Praxis Archives – Page 162 of 181

Database lists the top-cited physics papers

cernpapers1_12-01 — A family photograph from the international Particle Data Group. Its annual Review of Particle Physics encapsulates all of the latest experimental developments and measurements, and it is invariably the top-cited particle physics paper of the year. The group effort involves many more people than appear here. Left to right, front row: Maury Goodman (Argonne), Charles Wohl (Lawrence Berkeley Laboratory – LBL), Keith Olive (Minnesota), Kenzo Nakamura (KEK) and John March-Russell (CERN). Middle row: Michael Barnett (LBL), Vitaly Lugovsky (Protvino), Gail Harper (LBL), Betty Armstrong (LBL), Ken-ichi Hikasa (Tohoku), Wei-Ming Yao (LBL), Alberto Masoni (INFN Cagliari) and Petr Vogel (Caltech). Back row: Boris Filimonov (Protvino), Orin Dahl (LBL), Paul Gee (LBL), Matts Roos (Helsinki), Tom Trippe (LBL), Andreas Piepke (Alabama), Michelangelo Mangano (CERN), Gianni Conforto (Urbino), Ron Workman (George Washington University), Don Groom (LBL), Masaharu Tanabashi (Tohoku), Michael Doser (CERN) and Ramon Miquel (LBL).

The SPIRES-HEP database maintained by the library at the Stanford Linear Accelerator Center (SLAC) connects preprint or eprint versions to articles published in journals or conference proceedings, providing access to all phases of the publication history. The database lists virtually every high-energy physics paper published or even preprinted over the past 30 years.

In addition, most papers now have backward links to the papers that they cite and forward links to the papers citing them. These citation links provide a very effective means of searching the literature. In the past few years SPIRES-HEP has been automatically harvesting reference citations from eprints, creating a web of links that thoroughly indexes the literature.

As a by-product of this citation linkage, SPIRES-HEP can easily search out the papers most cited by publications in high-energy physics. The list of papers with the most citations in a given year provides a snapshot of the hottest topics that have engaged the attention of theorists and experimenters. For the past few years, SPIRES HEP has posted a scientific review of the year’s top-cited papers.

We have recently posted the “top-cited” lists for 2000. These materials include a list of the papers with more than 100 citations in the past year and a list of the papers with more than 1000 citations over the history of the SPIRES-HEP database.

So what are, by this measure, the hottest topics of 2000? Table 1 lists the top 10 cited papers and the number of citations of those papers in 2000. These papers represent major areas of activity that are discussed further in the review posted at the SPIRES Web site. The top-cited reference in high-energy physics is always the Review of Particle Properties. Below this in the list, the following areas are represented. (Papers appearing in the “top 10 cited list” are referred to by a number that indicates their position on the list.)

Maldacena’s duality

A broad swath of developments in string theory and related areas of mathematical physics has resulted from Maldacena’s 1997 paper (2), which propose a relation between supergravity and superstring theories in (d+1) dimensional anti-de Sitter space and supersymmetric Yang-Mills theories in d-dimensions.

Anti-de Sitter space, the homogeneous space of constant negative curvature, has a boundary in the sense that light signals propagate to space-like infinity in finite time. Maldacena proposed that, for a gravity theory living in the interior of the space, there would be a corresponding, and equivalent, scale-invariant quantum field theory living on the boundary. Subsequently, Witten (7), and Gubser, Klebanov and Polyakov (9), gave a precise relation between correlation functions in the boundary theory and S-Matrix elements for the gravity theory in the interior.

These developments have led to many insights, illuminating both the properties of strongly coupled Yang-Mills theory and quantum gravity theories. It is remarkable that Maldacena’s paper has managed, in just three years, to accumulate more than 1600 citations and to vault to position 25 on the all-time citation list.

Extra space dimensions

Though string theory predicts the existence of seven extra space dimensions, these have conventionally been considered to be unobservably small and irrelevant to ordinary particle physics. However, the next three papers on the “top-cited” list involve theoretical models in which extra space dimensions play a direct role in particle physics and, in particular, explain the mass scale of the Higgs boson. Randall and Sundrum (3, 4) have proposed two different scenarios in which our four-dimensional universe is a flat, three-dimensional surface in anti-de Sitter space.

