersion relations he was able to prove the ‘Pomeranchuk Theorem’ on the cross-sections of particles and anti-particles. In a later paper Jim refers to a publication by Pomeranchuk (1956, Soviet Phys. J.E.T.P. 3, p.306).

It was perhaps during this visit to Moscow that Jim, on returning one evening to his hotel room, had discovered that a note had been pushed under the door. There was someone sitting downstairs in the lobby who wanted to speak to him urgently. There was no hint as to the identity of the writer, so Jim ignored it. Anybody from the University who needed to contact him would be able to do so without this subterfuge. To agree to a clandestine meeting could cause him considerable personal difficulty and might compromise the whole conference program.

Transactions in currencies other than roubles were strictly forbidden : pro-western black market dealers loved to get their hands on foreign currency, particularly US dollars, and often approached visitors (who would be easily distinguished by their western-style clothing). On one occasion, not knowing where to buy tram tokens, Jim approached a member of the public at the tram stop. In fear of being observed, the citizen simply gave Jim a token and walked away without saying a word.

Later in the summer Jim briefly visited Annecy and Chamonix and attended the 1962 CERN International Conference on High-Energy Physics. Among those at the conference were Lovelace and Masson from Imperial College. Jim had fostered co-operation between his High Energy Physics Group at University College and the physicists at Imperial College (where Abdus Salam, his ex-Cambridge colleague, was professor). Around this time several publications involved collaborations between the colleges. Claud Lovelace would later take up a staff position at CERN.

Around September 1962 Sandy Donnachie arrived at UCL to take up a lectureship. Donnachie was from Glasgow and co-authored two papers with Jim, the first of which was received by the publishers in September 1963, so Donnachie’s arrival one year earlier seems plausible. Again, the writer was unable to obtain confirmation of the precise date, but it is likely that Brian Martin arrived at UCL as a Ph.D. student also in September 1962 (having graduated at Birmingham). When Jim left to take up a position at Nordita in September 1964, he arranged a place at the Copenhagen University Institute of Theoretical Physics for Martin, in order that Martin could complete the last year of his Ph.D. September 1962 therefore seems a reasonable estimate for Martin’s arrival at UCL. Another research student who joined the High Energy Physics Group at about this time was Graham Shaw, who worked with Donnachie for a while.

The Nordic Institute for Theoretical (Atom) Physics, or Nordita, was founded in 1957 by Niels Bohr and Torsten Gustafson (professor of theoretical physics at the University of Lund and science policy advisor to the then Swedish PM, Tage Erlander). Located for its first fifty years in Copenhagen (Nordita moved to Stockholm in 2006), its original fields of research were nuclear physics and elementary particle physics (the research program was later extended to include astrophysics, biophysics and condensed matter physics).

Nordita is not to be confused with what until 1965 was the University Institute of Theoretical Physics in Copenhagen. From 1965 the latter place has officially been called the Niels Bohr Institute (though many had been referring to it as ‘Bohr’s Institute’ long before then). NBI had started off in 1921 as a university department for theoretical physics and had received additional funding from private sources, notably the Carlsberg Foundation.

The idea of Nordita was conceived not long after the end of World War II – there was a general desire among physicists in Scandinavian countries to participate together at a ‘centre of excellence’ – very much in accordance with Niels Bohr’s philosophy to share the knowledge of the atom. At that time there were also discussions around Europe about establishing a European Nuclear Research Centre (CERN) and the CERN Theoretical Study Group was initially located at Copenhagen in 1952 : there would have been considerable overlap with the proposed Nordic Institute, so plans for Nordita were shelved. Then in 1957, when the CERN theoretical group relocated to Geneva in order to be closer to the CERN experimental group, the Nordita idea was back on. Within a year the new Institute was established, with funding from the Nordic Council of Ministers and the Danish State. Since its move to Stockholm, half of Nordita’s funding is still contributed by the Nordic Council of Ministers, the remainder being shared by Stockholm University and the Royal Institute of Technology (KTH).

During 1962 Jim was contacted by Nordita. Still a young institute, Nordita had ambitions to expand its research in elementary particle physics. Niels Bohr was the first chairman of the Nordita board and though he died in November 1962, it seems fair to assume that Bohr had sanctioned Nordita’s approach to Jim. Niels Bohr and Christian Møller both knew Jim from his earlier visit to Copenhagen in 1947, also Léon Rosenfeld had returned from Manchester in 1958 to take a professorship at Nordita. It would have been well known at Nordita that Jim had become one of the world’s leaders in particle physics and that he had built successful research groups at Cambridge and UCL. Jim was invited to visit Nordita for discussions with Nordita director Christian Møller and others. These discussions would result in Jim taking leave of absence from UCL during the spring of 1963 in order to spend five months in Copenhagen, to allow both parties to get to know each other better.

