Praxis Archives – Page 87 of 181

AdA – the small machine that made a big impact

AdA installed at LAL, where the first electron–positron collisions were observed.
Image credit: LAL.

The story of the world’s first electron–positron storage ring, the Anello di Accumulazione (AdA), started in Italy at INFN’s Frascati National Laboratory (LNF). Built there under the leadership of Bruno Touschek, it stored its first beams in February 1961. A year later, the machine travelled to France, to the Laboratoire de l’Accélérateur Linéaire (LAL) in Orsay – now part of CNRS/IN2P3 and Paris Sud University – so that it could benefit from the new state-of-the-art linac as injector. The first electron–positron collisions were observed and studied there from late 1963 to spring 1964, laying the foundations for a technique that would revolutionize investigations of fundamental particles and their interactions.

To celebrate this anniversary, LAL and LNF organized a special meeting in the series of Bruno Touschek Memorial Lectures, BTML 2013, which took place at LAL on Friday 13 September – a date chosen to take advantage of the following weekend of European Heritage Days in France. Associated public events took place during the three days, including a public lecture on “LAL and CERN” in the evening of 13 September and open days at LAL on 14–15 September.

The special BTML 2013 meeting began with a talk about Touschek and the memorial lectures. This was followed by recollections from LAL’s Jacques Haïssinski – who did his doctoral thesis work at AdA – and by the first showing of a new film on the period when AdA was at LAL. A second session focused on accelerators, their applications in society and the future programmes for both LAL and LNF. The afternoon’s more ceremonial events took place in the Pierre Marin hall, which hosts the Anneau de Collisions d’Orsay (ACO) – AdA’s successor at LAL (1965–1988) and now the core of the Sciences ACO museum. Events included the inauguration at the museum of the historic linac’s restored control room, which has been moved and reassembled exactly as it was.

AdA on display today, back at Frascati.
Image credit: LNF/INFN.

The linac at LAL delivered its first beam of electrons, at 3 MeV, near the end of 1958. By 1964 the beam energy reached 1.3 GeV – a world record for electron linacs at that time. However, from 1963, the accelerator was also equipped to deliver a positron beam, and this would become a valuable tool in the implementation of collider and storage rings at LAL, beginning with the pioneering studies on AdA.

AdA and LAL become EPS Historic Sites

In a ceremony on 5 December at the LNF, the European Physical Society (EPS) declared AdA an EPS Historic Site. The ceremony, which was chaired by LNF’s director, Umberto Dosselli, featured talks by Giorgio Salvini, LNF’s director in 1961 at the time that construction of AdA was agreed, and Carlo Bernardini, who gave a personal recollection of the main steps in building AdA and the exciting atmosphere pervading the LNF at that time. INFN’s president, Fernando Ferroni, also had the opportunity to comment briefly on the present status of the laboratory and its future perspectives. EPS vice-president, Luisa Cifarelli, spoke on the EPS Historic Sites initiative and also described the society’s foundation, development and links with INFN. The EPS Historic Site plaque was then unveiled by Ferroni and Cifarelli. The programme continued in the afternoon with the Frascati edition of BTML 2013, in which Samuel Ting, of the Massuchusetts Institute of Technology, presented the latest results from the Alpha Magnetic Spectrometer, which is studying antiparticle production in cosmic rays (CERN Courier October 2013 p22). CERN’s Luigi Rolandi then gave a public lecture on the recent discovery of a Higgs boson.

Two months earlier, during the special edition of BTML 2013, LAL and the LURE complex became the 8th EPS Historic Site. AdA’s shutdown at LAL was followed by the start-up of the ACO ring in 1965, allowing important measurements in accelerator and particle physics. Later, ACO and then SuperACO became leaders in the use of synchrotron light for other research fields, such as materials science and chemistry. The Laboratoire pour l’Utilisation du Rayonnement Électromagnétique (LURE) was created in 1973 to develop this activity, becoming independent from LAL in 1985. Today, LURE has led to the SOLEIL synchrotron on the Saclay plateau, a first-class third-generation light source.

The story of AdA

At the start of the 1960s, several groups worldwide were following up ideas for electron–electron and proton–proton colliders. In contrast, Touschek’s vision was to make electrons and positrons collide and annihilate in such a way that the centre of mass of the system is at rest in the laboratory frame and to produce time-like photons with enough energy to excite resonant modes of the vacuum corresponding to the masses of the vector mesons. With the blessing of Giorgio Salvini, LNF’s director at the time, a small group of inspired physicists started work on designing and building a prototype electron–positron storage ring, which they named AdA (Bernardini 2004).

Jacques Haïssinski at the LAL event.
Image credit: LAL.

AdA consisted of a ring-shaped vacuum chamber, 160 cm in diameter, which was embedded in a magnet of 8.5 tonnes to keep beams circulating with energies up to 200 MeV. Challenges included maintaining a high vacuum to guarantee the lifetime of the beam and working out how to inject both electrons and positrons. Injection was achieved through the conversion of γ rays in a tantalum plate installed in the vacuum chamber, the γ rays being produced by bremsstrahlung from the electron beam of LNF’s electron synchrotron. The first stored electrons and positrons circulated on 27 February 1961, but difficulties in siting AdA close to the synchrotron meant that the stored intensities were low and proof of collisions had to wait until the storage ring was taken to Orsay.

Control room at Orsay — The control room of the historic linac at Orsay, now a museum piece.
Image credit: LAL.

The move to LAL stemmed from a visit to Frascati in the summer of 1961 by Pierre Marin, who found AdA to be un vrai bijou. By the end of the year, preliminary studies for a 1.3 GeV electron–positron storage ring at LAL had started, but the project was soon considered too close to the proposal for the ADONE collider at Frascati. In early 1962, a small group of scientists and engineers from Orsay went to Frascati to discuss, among other items, ways of operating AdA at the Orsay linac to benefit from the high beam intensity and easier photo-injection from the linac. At the beginning of July, AdA was packed onto a lorry and set off across the Alps with a fully evacuated beam pipe, and batteries to last about three days to power the vacuum pumps and avoid losing the high vacuum that had taken months to obtain. A month later, the collider was installed in Orsay – although not without incident. While being positioned by a crane, AdA was almost smashed against a wall. Later, a heavy detector tipped over while being moved close to the ring and broke Marin’s foot.

Unveiling the EPS plaque for AdA, with Luisa Cifarelli, left, and Fernando Ferroni.
Image credit: INFN/LNF.

In Orsay, in a series of runs between December 1963 and April 1964, collisions were finally observed and important aspects of beam dynamics studied (Bernardini et al. 1964). One important effect was immediately explained by Touschek. Large-angle Coulomb collisions in the electron (or positron) bunches give rise to momentum transfers into the longitudinal phase space, which can in turn lead to particle loss, limiting the machine luminosity. Known as the Touschek effect, it is manifest through a progressive decrease in the beam lifetime while the number of stored particles increases – and it remains one of the factors that limit the beam lifetime in accelerators.

Experiments with AdA ended with these results. The project to build ADONE – a bigger 1.5 GeV collider proposed at the end of 1960 by Touschek and his collaborators – had already been approved at LNF and was to start up in 1967. However, despite AdA’s short scientific life, it remains a milestone in the history of science because it set the stage for many future electron–positron colliders. The configuration became one of the most powerful tools in modern high-energy physics, allowing, in 1974, the discovery of the J/ψ – a particle built of a new type of quark, charm, and its antiquark – and culminating in the late 1980s with the Large Electron–Positron collider at CERN.

