edited by Richard Brenner, Carlos P de los Heros and Johan Rathsman, World Scientific. Hardback ISBN 9812566627, £56 ($98).
The Lepton–Photon symposia are among the most popular conferences in high-energy physics, since they give in-depth snapshots of the status of the field as provided by leading experts. Inside this volume, readers will find the latest results on flavour factories, quantum chromodynamics, electroweak physics, dark-matter searches, neutrino physics and cosmology, from a phenomenological point of view. It also offers a glimpse of the immediate future through summaries on the status of the next generation of high-energy accelerators and planned facilities for astroparticle physics. The review nature of the articles makes the volume useful to students, as well as to established researchers in high-energy and astroparticle physics.
Edited by Cosmas K Zachos, David B Fairlie and Thomas L Curtright, World Scientific. Hardback ISBN 9812383840, £64 ($86).
Wigner’s quasi-probability distribution function in phase space is a special (Weyl) representation of the density matrix. It has been useful in describing quantum transport in quantum optics; nuclear physics; decoherence, quantum computing and quantum chaos. It is also important in signal processing and the mathematics of algebraic deformation. A remarkable aspect of its internal logic, pioneered by Groenewold and Moyal, has emerged in the last quarter-century, furnishing a third, alternative, formulation of quantum mechanics, independent of the conventional Hilbert space or path integral formulations. This book is a collection of the seminal papers on this formulation, with an introductory overview, an extensive bibliography, and simple illustrations, suitable for application to a broad range of physics problems.
by Mohsen Razavy, Imperial College Press. Hardback ISBN 1860945252, £51 ($84). Paperback ISBN 1860945309, £29 ($48).
The aim of this book is to elucidate the origin and nature of dissipative forces and to present a detailed account of attempts to study dissipative phenomena in both classical mechanics and quantum theory. It begins with an introductory review of phenomenological damping forces, and the construction of the Lagrangian and Hamiltonian for the damped motion, and moves on to investigate the use of the classical formulation in the quantization of dynamical systems, and finally the problem of dissipation in interacting quantum mechanical systems. A number of important applications, such as the theory of heavy-ion scattering and the motion of a radiating electron, are also discussed.
by James P Sethna, Oxford University Press. Hardback ISBN 019856676X, £49.95 ($99.50). Paperback ISBN 0198566778, £24.95 ($44.50).
In each generation, scientists must redefine their fields: abstracting, simplifying and distilling the previous standard topics to make room for new advances and methods. This book takes this step for statistical mechanics – a field rooted in physics and chemistry whose ideas and methods are now central to information theory, complexity and modern biology. Aimed at advanced undergraduates and early graduate students in all of these fields, Sethna limits his main presentation to the topics that future mathematicians and biologists, as well as physicists and chemists, will find fascinating and central to their work. The large supply of carefully crafted exercises, each an introduction to a whole field of study, covers everything from chaos through information theory to life at the end of the universe.
by Theodore Arabatzis, The University of Chicago Press. Hardback ISBN 0226024202, £44.50 ($70). Paperback ISBN 0226024210, £18 ($28).
Both a history and a metahistory, this book focuses on the development of various theoretical representations of electrons from the late 1890s until 1925, and the methodological problems associated with writing about unobservable scientific entities. Here, the electron – or rather its representation – is used as a historical actor in a novel biographical approach. Arabatzis illustrates the emergence and gradual consolidation of its representation in
physics, its career throughout old quantum theory, and its appropriation and reinterpretation by chemists. Furthermore, he argues that the considerable variance in the representation of the electron does not undermine its stable identity or existence. The book should appeal to historians, philosophers of science and scientists alike.
edited by Howard E Haber and Ann E Nelson, World Scientific. Hardback ISBN 9812388923, £105 ($172).
This book features three lecture-series courses given at the School of the Theoretical Advanced Study Institute (TASI) on Elementary Particle Physics in 2002. The phenomenology lectures cover a broad spectrum of the research techniques used to interpret present day and future collider data. The TeV-scale physics lectures focus on modern speculations about physics beyond the Standard Model, with an emphasis on supersymmetry and extra-dimensional theories. The series on astroparticle physics looks at recent developments in theories of dark matter and dark energy, the cosmic microwave background, and prospects for the upcoming era of gravitational wave astronomy. Researchers and graduate students in high-energy physics, mathematical physics and astrophysics will find topics of interest.
by Afsar Abbas, Indian Institute of Advanced Study. Hardback ISBN 8179860604, Rs150.
