Experimental Studies of Neutrino Oscillations

By Takaaki Kajita

World Scientific

This book on neutrino oscillations is mainly of historic interest. It consists of seven chapters that reproduce review articles written by the 2015 Nobel laureate in physics, Takaaki Kajita, which were previously published between 2000 and 2009, either in journals or in international conference proceedings (all World Scientific publications). The articles describe experiments on solar and atmospheric neutrino interactions performed using the Kamiokande and SuperKamiokande water Cherenkov detectors installed in the Kamioka mine in Japan. These experiments resulted in the 1998 discovery of atmospheric muon-neutrino (ν_μ) oscillation by observing ν_μ disappearance over a flight-path length of the order of the Earth’s radius. In addition, they have provided important hints on the oscillation of solar neutrinos, which was conclusively demonstrated in 2002 by the SNO experiment in Canada (the 2015 Nobel Prize in Physics was also awarded to A B McDonald for his leading role in this experiment).

Chapter 1 includes a short description of results from experiments using neutrinos from accelerators. These include the K2K experiment in Japan and MINOS at Fermilab, which confirmed the atmospheric neutrino oscillation, and the KamLAND experiment (also located in the Kamioka mine), which has observed the disappearance of electron antineutrinos (ν_e) from nuclear reactors over an average baseline of 180 km, therefore verifying solar-neutrino oscillation with “man-made” neutrinos. Although not up to date, the values of the oscillation parameters Δm²₁₂, Δm²₂₃, θ₁₂ and θ₂₃ quoted in this book are quite precise and close to the current ones.

Future directions and plans in the study of neutrino oscillations are also described. In particular, methods and plans to measure the mixing angle θ₁₃ (not yet measured in 2009) using neutrinos from both reactors and accelerators are discussed, as well as the impact of the θ₁₃ value on the possible detection of CP violation in the neutrino sector. Although the book was published in 2016, on this subject it is obsolete because θ₁₃ has been measured in the first half of the current decade by a number of experiments and is presently known to better than 10%.

Finally, chapter 2, written with four co-authors, addresses the physics capabilities of possible future experiments using a water Cherenkov detector with a mass of 1 Mton.