Arkani-Hamed, Dimopoulos and Dvali (5) have proposed a scenario in which our universe is a surface in a large, flat space-time, the size of which may approach the millimetre scale. Further consequences of this model are developed in paper 10. Both of the models 4 and 5 will have crucial tests at CERN’s LHC collider, which may give direct experimental evidence for the presence of new space dimensions (Discovering new dimensions at LHC).

Non-commutative field theory

Many ideas about quantum gravity lead to the idea that space-time co-ordinates are non-commuting operators. Non-commutative Yang-Mills theory, which was invented by Connes, gives a simple field theory model in which consequences of the possible non-commutativity of space can be studied. Paper 6, by Seiberg and Witten, explained the connection between Connes’ model and various compactifications of string theory, launching an intense investigation into non-commutative dynamics.

Neutrino physics

In experimental particle physics the most surprising development of the past few years has been the discovery by the Super-kamiokande collaboration of atmospheric neutrino oscillations (8). This experimental result indicates the presence of neutrino mass and large mixing among the lepton generations. It has led to many speculations on the origin of flavour mixing and to a new, intense level of experimentation on neutrino properties.

The complete list of the top 40 cited papers of 2000 and a more detailed scientific review can be found at the SLAC Web site. The site also includes a “top-cited” list for each eprint archive relevant to high-energy physics. In Table 2 the top-cited paper (exclusive of the Particle Data Group’s Review of Particle Properties) in each archive is shown.

We make no claim that the papers that we have listed here are currently the most important papers in high energy physics. Year-by-year accounting is influenced as much by fashion as by logical scientific development. Both the standard electroweak model and string theory spent many years in the cellar of the citation counts before rising to their current prominence. If you favour a trend, a model or an experiment that is not listed here, more power to you. We hope that your insights will be well represented on our lists before the end of the decade.

Table 1: Top-cited articles of 2000

Article	No. of citations	Article	No. of citations
1 Particle Data Group, 1998 Review of particle physics Eur. Phys. J. C3 1-794	1236	6 Nathan Seiberg and Edward Witten, String theory and noncommutative geometry (hep-th/9908142)	397
2 Juan Maldacena, 1998 The large N limit of superconformal field theories and supergravity Adv. Theor. Math. Phys. 2 231-252 (hep-th/9711200)	498	7 Edward Witten, 1998 Anti-de Sitter space and holography Adv. Theor. Math. Phys. 2 253-291 (hep-th/9802150)	347
3 Lisa Randall and Raman Sundrum, 1999 An alternative to compactification Phys. Rev. Lett. 83 4690-4693 (hep-th/ 9906064)	446	8 Y Fukuda et al., 1998 Evidence for oscillation of atmospheric neutrinos Phys. Rev. Lett. 81 1562-1567 (hep-ex/ 9807003)	325
4 Lisa Randall and Raman Sundrum, 1999 A large mass hierarchy from a small extra dimension Phys. Rev. Lett. 83 3370-3373 (hep-ph/9905221)	414	9 S S Gubser et al., 1998 Gauge theory correlators from noncritical string theory Phys. Lett. B428105-114 (hep-th/ 9802109)	316
5 Nima Arkani-Hamed, Savas Dimopoulos and Gia Dvali, 1998 The hierarchy problem and new dimensions at a millimeter Phys. Lett. B249 263 (hep-ph/9803315)	403	10 Ignatios Antoniadis et al., 1998 New dimensions at a millimeter to a Fermi and superstrings at a TeV Phys. Lett. B436 257-263 (hep-ph/9804398)	301

Table 2: Top citations within each eprint archive

Archive	Article	No. of citations
GR-QC	S W Hawking, 1975 Particle creation by black holesCommun. Math. Phys. 43 199-220	61
HEP-EX	Torbjorn Sjostrand, 1994 High-energy physics event generation with PYTHIA 5.7 and JETSET 7.4 Comput. Phys. Commun. 82 74-90	94
HEP-LAT	Herbert Neuberger, 1998 Exactly massless quarks on the lattice Phys. Lett. B417 141-144 (hep-lat/9707022)	68
HEP-PH	Y Fukuda et al., 1998 Evidence for oscillation of atmospheric neutrinos. Phys. Rev. Lett. 81 1562-1567 (hep-ex/9807003)	265
HEP-TH	Juan Maldacena, 1998 The Large N limit of superconformal field theories and supergravity Adv. Theor. Math. Phys. 2 231-252 (hep-th/9711200)	465
NUCL-EX	J P Bondorf et al., 1995 Statistical multifragmentation of nuclei Phys. Rept. 257 133-221	16
NUCL-TH	R Wiringa, V Stoks and R Schiavilla, 1995 An accurate nucleon-nucleon potential with charge independence breaking Phys. Rev. C51 38-51 (nucl-th/ 9408016)	53

