Alumnus Arthur McDonald Wins 2015 Nobel Prize in Physics

Arthur B. McDonald (PhD '70), director of the Sudbury Neutrino Observatory (SNO) in Ontario, Canada, and Takaaki Kajita, at the University of Tokyo, Kashiwa, Japan, have shared the 2015 Nobel Prize in Physics for the discovery that neutrinos can change their identities as they travel through space.

McDonald and Kajita lead two large research teams whose work has upended the standard model of particle physics and settled a debate that has raged since 1930, when the neutrino's existence was first proposed by physicist Wolfgang Pauli. Pauli initially devised the neutrino as a bookkeeping device—one to carry away surplus energy from nuclear reactions in stars and from radioactive decay processes on Earth. In order to make the math work, he gave it no charge, almost no mass, and only the weakest of interactions with ordinary matter. Billions of them are coursing through our bodies every second, and we are entirely unaware of them.

There are three types of neutrinos—electron, muon, and tau—and they were, for many years, assumed to be massless and immutable. The technology to detect electron neutrinos emerged in the 1950s, and it slowly became apparent that as few as one-third of the neutrinos the theorists said the sun should be emitting were actually being observed. Various theories were proposed to explain the deficit, including the possibility that the detectable electron neutrinos were somehow transmuting into their undetectable kin en route to Earth.

Solving the mystery of the missing neutrinos would require extremely large detectors in order to catch enough of the elusive particles to get accurate statistics. Such sensitive detectors also require enormous amounts of shielding to avoid false readings.

The University of Tokyo's Super-Kamiokande neutrino detector, which came online in 1996, was built 1,000 meters underground in a zinc mine. Its detector, which counts muon neutrinos and records their direction of travel, found fewer cosmic-ray neutrinos coming up through the Earth than from any other direction. Since they should not be affected in any way by traveling through the 12,742-kilometer diameter of our planet, Kajita and his colleagues concluded that the extra distance had given them a little extra time to change their identities.

McDonald's SNO, built 2,100 meters deep in a nickel mine, began taking data in 1999. It has two counting systems. One is exclusively sensitive to electron neutrinos, which are the type emitted by the sun; the other records all neutrinos but does not identify their types. The SNO also recorded only about one-third of the predicted number of solar electron-type neutrinos—but the aggregate of all three types measured by the other counting systems matched the theory.

The conclusion, for which McDonald and Kajita were awarded the Nobel Prize, was that neutrinos must have a nonzero mass. Quantum mechanics treats particles as waves, and the potentially differing masses associated with muons and taus gives them different wavelengths. The probability waves of the three particle types are aligned when the particle is formed, but as they propagate they get out of synch. Therefore, there is a one-third chance of seeing any particular neutrino in its electron form. Because these particles have this nonzero mass, their gravitational effects on the large-scale behavior of the universe must be taken into account—a profound implication for cosmology.

McDonald came to Caltech in 1965 to pursue a PhD in physics in the Kellogg Radiation Laboratory under the mentorship of the late Charles A. Barnes, professor of physics, emeritus, who passed away in August 2015. "Charlie Barnes was a great mentor who was very proud of his students," says Bradley W. Filippone, professor of physics and a postdoctoral researcher under Barnes. "It is a shame that Charlie didn't get to see Art receive this tremendous honor."

A native of Sydney, Canada, McDonald received his bachelor of science and master's degrees, both in physics, from Dalhousie University in Halifax, Nova Scotia, in 1964 and 1965, respectively. After receiving his doctorate, he worked for the Chalk River Laboratories in Ontario until 1982, when he became a professor of physics at Princeton University. He left Princeton in 1989 and became a professor at Queen's University in Kingston, Canada; the same year, he became the director of the SNO. In 2006, he became the holder of the Gordon and Patricia Gray Chair in Particle Astrophysics, a position he held until his retirement in 2013.

Among many other awards and honors, McDonald is a fellow of the American Physical Society, the Royal Society of Canada, and of Great Britain's Royal Society. He is the recipient of the Killam Prize in the Natural Sciences; the Henry Marshall Tory Medal from the Royal Society of Canada, its highest award for scientific achievement; and the European Physics Society HEP Division Giuseppe and Vanna Cocconi Prize for Particle Astrophysics.

To date, 34 Caltech alumni and faculty have won a total of 35 Nobel Prizes. Last year, alumnus Eric Betzig (BS '83) received the Nobel Prize in Chemistry.

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Summer Interns Return with a World of Experiences

Caltech undergraduate students returned to campus this week, many after spending the summer working at companies in biotechnology, technology, and finance, among other fields. These students have had the opportunity to learn firsthand about the career opportunities and paths that may be available to them after graduation. They also had the chance to put Caltech's rigorous academic and problem-solving training to the test.

In the summer of 2015, nearly a third of returning sophomores, juniors, and seniors were placed in an internship position through Caltech's Summer Undergraduate Internship Program (SUIP). The program, run through the Institute's Career Development Center (CDC), helps connect current undergraduate students with a wide range of companies and businesses that can provide practical skills and work experiences that give the students an edge in the future job market.

