Masataka Fukugita Tsutomu Yanagida Physics of Neutrinos and Application to Astrophysics
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Texts and Monographs in Physics Series Editors: R. Balian, Gif-sur- Yvette, France W. Beiglböck, Heidelberg, Germany H. Grosse, Wien, Austria E. H. Lieb, Princeton, NI, USA N. Reshetikhin, Berkeley, CA, USA H .Spohn ,~ünchen,Germany W.Thirring, Wien, Austria Springer-Verlag Berlin Heidelberg GmbH ONLINE L1BRARY Physics and Astronomy http://www.springer.de/phys/ Masataka Fukugita Tsutomu Yanagida Physics of Neutrinos and Application to Astrophysics With 111 Figures and 64 Tables , Springer Professor Masataka Fukugita University ofTokyo Institute for Cosmic Ray Research 277-8582 Kashiwa, Chiba Japan e-mail: [email protected] Professor Tsutomu Yanagida University ofTokyo Department of Physics Graduate School of Science 7-3-1 Hongo, Bonkyo-ku Tokyo 113-0033 Japan e-mail : [email protected] Library of Congress Cataloging-in-Publication Data Fukugita, M. Physics of Neutrino : and applications to astrophysics I Masataka Fukugita, Tsutomu Yanagida. p.cm. (Texts and monographs in physics, ISSN 0172-5998) Includes bibliographical references and index. (acid free paper) I. Neutrinos . 2. Neutrino astrophysics. I. Yanagida, T. (Tsutomu) , 1949- II. Title. III. Series . QC793 .5.N42 F84 2002 539.7'215--dc21 2002075782 ISSN 0172-5998 Tbis work is subject to copyright. All rights are reserved, whether the whole or part of the material is concemed, specifically the rights of translation, reprinting , reuse of illustrations, recitation , broadcasting, reproduction on microfilm or in any other way, and storage in data banks. Duplication of this publication or parts thereof is permitted only under the provisions of the German Copyright Law of September 9, 1965, in its current version, and permission for use must always be obtained from Springer-Verlag. Violations are liable for prosecution under the German Copyright Law. http://www.springer.de ISBN 978-3-642-07851-4 ISBN 978-3-662-05119-1 (eBook) DOI 10.1007/978-3-662-05119-1 © Springer-Verlag Berlin Heidelberg 2003 Originally published by Springer-Verlag Berlin Heidelberg in 2003 . Softcover reprint ofthe hardcover 1st edition 2003 Tbe use of general descriptive names, registered names, trademarks, etc. in this publication does not imply, even in the absence of a specific statement , that such names are exempt from the relevant probreak tective laws and regulations and therefore free for general use. Typesetting and production: LE-TeX Jelonek, Schmidt & Vöckler GbR Cover design : design & production GmbH , Heidelberg Printed on acid-free paper 55/3111 5 4 3 2 I SPIN 10970034 Preface This book aims to provide a survey of the current state of research in the physics of neutrinos, which has undergone dramatic development during the last decade, in a form accessible to the nonspecialist and the grad uate stu dent. The major issue during the last two decades has been the neutrino mass, whereas the interaction of neutrinos was well underst ood within the framework of the standard theory, which was established in the 1970s. In 1994, we published a textbook-format review art icle "Physics 01 Neutrinos' in "Physics and Astrophysics 01 Neutrinos" , in anticipation that the mass of the neutrino would be found in the near future. It was indeed found thanks to the Super-Kamiokande experiment four years afte r that book was written, and a flurr y of activi ty followed in the phenomenology of t he neutrino mass. From the theoretical point of view, the importance of this discovery sterns from the fact t hat it probably indicates the presence of a new energy scale beyond the standard theory. At the same t ime, the formalism for massive neutrinos and the techniques to find the neutrino mass have now realistic imp ortan ce and have become the subject of standard physics. On the other hand, experiment revealed that the pattern of the neutrino mass and mixing among generations appears in a way different from what has been speculated on the basis of exist ing theoretical models. For these reasons, we feel that it is timely to summarise the current st ate of our understanding - both success and failure - concerning the physics of neutrinos. We expand the book to include a range of subjects so that it provides a global view of the physics where neutrinos play important roles, including astrophysics and cosmology. We detail formulae and numbers , with the hop e that this book is useful as a handbook for researchers in this field. Emphasis is also given to the description of the principles of neutrino experiments. In early chapters, we discuss physical processes and physical effects that involve neutrinos. They are important subjects of neutrino physics in their own right, but also give a base for the exploration for t he neutrino mass and its origins, both t heoret ically and experimentally, as we discuss in later chapters. As in the previous book, the mathematical formulation for massive neutrinos is one of the cent ral subjects. We also discuss details concern ing the evidence for finite masses of neutrinos. VI Preface The reader will find a change between Chaps. 