Spin in Particle Physics

Elliot Leader, Cambridge University Press, ISBN 0521352819, hbk £90/$130.

Elliot Leader’s book – in the series of Cambridge Monographs on Particle Physics, Nuclear Physics and Cosmology – is a thorough introduction to the theory and experimental study of high-energy spin physics.

Both theoretically and experimentally, spin physics has always been a challenge. In recent years there has been considerable growth in research activities related to spin phenomena and their theoretical interpretation. There is an extensive list of review papers but few books devoted to the subject.

However, Leader’s book provides a comprehensive introduction, with a pedagogical approach to high-energy spin physics. The novelty of the book is also in the rather detailed description of experimental techniques and apparatus, as well as the standard theoretical part. A large number of appendices with technical details and formalism are valuable for the pedagogical treatment of spin problems and make for quick reference.

A significant part of the monograph deals with the problem of nucleon spin structure – the topic widely discussed since 1988 when the results of the European Muon Collaboration showed that the spin of the proton is not the sum of the spins of its individual quarks.

The small-x behaviour of the polarized structure function is one of the unsolved problems en route to a final resolution of the overall nucleon spin puzzle and is discussed from different points of view. The gluon anomaly and a general perturbative QCD approach to the nucleon spin problem are discussed in detail, including the evolution, scheme-dependence and phenomenology of the polarized parton distributions.

Alongside these topics, an introduction to the parton model, the Standard Model, QCD and the general formalism of polarized deep-inelastic scattering is presented. The helicity structure of QCD interactions is considered thoroughly and fermion spin structure is analysed for the case of massive and massless spinors. Possibilities of testing Standard Model and perturbative QCD predictions in the two-spin and parity-violating single-spin asymmetries measured at large angles are listed. Such experiments are useful tools for the detection of gluon polarization, which is a possible solution of the nucleon spin problem.

Another outstanding problem of spin physics is the observation of significant single-spin transverse asymmetry. In the framework of perturbative QCD, the polarization of an individual quark in a hard subprocess should vanish because of the vector type of the QCD interaction, which leads to chirality conservation. However, experimentally there is a mass of data showing large asymmetries or large polarizations, in both elastic and semi-inclusive reactions.

The different mechanisms for producing non-zero, single-spin transverse asymmetries, including final-state interactions, are considered. All such explanations are in fact beyond the standard QCD parton model. The most prominent single-spin asymmetry was observed in inclusive hyperon production, where over two decades ago it was discovered that highly polarized , L hyperons are produced in the collision of unpolarized protons. Most dramatic is that despite the large hyperon polarization, it has no tendency to decrease with the transverse momentum of the produced hyperon, as could be expected from perturbative QCD mechanisms. This whole area of high-energy physics is a challenge for the theory of strong interactions. Only phenomenological models have had any success in the quantitative description of hyperon polarization data.

One chapter is devoted to spin effects in elastic scattering at high energy, which is a most fundamental type of reaction and where a lot of experimental data exist at low and medium energies. There are also high-energy data that demonstrate a rising dependence of analysing power in proton-proton scattering with transferred momentum. A conclusion made in the book clearly indicates that QCD demands the opposite behaviour of the analysing power in elastic proton-proton scattering, but there are no specific predictions for analysing power based on QCD and it does not provide an estimate for where the decreasing behaviour begins. The experimental study of this process is an indispensable source of knowledge on the nucleon wavefunction and a clear and unambiguous way to check perturbative QCD as well as the models based on the non-perturbative approaches to hadron dynamics.

