8 July 2016

• Tunnel Visions • Statistical Methods for Data Analysis in Particle Physics • Path Integrals for Pedestrians • Books received

Tunnel Visions
By M Riordan, L Hoddeson and A W Kolb
University of Chicago Press
Also available at the CERN bookshop

The Superconducting Super Collider (SSC), a huge accelerator to be built in Texas in the US, was expected by the physicists who supported it to be the place where the Higgs boson would be discovered. Instead, the remnants of the SSC facilities at Waxahachie are now property of the chemical company Magnablend, Inc. What happened in between? What did go wrong? What are the lessons to be learnt?

Tunnel Visions responds to these historical questions in a very precise and exhaustive way. Contrary to my expectations, it is not a doom and gloom narration but a down to earth story of the national pride, good physics and bad economics of one of the biggest collider projects in history.

The book depicts the political panorama during the 10 years (~1983–1993) of life of the SSC project. It started during the Reaganomics, hand in hand with the International Space Station (ISS), and concluded during the first Clinton presidency after the 1990s recession and the end of the Cold War. The ISS survived, possibly because political justifications for space adventure are easier to find, but most probably because from the beginning it was an international project. The book explains the management intricacies of such a large project, the partisan support and disregard, until the final SSC demise in the US congress. For the particle-physics community this is a well-known tale, but the historical details are welcome.

However, the book is more than that, because it also sheds light on the lessons learnt. The final woes of the SSC signed the definitive opening of the US particle-physics community to full international collaboration. For 50 years, without doubt, the US had been the place to go for any particle physicist. Fermilab, SLAC and Brookhaven were, and still are, great stars in the physics firmament. Even if the SSC project had not been cut, those three had to keep working in order to maintain the progress in the field. But that was too much for essentially a zero-sum budget game. The show must go on, so Fermilab got the main injector, SLAC the BaBar factory, and Brookhaven the RHIC collider. Thanks to these upgrades, the three laboratories made important progress in particle physics: top quark discovery; W and Z boson precision measurements; Higgs boson mass hunt narrowing between 113 and 170 GeV; detection of possible discrepancies in the Standard Model associated with b-meson decay; and the discovery of the liquid-like quark–gluon plasma.

Why did the SSC project collapse? The authors explain the real reasons, not related to technical problems but to poor management in the first years and the clash of cultures between the US particle-physics community and the US military-industrial system. But there are also reasons of opportunity. The SSC was several steps beyond its time. To put it into context: during the years of the SSC project, at CERN the conversion of the SPS into a collider took place, along with the whole LEP programme and the beginning of the LHC project. That effort prevented any possible European contribution to the SSC. The last-ditch attempt to internationalize the SSC into a trans-Pacific partnership with Japan was also unsuccessful. The lessons from history, the authors conclude, are that at the beginning of the 1990s the costs of frontier experimental particle physics had grown too much, even for a country like the US. Multilateral international collaboration was the only way out, as the ISS showed.

The Higgs boson discovery was possible at CERN. The book avoids any “hare and tortoise” comparison here, however, since in the dawning of the new century, the US became a CERN observer state with a very important in-kind contribution. In my opinion, this is where the book grows in interest because it explains how the US particle-physics community took part in the LHC programme, becoming decisive. In particular, the US technological effort in developing superconducting magnets was not wasted. The book also talks about the suspense around the Higgs search when the Tevatron was the only one still in the game during the LHC shutdown after the infamous incident in September 2008.

Useful appendices providing notes, a bibliography and even a short explanation of the Standard Model complete the text.

• Rogelio Palomo, University of Sevilla, Spain.

Statistical Methods for Data Analysis in Particle Physics
By Luca Lista
Also available at the CERN bookshop

Particle-physics experiments are very expensive, not only in terms of the cost of building accelerators and detectors, but also due to the time spent by physicists and engineers in designing, building and running them. With the statistical analysis of the resulting data being relatively inexpensive, it is worth trying to use it optimally to extract the maximum information about the topic of interest, whilst avoiding claiming more than is justified. Thus, lectures on statistics have become regular in graduate courses, and workshops have been devoted to statistical issues in high-energy physics analysis. This also explains the number of books written by particle physicists on the practical applications of statistics to their field.

This latest book by Lista is based on the lectures that he has given at his home university in Naples, and elsewhere. As part of the Springer series of “Lecture Notes in Particle Physics”, it has the attractive feature of being short – a mere 172 pages. The disadvantage of this is that some of

the explanations of statistical concepts would have benefited from a somewhat fuller treatment.