This “new perspective” discusses the philosophical issues inherent within the research pursued by scientists at the forefront today. Examples from modern science, in particular the current hot topics in physics, have been provided to clarify the issues under discussion. The book is written so as to be accessible even to non-experts, but experts will find much that is new in the philosophy of science presented here. Detailed treatment of mathematics and space, along with time and matter, have also been provided.
In June 2005, the president of the CERN Council, Enzo Iarocci, proposed that an ad hoc scientific advisory group be established to produce a draft European strategy for particle physics. The Strategy Group was charged to meet at a one-week workshop during the first week of May at Zeuthen, near Berlin, to work out the draft strategy. Council met in Lisbon on 14 July 2006, discussed this draft, and adopted the European strategy for particle physics.
The Strategy Group brought together a broad competence. It had one member nominated by each of the CERN member states and the directors of the major European particle physics laboratories. In addition, there were eight members from the CERN Scientific Policy Committee and the European Committee for Future Accelerators, who, together with the scientific secretary and the co-chairs, made up the Preparatory Group charged with the work needed to bring the meeting in Berlin to a successful conclusion.
For the Strategy Group meeting seven representatives were also invited from the CERN observer states, and from the Astroparticle Physics European Coordination (ApPEC) Committee, the Nuclear Physics European Collaboration Committee (NuPECC) and the Funding Agencies for the Linear Collider (FALC).
The process towards the European strategy for particle physics had four essential elements: the Strategy Group Web page, an open symposium held in Orsay from 29 January – 1 February, a Briefing Book containing the information needed to develop the strategy, and the Zeuthen meeting of the Strategy Group.
The Strategy Group Web page was the main channel for communication with the community. Minutes of the Preparatory Group meetings were posted on the website, usually within 24 hours of the meeting. More importantly, it was possible to submit contributions to the discussions through the website; 71 individuals and groups did so. The website also provided a set of links to background material.
The Open Symposium hosted by the Laboratoire de l’Accélérateur Linéaire in Orsay was a key stage in, the process. It was attended by more than 400 people, with at least 70 more following the proceedings via a webcast. The programme comprised of a series of talks aimed at identifying the key issues for a range of different topics. A particular feature of the symposium was that more than half of the time was devoted to discussions, and this time was indeed filled with a lively exchange of views.
The Briefing Book consisted of three volumes, all of which are accessible from the Strategy Group Web page. The first volume was written by the Preparatory Group, and covered scientific activities (largely based on the presentations and discussions in Orsay) and more general issues. The second volume covered the input received via the website, reports from laboratories, funding agencies and others in response to written requests, and other information that the Preparatory Group felt would assist the development of the strategy. The third volume contained the agenda for the meeting in Zeuthen, procedural details, a standardized vocabulary to describe projects and scientific objectives, and the templates for the strategy statement itself.
The full Strategy Group and official observers met at DESY in Zeuthen on 2 May. This first day was open to anyone and was also broadcast via the Web. It was devoted to talks from three invited speakers, the directors of the invited laboratories and the representatives of the observer states. On the second day, six groups studied the frontier questions in particle physics; improved understanding of the Standard Model; non-accelerator physics and the interface to cosmos; the strong interaction and the interface with nuclear physics; organization issues for the universities, national laboratories and CERN; and inter-regional collaboration. On day three, a plenary session covered the reports from the working groups and agreed preliminary conclusions on elements of the strategy. The next day, while a draft working document was assembled based on the previous day’s discussions, five groups worked in parallel on the needs of theoretical particle physics, industry, technology and knowledge transfer, education and outreach.
The draft strategy document was discussed at Zeuthen in a plenary session on the fifth day. Participants reached a consensus on the general statements, scientific activities and organizational issues, and provided detailed guidance on the complementary issues, which were incorporated following consultations with the chairs of the appropriate working group, thus fulfilling the remit.
Now that Council has adopted the European strategy for particle physics, and with it the responsibility to maintain and update it, the work is done, and the Strategy Group has been dissolved.
Many people were engaged in this process: local organizing committees, speakers and participants at the different discussions. Colleagues submitted opinions and ideas, and all involved people were very committed. We are all very grateful for these contributions.