Significant attention is devoted to technical problems, in particular the mechanisms of polarized hadron and electron production and acceleration. In particular, polarized proton sources, polarized targets, difficulties in the acceleration of polarized particles (including “Siberian snakes”) and polarization at LEP, HERA and SLC are described. This increases the potential reader audience. Besides these problems, the book treats in detail the polarimetry issues that are essential for modern experimental high-energy spin physics, especially for the experimental programme with polarized protons at RHIC.

The first five chapters of the book consider the basic formalism and definitions of spin, helicity, spin-density matrix, transition amplitudes and observables of a reaction. The properties of helicity states and wavefunctions under Lorentz and discrete transformations are described in a clear, pedagogical manner. For example, an intelligible derivation of the famous Thomas precession is presented.

In conclusion, it should be stressed that in the light of ongoing major experimental studies (for example, COMPASS at CERN, RHIC-SPIN at Brookhaven and SPIN@U70 at IHEP), this book is useful and timely, describing the state of the field and providing reference points for the interpretation of forthcoming experimental data in high-energy spin physics – a subject that underwent rapid growth during the last decades of the past century. The book is suitable for students at graduate level and will be of interest to the broad high-energy physics community.

History centre publishes archiving guidelines

According to a recently released report by the American Institute of Physics (AIP) Center for the History of Physics, the documentation of collaborative scientific research needs urgent attention. The problems that need to be addressed range from the way in which the contributions of distinguished individuals (or records of a project conducted by one institution) are preserved, to the fact that, almost without exception, research institutions and federal science agencies fail to provide adequate support to programmes to save records of significant research.

To remedy this, the AIP History Center has issued Documenting Multi-Institutional Collaborations – the final report of its decade-long study of multi-institutional collaborations in physics and allied fields.

The main recommendations of the report are that:

* scientists and others should take special care to identify past collaborations that have made significant contributions;

* research laboratories and other centres should set up a mechanism to secure records of future significant experiments;

* institutional archives should share information.

The report makes a broad distinction between “core records” – to be saved for all collaborations – and other records to be saved for “significant collaborations”.

School returns to Switzerland

cernnews3_11-01 — An impressive backdrop at the 2001 European School of High-Energy Physics, held at Beatenberg in the Swiss Bernese Oberland. On the left loom the Eiger and Mönch peaks, with the Jungfrau summit obscured by a small cloud.

For the first time since its inception nearly 40 years ago, the European School of High-Energy Physics was held in Switzerland at Beatenberg in the Bernese Oberland. Running from 26 August to 8 September, it attracted 95 students from 30 countries. This year’s event was organized in association with the University of Bern, with Klaus Pretzl as school director. Funds for students from former Soviet Union countries came from the INTAS international association.

These schools have become a major event in the particle physics calendar. The tradition began in 1962 with a one-week course at St Cergue, Switzerland, for young students and senior physicists using the emulsion technique at CERN. The 1963 school also took place at St Cergue, but with the emphasis on physics rather than on techniques.

In 1964 the courses moved outside Switzerland and the programme was extended to include bubble chamber as well as emulsion techniques. By 1965 the focus had switched to teaching theoretical elementary particle physics to young experimentalists, where it has remained ever since.

International participation widened in 1970 when the school was held in Finland, in collaboration with the Joint Institute for Nuclear Research (JINR), which is based in Dubna, near Moscow. The following year, JINR organized a school in Bulgaria, in collaboration with CERN, after which biennial joint schools continued up to and including 1991, when the last JINR-CERN school has held in the Crimea in the USSR.

With the changed political scene in Europe, schools continued to be organized jointly every year, but under the title European School for High-Energy Physics, and with a four-year cycle consisting of three annual schools in CERN member states and the fourth in a JINR member state.

cernnews4_11-01 — Participants at the 2001 European School of High-Energy Physics at the Jungfraujoch station, 3580 m above sea level.

In 1993 the first such school took place, appropriately, in Zakopane, Poland, a member state of both CERN and JINR. Since then the school has been held in Sorrento, Italy (1994); Dubna, Russia (1995); Carry-le-Rouet, France (1996); Menstrup, Denmark (1997); St. Andrews, Scotland (1998); Bratislava, Slovakia (1999); Caramulo, Portugal (2000); and Beatenberg, Switzerland (2001).