Many undergraduates find paid summer internships through the CDC, says Lauren Stolper, the director of fellowships, advising, study abroad, and the CDC. The center organizes fall and winter career fairs and offers workshops related to finding internships; provides individual advising on internship options and conducting a job hunt for an internship; organizes interviews for students through its on-campus recruiting program; and provides web-based internship listings and company information through Techerlink, its online job-posting system.

Through the formal establishment of SUIP two years ago—thanks, in part, to the initiative of Craig SanPietro (BS '68, engineering; MS '69, mechanical engineering) and with seed money provided by him and three of his alumni friends and former Dabney House roommates, Peter Cross (BS '68, engineering), Eric Garen (BS '68, engineering), and Charles Zeller (BS '68, engineering)—the CDC has been able to dedicate even more time and attention to helping undergraduates secure these important positions, Stolper says.

"Through internships, students have the opportunity to learn more about the practical applications of their knowledge by contributing to ongoing projects under the guidance of professionals," says Aneesha Akram, a career counselor for internship development/advising, who oversees SUIP.

"Completing summer internships help undergraduates become competitive candidates for full-time positions," says Akram. "When it comes to recruiting for full-time positions, companies seek out candidates with previous internship experience. We have found that many large companies extend return offers and full-time conversions to students who previously interned with them."

The infographic at the above right provides a snapshot of Caltech undergraduate internships over this past summer. Students seeking internships for next summer can contact Akram or look at the CDC website for more information.

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New Courses for the 2015–16 School Year

The start of the 2015–2016 school year brings not only new freshmen and faculty, but also new courses.

Several new classes have been added in the Division of the Humanities and Social Sciences. These include a course on Old English Literature, in which students will study literature written in the earliest form of the English language, commonly used in England from roughly 450 to 1100 AD. The new course will be taught by the Weisman Postdoctoral Instructor in Medieval British Literature, Benjamin Saltzman.

"When we speak and write in English, we rarely think about the paths the language took to get to where it is today with all its quirks and varieties: why is it that we say 'one mouse,' but 'two mice'? And if you can figure that out, then why do we say 'two houses'?" Saltzman says. "Once we take a closer look at this early stage of the language, we gain access to some extraordinary pieces of literature—from riddles to poems about war—and in the process we'll learn about some of the idiosyncrasies that have persisted in the modern form of the language."

The Division of Engineering and Applied Science is also introducing three new interdisciplinary mechanical engineering courses, one of which is the Mechanics of Soils. The class will be taught by Professor of Mechanical and Civil Engineering Domniki Asimaki, and will focus on the basic principles of stiffness, deformation, stress, and strength of soils, sands, clays, and silts.

"Soils are very heterogeneous materials. Some are plastic like soft clays, others are brittle like cemented sands, and others are purely frictional like granular media. More frequently we see some mix of these," Asimaki says. "The top few hundred meters of the earth's crust, where most of the infrastructure of modern cities is founded on, is roughly made of 'soils'. Thus, we want to make predictions about the deformation and failure of soils, such as consolidation from groundwater pumping, slope stability failures, foundation capacity of buildings, or liquefaction of sands—so called quick-sands." The class, she says, aims to provide an understanding of soil behavior from laboratory experiments and field observations, and to develop idealized predictive models that capture aspects of that behavior.

A new course in the medical engineering department, New Frontiers in Medical Technologies, will examine space technologies, instruments, and engineering techniques with respect to their current and potential applications in medicine. The course will allow students to interact with both Caltech researchers in medical engineering and scientists at the Jet Propulsion Laboratory (JPL).

"The history of space exploration and its many spinoffs have taught us that many space technologies are very useful for on-earth medicine," says Shouleh Nikzad (PhD '90), a visiting associate in astrophysics and senior research scientist at JPL. She will teach the new course in the spring term.

Lori Dajose
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Thursday, October 1, 2015
Cahill, Hameetman Auditorium – Cahill Center for Astronomy and Astrophysics

Launch of Engineers Week at Caltech

Friday, October 23, 2015
Winnett Lounge – Winnett Student Center

Flat Space, Deep Learning: A Workshop by Eric Mazur

Wednesday, October 21, 2015
Beckman Institute Auditorium – Beckman Institute

The Teaching and Learning Project, a National Photographic Essay on Higher Education Featuring Caltech

Tuesday, October 20, 2015 to Wednesday, October 21, 2015
Center for Student Services 360 (Workshop Space) – Center for Student Services

Guest Consultations on Teaching, with Chris Duffy

Tuesday, October 20, 2015
Dabney Hall, Lounge – Dabney Hall

Bringing Joy into Your Teaching: A Workshop by Chris Duffy

Monday, October 19, 2015
Guggenheim 101 (Lees-Kubota Lecture Hall) – Guggenheim Aeronautical Laboratory

The Future of Teaching and Learning at Caltech: An Innovation Showcase

Monday, October 19, 2015 to Friday, October 23, 2015

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