LAL today

Although the large linear accelerator, which gave its name to LAL, was turned off at the end of 2003, the lab’s involvement in the particle-accelerator field continues to be important. R&D activities at PHIL – a 10 MeV electron accelerator built in the lab and recently completed – will allow the development of future particle injectors (CERN Courier September 2008 p9). The facility will also be open to a large community that will use its unique beam-properties for dedicated experiments. The lab is also responsible for the building and conditioning of the 640 couplers for the new free-electron laser, XFEL, under construction at DESY.

In addition, LAL has started the construction of an innovative X-ray source, ThomX. This first-class equipment – designated Equipement d’Excellence by the French National Research Agency in 2011 – will have many applications, from medical research to non-invasive studies of art masterpieces. Thanks to its small size and limited cost, it is likely to interest many labs and private companies worldwide. More fundamental activities are also ongoing, such as the commissioning of beams with record emittance at the Accelerator Test Facility 2 at KEK, in Japan, and the UA9 experiment at CERN, which is investigating a new collimation method for beam-halo studies in the Super Proton Synchrotron and LHC.

How the Particle Physics Masterclasses began

Today, the Particle Physics Masterclasses are so well established that they seem always to have been there. As many as 10,000 school students in 37 countries participate each year at an international level. Perhaps those who are involved in these events that enthuse and inform the younger generation never wonder about how they started. But there was a time when there were no such things as masterclasses in particle physics and they had to be invented.

The start can be dated precisely: it was in a discussion between Ken Long and myself that took place during a coffee break at the committee meeting of the UK Institute of Physics (IOP) High-Energy Particle Physics (HEPP) group on 17 October 1996. We were frustrated at difficulties with outreach – or the public understanding of science, as it was then called – to schools. Particle physics had a great story to tell, with fine pictures and enthusiastic speakers, but schools were slow to respond to our offers to visit and give talks. Our words and pictures could not compete with the colour and noise of chemists and the experiments they included in their lectures. Surely it was impossible to show real particle physics in the classroom? As Ken and I talked, bits of the answer came together and more followed over e-mail discussions in the succeeding weeks:

• Rather than go to schools and talk to a dozen pupils, we would invite them to come to us, in university lecture theatres that could accommodate hundreds of people.

• A full-day event would make the trip worth their while and allow time for a range of topics and activities.

• We would run the event from local universities but consider it a national event and organize publicity centrally using the IOP.

• Most important, we would use the new computer clusters that were being installed for undergraduates but not used much outside of university term time.

The computer clusters could run serious software experiments directly related to real particle physics – participants could learn through doing. The World Wide Web, which was new at that time, could be used for distributing the programs and data. Today, we just point and click, but in the early days we had to be concerned with network speed, so the programs were painstakingly pre-loaded to each PC before the sessions.

I suggested the name “Masterclasses” with some hesitation because it seemed pretentious: we were not offering one-to-one violin tuition with Yehudi Menuhin. However, it did capture something of what we were trying to do and the name has stuck. At the meeting of the IOP HEPP group committee in January 1997, Ken and I presented our plans for Imperial College and Manchester University (where I worked then), and people liked them. Christine Sutton at Oxford, Mike Pennington at Durham and Tim Greenshaw at Liverpool decided to take part. These were the individual enthusiasts but we also received tremendous support from many colleagues, both in the particle-physics groups and from the computing staff.

We decided that although we could not provide a big-name speaker for every session, we could distribute a video of a public session arranged as part of the IOP HEPP group conference, which in 1997 was to be held in Cambridge to celebrate the centenary of J J Thomson’s discovery of the electron at the Cavendish Laboratory. Ken arranged for video recording (with all of the legal and copyright details) of the talks given by Stephen Hawking and Frank Close. The videos were shown at the masterclasses just a few days later and each participating school was given a copy to take home.

While Ken was arranging the video, I was organizing the universities. On 13 February we had a planning meeting in Manchester, with Swansea and Lancaster joining as well. We also discussed publicity, arrangements and the provision of “goody bags” for pupils and teachers. We tried out the software, which included the Lancaster relativistic-kinematics package and Terry Wyatt’s web-based “Identifying Interesting Events at LEP”.

The real thing

Terry’s package was revolutionary in that it gave school students real particle-physics data and real tools, and asked them to make decisions. Presented with simple Z decays from the OPAL experiment at CERN’s Large Electron–Positron (LEP) collider, the students had to classify them as electron, muon, tau or quark decays, according to the patterns in the detector. The only difference from actual analysis was that such a classification would not be done by a physicist, but by a program using criteria devised by a physicist. Terry and I had spent a lot of time puzzling over the OPAL event display to understand the detector for the first muon-pair results, so I can certify that this exercise was close to real research.

Students get down to some basic physics — National labs also took up the idea. Here students get down to some basic physics with the “left-hand rule” at the 2012 classes organized by the Cockcroft Institute and Daresbury Laboratory.
Image credit: STFC.

After the annual IOP conference in Cambridge I came back to Manchester, and the next day – 11 April – we ran our first Particle Physics Masterclass. In my journal I wrote “nice talks, kids co-operate and teachers are enthusiastic and appreciative”. The only glitch was that we under-estimated appetites and lunch ran out. We learnt our lesson and the following year we provided smaller plates. The other pilot sites were similarly positive. There was high demand from the schools – some places ran a second day – and both pupils and teachers who attended were enthusiastic afterwards.

The basis for the masterclasses was “Think globally, act locally”. It was a national campaign – we always specifically referred to it as the National Particle Physics Masterclass – with central publicity and preparation of materials. However, the shows were run by local groups, in their own way and with local variations. They could plug their own institution as much as they pleased – the Oxford website managed to include the word “Oxford” six times on one small page – and adapt the material freely, using events from the DELPHI experiment, rather than OPAL, for example.

The scheme was written up in the HEPP group newsletter (January 1998), stressing what we saw as the key parts of the scheme:

• It is not just talks. Using PC clusters can get the participants involved in an activity that is not far from real research.

• A central organization spreads the administrative load.

• A national scheme spreads the publicity.

• It runs every year at the same time, linked to the annual IOP HEPP group conference in the spring vacation, so there is no problem in deciding when to do it.

The idea snowballed, so that in 1998 nearly every university particle-physics group in the UK ran a masterclass – and have done ever since. The national Rutherford and Daresbury labs joined a year or so later.

There was continued strong support from the IOP HEPP group

The Particle Physics Masterclasses have flourished. There was continued strong support from the IOP HEPP group – Val Gibson took over the co-ordination when I came off the committee – and from the Particle Physics and Astronomy Research Council, where Andrew Morrison did a splendid job of liaison. They provided co-ordination and literature, respectively, but not money. We received repeated offers of financial assistance but turned them down as the scheme basically cost nothing. It was run by enthusiast particle physicists who did not need extra support.

Onwards and upwards

The masterclasses have adapted with time. The LEP events were replaced by ones from the Tevatron and from the LHC. The number of pupils who have attended the classes must be into the tens of thousands. A prime minister has been photographed with participants, and the masterclasses idea has spread to continental Europe and across the Atlantic.

I think this success comes from a combination of many factors. Particle physics has, of course, a great story to tell. Masterclasses are run by enthusiasts who do it purely for fun and because they want to, and they treat the material with familiarity rather than respectful awe. We grasped the technical development of the university PC clusters for analysis and the power of the web for distribution at the right moment.

This success has brought benefits: applications to study physics in UK universities are rising, and the public and the media are interested and excited about the LHC and the Higgs boson. Agreed, the masterclasses cannot claim all of the credit for this, but they can certainly claim some of it.

Now, the Particle Physics Masterclasses face the challenge of evolving as technology moves on and people – especially young people – change with it. I hope they see continued success by building on the basic ideas that they started with, and that they will continue to provide fun for students and organizers for many years to come.