Quaero makes particle detector datasets available for all

cernnews5_11-01 — Opening up the data – the D0 collaboration at Fermilab’s Tevatron.

A major step towards “transparent” particle physics has come from a new scheme that opens up data collected by the D0 experiment at Fermilab’s Tevatron proton-antiproton collider.

When physicists started to study the behaviour of the atomic nucleus 90 years ago, they carefully watched scintillating screens for the tiny flashes produced as alpha particles were scattered by nuclear targets. The scintillating screen was the detecting medium and the experimenters’ own eyes provided the “read-out”.

Later came track chambers, such as cloud and bubble chambers. These were of immense appeal because physicists could directly see what happened in particle interactions. However, these instruments have been relegated to science museums, and today’s research relies instead on fast electronics. When today’s high-energy particle beams are made to collide, the big detectors surrounding the collision point are the physicists’ “eyes”.

One of the big challenges facing a newborn baby is to make sense of all of the jumbled visual signals that it sees and to learn to recognize and interpret patterns – people, objects and their surroundings. In the same way, the physicists operating a large electronic detector have to convert the raw impulses received by the various detector components and be able to say, for example, that a certain bunch of signals represents a 50 GeV pion travelling in a certain direction. Tracking is still there but the tracks are the results of computers analysing the impulses recorded in successive layers of the detector rather than direct “snapshots”.

Analysing the results of an experiment thus has to be carried out by physicists who “know” the detector. Another physicist who is not intimately acquainted with the detector but who has a hypothesis and wants to test this against actual data has to ask physicists from the experiment for help.

cernnews6_11-01 — University of Chicago physicist Bruce Knuteson.

In the new development – called Quaero from the Latin for “I search” – the interpretation of certain datasets collected by the Fermilab D0 experiment from 1992 to 1996 has already been done and is openly available to other physicists to use as a testbed for models and theories. The data are classified according to the type of particles produced and include several of the datasets that led to the discovery of the top quark at Fermilab in 1995. This opening up of carefully collected data has become standard practice in astronomy.

Chicago physicist Bruce Knuteson, who masterminded Quaero, is currently at CERN to see if similar procedures can be established for the data archives of the four big experiments at CERN’s LEP electron-positron collider, which closed last year. He is optimistic. Electrons and positrons are pointlike, so electron_positron collisions are “cleaner” and less complicated than the proton-antiproton interactions studied at the Tevatron. Protons and antiprotons are in fact bunches of quarks and gluons, each of which can have its own collision products.

In the past, testing a model against actual data could take at least a few years. Quaero can do this in an hour. Until now there was no way of publishing a complete dataset of a high-energy physics experiment. Published plots show data in just two dimensions, making it difficult for another physicist to take the data as presented in a publication and translate them into some other context. The Quaero paper has been accepted for publication in Phsical Review Letters.

If Quaero is extended to LEP data, then anyone who wants will be able to sift for Higgs particles or other physics.

Report urges scientists to secure their records

cernarch1_9-01 — The TESLA test facility at the DESY laboratory, Hamburg, has achieved record results for a free-electron laser.

According to a recently released report by the American Institute of Physics (AIP) Center for the History of Physics, there are many problems facing the documentation of collaborative research. These range from the way in which the contributions of distinguished individuals (or records of a project conducted by one institution) are preserved, to the fact that, almost without exception, research institutions and federal science agencies fail to provide adequate support to programmes to save records of significant research.

To help to find solutions, the AIP History Center has issued Documenting Multi-Institutional Collaborations – the final report of its decade-long study of multi-institutional collaborations in physics and allied fields.

The main recommendations of the report are that:

* scientists and others should take special care to identify past collaborations that have made significant contributions;

* research laboratories and other centres should set up a mechanism to secure records of future significant experiments;

* institutional archives should share information.

The long-term study focused on high-energy physics, space science, geophysics, ground-based astronomy, materials science, medical physics, nuclear physics and an area called computer-mediated collaborations. The main goal of the project was to learn enough about these transient communities to be able to advise on how to document them.

The study was built on interviews with more than 600 scientific collaborators; numerous site visits to archives, records offices and US federal agencies; and advice from working groups of distinguished scientists, archivists, records officers, historians and sociologists. The study group gathered and analysed data on characteristics of collaborations, such as their formation, decision-making structures, communication patterns, activities and funding.

