M. Fukugita · A. Suzuki (Eds.)

Physics and Astrophysics

of Neutrinos

Springer Japan KK

Professor MAsATAKA FuKUGITA Yukawa Institute for Theoretical Physics, Kyoto University, Sakyo-ku, Kyoto, 606-01 Japan; Institute for Advanced Study, Princeton, NJ 08540, USA

Professor ATsuTo SuzuKI Faculty of Science, Tohoku University, Aoba-ku, Sendai, 980 Japan

ISBN 978-4-431-67031-5 ISBN 978-4-431-67029-2 (eBook) DOI 10.1007/978-4-431-67029-2

© Springer Japan 1994

Origina11y pub1ished by Springer-Verlag Tokyo in 1994.

This work is subject to copyright. Ali rights are reserved, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in other ways, and storage in data banks. The use of 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 protective laws and regulations and therefore free for general use.

Preface

Ever since it was first introduced by Pauli, the neutrino has played a crucial role in the development of particle physics, from the early formulation of the four Fermi theory till the completion of the unified theory of electromagnetic and weak interactions by Glashow, Weinberg, and Salam. Its role is not over yet: we have good reason to anticipate that the neutrino will still be at the vanguard of particle physics beyond today's standard theory. Whether or not neutrinos are strictly massless is among the most important issues from this point of view. This is also the most important theme of recent experiments concerning neutrino physics: whilst a variety of topics have been explored using a variety of methods, the essential point of these experiments lies in the quest for a very small mass of the neutrino, which, if it happens to be discovered, should have vast implications for our understanding of particle physics, especially in that it probably implies new physics beyond the standard theory.

Current interest in the neutrino, in particular in the massive neutrino, has been magnified by the fact that it plays an important role in the astrophysical and cosmological environment. Increasing effort has recently been focused on the observation of neutrinos of astrophysical origin, which not only brings us new in­sights for astrophysics, but also provides a new method of exploring particle physics which cannot be carried out in laboratories. The detection of the neutrino burst from SN1987 A was an epoch-making event in that it demonstrated an intimate interplay of astrophysics with particle physics. Recently, additional significant de­velopments have been made in solar neutrino physics as well: thanks to the new experiments and theories developed over the last several years, the solution to the long-standing problem posed by Davis now seems to be emerging on the horizon, which lends us hope that the question as to whether the original problem should be ascribed to a nonstandard property of the neutrino will be resolved within the coming decade. Whether the massive neutrino is (a part of) dark matter in the universe is also a question of utmost importance in both fields of physics.

Against this background we have experienced a flurry of activity in neutrino physics and astrophysics research worldwide over the last decade. This was also true in Japan. From 1988 to 1990, research in Japan was, in fact, supported by the Ministry of Education with a significant amonut of funding under The Grant­in-Aid for Scientific Research on Priority Areas. This book is a product of this neutrino physics and astrophysics research done in Japan.

In order to document the outcome of this research and make it available to general readers in textbook format, we asked for contributions from our Japanese

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colleagues who are carrying out unique work in this field, the most typical and well-known of which is represented by the Kamiokande experiment. The top­ics covered also include the electron neutrino mass experiment, the double beta decay experiment, and the neutrino oscillation experiment, especially that using an emulsion technique, and R&D studies for new solar neutrino experiments, as well as subjects concerning atmospheric neutrinos, supernova neutrinos, and very high-energy neutrinos from astronomical objects.

The aim of the present book is to present a comprehensive account of this work, which cannot be found in journal papers, conference proceedings, or review articles, and to describe these subjects starting from elementary levels so that they are readily accessible to nonexperts, including graduate students. This book is also intended to serve as a handbook for researchers in the relevant fields. A general introduction was added to introduce the state-of-art theory of neutrino physics which is the basic background behind the experimental work described in this book.

It was not our intention to cover the entire range of subjects in this field; rather, we have concentrated on those to which Japanese physicists made significant con­tributions. Therefore, some important topics in this field are not included. We expect that readers will supplement the missing parts with other modern text­books, which have rapidly become available to us in the last few years.