A celebration of science for peace

CCvie1_01_14 — On 17 May 1954, the seeds for peaceful scientific research were sown as the first shovels of earth were turned on CERN’s Meyrin site.

On 29 September 1954, the European Organization for Nuclear Research officially came into being, after the convention to establish the organization had been ratified by a sufficient number of the 12 founding member states. Since then, CERN has in many ways become a model for what Europe can do when it unites, bridging nationalities and bringing different cultures together to work towards a common goal.

During the past 60 years, CERN has grown to become a world-leading physics laboratory, fulfilling the dreams of its founders as summarized in the convention, which states that “The Organization shall provide for collaboration among European States in nuclear research of a pure scientific and fundamental character, and in research essentially related thereto. The Organization shall have no concern with work for military requirements and the results of its experimental and theoretical work shall be published or otherwise made generally available.” The convention goes on to assert that, in addition to the construction of accelerators, experiments and infrastructure, the basic programme should encompass international co-operation in research, along with the promotion of contact between scientists, training of scientists and dissemination of knowledge across borders.

Times have changed, but the spirit of openness and peaceful collaboration enshrined in the visionary words of the convention continues to shape CERN to this day. The nature of the laboratory’s research has gone far beyond the atomic nucleus to encompass the basic particles of matter and how they interact through fundamental forces to form the fabric of the universe. The organization’s collaboration now extends far beyond the boundaries of Europe, as scientists and engineers from around the world work together at CERN – and those from CERN contribute to projects around the world. The dissemination of information, education and training also continue to be key guiding factors in the programme today – all in the spirit of the convention. Knowledge gained through the laboratory’s frontier research is made available for applications that benefit society. CERN schools held in many different countries allow a new generation of scientists and engineers not only to learn about frontier research but also to form friendships across national boundaries.

As we advance further into the 21st century, the organization is still going strong and maintaining its attraction of international scientific collaboration. It has grown steadily since 1954, with the latest country to join – Israel – bringing the total number of member states to 21. Other countries are in the stages leading up to becoming members or associates and still others are expressing interest. CERN is becoming a global success, while retaining its original, European flavour.

This year’s events for the 60th anniversary will celebrate the theme of international collaboration. In particular, there will be activities in all of the member states, reflecting the fact that CERN is their laboratory. While the main celebration at CERN will be on 29 September – the exact anniversary of when the organization came into being – an earlier event will take place at the headquarters of the United Nations Educational, Scientific and Cultural Organization (UNESCO) in Paris on 1 July. CERN was born under the umbrella of UNESCO, and it was in Paris on that day in 1953 that the convention was signed.

What drives this huge collaborative effort is, of course, the science – the fundamental physics remains as exciting as ever and continues to attract people to CERN, from bright young scientists and engineers to the general public of all ages and from all walks of life. The discovery of a new particle at the LHC and the confirmation last year that it was indeed a Higgs boson, emissary of the Brout–Englert–Higgs mechanism that endows fundamental particles with mass, has been the latest success – and a major reward for the effort, in many countries, that went into the design, construction and running of the LHC and its experiments. The award of the 2013 Nobel Prize in Physics to François Englert and Peter Higgs (Robert Brout sadly passed away in 2011), which recognized the importance of this key piece of fundamental physics, was a marvellous early 60th birthday present.

The result of more than two decades of effort by thousands of scientists and engineers from around the world, this discovery exemplifies the collaborative nature of research at CERN. It also reflects the freedom to work together with open minds towards a common goal – a freedom that has underpinned advances in science throughout the ages. This freedom to think and to communicate was prominent in the minds of those who came together more than 60 years ago to establish an organization in which fundamental science could flourish. Thanks to the work of the many people who have been involved with the organization since then, I believe that CERN has more than fulfilled the hopes and dreams of advancing science for peace.

The Adventurous Life of Friedrich Georg Houtermans, Physicist (1903–1966)

By Edoardo Amaldi (Saverio Braccini, Antonio Ereditato and Paola Scampoli eds.)
Springer
Paperback: £44.99 €52.70 $49.95
E-book: £35.99 €41.64 $39.95

Before visiting a university or physics laboratory, most people imagine today’s physicists as peaceful men or women wearing white lab coats and dealing with test tubes, clouds of coloured smoke and mathematical equations. Although the description would be more appropriate for ancient alchemists rather than modern physicists, one word should still stand out – peaceful. However, there was a time when physicists were investigating dangerous radiation, fissile nuclei and particles to trigger a nuclear-reaction chain. These were also the times when Europe was a battlefield and scientific results were regarded as potential material for spies and the tellers of spy stories. In those days, almost every scientist could have made a good subject for writers and Hollywood.

Friedrich “Fritz” Houtermans is no exception. Indeed, his private and professional lives make a good subject for a book. However, in my opinion, the most intriguing aspect of this book is the author – Edoardo Amaldi – and the reason why he decided to write about Fritz, a man who was married four times, spent a few years in Lubianka and other prisons and published several important physics results along the way. Amaldi had seen L’Aveu – the film by Costa Gravas about Artur London, the Czechoslovakian communist minister falsely arrested and tried for treason and espionage – and was struck by similarities with the story of Houtermans. Amaldi began to write about Houtermans but died in 1989. Twenty years later, Edoardo Amaldi’s son Ugo gave his father’s unpublished manuscript to the Laboratory for High Energy Physics at the University of Bern, where Fritz had done much to initiate research on particle physics. I share the fascination of the editors when they describe how grateful they were to have the opportunity to “meet two outstanding physicists” – Fritz and Edoardo.

The result is a detailed description of both the life of Houtermans and the lives of other friends of Amaldi. It is a beautiful description of Europe and science during the years before, during and after the Second World War. The words Amaldi uses – which are well edited – are not those of a storyteller. Instead, he provides a detailed – almost scientific – report of this almost unknown physicist.

Although Houtermans is an interesting subject, more interesting to me are the chapters where Amaldi explains the “making of” the book and his research into accurate information sources about its subject. I think that soon I will be looking for an equivalent book about Amaldi’s life.

Time Reborn: From the Crisis of Physics to the Future of the Universe

By Lee Smolin
Allen Lane
Hardback: £20
E-book: £11.99

This is a fascinating and thought-provoking book about the nature of time and its role in explaining the universe. Smolin is an original thinker who is unafraid to challenge established orthodoxy. He argues that modern attempts to understand the universe have reached an impasse as a result of the extraction of time from our concept of reality.

The book is presented in two parts. The first offers an historical and philosophical account of how we have arrived at a timeless view of the world. The second develops ideas for a new approach to physics, which incorporates time as a central and fundamental theme. While both parts are interesting and relevant, physicists might find it more satisfying to read the second part first. There is also an epilogue where Smolin discusses some of the implications of redefining our concept of time and reality and how we might meet the challenges of the future, such as climate change and market economics. Finally, he considers the nature of consciousness.

Smolin begins by illustrating, with the simple example of projectile motion, how time can be excluded from our understanding of a physical system by using mathematical constructs. The role of mathematics is to make a physical system abstract, rendering it eternal and timeless. Here Smolin gives an excellent account of the history of the Copernican Revolution, Johannes Kepler and Galileo Galilei. His unique perspective gives new insight into how each world view might have developed and persisted. At each stage the concept of time becomes increasingly obsolete, culminating in the determinism of the Newtonian paradigm. Relativity is no less deterministic, leading us to a timeless “block universe” picture where reality is the whole history of the universe at once.