The older son was often left to his own devices. Patrick was still very much a youngster, so it was best for all concerned that the older boy wasn’t hanging around and being a nuisance. During the 1962-3 winter the pond was frozen for many weeks, and at times the ice was thick and would support children sliding across on milk crates. Though Jim had walked with the boy on the ice during one of the coldest periods he warned him not to attempt this on his own, rightly fearing that the boy’s judgement of the thickness and quality of ice might not always be sound. Sure enough, Jim’s fears were realised. The boy must have been talking about the pond to two school friends, brothers, and the three had between them decided to visit the place after school. One of the brothers went through the ice, but fortunately close enough to the bank for the other boys to pull him out. They all quickly returned to the Hamilton house, it being the nearest of their two homes, so that the wet one could get a change of clothes and warm up a little. Jim immediately asked the two dry members of the group whether there had been anybody else with them who had fallen in. That was all he wanted to know, he wasn’t concerned with reproaches.

The family all travelled with Jim to Midlothian for the 1963 Scottish Summer School. Accommodation for families was at Newbattle Abbey, close by Dalkeith and some five miles from Edinburgh. It rained only once, but the period of rain spanned almost the entire week of the summer school. Jim wrote a review article in ‘Strong Interactions and High Energy Physics’ from this summer school.

Glen’s mother had died during the winter of 1962-3, and a few months later her father sold up the house at Verwood and emigrated. With no longer any particular reason to visit Dorset, the family spent some weeks of each of the next two summers in Donegal. Joe Hamilton, aged 79 in 1963, had been in the process of running down the business in Larne in preparation for selling up and retiring to the house at Tullaghcullion. He had been, bit by bit, moving items from Larne to Donegal, a car journey of some three or four hours, and spending some time at Tullaghcullion making the house habitable. When the Scottish Summer School finished, the family journeyed over to Ireland, a considerably shorter distance from Dalkeith than from Epsom.

Jim would very much look forward to these visits, as did the family. Jim was able to catch up on local news with Joe and Bertie and could help Joe with work on the house while the two older children assisted Bertie’s sons, Willie and Eddie, with the cows. Such visits were also an opportunity for Jim to show the family around Donegal, along the coast to Slieve League, stopping for a swim at Fintragh Bay on the return journey, or north up to Burtonport, where his mother Jessie had spent some years of her childhood.

Also he would take the family further afield, driving down through Sligo to Mayo and Galway, along routes he had cycled as a teenager. In Mayo, travelling from Louisburgh to Leenane, the road gradually climbs (it is not so difficult to cycle this route) to a bealach, nearly 900 feet above sea level, between the Sheffrey Hills on the left and the peak of Mweelrea to the right. There is a feeling of great peace in this place, known as Dhulough Pass. The road then runs beside Dhu Lough for a time before passing through a settlement called Delphi and dropping down to Killary Harbour, Lennane and Galway beyond. The stretch between Louisburgh and Leenane is also the route known simply as the ‘Famine Walk’, where in 1847 dozens, maybe hundreds, of famine victims died out in the open during bitter winter conditions. It is said that the Poor Commissioners at Delphi Lodge were having dinner, and wouldn’t be disturbed, and that they instructed the guards to chase away the starving, frozen people. Each year in March there is a walk to commemorate the event and there is also a plaque near Delphi, inscribed with Mahatma Gandhi’s words : “How can men feel themselves honoured by the humiliation of their fellow beings ?”

In September 1963 Jim again visited CERN in Geneva, before the start of the new academic year. Close on the heels of the CERN visit (in October) came the news that the Nordita board had approved his appointment as professor. To allow Jim time to properly conclude his work at UCL, the appointment would commence in October 1964. One of Jim’s foremost concerns was that his research group at UCL should continue to flourish after his departure.

At the time of Bill Woolcock’s departure to Brisbane, in August 1961, Jim had said that, when the time was right for Bill to return to England, he should contact Jim. Jim would try to arrange a lectureship at UCL for him. Woolcock had indeed contacted Jim, towards the end of 1962, Jim had discussed the issue with Massey, and in due course the appointment had been agreed, to commence January 1964.

Günther Rasche arrived from Zürich in February or March 1964. He had met Jim the previous year at one of the legendary Black Forest meetings (Rasche explains that the 1960s Black Forest meetings became legendary amongst pion-nucleon physicists because every second year or so the assembled researchers would produce tables with the latest numerical values for various constants – these would be very useful for many different lines of investigation) and Jim had invited him to come to UCL as a visiting research assistant. Though Jim would only be at UCL for a further 6 months, Rasche’s visit worked out well. Jim had arranged for the US Air Force funding to continue after his departure, and Rasche was able to remain at UCL for some time longer. He and Woolcock soon became good friends and are still in collaboration at the time of writing, 44 years on.

How did Jim’s group see him ? Bill Woolcock writes : “I got along with him pretty well. He had a rather gruff manner which I found off-putting at first, but I got used to it. He could be stubborn, and resistant to points of view different from his own. He was known to argue strongly against a new idea, only to turn up some time later and present it as if it was a new idea of his. We had some strong arguments and Rasche and I could not shake his faith in the N/D method. I owe him a great debt for introducing me to physics research, for many stimulating discussions about our work together, for getting me the lecturer position at UCL, and above all for the huge task of writing that review paper which became so well known and widely quoted. I should say that, in all the work we published together, we were always able to come to agreement about every point in the final text.”