Finally, we would like to express our sincere thanks to Hirotaka Sugawara, Director of KEK, who served as the Principal Investigator of the Grant-in-Aid project; Jiro Arafune, Director of the Institute for Cosmic Ray Research; and Masatoshi Koshiba, the founding father of the Kamiokande project. We are greatly indebted to their enthusiastic engagement and continuous encouragement through­out the project. We also thank Masaki Mori for his invaluable assistance in the time-consuming editorial process. The greater part of the work described in this book was supported by a Grant-in-Aid for Scientific Research on Priority Areas of the Ministry of Education, Science and Culture (No. 029) for the fiscal years of 1988-1990; this publication was also supported in part by a Grant-in-Aid for Publication of Scientific Research Result (No. 3001) for the fiscal year 1993. We wish to thank the Ministry for its generous support, which made the publication of this book possible.

Kyoto-Sendai, 1 January 1994 Masataka Fukugita Atsuto Suzuki

Guide to this book

The first article by M. Fukugita and T. Yanagida is a textbook-style review of the present status of the theory of neutrino physics. This article is intended to provide the background for the research presented in this volume. The key notions are explained in detail and derivations are given for fundamental equations, whenever possible. The knowledge of no more than elementary field theory is required for full comprehension of this article.

The next two articles describe the Kamiokande experiment. All details of the experiment, which were previously reported only as internal documents, are presented, starting from an elementary level, by K. Nakamura, T. Kajita, M. Nakahata, and A. Suzuki. A description of the detector concepts, geography and geology of the site, detector performance, and an explanation of the Monte-Carlo code is followed by a review of the physics output it has achieved. A historical account of the Kamiokande experiment is provided by A. Suzuki, one of the original researchers involved in the experiment.

The following three articles are reports by the representatives of groups which carried out neutrino mass experiments. T. Ohshima and H. Kawakami review the status and problems of current neutrino mass experiments using tritium beta decay, with particular emphasis given to their own experiment carried out at the Institute of Nuclear Study at the University of Tokyo. This experiment, together with those of Zurich and Los Alamos, marked the second generation of experiments after the Moscow result of a finite electron neutrino mass. H. Ejiri, who has been conducting a double beta decay experiment at the Kamioka mine using the "ELEGANTS" detector he developed, contributes a short summary of the present status of double beta decay experiments. K. Niwa presents a detailed account of unique neutrino oscillation experiments using a hybrid emulsion-counter system which are being carried out at Fermilab and CERN with his colleagues. The new experiments are expected to achieve a sensitivity that will result in a strong constraint on the hypothesis of the tau neutrino being cosmic dark matter.

Results from the atmospheric neutrino experiments conducted at Kamiokande and IMB have ignited controversy over whether or not the deficit of muon-neutrino flux can be ascribed to neutrino physics. T. Kajita, who has been engaged in the analysis of atmospheric neutrinos as a member of the Kamiokande group, examines the experimental procedure of the existing atmospheric neutrino experiments in detail and presents a review on this issue. This article is supplemented by a report by M. Honda explaining the key points of calculations of the atmospheric neutrino flux in the hope of clarifying the degree of reliability of the existing flux predictions and possible problems posed by these calculations.

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Y. Totsuka, who is currently conducting the Kamiokande experiment, presents an overview of the detection methods for low-energy astrophysical neutrinos, in particular for solar neutrinos, with both real-time detection and radiochemical methods. The fundamentals of these detection methods are described in detail. This article is followed by two reports on low-energy neutrino detection using indium (by Y. Suzuki and K. Inoue) and cryogenic techniques (by T. Ebisu and T. Watanabe), which are still in the R&D stage.

The theory of supernova neutrinos is discussed by H. Suzuki, who has been carrying out a calculation of the neutrino flux from supernovae for several years. Following an elementary account of the dynamics of supernovae, details of his neu­trino flux calculation and an extensive comparison with other work are presented.

The last two articles are dedicated to reviews of very high-energy gamma rays and neutrinos from astronomical objects. T. Kifune and M. Mori provide an ex­tensive review of the status of very high-energy gamma ray observations and also discuss the future prospects of very high-energy neutrino detection. The article by F. Takahara is a textbook-style description of particle acceleration around ac­tive compact astronomical objects, in connection with very high-energy gamma ray /neutrino production.

Among a number of available textbooks related to the present subject we par­ticularly recommend Neutrino Astrophysics by J. N. Bahcall (Cambridge Univer­sity Press, 1988), especially for the astrophysics of solar neutrinos, and Neutrino Physics, edited by K. Winter (Cambridge University Press, 1991), which appeared during the preparation of this book, for physics of neutrino-hadron interactions, since these subjects are not covered in this book.