According to the report, scientists in multi-institutional collaborations are well aware that their way of doing research is unlike that of others working alone or in small groups. All too often, however, scientists fail to realize how records needed to document research are prone to destruction. It may appear to them that their recollections and those of their colleagues are sufficient. This is thought to be unfortunate from the standpoint of present needs. From the standpoint of the future it is disastrous, for even the imperfect recollections will die with the scientists and later generations will never know how some of today’s important scientific work was done. For particle physics, the report has some specific suggestions.

Core records

The report makes a broad distinction between “core records” — those records to be saved for all collaborations — and records to be saved for “significant collaborations”. The definitions of the former are slanted towards traditional US procedures with Department of Energy or National Science Foundation funding for experiments carried out at major US laboratories. However, these can be paraphrased unambiguously for a more global audience without too much trouble.

The additional records for significant collaborations include correspondence between the experiment spokesperson, the experiment collaboration and laboratory administrators. Intracollaboration meetings, collaboration groups, interinstitutional committees, and project management and engineering documents are also deemed to be important under this heading.

Oeuvre et engagement de Frédéric Joliot-Curie

eds Monique Bordry and Pierre Radvanyi, EDP Science, ISBN 2868835252.

Frédéric Joliot-Curie, a major French scientific figure, was born in 1900 and the 100th anniversary of his birth called for a special celebration. This took place on 9-10 October 2000 at the Collège de France, where he was a professor until his death in 1958 and where he long communicated his insight and enthusiasm to the many members of his laboratory.

The symposium consisted of three series of formal talks, each followed either by numerous testimonies from many of those who had the privilege to work with Joliot Curie, or know him well, or by round-table discussions with invited participants. These three main themes covered artificial radioactivity (the discovery for which he, together with his wife Irène, received the 1935 Nobel Prize for Chemistry), nuclear energy, and social and political commitments.

Joliot-Curie was not only a great scientist but he also played a key role in the early development of nuclear energy in France, and was for more than two decades a very important figure in French political and social circles.

The symposium was opened by Hubert Curien, former president of the CERN council, and closed by an address from Minister of Research Roger-Gérard Schwartzenberg. A plaque commemorating the discovery of artificial radioactivity was unveiled at the Institut du Radium.

This beautifully edited book brings together the texts of all of the invited talks, testimonies and round-table presentations during the symposium. It is in French except for two historical texts in English. The book pays ample tribute to Joliot-Curie but also provides much topical matter. It not only brings the past alive, but also shows in a brilliant and well documented way how many questions on which Joliot-Curie strongly made his mark are still very important today. There are many historical photographs and a good biographical summary. The cover is graced by a Picasso portrait.

Heavy Quark Physics

by Aneesh V Manohar and Mark B Wise, Cambridge University Press, ISBN 0521642418 (hbk) £40/$64.95.

Most of the achievements in the understanding of the physics of particles containing heavy quarks date from the past decade, both on the experimental and on the theoretical side. More and more precise measurements of b hadron properties carried out at CESR, LEP and the Tevatron colliders have gone in parallel with the development of the Heavy Quark Effective Theory (HQET), which has become the key tool for a quantitative description of the interactions of heavy particles. Such important theoretical developments were up to now documented in a fairly large number of papers, published over the years by the pioneers of the field. Manohar and Wise now provide us with a valuable textbook on heavy quark physics. The presentation of the material is clear and concise, covering the majority of the fundamental theoretical results currently available in the field.

The book starts with a review of the Standard Model. A discussion of spin-flavour symmetry follows, including the implications for the heavy hadron spectroscopy and for the hadron production rates in the heavy quark hadronization. Then HQET is developed, first at one loop in the infinite mass limit, then including radiative corrections and 1/m_Qcorrections. Many important results are derived, such as the heavy meson decay constants, the form factors in the semileptonic decay of B mesons to D and D* mesons, and the semileptonic decays of L_b to L_cbaryons (heavy-to-heavy currents) and L_c to L (heavy-to-light).

Chiral perturbation theory is also discussed, deriving the matrix elements for the semileptonic decay of heavy-to-light mesons, as well as corrections to heavy-to-heavy transitions (BÆ D(*)en). The powerful operator product expansion formalism is finally developed and used to calculate inclusive weak decays of b hadrons.

