Wednesday, May 9, 2012

Book Review: Neutrino

Close, F. E. (2010). Neutrino. Oxford: Oxford University Press.

In 2006 Oxford University physics professor and accomplished popularizer of science Frank Close was invited to write an obituary of nuclear chemist and physics Nobel laureate Raymond (Ray) Davis Jr. When that obituary won the UK Science Writer's Prize for the "Best Science Writing in a Non-Scientific Context," Close decided to expand it into a popular book.
Neutrino is the story of the elusive particle conjured by Wolfgang Pauli as a "desperate remedy" to save the law of conservation of energy. Pauli was hesitant about publishing his idea; he even turned down an invitation to present it at a conference in Tübingen, Germany. Instead, in a famous open letter to the conference attendees, addressed to the "Dear Radioactive Ladies and Gentlemen," Pauli described why he proposed the neutrino. (It's likely that neither he nor they were aware that their own bodies were radioactive—due to potassium-40 decaying in their bones—and emitting neutrinos, no less.)
Soon afterward Enrico Fermi developed a theory modeled after electromagnetism that described neutrino interactions. Several theorists worked out the interaction cross section of neutrinos with matter and found it to be exceedingly small, which led physicists to believe that there was no practical way of observing the neutrino. Despite that prevailing view, atomic physicist Bruno Pontecorvo, at one time Fermi's assistant, realized that however elusive neutrinos may be, they can be detected by observing the radioactive argon nuclei produced when a sufficiently intense neutrino source interacts with a large enough chlorine target.
Enter Davis, who, after joining the Brookhaven National Laboratory, was told to go to the library, do some reading, and choose a project. In searching the literature, Davis came across Pontecorvo's work and decided to give his idea a go. Thus began Davis's hunt for neutrinos produced by the Sun. Eventually, Davis teamed up with John Bahcall, who carefully calculated the neutrino–chlorine interaction cross section and the solar neutrino flux. Eventually, the hunt for neutrinos would involve many experiments that looked not only to the Sun, but also to reactors, accelerators, and the atmosphere.
Close tells the story well. In particular, he does an excellent job of describing the early 20th-century understanding of radioactivity that led to Pauli's "desperate remedy." Almost as good is the way Close charts our evolving comprehension of the origin of solar energy. The book is full of gems that would equally interest the casual reader and the professional physicist. Such tales include the story of the seminal paper by Fermi being rejected by Nature as "too speculative" and the comment by Bahcall, who heroically kept the solar-neutrino problem interesting for three decades, that the hardest thing he had ever done was wooing his future wife.
For a neutrino aficionado like me, this book is too short. It does not cover many fascinating aspects of neutrino physics and its history, and I think that some of the presentation will be difficult for the uninitiated reader to grasp; one example is the way Close distinguishes neutrinos from antineutrinos. Also, it is satisfying to see Pontecorvo given due credit, but another equally captivating figure, Ettore Majorana—also a Fermi protégé—is not mentioned at all. Consequently, alluring topics such as Majorana mass, neutrinoless double-beta decay, and the question of whether neutrinos are their own antiparticles are omitted. Perhaps Close wanted to restrict himself to experiments that have so far seen undisputed positive results.
Given Close's research focus in particle physics, it is no surprise that the particle aspect of neutrinos is covered in more depth than the role neutrinos—besides the solar variety—play in astrophysics. Astrophysical neutrinos are important because a neutrino's weak interactions allow it to travel very long distances in the cosmos, thus giving us a peek into the environment that created it. Perhaps in a subsequent edition astrophysical neutrinos will be covered in more detail.
Overall I much enjoyed reading Neutrino, and despite its minor shortcomings, I would recommend it as an excellent introduction to the subject. Three-quarters of a century after Pauli, neutrino physics is now a precise science. Many experiments, ongoing and planned, will doubtless reveal much more about these fascinating particles.
Submitted by Baha Balantekin
This review is reprinted by permission from American Institute of Physics: Physics Today 64:4, 58 (April 2011), copyright 2011

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