In what he calls “doing physics in a box”, Smolin examines the applicability of the Newtonian paradigm to cosmology. A physical system can never be isolated from external influences, so the solutions are an approximation to reality. The approximation can be removed by taking the universe as a whole into consideration but such a step cannot be justified because the Newtonian paradigm necessarily applies to a system that is part of a whole. Smolin calls the inappropriate application of physical laws to the universe a “cosmological fallacy”. His reasoning draws attention to the distinction between physics-in-a-box and cosmology. “The universe is an entity different in kind from any of its parts.”

Smolin is a strong proponent of Leibnitz and the principle of sufficient reason, which states that if there is more than one possibility for things to be as they are, then there must be a sufficient reason for the actual outcome being the case. He uses this to great effect in defining his principles for a new cosmology. In particular, “there should be nothing in the universe that acts on other things without itself being acted upon.” This expresses the philosophy of relationism, where every entity in the universe evolves dynamically, including the physical laws governing the universe. These laws then “become explicable only when they participate in the dance of change and mutual influence that makes the world a whole”. A consequence of relationism, Smolin argues, is that symmetries and conservation laws can only be approximations to reality.

Smolin is keen to emphasize a new approach to a theory of the universe that is not constrained by the Newtonian paradigm. He attempts to provide a framework for a new theory, insisting that it must be able to provide falsifiable predictions. In this sense he is less speculative than those who opt for a multiverse of universes that are not causally connected to our own. He proposes the existence of many universes but with causal connections, which in principle allow their existence to be detected. A possible candidate for the new theory is cosmological natural selection – the subject of his earlier book The Life of the Cosmos – in which universes reproduce through the creation of new universes within black holes. The presence of a large number of black holes in a universe is a measure of its fitness in evolutionary terms. The analogy with Darwinian evolution raises the fascinating possibility of novel outcomes, similar to the emergence of new species through natural selection.

This book is great for providing numerous thought-provoking ideas. The reader does not have to agree with all of them to be stimulated into pondering the nature of time. Unsettling and controversial in places, it offers a much needed re-examination of some of our most cherished views.

Madam Wu Chien-Shiung: The First Lady of Physics Research

By Chiang Tsai-Chien (translated by Wong Tang-Fong)
World Scientific
Hardback: £65
Paperback: £32
E-book: £24

The discovery of parity non-conservation was honoured with a Nobel Prize in Physics awarded to Chen-Ning Yang and Tsung-Dao Lee who raised the “question of parity conservation in weak interactions” in 1956 (Phys. Rev. 104 254). Originally the preprint contained a question mark – “Is parity conserved in weak interactions?” – but the editors of Physical Review at that time discouraged question marks in the titles of regular articles. The crucial question mark was eliminated forever the same year by the valiant effort of Chien-Shiung Wu and her collaborators – Ernest Ambler, Raymond Hayward, Dale Hoppes and Ralph Hudson. They conducted a memorable experiment at the National Bureau of Standards and the results were published in the first few months of 1957 (Phys. Rev. 105 1413). The concept of their experiment was remarkably simple: take a β-decay source (cobalt-60) and magnetize it with a circular current flowing first in one direction and then in the opposite sense, so that the initial states are the mirror images of each other. The β decays of the mirror-symmetric initial states turned out to be non-mirror-symmetric. Immediately afterwards, two other groups published similar evidence for parity non-conservation – Richard Garwin, Leon Lederman and Marcel Weinrich in Columbia University and Jerome Friedman and Valentine Telegdi in Chicago.

Weak interactions are at the heart of this interesting biography. Of course, Wu was not the first lady working in physics – other remarkable women preceded her in the path to great discoveries. However, as the author argues, she was a person of many “firsts”, such as the first recipient of the Wolf prize and the first female president of the American Physical Society.

The biography tells the exciting story of a young woman who left the rural China vividly described in the novels of Pearl S Buck and became one of the recognized authorities in the physics of β decay. Wu joined the Manhattan Project and later worked on several other topics, ranging from the Mossbauer effect to exotic atoms. However, her main contributions remain connected to weak interactions. In collaboration with her group in Columbia she also tested the conserved vector-current hypothesis and the universality of Fermi interaction proposed by Richard Feynman and Murray Gell-Mann – a discovery that was essential for the subsequent development of the Standard Model of electroweak interactions.

Wu was above all a scientist who did not like much exposure and dramatic headlines. She also had a wonderful family and various interests, including the rights of women in science. After leaving Shanghai in 1936, she was not allowed back into mainland China for 37 years and so never again saw family members who had died in the meantime. The Cultural Revolution threatened Chinese science but did not succeed. A number of remarkable Chinese scientists, including Wu, contributed enormously to the current success of the standard electroweak theory.

CERN School of Computing: 10 years of renewal

Students at the 2013 CSC in Nicosia in August.
Image credit: G Lo Presti.

On 29 August 2013, on the ground floor of Building FST01 of the Faculty of Pure and Applied Sciences at the University of Cyprus in Nicosia, 31 students filed silently into the two classrooms of the CERN School of Computing and took a seat in front of a computer. An hour later they were followed by a second wave of 31 students. They were all there to participate in the 12th occasion of a unique CERN initiative – the final examination of its computing school.

The CERN School of Computing (CSC) is one of the three schools that CERN has set up to deliver knowledge in the organization’s main scientific and technical pillars – physics, accelerators and computing. Like its counterparts, the CERN Accelerator School and what is now the European School of High-Energy Physics, each year it attracts several-dozen participants from across the world for a fortnight of activities relating to its main topic.

How and why was the CSC set up? On 23 September 1968, future director-general Léon van Hove put forward a proposal to the then director-general, Bernard Gregory, for the creation of a summer school on data handling. This followed a recommendation made on 21 May 1968 to the Academic Training Committee by Ross MacLeod, head of the Data and Documents Division, the forerunner of today’s Information Technology Department. The proposal recommended that a school be organized in summer 1969 or 1970. The memorandum from van Hove to Gregory gave a visionary description of the potential audience for this new school: “It would address a mixed audience of young high-energy physicists and computer scientists.” Forty-five years later, not a word needs to be changed.

The justification for the school was also prophetic: “One of the interests of the Data Handling Summer School lies in the fact that it would be useful not only for high-energy physicists but also for those working in applied mathematics and computing. It would be an excellent opportunity for CERN to strengthen its contacts with a field which may well play a growing role in the long-range future.” With the agreement of Mervyn Hine, director of research, Gregory approved the proposal on 15 November 1968 and on 20 December MacLeod proposed a list of names to van Hove to form the first organizing committee. Alongside people from outside CERN – Bernard Levrat, John Burren and Peter Kirstein – were Tor Bloch, Rudi Böck, Bernard French, Robert Hagedorn, Lew Kowarski, Carlo Rubbia and Paolo Zanella from CERN.

Students take the final exam — With the CSC Diploma in their sights, students take the final exam.
Image credit: F Fluckiger.

The first CSC was not held at CERN as initially proposed but in Varenna, Italy, in 1970. It was realized quickly that the computing school – with the physics and accelerator schools – could be effective for collaboration between national physics communities and CERN. Until 1986 the CSC was organized every other year, then yearly starting with the school in Troia, Portugal, in 1987. To date there have been 36 schools, attended by 2300 students from five continents.

Ten years ago, I took over the reins of the school and proposed a redefinition of its objectives as it entered its fourth decade: “The school’s main aim is to create and share a common culture in the field of scientific computing, which is a strategic necessity to promote mobility within CERN and between institutes, and to carry out large transnational computing projects. The second aim is the creation of strong social links between participants, students and teachers alike, to reinforce the cohesion of the community and improve the effectiveness of its shared initiatives. The school should be open to computer scientists and physicists and ensure that both groups get to know each other and acquire a solid grounding in whichever of these domains is not their own.”

