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Pakistan: fulfilling Salam’s wish

Hafeez Hoorani.
Image credit: Muhammad Imran/NCP.

In September 1954, the European Organization for Nuclear Research – CERN – officially came into existence. This was just nine years after the Second World War, when Europe was completely divided and torn apart. Founders of CERN hoped that “it would play a fundamental role in rebuilding European physics to its former grandeur, reverse the brain drain of the brightest and best to the US, and continue and consolidate post-war European integration”. Today, as one of the outstanding high-energy physics laboratories in the world, CERN has not only more than fulfilled the goals of its founders, but is also a laboratory for thousands of physicists and engineers from all over the world.

CERN is a fine example in which high technology and science reinforce both each other and international collaboration. Exploration of the unknown is the hallmark of fundamental research. This requires, on one hand, cutting-edge technology for developing detectors for the LHC, the world’s largest accelerator. On the other hand it necessitates new concepts in computer software for the storage and analysis of the enormous amount of data generated by LHC’s experiments.

On 31 July, Pakistan officially became an associate member of CERN. There is one respect in which CERN has a very special relationship with Pakistan. Experiments done at CERN in 1973 provided the first and crucial verification of one of the predictions of electroweak unification theory proposed by Sheldon Glashow, Abdus Salam and Steven Weinberg, which resulted in the award of the 1979 Nobel Prize in Physics to these three physicists. In a speech made by Salam on 11 May 1983 in Bahrain, he said: “We forget that an accelerator like the one at CERN develops sophisticated modern technology at its furthest limit. I am not advocating that we should build a CERN for Islamic countries. However, I cannot but feel envious that a relatively poor country like Greece has joined CERN, paying a subscription according to the standard GNP formula. I cannot rejoice that Turkey, or the Gulf countries, or Iran or Pakistan seem to show no ambition to join this fount of science and get their people catapulted into the forefront of the latest technological expertise. Working with CERN’s accelerators brings at the least this reward to a nation, as Greece has had the perception to realize.” Salam’s wish has now been fulfilled.

Pakistan has had an established linkage with CERN for more than two decades. The CERN–Pakistan co-operation agreement was signed in 1994. In 1997, the Pakistan Atomic Energy Commission signed an agreement for an in-kind contribution worth $0.5 million for the construction of eight magnetic supports for the CMS detector. This was followed by another agreement in 2000, where Pakistan assumed responsibility for the construction of part of the CMS muon system, increasing Pakistan’s contribution to $1.8 million. Through the same agreement, the National Centre for Physics (NCP) became a full member of the CMS collaboration. In 2004, the NCP established a Tier-2 node in the Worldwide LHC Computing Grid, the first in south-east Asia.

Since then, there has been no looking back. Pakistan has contributed to all of the four big experiments at the LHC, as well as in the consolidation of the LHC accelerator itself. Above all, Pakistani physicists and hardware built in Pakistan for the CMS detector played an important role in the discovery of the Higgs boson in 2012, the last missing piece of the Glashow–Salam–Weinberg model.

Pakistan’s collaboration with CERN has already resulted in numerous benefits: manufacturing jobs in engineering, benefiting Pakistani industry; engineers learning new techniques in design and quality assurance, which in turn improves the quality of engineering in Pakistan; a unique opportunity for interfacing among multidisciplinary groups in academia and industry working at CERN; and working in an international environment with people from diverse backgrounds has advantages of its own.

It is hoped that CERN has also benefited from the expertise brought in by Pakistani scientists, students, engineers and technicians to save time and money. It has certainly been satisfying for Pakistan to contribute in a small way in this great enterprise.

We also plan to get involved in CERN’s future research and development projects. In particular, there is keen interest in the Pakistani physics community to participate in R&D for future accelerators. Discussions are already underway to understand where we can contribute meaningfully, keeping in mind our resources and other limitations. In particular, there is strong interest among Pakistani physicists to be involved in the R&D for a future linear collider.