The range of topics covered is remarkably wide. The book starts with definitions of probability, while the final chapter is about discovery criteria and upper limits in searches for new phenomena, and benefits from Lista’s direct involvement in one of the large experiments at CERN’s LHC. It mentions such topics as the Feldman–Cousins method for confidence intervals, the CLs approach for upper limits, and the “look elsewhere effect”, which is relevant for discovery claims. However, there seems to be no mention of the fact that a motivation for the Feldman–Cousins method was to avoid empty intervals; the CLs method was introduced to protect against the possibility of excluding the signal plus background hypothesis when the analysis had little or no sensitivity to the presence or absence of the signal.

The book has no index, nor problems for readers to solve. The latter is unfortunate. In common with learning to swim, play the violin and many other activities, it is virtually impossible to become proficient at statistics by merely reading about it: some practical exercise is also required. However, many worked examples are included.

There are several minor typos that the editorial system failed to notice; and in addition, figure 2.17, in which the uncertainty region for a pair of parameters is compared to the uncertainties in each of them separately, is confusing.

There are places where I disagree with Lista’s emphasis (although statistics is a subject that often does produce interesting discussions). For example, Lista claims it is counter-intuitive that, for a given observed number of events, an experiment that has a larger than expected number of background events (b) provides a tighter upper limit than one with a smaller background (i.e. a better experiment). However, if there are 10 observed events, it is reasonable that the upper limit on any possible signal is better if b = 10 than if b = 0. What is true is that the expected limit is better for the experiment with smaller backgrounds.

Finally, the last three chapters could be useful to graduate students and postdocs entering the exciting field of searching for signs of new physics in high energy or non-accelerator experiments, provided that they have other resources to expand on some of Lista’s shorter explanations.

• Louis Lyons, University of Oxford, UK.

Path Integrals for Pedestrians
By E Gozzi, E Cattaruzza and C Pagani
World Scientific

The path integral formulation of quantum mechanics is one the basic tools used to construct quantum field theories, especially gauge-invariant theories. It is the bread and butter of modern field theory. Feynman’s original formulation developed and extended some of the work of Dirac in the early 1930s, and provided an elegant and insightful solution to a generic Schrödinger equation.

This short book provides a clear, pedagogical and insightful presentation of the subject. The derivations of the basic results are crystal clear, and the applications worked out to be rather original. It includes a nice presentation of the WKB approximation within this context, including the Van Vleck and functional determinant, the connections formulae and the semiclassical propagator.

An interesting innovation in this book is that the authors provide a clear presentation of the path integral formulation of the Wigner functions, which are fundamental in the study of quantum statistical mechanics; and, for the first time in an elementary book, the work of Koopman and von Neumann on classical and statistical mechanics.

The book closes with a well selected set of appendices, where some further technical details and clarifications are presented. Some of the more mathematical details in the basic derivations can be found there, as well as aspects of operator ordering as seen from the path integral point formulation, the formulation in momentum space, and the use of Grassmann variables, etc.

It will be difficult to find a better and

more compact introduction to this fundamental subject.

• Luis Álvarez-Gaumé, CERN.

Books received

Bananaworld: Quantum Mechanics for Primates
By Jeffrey Bub
Oxford University Press


This is not another “quantum mechanics for dummies” book, as the author himself states. Nevertheless, it is a text that talks about quantum mechanics but is not meant for experts in the field. It explains complex concepts of theoretical physics almost without bringing up formulas, and makes no reference to a specialist background.

The book focuses on an intriguing issue of present-day physics: nonlocality and the associated phenomenon of entanglement. Thinking in macroscopic terms, we know that what happens here affects only the surrounding environment. But going down to the microscopic level where quantum mechanics applies, we see that things work in a different way. Scientists discovered that in this case, besides the local effects, there are less evident effects that reveal themselves in strange correlations that occur instantaneously between remote locations. Even stronger nonlocal correlations, still consistent with relativity, have been theoretically supposed, but have not been observed up to now.

This complex subject is treated by the author using a particular metaphor, which is actually more than just that: he draws a metaphoric world made of magic bananas, and simple actions that can be performed on them. Thanks to this, he is able to explain nonlocality and other difficult physics concepts in a relatively easy and comprehensive way.

Even if it requires some general knowledge of mathematics and familiarity with science, this book will be accessible and interesting to a wide range of readers, as well as being an entertaining read.

Particles and the Universe: From the Ionian School to the Higgs Boson and Beyond
By Stephan Narison
World Scientific


This book aims to present the history of particle physics, from the introduction of the concept of particles by Greek philosophers, to the discovery of the last tile of the Standard Model, the Higgs boson particle, which took place at CERN in 2012. Chronologically following the development of this field of science, the author gives an overview of the most important notions and theories of particle physics.