Moreover, the new management proposed three major changes of direction. First, they vowed to reinvigorate the resolutely academic dimension of the CSC, which during the years had gradually and imperceptibly become more like a conference. Conferences are necessary for scientific progress – they are forums where people can present their work, have their ideas challenged, have fruitful discussions about controversial issues and talk about themselves and what they do. The interventions at conferences are short, sometimes redundant or contradictory. The transmission of facts and opinions becomes more prominent than the transfer of knowledge. I took the view that this should not be the primary role of the CSC, since conferences such as the Computing in High-Energy Physics series serve this purpose perfectly. The academic dimension was therefore progressively re-established through the implementation of three principles.

Three principles

The first academic principle concerns the organization of the teaching. A deliberately limited number of teachers – each giving a series of lessons of several hours – ensures coherence between the different classes, avoids redundancy and delivers consistent content, more than a series of short interventions. Moreover, for several years now all of the non-CERN teachers have been university professors. This is not the result of a strict policy but it is worthy of note that the choice of teachers has been consistent with this academic ambition.

Sea kayaking — The social dimension – discovering sea kayaking.
Image credit: J Hammer.

The second principle for restoring the academic dimension concerns the school’s curriculum. The main accent is on the transmission of knowledge and not of know-how. In this way, the CSC differs from training programmes organized by the laboratories and institutes, which are focused on know-how. The difference between knowledge and know-how is an important principle in the field of learning sciences. To get a better understanding of this distinction, the management of the school established relations with experts in the field at an early stage, particularly at the University of Geneva.

Knowledge is made up of fundamental concepts and facts on which additional knowledge is built and developed to persist over time

What are the differences? Knowledge is made up of fundamental concepts and facts on which additional knowledge is built and developed to persist over time. Moreover, the student acquires knowledge, incorporates it into his or her personal knowledge corpus and transforms it. Two physicists never have the same understanding of quantum mechanics. On the other hand, know-how – which includes methods and the use of tools – can generally be acquired autonomously with few prerequisites. With the exception of physical skills – such as knowing how to ride a bike or swim – which we tend not to lose, know-how requires regular practise so that it is not forgotten. Knowledge is more enduring by nature. Finally – and this is one of the main differences – knowledge can be transposed more readily to other environments and adapted to new problems. That at least is the theory. In practice, the differences are sometimes less clear. This is the challenge with which the CSC tries to get to grips each year when defining its programme – are we really operating mainly in the field of knowledge? The school is made up in equal parts of lectures and hands-on sessions, so do the latter not relate more to know-how? Yes, but the acquisition of this know-how is not an end in itself – it provides knowledge with a better anchorage.

The third principle of the academic dimension is evaluation of the knowledge acquired and recognition of the required level of excellence with a certificate. Following requests from students who wanted the high level of knowledge gained during the school to be formally certified, the CSC Diploma was introduced in 2002 to recognize success in the final exam and vouch for the student’s diligence throughout the programme. To date, 671 students have been awarded the CSC Diploma, which often figures prominently in their CVs. But that’s not all. Since 2008, the academic quality of the school, its teachers and exam has been formally audited each year by a different independent university. Each autumn, the school management prepares a file that is aimed at integrating the next school into the academic curriculum of the host university. The universities of Brunel, Copenhagen, Gjøvik, Göttingen, Nicosia and Uppsala have analysed and accepted CERN’s request. As a result, they have each awarded a formal European Credit Transfer System (ECTS) certificate to complement the CERN diploma.

This academic reorientation of the school is one of the three main renewal projects undertaken during the past 10 years. The second relates to the school’s social dimension. The creation of social links and networks between the participants and with their teachers has become the school’s second aim. This is considered to be a strategic objective because not only does it reinforce the cohesion of the community, it also improves the efficiency of large projects or services, such as the Worldwide LHC Computing Grid, through improved mutual understanding between the individuals contributing to them.

The 1968 memorandum from Léon van Hove to Bernard Gregory — How it all began – the 1968 memorandum from Léon van Hove to Bernard Gregory, then director-general of CERN.

The main vehicle chosen for socialization is sport. Every afternoon, a large part of the timetable is freed up for a dozen indoor and outdoor sports. Tennis, climbing or swimming lessons are given, often by the school’s teachers. Each year, participants discover an activity that is new to them, such as horse riding, sailing, canoeing, kayaking, scuba diving, rock climbing, cricket and mountain biking. The sport programme is supported by the CERN Medical Service and is associated with the “Move! Eat better” initiative. A second vehicle for socialization – music – is being considered and could be introduced for future schools. The intention is to give those who are interested the opportunity each afternoon to take part in instrumental music or choral singing or to discover them for the first time, with the same aim as for sport of “doing things together to get to know each other better”.

The third renewal project is plurality. In contrast to CERN’s high-energy physics and accelerator schools, which have organized several annual events for a number of years, the CSC has long remained the organization’s only school in the field of computing. However, since 2005 the CSC management has organized the inverted CSC (iCSC, “Where students turn into teachers”) and starting in 2013 the thematic CSC (tCSC). The idea behind the inverted school is simple – to capitalize on the considerable amount of knowledge accumulated by the participants in a school by inviting them to teach one or more lessons at a short school of three to five half-days, organized at CERN at the mid-point between two summer schools. To date, 40 former students have taught at one of these inverted schools.

It should be noted that the academic principle is still predominant. The goal is not to talk about oneself or one’s project but to present a topic, an innovative one if possible. This is not always easy, so each young teacher who is selected is assigned a mentor who follows the design and production of the lesson across three months. The inverted school has another aim – it is also a school for learning to teach. It represents the second link in a chain of training stages for new teachers for the main school. The first link, for those who are interested, is to give a short academic presentation while attending the main school. After the iCSC, i.e. the second link, some are invited to give an hour’s lesson at the main school before the last stage – their full integration into the teaching staff. This process generally takes several years.

During the latest CSC in Nicosia, five out of the 11 teachers were younger than 35. Three of them had passed through the CSC training chain. Along with their forthcoming colleagues, they are the future of the school. Leaving the CSC after 11 years as its director, I am confident that the next generation is ready to take up the baton.

The multifaceted life of Pontecorvo

Fig. 1. The boys of Via Panisperna. Right to left: Enrico Fermi, Franco Rasetti, Edoardo Amaldi, Emilio Segrè, Oscar D’Agostino… so where is Bruno Pontecorvo?
Image credit: Wikipedia commons.

Bruno Pontecorvo (1913–1993) was born in Pisa but his scientific life began in Rome, when he was accepted into the group of physicists working at Sapienza University of Roma with Enrico Fermi. It was a small but exceptional group of young people attracted by the strong personality of Fermi, who were later known as “the boys of Via Panisperna” from the name of the street where the physics institute was located at that time. Pontecorvo arrived in Rome in time to participate in the discovery of radioactivity induced by slow neutrons, for which Fermi was to receive the Nobel Prize in Physics in 1938. A famous picture shows the group at the time of the discovery, with the notable absence of Bruno (figure 1). This was for good reason – he was behind the camera, taking the picture.

On 11–12 September 2013, Sapienza University of Rome celebrated Pontecorvo’s centenary with an international scientific symposium – The Legacy of Bruno Pontecorvo: the Man and the Scientist. (Another was held later in Pisa.) Inaugurated in the presence of the president of the republic, Giorgio Napolitano (figure 2), it was attended by distinguished physicists from Italy and other European countries, as well as Japan, Russia, the US and CERN. The talks revisited different sides of Pontecorvo’s long and multifaceted scientific life, which was marked by his lucid and deep passion for science and his important contributions to several branches of nuclear and particle physics.