In this new phase of Pakistan–CERN co-operation, which started on 19 December 2014 with the signing of the document for associate membership (CERN Courier January/February 2015 p6), the emphasis will shift to finding work opportunities at CERN for young scientists and engineers, as well as to the training of young Pakistani scientists at CERN. It will also be an opportunity for Pakistan to be more deeply involved in fundamental research in physics. For this purpose, we would involve our graduate students in work with physics groups at CERN as a part of their PhD studies. This would provide an opportunity for our young scientists and engineers to contribute to knowledge at the very frontiers of physics.

Particle Accelerators: From Big Bang Physics to Hadron Therapy

By Ugo Amaldi
Springer
Paperback: £19.99 €36.01 $34.99
E-book: £14.99 €29.74 $19.99
Also available at the CERN bookshop

There was a time when books on particle physics for the non-expert were a rarity; not quite as rare as Higgs bosons, but certainly as rare as heavy quarks. Then, rather as the “November revolution” of 1974 heralded in the new era of charm, beauty and top, so the construction of the LHC became the harbinger of a wealth of “popular” books on particle physics, and the quest to find the final piece of the Standard Model and what lies beyond. These books can be excellent in what they set out to do, but few venture where Ugo Amaldi goes – to look at the basic tools that have made this whole adventure possible, and in particular, the accelerators and their builders. Without the cyclotron and its descendants, there would be no Standard Model, no CERN, no LHC. Nor would there be the applications, particularly in medicine, which Amaldi himself has done so much to bring about.

As the son of Edoardo Amaldi, one of CERN’s “founding fathers”, Ugo Amaldi must have the history of particle physics in his bones, and he writes with feeling about the development of particle accelerators, introducing each chapter with personal touches – photos of roads at CERN named after important protagonists, anecdotes of his personal experience, quotes from people he admires. There is a passion here that makes the book interesting even for those who already know the basic story. Indeed, while particle physicists may not be the main audience the author had in mind, they can still learn from many chapters, “speed-reading” the parts they are familiar with, then dwelling on some of the historical gems – such as the rather sad story of the co-inventor of strong focusing, Nick Christofilos, about whom I had previously known little beyond his being Greek and a lift engineer.

For the non-expert, the book has much to absorb, the result of containing quite a thorough mini-introduction to the Standard Model and beyond – the author’s inner particle physicist could clearly not resist. Yet it is worth persevering and reaching the chapters on “accelerators that care”, to use Amaldi’s phrase, to discover the medical applications of the 21st century.

So, this is a book for everyone, and in particular, I believe, for young people. Books like this inspired my studies, and I would like to think that Amaldi will inspire others with his passion for physics.

High Gradient Accelerating Structure

By W Gai (ed.)
World Scientific
Hardback: £65
E-book: £49

This proceedings volume, for the symposium in honour of Juwen Wang’s 70th anniversary, is dedicated to his many important achievements in the field of accelerator physics. Wang has been a key member of SLAC for many years, working on accelerating structures for linear colliders, up to and including the CLIC project at CERN, as well as the Linac Coherent Light Source at SLAC. The book includes discussions of recent advances and challenging problems by experts in the field of high-gradient accelerating structures.

International Seminars on Nuclear War and Planetary Emergencies 46th Session: The Role of Science in the Third Millennium

By A Zichichi and R Ragani (eds)
World Scientific
Hardback: £98
E-book: £74

The 46th Session of the International Seminars on Nuclear War and Planetary Emergencies, held in Erice, Sicily, gathered again, in 2013, more than 100 scientists from 43 countries. This is the latest output from an interdisciplinary effort that has been going on for the past 32 years, to examine and analyse planetary problems that are followed up, throughout the year, by the World Federation of Scientists’ Permanent Monitoring Panels.