The text is divided into seven sections. The first part provides the basics concepts and a summary of the history of physics, arriving at the modern theory of forces, which are the subject of the second part. It carries on with the Higgs boson discovery and the description of some of the experimental apparatus used to study particles (from the LHC at CERN to cosmic rays and neutrino experiments). The author also provides a brief treatment of general relativity, the Big Bang model and the evolution of the universe, and discusses the future developments of particle physics.

In the main body of the book, the topics are presented in a non-technical fashion, in order to be accessible to non-experts. Nevertheless, a rich appendix provides demonstrations and further details for advanced readers. The text is accompanied by plenty of images, including paintings and photographs of many of the protagonists of particle physics.

Beyond the Galaxy: How Humanity Looked Beyond our Milky Way and Discovered the Entire Universe
By Ethan Siegel
World Scientific


This book provides an introduction to astrophysics and cosmology for absolute beginners, as well as for any reader looking for a general overview of the subject and an account of its latest developments.

Besides presenting what we know about the history of the universe and the marvellous objects that populate it, the author is interested in explaining how we came to such knowledge. He traces a trajectory through the various theories and the discoveries that defined what we know about our universe, as well as the boundary of what is still to be understood.

The first six chapters deal with the state-of-the-art of our knowledge about the structure of the universe, its origin and evolution, general relativity and the life of stars. The following five address the most important open problems, such as: why there is more matter than antimatter, what dark matter and dark energy are, what there was before the Big Bang, and what the fate of the universe is.

Written in plain English, without formulas and equations, and characterized by a clear and fluid prose, this book is suitable for a wide range of readers.

Modern Physics Letters A: Special Issue on Hadrontherapy
By Saverio Braccini (ed.)
World Scientific


The applications of nuclear and particle physics to medicine have seen extraordinary development since the discovery of X-rays by Röntgen at the end of the 19th century. Medical imaging and oncologic therapy with photons and charged particles (specifically hadrons) are currently hot research topics.

This special issue of Modern Physics Letters is dedicated to hadron therapy, which is the frontier of cancer radiation therapy, and aims at filling a gap in the current literature on medical physics. Through 10 invited review papers, the volume presents the basics of hadron therapy, along with the most recent scientific and technological developments in the field. The first part covers topics such as the history of hadron therapy, radiation biophysics, particle accelerators, dose-delivery systems and treatment planning. In the second part, more specific topics are treated, including dose and beam monitoring, proton computer tomography, innoacustics and microdosimetry.

This volume will be very useful to students, researchers approaching medical physics, and scientists interested in this interdisciplinary and fast-moving field.

The Penultimate Curiosity: How Science Swims in the Slipstream of Ultimate Questions
By R Wagner and A Briggs
Oxford University Press

Wagner, Briggs

This book uses an original perspective to trace the history of the human quest for making sense of the world we live in. Written in collaboration by a painter specialising in religious subjects and a physical scientist who is a professor in the UK and also the director of a centre for research in quantum information processing, it starts from the assumption that both religion and science are manifestations of human curiosity.

Science and its methods, based on reproducible experiments and evidence-based conclusions, are able to find answers to the “how” questions, to explain how nature works. This is what the authors call the “penultimate curiosity”. But the “ultimate curiosity” is “why” the world is like it is. Science doesn’t necessarily have the answer to such a question. Religions were born to try and give an answer to this.

In the book, science and religion are not placed in opposition to one another. On the contrary, it is shown how they can live in a mutually enriching relationship. The authors sweep human history from caveman times to the present day, explaining the nature and evolution of the entanglement between the two. The text is also accompanied by many beautiful illustrations that are an integral part of the argument.

Entropy Demystified: The Second Law Reduced to Plain Common Sense (2nd edition)
By Arieh Ben-Naim
World Scientific


In this book, the author explains entropy and the second law of thermodynamics in a clear and easy way, and with the help of many examples. He intends, in particular, to show that these physics laws are not intrinsically incomprehensible, as they appear at first. The fact that entropy, which is defined in terms of heat and temperature, can be also expressed in terms of order and disorder, which are intangible concepts, together with the evidence that entropy (or, in other words, disorder) increases perpetually, can puzzle students. Some mystery seems to be inevitably associated with these concepts. The author asserts that, looking at the second law from the molecular point of view, everything clears up. What a student needs to know is the atomistic formulation of entropy, which comes from statistical mechanics.

The aim of the book is to clarify these concepts to readers who haven’t studied statistical mechanics. Many dice games and examples from everyday life are used to make readers familiar with the subject. They are guided along a path that allows them to discover by themselves what entropy is, how it changes, and why it always changes in one direction in a spontaneous process.

In this second edition, seven simulated games are also included, so that the reader can experiment with and appreciate the joy of understanding the second law of thermodynamics.

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