It was a life sharply divided in two parts by his sudden move to the Soviet Union in the summer of 1950, when he went from England via Italy and Sweden, to reappear five years later in Dubna as part of the Soviet scientific establishment. Presenting an historical perspective of Pontecorvo’s life, Frank Close spoke of “a life of two halves”. One could add a third life – the one lived during the decline and dissolution of the Soviet system, with periodic visits to Italy and disenchantment in the 1980s, which are well described in a book by Miriam Mafai, Il lungo freddo (The Long Cold), published in 1990.

Fig. 2. Giorgio Napolitano, left, president of the Italian Republic, greets some of the speakers at the symposium celebrating Bruno Pontecorvo’s centenary. From right to left: Carlo Bernardini, Fernando Ferroni, Jack Steinberger, Carlo Dionisi.
Image credit: Antonio Di Gennaro, Ufficio Stampa del Quirinale.

Jack Steinberger opened the meeting by speaking about when he was a student of Fermi and Pontecorvo came to Chicago from Canada to visit his old mentor. Pontecorvo had discovered that the capture of the muon by nuclei, measured by Marcello Conversi, Ettore Pancini and Oreste Piccioni in Rome, was consistent with having the same strength as electron capture – that is, that the muon and the electron, besides having the same electric charge, share the same coupling in the weak interaction. It was the start of the lepton family and the universality of the weak interaction, which would eventually evolve into the long story of electroweak unification. Steinberger was doing his thesis with Fermi on muon decay, which led him to discover the continuum character of the electron’s spectrum, entirely analogous to nuclear beta decay.

Pontecorvo’s research during his Canadian period was presented by Giuseppe Fidecaro, who delved into the development of the radiochemical method to detect neutrinos – later applied by Raymond Davis to detect solar neutrinos. Luigi Di Lella described the studies by Pontecorvo and Ted Hincks on muon decay, including the search for the decay μ → e γ – a long saga, which also saw Steinberger as a protagonist and which continues today with the MEG experiment at PSI. Di Lella ended with the ideas that Pontecorvo developed in Dubna on high-energy neutrino interactions, somehow anticipating the independent line of research carried out at Brookhaven by Leon Lederman, Melvin Schwarz and Steinberger, which eventually led to the discovery of the two kinds of neutrino in 1962 and the award of the Nobel prize in 1988.

An important part of the conference was dedicated to neutrino oscillations – Pontecorvo’s other great intuition – with an update on solar and atmospheric neutrino oscillations by Till Kirsten and Yoichiro Suzuki, respectively. An overall view was given by Samoil Bilenky from Dubna, who was a collaborator and friend of Pontecorvo for a long time.

Fig. 3. (Left) Bruno Pontecorvo with N N Bogolioubov, Dubna’s director and (right) talking to Vicky Weisskopf, CERN’s director-general.

In Dubna, Pontecorvo became the reference figure for many Russian physicists and also for the physicists from Western Europe and CERN who visited countries in the East (figure 3). Ettore Fiorini brought his recollections of Pontecorvo at the Balaton School, in Hungary, at the time of the discovery of neutral currents, while Ugo Amaldi spoke of his relations with Pontecorvo at Dubna, when the Russian participation in the DELPHI experiment at the Large-Electron Positron collider was taking shape.

Two historical talks gave an idea of the depth of Bruno Pontecorvo’s personality.

Nadia Robotti documented the path of Pontecorvo in the Panisperna group. From his initial position as the youngest and most inexperienced member of the group – he was called “the cub” – he went on to become in few years a respected researcher, signing one publication with Fermi and Rasetti alone, and owner of part of the slow-neutron technologies. Later, when the group in Rome started to split up, Pontecorvo moved independently from Fermi to find a position in Paris, in the laboratory of Frédéric Joliot and Irène Curie, where he arrived in spring 1936 as a fully formed and independent investigator in the most advanced fields of nuclear physics.

Precious testimony

In a second historical talk, Rino Castaldi brought a precious testimony from when Pontecorvo arrived in Dubna. It was a hand-written log book begun on 1 November 1950, which Gloria Spandre and Elena Volterrani obtained from Pontecorvo’s eldest son, Gil. Page after page, written in minute but precise writing with remarkably few cancellations, reconstruct a picture of Pontecorvo building up his future activity in particle physics in the new laboratory where he had chosen to spend his life. From issues in the life of an experimental physicist and ideas about new experiments, through glimpses about his thoughts on the mysterious strongly produced but long-lived particles (the strange particles), to a tantalizing formula for muon beta decay, with one neutrino encircled and the other in a box (figure 4) – could this be a hint that the two neutrinos might be different? We can leave the answer to Pontecorvo himself. Much later, he described his earlier activity on the weak interaction in a contribution to the International Colloquium on Particle Physics in Paris in July 1982:

Fig. 4. A page from Pontecorvo’s log book started in Dubna on 1 November 1950: “On the transformations of mesons”. Note the formula at the end of the page with a different characterization for the two neutrinos from muon decay.
Image credit: G Pontecorvo.

“I have to come back a long way (1947–1950). Several groups, among which J Steinberger, E Hincks and I, and others were investigating the (cosmic) muon decay. The result of the investigations was that the decaying muon emits 3 particles: one electron…and two neutral particles, which were called by various people in different ways: two neutrinos, neutrino and neutretto, ν and ν´, etc. I am saying this to make clear that for people working on muons in the old times, the question about different types of neutrinos has always been present…for people like Bernardini, Steinberger, Hincks and me…the two neutrino question was never forgotten.”

The centenary symposium took place in the Aula Magna of Sapienza University in Rome, where Fermi worked from 1935 to 1938, the year of his departure to Stockholm (for the Nobel prize) and then to the US. Organized with efficiency by the indefatigable Carlo Dionisi, professor of physics at Sapienza, it was an occasion for the larger Pontecorvo family – the Italian and Russian branches – to gather, cheer and greet friends and colleagues.

• For all of the presentations at the symposium, see https://agenda.infn.it/conferenceOtherViews.py?view=standard&confId=6051

A network for the Balkans

SEENET-MTP developed from the vision of Julius Wess (left) to re-establish scientific co-operation in Balkan countries post-1990.
Image credit: Jelena Djordjević.

From 1945 to 1990, the development of scientific educational and research capacities in physics in the Balkans followed the political and economic courses of the relevant countries. Yugoslavia and the six republics in its federation developed ties – to a greater or lesser extent – with both the East and the West, while Romania and Bulgaria became well integrated into the scientific system of the Soviet Union and the Eastern Bloc. In these countries and in the entire Balkans, the period was marked by a significant increase in the number of scientists – primarily in the field of physics – and scientific publications. There was also a substantial rise in the level of university education and scientific infrastructure, which had been lower before the Second World War or limited to a small number of exceptional yet isolated individuals or smaller institutions. Greece and Turkey were connected mainly to the US or Western Europe, while Albania was in self-imposed isolation for much of this period.

The years following 1990 brought significant changes, which were particularly dramatic and negative for the countries that were created after the break-up of Yugoslavia. The wars waged on the territory of the former Socialist Federal Republic of Yugoslavia and enormous economic problems resulted in the devastation of scientific capacities, the leaving of mainly young physicists and the stopping of many programmes and once-traditional scientific meetings – in particular the world-renowned “Adriatic meetings”. Less dramatic but more significant changes took place in Bulgaria, Romania and even Moldavia and the Ukraine – countries on the periphery of the Balkans but in the same neighbourhood. The number and quality of students graduating in physics, as well as financial investment in all forms of scientific educational work, plummeted. The number of researchers and PhD students, in particular, dropped so significantly in the majority of university centres that the critical mass necessary for teaching at graduate level as well as for teamwork and competitiveness was lost. The remaining young research groups and students – some only 100 km apart – had no form of communication, exchange or co-operation. European integration – if it began at all – proceeded slowly, while many previously established ties were severed.