Raymond Davis Jr, discoverer and grand pioneer of the solar-neutrino problem, died on 31 May at the venerable age of 91. In 1968 he discovered the solar-neutrino anomaly and more than three decades later he received the 2002 Nobel Prize in Physics. This followed other experiments based on different techniques, which demonstrated that the anomaly was neither an artifact of his experiment nor an error in the late John Bahcall’s theoretical calculations of the neutrino flux from the Sun; it was indeed a real physical effect. Simultaneously, Davis had shown that the Sun generates its energy by nuclear fusion of hydrogen into helium, and that the electron-type neutrinos created in this process change into other types of neutrino during their eight minute journey to Earth.
By his own account, Davis was drawn to the study of neutrinos out of a sense of adventure. He was invited to join the fledgling Brookhaven National Laboratory in 1948 and asked the chairman of the chemistry department about his duties. To his “surprise and delight” Davis was told to choose his own project. In the library he found a review article on neutrinos by H R Crane that clearly indicated that the field was wide open for exploration and rich in problems. Here was the path, leading he knew not where, which would enable Davis to follow his goal of studying nuclear physics using the techniques of physical chemistry.
His vehicle was a nuclear reaction suggested by Bruno Pontecorvo in 1946: a neutrino captured by a specific isotope of chlorine produces an electron and a radioactive isotope of argon. Sources of chlorine were plentiful and cheap, and argon, a noble gas, could easily be extracted from a chlorine solution. Davis counted the atoms of the argon isotope by observing the decay back to chlorine. Over the years, he tested and refined the method so that it became totally reliable as a procedure for measuring even a tiny number of argon atoms produced in Pontecorvo’s chlorine reaction.
The only copious sources of low-energy neutrinos are nuclear reactors and the Sun. Reactors produce antineutrinos from the beta-decay of heavy nuclei following the fission of uranium, while the Sun produces neutrinos in the fusion of hydrogen nuclei into helium. When Davis was beginning his experiments, the distinction between neutrino and antineutrino was not well understood and there was a serious possibility that they were identical particles. It was therefore natural for him to use reactors as the neutrino source. In fact, he worked at the Savannah River reactor at the time when Clyde Cowan and Fred Reines were performing their Nobel prize-winning experiment there using inverse beta-decay as their signal. Whereas they obtained a positive result, making the first observation of the antineutrino, Davis obtained a null result with the chlorine reaction, indicating a distinction between neutrino and antineutrino.
Davis then turned his attention to detecting neutrinos from the Sun and recognized that it was necessary to go deep underground to avoid cosmic-ray backgrounds. He also realized that observing neutrinos from the Sun would be a way of demonstrating that it generates its energy via nuclear fusion. In the early 1950s, it was known that the proton–proton fusion chain did not produce neutrinos of sufficient energy to reach the threshold for the chlorine reaction, but by the end of the decade new discoveries in nuclear physics suggested that there were additional fusion chains that produced neutrinos well above the threshold. Davis began to collaborate with Bahcall to design an experiment to observe these neutrinos.
By 1964, they were ready to propose an experiment and they published side-by-side papers in Physical Review Letters. Bahcall combined the standard model of the Sun with the relevant nuclear physics to calculate the energies and fluxes of the various branches of the solar-neutrino spectrum. Davis described an experiment to observe the higher-energy neutrinos using a 100,000 gallon tank of cleaning fluid (perchlorethylene) located deep underground. Bahcall tells an interesting story of how Davis persuaded Maurice Goldhaber, then director of Brookhaven National Laboratory, to support the experiment. Knowing that Goldhaber was very sceptical of astrophysical calculations, Davis instructed Bahcall not to mention the solar astrophysics, but to emphasize instead the novel nuclear physics involved in the chlorine reaction. Goldhaber loves a clever idea, having generated many himself, and so, as Davis predicted, he responded positively to Davis’ request.
In 1968, Davis reported that the first measurements from the experiment carried out 4850 ft underground in the Homestake gold mine in Lead, South Dakota, yielded a solar-neutrino capture rate approximately a third of that predicted by Bahcall and G Shaviv. This “socially unacceptable result”, as Bahcall later described it, caused widespread concern among both physicists and astrophysicists. Some thought that the problem lay with the experiment, others with the theory and a few with the neutrino. In the end the third option turned out to be correct, but it required an experimental and theoretical odyssey that lasted three and a half decades and ranged all over the world, from the mine in South Dakota to other mines and laboratories deep inside mountains in Japan, Russia and Italy, and finally to a nickel mine at Sudbury in northern Ontario, Canada.