Some of the calculations are reported step by step, especially when they involve techniques and subtleties developed for the purpose that have become key tools in HQET. Each chapter is complemented with problems that are non-trivial applications of the theory discussed, and a collection of bibliographical references.

The book is aimed at readers with a solid background in quantum field theory who are aiming to get acquainted with the techniques of HQET. The illuminating discussions of the approximations and assumptions made at each step, and of their implications on the validity of the results derived, make it valuable reading for all physicists who want to get a better insight into heavy quark physics, even without going through all of the calculations.

Heavy quark physics is now entering an exciting new era in which high-luminosity machines will significantly improve our experimental knowledge, demanding corresponding progress in the precision of theoretical predictions. This text provides a concise and systematic summary of today’s knowledge, and will stay as a bibliographical milestone while new developments take place.

At the Frontier of Particle Physics: Handbook of QCD – Boris Ioffe Festschrift

edited by M Shifman, three volumes, World Scientific, ISBN 9810244452, set £112.

As would be expected from such a meticulous editor (see The Supersymmetric World – The Beginnings of the Theory edited by G Kane and M Shifman, World Scientific, ISBN 981024522X), these three volumes contain a wealth of well-prepared and highly valuable information. They bring together 33 reviews covering all aspects of the analytical aspects of the theory of quantum chromodynamics (QCD), assembled to mark the 75th birthday of Boris Ioffe. The majority of the work provides an encyclopedia of QCD that is useful for students and for research workers.

The first part of the work is more historical, and it includes contributions from Ludwig Faddeev on quantizing Yang-Mills fields, and from David Gross on the discovery of asymptotic freedom and the emergence of QCD. These are followed by an amusing aside by Shifman: “How the asymptotic freedom of the Yang-Mills Field could have been discovered three times before Gross, Wilczek and Politzer, but was not”.

Introducing all of this is the material specifically on Ioffe and on events in Russia at the end of the 20th century, with very useful editorial explanations. After the introductory festschrifts, Boris Ioffe’s Top Secret Assignment (which won the 1999 Novy Mir prize after being published in that magazine) and Yuri Orlov’s Snapshots from the 1950s (based on excerpts from Orlov’s book Dangerous Thoughts – William Morrow 1991, New York) are full of fascinating insights.

Superconducting Materials for High Energy Colliders

edited by L Cifarelli and L Maritato, World Scientific Science and Culture Series – Physics, ISBN 080243197.

cernbooks1-10-01 — Test string for superconducting magnets for CERN’s LHC collider. Particle physics is a major focus for research and development work in applied superconductivity.

Imagine the ultimate high-energy physics project – 10 times as powerful as CERN’s mighty LHC collider. This ambitious goal, which is aiming for a hadron collider with a collision energy of 200-1000 TeV and with a luminosity as high as 10³⁶, is the theme of Antonino Zichichi’s foreword to this book. The vision of the multihundred TeV “ultimate collider”, the Eloisatron, is supported by the conviction that no energy threshold well beyond the Standard Model seems near.

The book is dedicated to the memory of Tom Ypsilantis and gives a full description of a workshop held in Erice, Sicily, at the end of 1999 on superconducting materials for future high-energy colliders. This marked the return of a full European perspective of the Eloisatron workshops, after a period during which the European community had been busy designing the LHC, while our US colleagues emerged from the trauma of the cancelled SSC and set up a new programme that is now focused on the VLHC.

With the LHC on track to produce physics by 2006, European scientists began to look beyond the present horizon. The workshop provided an excellent forum where materials scientists met with accelerator specialists to exchange information and to focus R&D towards common goals.

Superconductivity is the key accelerator technology, and the communities striving for high field (magnets) and for high gradient (radiofrequency cavities) exploit the absence of electrical resistance at low temperatures. In the reverse direction, high-energy physics has provided the right environment (and resources) to achieve real progress in applied superconductivity, by developing high-critical current density cables with fine filaments and achieving mass-production. A good example is magnetic resonance imaging (MRI), which could not have progressed from a laboratory-scale experiment to a general medical technique without the impetus of high-energy physics cryogenics.