Wess and WIGV

The origins of the Southeastern European Network in Mathematical and Theoretical Physics (SEENET-MTP) are linked to Julius Wess and his initiative “Wissenschaftler in globaler Verantwortung” (WIGV) – “Scientists in global responsibility” – launched in 1999 (Möller 2012). Wess was professor at the Ludwig Maximilian University (LMU) of Munich and director of the Max Planck Institute (MPI) for Physics in Munich. Like most people in Europe, he deplored the Yugoslav Wars of the 1990s and this eventually turned into a resolve to engage hands-on in re-establishing scientific co-operation with the scientists of former Yugoslavia during the “Triangle meeting” in Zagreb in 1999. Wess collected information about the remaining links between scientists in the new countries of the former Yugoslavia and the rest of the world, and especially between the former Yugoslav countries. He also found out about the institutional and economic situation of the universities and institutes.

The first network meeting of WIGV was organized in Maribor, Slovenia, in May 2000

The first network meeting of WIGV was organized in Maribor, Slovenia, in May 2000. It was followed by activities such as the Eighth Adriatic Meeting in Dubrovnik, Croatia, and the First German-Serbian School in Modern Mathematical Physics in Soko Banja, Serbia, in 2001. Three postdoc positions and many short-term fellowships were established in Munich, supported by the German Academic Exchange Service (DAAD), the German Research Foundation (DFG) and the Federal Ministry of Education and Research (BMBF). The biggest and, in a sense, the most important action was the Scientific Information Network for South East Europe (SINSEE/SINYU) project to establish new high-speed fibre capacity across large distances, especially for the scientific community, with SINYU covering the region of the former Yugoslavia.

The network’s first meeting was the Balkan Workshop 2003 in Serbia.
Image credit: Milan Milosevic.

Unfortunately, between the summers of 2002 and 2003 the WIGV initiative lost its momentum. Many of the financial ad-hoc instruments created for the region ended during this time. Wess also needed to pause because of serious health problems in 2003. However, between October 2000 and December 2002 the idea of a “southeastern European” rather than “Yugoslav” network in mathematical and theoretical physics emerged and evolved in discussions between Wess, myself and other colleagues who visited Munich or took part in numerous meetings supported by WIGV.

Our impression was that a critical mass of students and researchers in the region of the former Yugoslavia could not be achieved and that a larger context should be attempted – the Balkans. In addition to the former Yugoslavia, this would include Bulgaria, Greece, Romania, Turkey, etc. We hoped that this kind of approach would have a political as well as scientific dimension, alongside other benefits. Agreement was quickly reached and the name Southeastern European Network in Mathematical and Theoretical Physics (SEENET-MTP) was created. With the personal recommendations of Wess, I visited CERN, the International Centre for Theoretical Physics (ICTP), the UNESCO headquarters in Paris and the UNESCO Venice office to promote the idea. In the course of discussions, the foundations were laid for support for the future network.

The SEENET-MTP Network

The founding meeting of the network was set up as a workshop – the Balkan Workshop (BW2003) on Mathematical, Theoretical and Phenomenological Challenges Beyond the Standard Model, with Perspectives of Balkans collaboration – that was held as a satellite meeting of the Fifth General Conference of the Balkan Physical Union, in Vrnjačka Banja, Serbia, in August 2003. This made it possible to have a regional meeting, with representatives from nearly all of the relevant countries present. Unlike the First German–Serbian School and some other actions, Germany’s contribution to the budget of BW2003 was no more than a third. The organization of the workshop was not without some controversy. It was a difficult but important lesson in the writing of applications for funding, proposals for projects and their implementation. The meeting, which had excellent lecturers, ended with the ratification of a letter of intent, followed by the election of myself as co-ordinator of the Network and Wess as co-ordinator of the Scientific-Advisory Committee (SAC) for the network (Djordjević 2012).

The most complex meeting of the network was the Balkan Summer Institute (BSI2011) with 180 participants and four associated events

While singling out the role of individuals might seem disproportionate, it is a pleasure to underline the role of Boyka Aneva in motivating colleagues from Sofia, Mihai Visinescu for those from Romania, Goran Senjanović of ICTP for his service as co-ordinator of the Network SAC (2008–2013) and the first and the current presidents of the Representative Committee of the SEENET-MTP Network, Radu Constantinescu of Craiova (2009–2013) and Dumitru Vulcanov of Timisoara, respectively. Starting in 2003 with 40 members and three nodes in Niš, Sofia and Bucharest, the network has grown steadily to its current size, now covering almost all of the countries in the Southeastern European region plus Ukraine. The Balkan Workshops series is an important part of the SEENET-MTP programme (see box). The most complex meeting of the network was the Balkan Summer Institute (BSI2011) with 180 participants and four associated events.

The main goals of the network and its activities and results can be summarized as follows.

• To organize scientific and research activities in the region and the improvement of interregional collaboration through networking, the organization of scientific events and mobility programmes. The network has organized 15 scientific meetings (schools and workshops) and supported an additional 10 events. Around 1000 researchers and students have taken part in these meetings. Through UNESCO projects, followed by the ICTP project “Cosmology and Strings” PRJ-09, there have been more than 200 researcher and student exchanges in the region, about 150 seminars and 100 joint scientific papers. In co-operation with leading publishers both in the region and the rest of the world, the network has published numerous proceedings, topical journal issues and two monographs. It has also implemented 15 projects, mainly supported by UNESCO, ICTP and German foundations.

At the Balkan Workshop 2013 (left to right), Luis Álvarez-Gaumé, Goran Djordjević, Guido Martinelli, Paolo Creminelli and Raul Jimenez.
Image credit: Milan Milosevic.

• To promote the exchange of students and encourage communication between gifted pupils motivated towards natural sciences and their high schools. Three meetings and contests in the “Science and society” framework have been organized in Romania with 100 high-school pupils and undergraduate students. The network was a permanent supporter and driving force in establishing and supporting the first class for gifted high-school pupils in Niš, Serbia, and its networking with similar programmes.

• To create a database as the foundation for an up-to-date overview of results obtained by different research organizations and, through this, the institutional capacity-building in physics and mathematics. The SEENET-MTP office in Niš, established in 2009, in co-operation with the University of Craiova and UNESCO Venice office, set up the project “Map of Excellence in Physics and Mathematics in SEE – the SEE MP e-Survey Project”. It has collected a full set of data on 40 leading institutions in physics and mathematics in seven Balkan countries.

BW2013: 10 years of the network

This year’s Balkan workshop – BW2013 Beyond the Standard Models – was held on 25–29 April in Vrnjačka Banja, Serbia, just like the first one. The meeting also provided an opportunity to mark 10 years of the network, which now consists of 20 institutions from 11 countries in the region and has 14 partner institutions and more than 350 individual members from around the world. It was organized by the Faculty of Science and Mathematics and SEENET-MTP office, Niš, in co-operation with the CERN Theory Group, the International School for Advanced Studies (SISSA) and ICTP, with the Physical Society Niš as local co-organizer.