The experiments themselves were remarkable in their uniqueness. Davis’ experiment required a 100,000 gallon tank specially built by the Chicago Bridge and Iron Company, and it took 10 railroad tank cars of cleaning fluid to fill it. The detector in Japan was the size of a 10 storey building. It was filled with extremely pure and continuously purified water and was surrounded by 11,000 20-inch phototubes. The neutrino detector in Russia, located deep inside the Caucasus Mountains, contained the world’s total supply of gallium, about 60 tonnes. It took two years to produce an additional 30 tonnes of gallium for an independent experiment under the Gran Sasso Mountain of central Italy. The experiment in Canada, originally proposed by the late Herbert Chen many years ago, would not have been possible without the loan of a kilotonne of heavy water from the Canadian government.
Throughout this journey, Davis continued his role as grand pioneer of the solar-neutrino problem. He kept the chlorine experiment going long after he retired from Brookhaven National Laboratory in 1984. He helped to develop the radiochemical experiment based on gallium, sensitive to the most-copious and lowest-energy solar neutrinos from the proton–proton chain, and he followed all the latest developments with a keen interest. Ultimately, at the beginning of the 21st century, the heavy-water experiment at Sudbury measured both the total highest-energy neutrino flux from the Sun and its electron–neutrino component. It confirmed Davis’ original results as well as Bahcall’s theoretical calculations, and it crowned Davis’ claim on the Nobel prize.
Davis had a truly inquiring and adventurous mind. “When I began my work, I was intrigued by the idea of learning something new,” he once said. “The interesting thing about doing new experiments is that you never know what the answer is going to be!” He was a scientist of great integrity and modesty: what mattered to him was not himself, but the science in which he was involved. Whenever colleagues asked questions or offered criticisms of his experiment, he would always devise new tests to check their ideas and make any necessary corrections. But he also had a wry sense of humour: when asked at a conference in the 1970s how much his experiment cost, he replied: “Ten minutes time on commercial television.”
Through his persistence, integrity and humility Davis spawned a revolution in neutrino physics and gave us a beautiful example of how different sciences can help one another to make fundamental discoveries. He stands as a model for all aspiring scientists to emulate.
I am not a particle physicist. I have spent most of my career as an economist and a university president with a sustained interest in science policy and its relationship to the health of the scientific enterprise and to long-term economic growth. But when the US National Research Council asked me to chair an independent committee of both physicists and non-physicists to look at the future role of the US programme in elementary-particle physics, I welcomed the chance to learn more about this intriguing area of science.
Some might wonder why such an unusual group of experts would be convened to provide advice to the US federal government on particle physics. Indeed, the committee that I chaired included members with expertise in particle physics, other branches of physics, engineering, scientific fields outside of physics, and even several non-scientists. Members from the larger international community of particle physicists were included as well. In many respects the nature of the strategic issues facing the US programme in particle physics required both fresh perspectives from a broader context and penetrating analysis to provide a credible path forward. To be frank, one of the first questions facing the committee was simply, “Does particle physics, especially accelerator-based experiments, still matter?”
During its work, the committee engaged in a comprehensive set of data-gathering activities, including public meetings, letters to and from the global community, and numerous formal and informal discussions with stakeholders around the world. As part of our work, I travelled to the major particle-physics facilities in the US, Europe and Japan. In the US, most of the major facilities are scheduled to be shut down or converted to other uses within the next few years. Europe and Japan, in contrast, have recognized the scientific potential of particle physics and have been increasing their investments.
With respect to the US programme, what I found was a scientific field at a crossroads. Particle physicists could be on the verge of answering questions that human beings have asked for millennia. What are the origins of mass? Can the basic forces of nature be unified? How did the universe evolve? Why does it have the properties that it does? But even as the scientific opportunities have blossomed, our political and social will to sustain US commitment to this field has faltered. US leadership, together with that of our colleagues abroad, is important because it is critical to reaping the scientific, technological, economic and cultural dividends that come from advancing the scientific frontier.