Contents

Physics of Neutrinos 1 M. Pukigita and T. Yanagida

I. Introduction 1 1 Why neutrinos? . . . . . . . . . . . . . . . . . 1 2 Physics of massive neutrinos- general survey 3

II. Standard theory of the weak interaction and properties of the neutrinos 6 3 Classical theory of the weak interaction . . . . . . . . 6 4 Weinberg-Salam theory of the electroweak interaction 7 5 Electromagnetic properties of the neutrino 23 6 Limit on the mass of neutrinos . . . . . . . . . 29 7 Number of generations . . . . . . . . . . . . . 33 8 Examples of neutrino scattering cross sections 34

III. Massive neutrinos 49 9 Massive neutrinos- overview 49 10 Dirac matrices . . . . . . . . 50 11 Massless neutrinos . . . . . 12 Massive Majorana neutrinos 13 Massive Dirac neutrinos .. 14 Massive neutrinos in the Weinberg-Salam theory . 15 Seesaw mechanism ................ .

IV. Quantisation of the Majorana field 16 Necessity of quantisation ................ . 17 Unitary equivalence of the Majorana and the Weyl fields 18 Quantisation of the Majorana fermions ..... . 19 Path integral derivation of Feynman propagators 20 Simple examples of applications 21 Double beta decay . . . . . . . . .

51 52 53 54 55

57 57 57 60 64 65 69

V. Generation mixing of neutrinos 83 22 Generation mixing - the case of Dirac neutrinos . . . . . . . . . . . 83

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23 Generation mixing - the case of Majorana neutrinos . 24 Phases of the mixing matrices . 25 Neutrino oscillation in vacuum . 26 Neutrino oscillation in matter . 27 C P violation . . . . . . . . . . 28 Heavy neutrinos and neutrino decays

84 86 88

104 124 127

VI. Models for massive neutrinos 131 29 Classification of models 131 30 The left-right symmetry model . . 132 31 Left-right symmetry in S0(10) . . 135 32 General discussion of S0(10) grand unification 140 33 Phenomenology of grand unified theories . 148 34 Seesaw mechanism with other symmetries . . 153 35 Model for the fourth generation neutrino . . . 155 36 Peccei-Quinn symmetry and the neutrino mass 157 37 Model with horizontal gauge symmetry . . . . . 163 38 Neutrino mass induced by radiative corrections 164 39 Seesaw models for Dirac neutrinos . . . . . . . . 166 40 Model with a Fritzsch mass matrix- a phenomenological description 167

VII. Magnetic moment of the neutrino 170 41 Neutrino magnetic moment in the Weinberg- Salam model . 170 42 Neutrino magnetic moment in the left-right symmetric model . 173 43 Models with a charged scalar particle . . . . . . . . . . . . . . 177 44 Variations of the scalar model . . . . . . . . . . . . . . . . . . 184 45 Phenomenological significance of the neutrino magnetic moment 186

VIII. Baryon numbers in the early Universe and neutrinos 193 46 Introduction . . . . . . . . . . . . . . . . . . . . . . . . 193 47 Baryon number and the neutrino mass in S0(10) GUT 194 48 Sphaleron-induced baryon-number violation . . . . . . 197

Appendices 209 A Triangle anomaly and anomaly cancellation . 209 B Beta decay . . . . . . . . . . . . 210 C Representation of S0(10) group . . . . . . . . 213

Kamiokande 249 K. Nakamura, T. Kajita, M. Nakahata, and A. Suzuki

1 Introduction . . . . . . . . . . . . . . . . . 249 2 Laboratory and Detector . . . . . . . . . . 252 3 Measurement of Neutrinos in Kamiokande 280 4 5 6

Detector Simulation . . . . . . . . . . . . Investigation of Atmospheric Neutrinos . Investigation of Astrophysical Neutrinos

0 297 300

0 310

7 Search for Baryon-Number Violating Processes . 8 Superkamiokande 9 Conclusion . . . . . . . . . . . . . . . . . . . . .

Kamiokande : Historical Account A. Suzuki

1 Idea of Kamiokande . . . . . . 2 Design of Kamiokande . . . . 3 Construction of the Detector . 4 Kamiokande Ready . . . . . . 5 Construction of Kamiokande-II 6 Toward Low-Background Detector . 7 Supernova SN1987 A ... 8 Solar Neutrino Detection . 9 Kamiokande-III . 10 Superkamiokande .....