8 and 9. Chapters up to and inc1uding Chap. 8 summarise knowledge which is established or well under stood, at least as a matter of principle. On the contrary, subjects discussed in Chap. 9 and furt her chapters are theories from workshops of theorists. It is possible that these ideas will be completely revised or abandoned some day as our understanding evolves. The problem is that we are not successful yet in understanding the mass pattern and mixing of the neutrino mass, although we have good reasoning as to why neutrinos have very small masses and how they are generated. Notwithstanding this, we decided to document these ideas to convey our struggle to understand the neutrino mass matrix, as we believe that even failed attempts will not be completely useless in the process of the development of understanding. This is in fact the prime reason why theorists are attracted to the neutrino mass. Particular care has been taken so that this book serves graduate stu dents who want to learn the physics of neutrinos and related topics. We start the description at an elementary level, which is readily accessible to graduate students who have finished an elementary course in quantum field theory. Knowledge of the Weinberg-Salam theory of electroweak unification is a cornerstone of this book, but it is not assumed; we start with a prac tical introduction to the electroweak theory. We do not assurne knowledge other than that within a standard course in elementary physics, such as that given in Landau and Lifshitz's textbooks on physics. We supply introductory materials for advanced subjects, although we limit ourselves to those which are inevitable to understand the subject relevant to the physics of neutrinos. A general problem for students is the presence of a gap between textbooks and advanced research papers. We intend to fill this gap; we try to embark from elementary concepts and to show intermediate steps in calculations of fundamental equations often used in research papers without any derivations, as much as space permits. We are indebted to many colleagues in completing this book. In particu lar, we would like to express our sincere thanks to Jiro Arafune (Tokyo, ICRR), John Bahcall (Princeton, lAS), Samoil Bilenky (Munich), Alexander Friedland (Princeton, lAS), Morihiro Honda (Tokyo, ICRR), Takaaki Kajita (Tokyo, ICRR), Masahiro Kawasaki (Tokyo, Hongo), Kuniharu Kubodera (South Carolina), Takahiro Kubota (Osaka), Masato Morita (Osaka, emeri tus), Masayuki Nakahata (Tokyo, ICRR), Kazuhiko Nishijima (Tokyo/Kyoto, emeritus), Atsuto Suzuki (Tohoku) , Hideyuki Suzuki (Tokyo Science Uni versity), Yoichiro Suzuki (Tokyo, ICRR), Gyo Takeda (Tohoku, emeritus), Morimitsu Tanimoto (Niigata), Toshiaki Tomoda (Aomori) , Yoshio Yama guchi (Tokyo, emeritus), and Motohiko Yoshimura (Tokyo, ICRR) for in valuable advice , comments, and help in various stages of writing. Tokyo Masataka Fukugita January, 2003 Tsutomu Yanagida Table of Contents 1 Historical Introduction 1 1.1 Neutrinos and the Law of Weak Interactions ............... 1 1.2 Detection of the Neutrino and the Discovery of Generations ......................... 7 1.3 Search for Intermediate Bosons to the Unified Theory of Electroweak Interactions .............................. 12 1.4 The Neutrino-Mass Quest ............................... 15 1.5 The Interest in Neutrinos Today . .. 19 2 Standard Theory of Electroweak Interactions ............. 23 2.1 Classical Theory of Weak Interactions ................... .. 23 2.2 Weinberg-Salam Theory of Electroweak Interactions . 24 2.2.1 SU(2) x U(I) Symmetry ........................ .. 24 2.2.2 The Gauge Fields 25 2.2.3 Spontaneous Symmetry Breaking and the Higgs Mechanism 27 2.2.4 Gauge Boson Mixing . .. 29 2.2.5 Fermion Mass . 30 2.2.6 Introduction of Quarks ............................ 31 2.2.7 Low-Energy Weak Interactions ................... .. 31 2.2.8 Introduction of the Generations. ................. .. 33 2.3 Quantum Field Theory: The Renormalisable Gauge. 35 2.4 Consistency of the Quantum Field Theory: Anomaly Cancellation. .................................. 37 2.4.1 Renormalisability ..... .. ... .. .. .... .... ... 37 2.4.2 Triangle Anomaly .............................. .. 38 2.4.3 Implications of Anomaly 43 2.5 Experimental Test. ..................................... 44 2.5.1 Electroweak Parameters ......................... .. 44 2.5.2 Higher Order Perturbations. ....................... 46 2.5.3 Other Elementary Parameters in the Weinberg-Salam Theory ..................... 52 2.6 The Problem with the Higgs Sector and the Search for the Higgs Particle 52 2.6.1 Theoretical Considerations on the Higgs Mass . .. 52 VIII Table of Contents 2.6.2 Empirical Limits on the Higgs Mass 56 2.6.3 Theoretical Implications of a 'Small' Higgs Mass 56 3 Applications of the Electroweak Theory 59 3.1 P hysics with the Charged Current ........................ 59 3.2 Muon Decay . ... ........... .. ......... .. ...... .. 60 3.3 Weak Decays Involving Hadrons: Classificat ion . .. 62 3.4 Leptonic Decays of Mesons 64 3.5 Semileptonic Decays of Mesons . 65 3.6 Theory ofNuclear Beta Decays........................