At the Erice workshop, Philippe Lebrun, head of CERN’s LHC division, addressed the problem of technical management of megascience projects and described what we are learning with the LHC, the first global accelerator project, and reviewed the main machine subsytems, including the powerful cryogenics needed to keep some 50,000 tons of superconducting magnets at 1.9 K – the coldest point of the universe and twice as cold as the relic cosmic microwave radiation. Also for the LHC, Tom Taylor covered the vigorous technical effort that is under way to design and build the LHC’s superconducting components to conform to stringent energy and luminosity requirements, and the room for improvements.

Kjell Johnsen, the designer of CERN’s ISR, the first hadron collider, reviewed the tentative feasibility study of the Eloisatron, just 10 years after it was issued, showing that the machine, although very ambitious, is technically feasibly with a 300 km ring where some 16,000 dipoles reaching 10 Tesla can provide 100 TeV proton beams (200 TeV collisions).

On basic superconductivity, C Grimaldi (Lausanne) introduced the present understanding of high-temperature superconductors (HTS), stressing that much work still needs to be done, but the reward would be the cheap and easy cryogenics of liquid nitrogen.

J Halbrittner (Karlsruhe) described the detailed analysis of radiofrequency losses in superconducting cavities, showing the present superiority of bulk niobium cavities over sputtered ones for very high power.

Superconducting cavities for frontier colliders were the topic of an extensive review by H Padamsee (Cornell) on the impressive progress with bulk niobium and niobium-sputtered copper cavities. With proper selection and treatment of the material, the road is open to 40 MV/m and a TeV electron_positron superconducting linear collider. A Cassinese (INFM-Naples) described microwave measurements of superconducting films of niobium and niobium-tin, stressing the need to understand surface resistance.

L Rossi (Milan) turned to the design and characteristics of accelerator magnets, highlighting the demands on superconductor performance to build 5-15 T dipole and quadrupole magnets. He included an overview of worldwide R&D for magnets beyond the LHC-phase1, emphasizing the necessity of a vigorous effort to improve niobium-tin characteristics to reach a critical current of 1000 A/mm² at 18 T (LHC-phase1 material reaches this level at 8 T and 4.2 K) and showed the novel magnet designs being explored in the US for VLHC studies.

The Japanese effort on doped niobium-tin reinforced with a copper-niobium matrix was covered by K Watanabe (IMR, Tohoku) who showed the potential of this technique to overcome the problems posed by the brittleness of niobium-tin. Japan is also leading the effort on the less brittle niobium-aluminium superconductor, and K Inoue (NRIM, Tsukuba) described the potential of the recently developed, rapid-quenching and transforming process. Although very difficult, this process could achieve interesting current densities.

For HTS, K Salama (Houston) reviewed the fabrication technique for bismuth- and yttrium-based, silver-stabilized superconducting tapes, reporting an improvement in critical current of almost an order of magnitude using suitable heat treatment. His former assistant, L Martini (ENEL-Ricerca, Milan), reported on his unique “accordion-folding method” to produce short (0.1-1 m) Bi-2223 samples with a very low silver content, useful for low-consumption multi-kA current leads (needed in large quantities for the LHC).

J Scudiere (American Superconductor Corporation) reviewed the results obtained by the leading company in HTS development and production. The impressive results on short samples have yet to be reproduced in long samples. However, for fields above 18 T, HTS could become a viable alternative to niobium within a few years. He highlighted the necessity of reasonable homogeneity and reliability of such a delicate (ceramic) material under “industrial” conditions and indicated that a production rate of at least 2000 km/year of tapes is needed to reduce prices to a reasonable level. Considering that such a quantity is approximately equivalent to about 50 LHC dipoles, major projects are needed to drive this promising material to market (as for MRI). Finally, C M Friends (BICC General Superconductors) reported on 13 kA HTS current leads for the LHC and the development of Bi-2223 tapes and of round wires (radial filaments) for low losses in AC conditions.

The book gives the impression that accelerator technology is far from saturation and there is plenty of room yet for exciting developments and significant breakthroughs. On an optimistic note, in the two years since the workshop was held, the increase in conductor performance from LHC values to final goals is already half-achieved. A field of 14.5 T at 4.2 K was attained earlier this year at Berkeley in a short model with a new niobium-tin coil configuration.

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