XI

. 356

. 367

. 377

388

. 388

. 389

. 393

. 394

. 397

. 401

. 407

. 409

. 414

. 414

Direct Measurement of Electron Antineutrino Mass 448 T. Ohshima and H. Kawakami

1 Introduction . . . . . . . . . . . . . . . . 448 2 Experimental Principle and Objectives . 451 3 Review of the Experimental Progress . 457 4 INS Experiment . . 4 70 5 Discussion . . . . . . . . . . . . . . . . 486

Double Beta Decys and Neutrinos 500 H. Ejiri

1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 500 2 Theories of Double Beta Decay . . . . . . . . . . . . . . . . . 501 3 Nuclear and Detection Sensitivities for Double Beta Decays . . 505 4 Double Beta-Decay Experiments. . . . . . 506 5 Nuclear Matrix Elements for fJfJ Decays . 513 6 Concluding Remarks . . . . . . . . . . . . 514

Neutrino Oscillations in Emulsion Experiment 520 K. Niwa

1

2

3

Emulsion experiments for high energy physics Hybrid emulsion detector . Application .................. .

. 520

. 524

. 541

XII

Observation of Atmospheric Neutrinos 559 T. Kajita

1 Introduction . . . . . . . . . . . . . . . . . . . . 559 2 Simulation of the interactions of atmospheric neutrinos in the detector561 3 Detectors . . . . . . . . . . . . . . . . . . . . . . . . 567 4 5 6 7

Experimental results on atmospheric neutrinos . . . Interpretation of the result - neutrino oscillations -Upward-going muons Future prospect ................... .

Calculation of Low-Energy Atmospheric Neutrino

. 576

. 590

. 594

. 599

Fluxes 606 M. Honda

1 Introduction . . . . . . . . . . . 606 2 Primary Flux of Cosmic Rays . 606 3 Interaction of Cosmic Rays . . . 610 4 Decay of Mesons . . . . . . . . 615 5 The Flux of Atmospheric Neutrino . 617 6 Conclusion . . . . . . . . . . . . . . . 622

Experiments for Solar Neutrinos and Supernova Neu-trinos 625 Y. Totsuka

1 Introduction . 2 3 4

Real-Time Experiment for Solar Neutrinos . . . Radiochemical Experiment for Solar Neutrinos . Real-Time Experiment for Supernova Neutrinos

Indium Solar Neutrino Experiments Y. Suzuki and K. Inoue

1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 Characteristics of a signature and detection principles . 3 Problems to be addressed . . . . . . . . . . . . . . . 4 Detector development . . . . . . . . . . . . . . . . . . 5 Design consideration for a 7Be-pep neutrino detector . 6 Summary ....................... .

. 625

. 629

. 645

. 677

694

. 694

. 694

. 695

. 700

. 712

. 716

Superheated Superconducting Granules for a Particle Detector 720 T. Ebisu and T. Watanabe

1 Introduction . . . . 2 Thermodynamics of SSGs

. 720

. 724

3 Materials for SSG-targets . . . . . . . . . . . . . . . . 4 Responses of tin-SSGs to increment of an applied field 5 Responses of tin-SSGs to alpha-ray irradiations 6 A prototype detector . . . . . . . . . . . . . 7 Responses of a tin-SSG to "(-ray irradiation . 8 Some plans . . . . . . . . . . . . . . . . . .

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. 731

. 735

. 739

. 749

. 752

. 757

Supernova Neutrinos 763 H. Suzuki

1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . 763 2 Collapse-Driven Supernova Explosion and Neutrinos . 767 3 Observation of Supernova Neutrinos . . . . . . . . . . 813

Appendix 823 A Basic Equations for Hydrodynamics and Neutrino Transfer . 823

Detection of VHE ')'-Rays and Neutrinos 848 T. Kifune and M. Mori

1 Introduction . . . . . . . . . . . . . . . . . . . . 848 2 Production mechanism of high energy "(-rays . 849 3 Detection methods of high energy "(-rays . . . . 851 4 Observational results in high energy "(-rays . . . 860 5 Implications and prospects of VHE gamma-ray astronomy . 875 6 High-energy neutrino astronomy . . . . . . . . . . . . . . . . 884

Particle Acceleration Mechanisms in Astrophysics 900 F. Takahara

1 Introduction . . . . . . . . . . . 900 2 Acceleration by Strong Waves . 902 3 Unipolar Induction . . . . . . . 906 4 Accretion Disks . . . . . . . . . 909 5 Fermi Acceleration by Shock Waves . 912 6 Current Problems of Shock Acceleration . 918 7 Astrophysical Sites of Shock Acceleration . . 926 8 Summary . . . . . . . . . . . . . . . . . . . 931