Stubbornness aside, it appears that Jim was consistently a unifying force : this is illustrated during his time at London by the co-operation he encouraged between University College and Imperial College, and would later be evident in the collaboration he built up among physicists in Scandinavia and further afield.

As for the N/D method, this was a method developed in 1960 by Chew and Mandelstam (Phys. Rev. 119, p.467) which sets up integral equations for N-functions and D-functions. Jim’s 1964 collaboration with Sandy Donnachie ‘Semi-phenomenological Solutions of Pion-Nucleon Partial-Wave Dispersion Relations’ (Phys. Rev. 133, p.B1053) warns of disadvantages in using the N/D method for solving partial-wave dispersion relations and instead proposes a variational method of solving pion-nucleon dispersion relations, an application of the method confirming earlier analysis of s-wave pion-nucleon scattering. There is caution about the variational method too : “The only problem about the solution is the validity of the short-range interaction term which is used. Crossing of the real part of the amplitude verifies that it is accurate, but it is not obvious why the variational method should give such a good result.”

Another paper published in 1964 was Jim’s collaboration with Donnachie and Lea ‘Prediction of p-, d- and f-Wave Pion-Nucleon Scattering’ (Phys. Rev. 135, p.B515). In this work they developed a peripheral method, in which the very short range part of the interaction was almost completely suppressed, for predicting pion-nucleon shifts up to moderate energies. Precise values are given for the p-, d- and f-wave phase shifts. In ‘On Mesons and Methods’ Jim later says of this work : “It turned out within two years that a polarization measurement was wrong, and the theory prediction was indeed correct. The theoretical small partial wave amplitude predictions were taken up by Claud Lovelace and Sandy Donnachie (1964, Phys. Lett. 12, p.76 and 1965, Phys. Lett. 19, p.146) and improved to form a powerful tool in selecting the correct solution out of the numerous ambiguities which appeared in the large pion-nucleon phase shift analyses made in the late 1960s.”

Also in 1964, Jim’s 89-page review article ‘Applications of Dispersion Relations to Pion-Nucleon and Pion-Pion Phenomena’ was published in ‘Strong Interactions and High Energy Physics’ (ed. Moorhouse, Oliver & Boyd). The article comprises texts of lectures in three main sections. The first section deals with the use of forward and fixed momentum transfer dispersion relations to determine the main parameters of low energy pion-nucleon physics from the experimental data, as described in the paper with Woolcock ‘Determination of Pion-Nucleon Parameters and Phase Shifts by Dispersion Relations’. Additionally there are references to methods developed by Atkinson and by Höhler and Dietz. The second section discusses the use of partial wave pion-nucleon dispersion relations to derive information about low energy pion-pion interactions, primarily the work presented in ‘Low Energy Pion Scattering’; ‘Evidence for Pion-Pion Interactions from S-wave Pion-Nucleon Scattering’; and ‘Pion-Nucleon Scattering and Pion-Pion Interactions’. The third section examines the validity of the N/D method and looks at the variational method described in ‘Semi-phenomenological Solutions of Pion-Nucleon Partial-Wave Dispersion Relations’.

Jim published two further papers from his work at UCL, both in 1965 and both collaborations with Sandy Donnachie. ‘The Quantum Numbers of the Nucleon Isobars’ (Annals of Physics 31, p.410) discusses the quantum numbers of the 200, 600, 900 MeV and 1.35 BeV nucleon isobars and shows that they are determined by the systematic properties of the longer range parts of the pion-nucleon interactions. There is reference to Regge’s work (1951, Nuovo Cimento 14, p.951 and 1960, Nuovo Cimento 18, p.947), and interpretation of the Regge plot in terms of the interactions which produce the several families of isobars.

‘Very Short Range Interaction in Pion-Nucleon Scattering’ (Phys. Rev. 138, p.B678) provides improvements to the peripheral methods developed in ‘Prediction of p-, d- and f-Wave Pion-Nucleon Scattering’. Jim and Donnachie also showed that the requirement of dispersion relations for partial-wave amplitudes to obey a high-energy boundary condition gives rise to a unitary sum rule which could be used to estimate the short-range parts of the pion-nucleon interaction, making it possible to give accurate predictions of p-, d- and f-wave amplitudes at higher energies than had been possible a year earlier.

During the 4 years to August 1964, when Jim finished up at UCL, he had built a thriving elementary particle research group. The group he left behind comprised lecturers Donnachie and Woolcock, research assistants Lea and Oades, and seven research students. All the students who obtained their Ph.D.s under Jim went on to forge successful careers in physics. Jim would later say “We got much pleasure and a variety of interesting results out of the work which began as a search for the causes of S-wave pion-nucleon scattering. The work was done with various younger colleagues, beginning in Cambridge and London and continuing for a number of years at Nordita.”