As the field of particle physics took shape in the middle of the 20th century, America’s scientists focused on experiments designed to measure and explain the properties and forces governing the ultimate constituents of matter. Since then, even as the field became increasingly internationalized with distinguished centres abroad, the US has been home to some of the world’s most accomplished theorists, a diverse array of experiments, and some of the largest particle accelerators. Moreover the US has welcomed and greatly benefited from the intellectual and financial input of scientists from around the world. The US role in particle physics both anchored and symbolized the growing distinction and reach of the overall US scientific enterprise.
Before continuing, let me say something about the word “leadership,” especially with such an international audience where this term may carry nationalistic or even imperialistic overtones. In the context of current discussions about globalization, “the flat world” and the growing interdependence of national efforts around the world, what does leadership mean for the US in a field such as particle physics? Leadership does not mean dominance, but rather taking initiative at the frontiers, accepting appropriate risks, and catalysing partnerships both at home and abroad. Given the wide distribution of talent and facilities it is not only futile but an irresponsible use of public resources for any country or region to aspire to dominance. In the world that lies before us, leadership will be a shared phenomenon that flows from developing and brokering mutual gains among equal partners. In articulating a strategy for the US, the committee sought a path that leveraged US strengths for the benefit of not only the domestic programme, but also the global enterprise. In terms of scientific facilities, this means that we must move from a paradigm of “We’re going to build this, will you help us?” to one of “What can we build together that will benefit us all?”
The US is now on the verge of forfeiting its role among the international leaders in particle physics. Operations at the Large Hadron Collider (LHC) in Europe will soon begin and it will become the world’s most powerful accelerator. Like many other fields in the physical sciences, federal funding for particle physics in the US has stagnated for more than a decade, and the field is gradually losing US researchers and students. Within a few years, the majority of US experimental particle physicists will be working on experiments that are being conducted in other countries. Simply put, the intellectual centre of gravity is moving abroad and the US has not put forward a compelling strategic vision to contribute to the global enterprise.
This potential retreat of the US programme in particle physics from the scientific frontiers could not be happening at a worse time. Particle physics is entering one of the most exciting periods in its history. The technologies needed to do experiments at the terascale are now available, and both theoretical and experimental results point towards revolutionary new discoveries that will be made at this scale. Physicists could not only discover new dimensions and the particles responsible for mass (or other phenomena unimagined today), but these experiments could also provide clues to the nature of dark energy and dark matter, which are essential to our comprehension of the universe. Indeed in the next few decades particle physics could yield a radical new view of the cosmos.
Even as the Europeans have been finishing the LHC, particle physicists worldwide have been designing the next generation of particle accelerator. Known as the International Linear Collider (ILC), this new tool would comprise two accelerators that fire electrons and anti-electrons at each other head-on, probing conditions that existed just a fraction of a second after the birth of the universe. The ILC is so important and so large an undertaking that it can only arise from a global effort. The potential role of the US in building, supporting, and perhaps hosting the ILC is now a key to the continued distinction of the US programme. Indeed, participation in the scientific opportunities addressed by the ILC is likely to be important for any nation actively engaged in particle physics, but it is particularly important now for the US because of the absence of any other key strategic focus.
To ensure its vitality in particle physics and to contribute effectively to the global effort, the US must be willing to do three things. First, it must maintain a broad range of theoretical and experimental programmes, since new discoveries often come from unexpected places. Second, it must make a commitment to participating in the direct and controlled exploration of the terascale. In part, that means supporting the work of US scientists at the LHC. It also means investing the risk capital so that the US can be in a position, four or five years from now, to mount a compelling bid to host the ILC – if the US decides then that it is still in its best interests to compete for the ILC. For the US to mount a compelling bid, however, it must not only demonstrate the technical capabilities and economic resources necessary for hosting the ILC, but it must also demonstrate the energy, enthusiasm and commitment that are required to be a credible international partner. Moreover, the science of the terascale is so compelling that the US should play a strong role in the ILC no matter where it is sited. Third, to ensure a responsible use of public funds, the US must make an increased commitment to establishing mutually advantageous joint ventures with its colleagues abroad.
Scientific leadership, like competitiveness, is won generation by generation, but once it is lost it is difficult for the next generation to win it back. Students stop enrolling in graduate programmes, university departments scale back or shut down, researchers emigrate, retire or move to other fields. Maintaining the leading role of the US will need continued federal support, probably at a greater level than at present if the US mounts a compelling bid and is chosen to host the ILC. But the history of science demonstrates that our investments can be expected to repay themselves many times over.
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