Nuclear Radiation Interactions

By Sidney Yip
World Scientific
Hardback: £49

Based on a first-year graduate-level course that the author taught in the Department of Nuclear Science and Engineering at MIT, this book differs from traditional nuclear-physics texts for a nuclear-engineering curriculum by emphasizing the understanding of nuclear radiations and their interactions with matter. In generating nuclear radiations and using them for beneficial purposes, scientists and engineers must understand the properties of the radiations and how they interact with their surroundings. Hence, radiation interaction is the essence of this book.

Birds and Frogs: Selected Papers, 1990–2014

By Freeman J Dyson
World Scientific
Hardback: £38
Paperback: £18

Birds and Frogs is a wonderful collection of essays and papers by Freeman Dyson from 1990 to 2014, and a sequel to a volume of earlier papers. It consists of a short introductory section followed by four more: “Talks about Science”, “Memoirs”, “Politics and History” and “Technical Papers”.

The book takes its title from one of the “Talks about Science”, in which Dyson classifies mathematicians – and, I would add, physicists – as either “birds” or “frogs”. He writes: “Birds fly high in the air and survey broad vistas of mathematics out to the far horizon. They delight in concepts that unify our thinking and bring together diverse problems from different parts of the landscape. Frogs live in the mud below and see only the flowers that grow nearby. They delight in the details of particular objects, and they solve problems one at a time. I happen to be a frog, but many of my best friends are birds.” This section contains a wealth of fascinating thoughts on, for example, the origins of life, resistance to new ideas in physics, and the nature of computation in the human brain.

Despite his claim to be a frog, much of the book is written with a bird’s-eye view. Dyson is perhaps uniquely placed among living scientists in having been privy to much that went on in the early days of quantum field theory, and to have met and be able to write about personal experiences with many of our modern-day heroes. In the “Memoirs” section, and elsewhere, he offers insights not only into their work, but also their lives and beliefs.

“Politics and History” ranges from science and religion to ethics, and education from the points of view of Tolstoy and Napoleon. His recollections and observations about the Second World War are as unique as they are fascinating. Ultimately, he shares spectacular and optimistic visions for our future as a species that can spread life throughout the universe.

It is the section on “Technical Papers” that shows Dyson the frog. Here, number theory, bounds on variation of the fine structure constant, detectability of gravitons and game theory all appear.

Whether you’re a frog or a bird or neither – Dyson has a penchant for classifying things into a small number of categories, often just two – you are certain to find much to delight you in this eclectic and yet somehow unified collection.

Cosmic Ray Origin: Beyond the Standard Models

By Omar Tibolla et al. (eds)
Elsevier
Nuclear Physics B (Proc. Suppl.) 256–257 (2014)

Where do cosmic rays, discovered more than a century ago, come from? The standard model of their origin points to natural particle accelerators in the form of shock waves in supernova remnants, but there is mounting experimental evidence that there are other sources. This conference brought together a range of experts to examine the evidence and to consider some of the key questions. What other sources might there be in the Galaxy? What causes the knee? Where (in energy) is the transition to an extragalactic component? What extragalactic sources are conceivable?

LHCb reports observation of pentaquarks

Fig. 1. Dalitz plot showing m²(K^–p) versus m²(J/ψ p). The horizontal band is produced by pentaquark particles decaying into J/ψ p.

In 1964, Murray Gell-Mann and George Zweig independently predicted a substructure for hadrons: baryons would be comprised of three quarks, mesons of a quark–antiquark pair. They also said that baryons with four quarks and one antiquark were possible, as were mesons with two quarks and two antiquarks – dubbed, respectively, pentaquarks and tetraquarks, after the number of constituents. Since then, the picture for baryons and mesons has been thoroughly established within QCD, the theory of the strong interaction. Claims of the sighting of pentaquarks, meanwhile, have been thoroughly debunked. Nevertheless, their existence could cast important new light on QCD.

Fig. 2. The mass of the J/ψ p system in Λ_b→ J/ψ K^– p decays.