The workshop offered a platform for discussions on three topics: beyond the Standard Model, everyday practice in particle physics and cosmology, and regional and interregional co-operation in science and education. The first two days were devoted to purely scientific problems, including new trends in particle and astroparticle physics: theory and phenomenology, cosmology (classical and quantum, inflation, dark matter and dark energy), quantum gravity and extra dimensions, strings, and non-commutative and non-archimedean quantum models. It was an opportunity to gather together leading experts in physics and students from the EU and Eastern Europe to discuss these topics. The third day was organized as a series of round tables on building sustainable knowledge-based societies, with a few invited lecturers and moderators from the Central European Initiative (CEI), UNESCO, the European Physical Society (EPS) etc.

Participants at the Balkan Workshop 2013, which was held in Vrnjačka Banja, Serbia, as was the first one.
Image credit: M Milosevic.

In total, 78 participants from 25 countries came to the events. Around 30 invited scientific talks, 15 panel presentations and several posters were presented. The EPS president John Dudley, EPS-CEI chair Goran Djordjević and former EPS presidents Macie Kolwas and Norbert Kroó were among the panellists. Mario Scalet (UNESCO Venice), Fernando Quevedo (ICTP), Luis Álvarez-Gaume, Ignatios Antoniadis and John Ellis (CERN), Alexei Morozov (ITEP, Moscow), Guido Martinelli (SISSA), Radomir Žikić (Ministry of Education and Science, Serbia) and others contributed greatly to the overall discussion and decisions made towards new projects. Dejan Stojković (SUNY at Buffalo) was unable to attend but has contributed a great deal as lecturer, adviser and guest editor in many network activities. Under the aegis and with the support of the EPS, the first meeting of the EPS Committee of European Integration (EPS-CEI) took place during the workshop and the first ad-hoc consortium based on the SEENET-MTP experience for future EU projects established.

SEENET-MTP: main network meetings

• BW2003 Workshop, Vrnjačka Banja, Serbia
• BW2005 Workshop, Vrnjačka Banja, Serbia
• MMP2006 School, Sofia, Bulgaria
• BW2007 Workshop, Kladovo, Serbia
• MMP2008 School, Varna, Bulgaria
• SSSCP2009 School, Belgrade-Niš, Serbia
• EBES2010 Conference, Niš, Serbia
• QFTHS2010 School and Workshop, Calimanesti, Romania
• BSI2011 Summer Institute, Donji Milanovac, Serbia
• QFTHS2012 School and Workshop, Craiova, Romania
• BW2013 Workshop, Vrnjačka Banja, Serbia

Despite the unexpected success of the SEENET-MTP initiative, its future faces challenges: to provide a mid-term and long-term financial base through EU funds, to prove its ability to contribute to current main lines of research, to extend the meeting’s activities from Bulgaria, Romania and Serbia and to other countries in the network, to organize a more self-connected and permanent training programme through topical one-week seminars for masters and PhD students in its nodes and, possibly in the future, joint masters or PhD programmes.

SEENET-MTP and physicists in the SEE region still need a partnership with leading institutions, organizations and individuals, primarily from Europe. In addition to LMU/MPI, the role of which was crucial in the period 2000–2009, and the long-term partners UNESCO and ICTP, the most promising supporters should be EPS, SISSA and CEI, as well as the most supportive one in the past few years – CERN and its Theory Group.

Golden jubilee in Protvino

Collage of Provotino — (Top left) Signatures of those involved or present at the start-up of the U-70 in October 1967. (Bottom left) The 30 MeV RFQ linac – injector. (Centre) The main ring of the 70 GeV synchrotron. (Top right) An aerial view of IHEP. (Bottom right) The main experimental area at the U-70.
Image credits: IHEP.

The Institute for High Energy Physics (IHEP), Protvino, was established as a new Soviet particle-physics laboratory 50 years ago in November 1963. Four years later, the 70-GeV proton synchrotron U-70 – which became known as the “Serpukhov accelerator” – was commissioned, reaching a world-record proton energy of 76 GeV on the night of 14 October 1967. Physics research started at the beginning of 1968, conducted by several groups with unprecedented international participation for that time, in teams from CERN and the French Atomic Energy Commission (the CEA).

Only four years had passed since the theoretical proposal of quarks as elementary constituents of matter, so searching for them in the new energy range became one of the top priorities for the experiments at the U-70. Free quarks were not found but this negative result appears to have been the first of a long list from similar attempts that resulted finally in the well-known hypothesis of quark confinement.

Meanwhile, among many interesting new results that were obtained at the IHEP accelerator during its first years of operation, two in particular stand out: discovery of the growth of hadronic cross-sections with energy and the scaling behaviour of hadronic inclusive distributions. It is worth noting that both phenomena are poorly understood still, even in the framework of modern theory.

Today, IHEP is continuing to carry out a programme of fundamental research at the U-70 in the areas where the accelerator’s parameters offer the opportunity for significant outcomes. In particular, the upgrade of the accelerator complex for higher intensity will create a unique beamline of separated K mesons and a new experimental facility OKA for an extensive programme of research with kaons.

The current physics research programme covers a variety of topics. The spectroscopy of mesons and baryons is served by several experimental facilities: VES, SVD, HYPERON and MIS-ITEP. The search for rare decays of K mesons and for CP violation is the focus for ISTRA+ as well as for OKA. The study of the structure of nucleons takes place with polarized beams in the Spin Asymmetry in Charm production (SPASCHARM) experiment and the FODS double-arm spectrometer, while FODS also investigates hard processes. Last, the SPIN experiment is looking at the properties of baryonic matter. In theoretical particle physics, the main achievements and current activities of the IHEP physicists are related to the physics of heavy quarks, strong interactions at high energies, quantum field theory, gravitation and cosmology.

Collage of pics — (Top left) On 4 July 1967, CERN’s director-general, Bernard Gregory, and Andrey Petrosiants sign the agreement between CERN and IHEP. (Bottom left) International co-operation at the U-70. (Top centre) Construction at IHEP of the first test module for the LHCb hadron calorimeter.

Alongside the fundamental physics research, IHEP also undertakes extensive studies in accelerator physics and technology. Here, the principle and techniques of radio-frequency quadrupole (RFQ) acceleration proposed and developed at IHEP have been one of the notable achievements in accelerator science. IHEP also put forward the use of bent-crystal deflectors for the extraction of particle beams and for collimation. This technique is now widely used at the U-70 accelerator as well as at Fermilab and at CERN.

An important recent achievement at the U-70 was the commissioning in 2010 of stochastic slow beam extraction, which has significantly improved the performance of the machine and increased the efficiency of the experiments. Since 2011, the U-70 has been upgraded to accelerate carbon nuclei to 24.1–34.1 GeV per nucleon. This has allowed IHEP to proceed with experiments in the field of fixed-target relativistic nuclear physics.

In the area of applications, in 2004–2010 IHEP developed and constructed a unique proton radiography facility, which has been successfully used in co-operation with physicists from the All-Russian Research Institute of Experimental Physics (VNIIEF) in Sarov. In 2011, the U-70 received a new slow-extraction system at flat bottom, which delivers a beam of carbon nuclei at 450–455 MeV per nucleon for applied research.

Last but not least, IHEP contributes significantly in broad international collaborations with CERN, Fermilab and Brookhaven National Laboratory. Examples include the production of an endcap muon wall for the DØ experiment at Fermilab’s Tevatron, an electromagnetic calorimeter for the PHENIX experiment at Brookhaven’s Relativistic Heavy-Ion Collider, electrical feedboxes, dump resistors, septum magnets and beam-loss monitors for CERN’s LHC, monitored drift-tube chambers and tiles for hadron calorimetry in the ATLAS detector at the LHC, crystals for electromagnetic calorimetry in the CMS experiment, and modules for LHCb’s hadron calorimeter. IHEP is also a Tier-2 site in the Wordwide LHC Computing Grid.

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