Now, the LHCb collaboration has announced the observation of two pentaquark states, P⁺_c, in analysis of data collected during Run 1 of the LHC at CERN. The discovery was made during the analysis of the decay Λ_b→ J/ψ K^– p, a decay mode used in the precision measurement of the Λ_b lifetime (CERN Courier July/August 2013 p8). There was, however, an apparent anomaly in the pattern of these decays. The Dalitz plot, in which only 5.4% is background, shows several expected Λ*→K^– p resonances as vertical bands, but there is also a horizontal band, indicative of a resonance decaying into J/ψ p, which was completely unexpected (figure 1).

Fig. 3. An example of the Λ_b decay. In the top image, the Λ_b (purple dotted line) travels 3.9 cm before it decays into μ⁺μ^–K^–p, whose tracks are shown in the image below. The μ⁺μ^– are the decay products of the J/ψ.

A resonance decaying into J/ψ p would be a pentaquark state (with quarks uudcc). So LHCb investigated more deeply, with a full six-dimensional amplitude analysis of the two interfering decay sequences: Λ_b→ J/ψ Λ*, Λ* → K^– p, and Λ_b→ P⁺_c K^–, P⁺_c→ J/ψ p. This analysis not only fit the invariant mass of the decay products, the angular distributions for the decays were also fit, along with the invariant mass – this was not a simple “bump hunt”.

The first attempt was to fit the data without any P⁺_c states, with the belief that the structure could be built up from Λ* interferences. This failed. The next attempt was with one P⁺_c state, but the fit was deficient. Finally, a fit with two P⁺_c states proved to be acceptable. The masses of the states are 4380±8±29 MeV and 4449.8±1.7±2.5 MeV, with widths of 205±18±86 MeV and 39±5±19 MeV, respectively. The states have opposite parities, with one state having spin 3/2 and the other spin 5/2. The final fitted J/ψ p mass spectra show the two states (figure 2). The significances of each state are more than 9σ.

LHCb has subjected the results to a great many systematic checks. These include ensuring that tracks were not “clones” or “ghosts”, splitting the data into different subsets, such as Λ_b versus Λ_b, data from 2011 versus 2012, magnetic field up versus down, etc. All of these tests have been passed.

One interesting fact is that these pentaquarks decay into J/ψ, as do candidate states for tetraquark mesons (CERN Courier June 2014 p12). This suggests that two heavy quarks may be needed to provide the binding for these exotic states.

Pakistan becomes associate member state of CERN

The Islamic Republic of Pakistan became an associate member state of CERN on 31 July, following notification that Pakistan has ratified an agreement signed last December, granting this status to the country (CERN Courier January/February 2015 p6).

Pakistan’s new status will open a new era of co-operation that will strengthen the long-term partnership between CERN and the Pakistani scientific community. Associate membership will allow Pakistan to participate in the governance of CERN, through attending CERN Council meetings. Moreover, it will allow Pakistani scientists to become CERN staff members, and to participate in CERN’s training and career-development programmes. Finally, it will allow Pakistani industry to bid for CERN contracts, thus opening up opportunities for industrial collaboration in areas of advanced technology.

CERN superconducting dipole-magnet model reaches record performance levels

On 16 June, an 11 T superconducting dipole-magnet model manufactured at CERN for the High-Luminosity LHC project reached record performance levels in tests in hall SM18. Its magnetic-field intensity exceeded 11 T after just six quenches – a much faster increase than in previous models. In addition, it reached 12 T – corresponding to a current of 12,800 A – which is higher than in earlier models. The new magnets, based on a niobium-tin (Nb₃Sn) superconductor, are being developed in a collaboration between Fermilab and CERN. Models constructed on both sides of the Atlantic have previously reached the required 11 T, but only after many quenches. The models are shorter than the final magnets – 2 m rather than 5.5 m – and have only a single bore, rather than two bores for the two LHC beams.

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