Introduction to the Physics of Massive and Mixed Neutrinos

283 Pages·2018·3.161 MB·English

by  Bilenky, Samoil

Lecture Notes in Physics 947
Samoil Bilenky
Introduction
to the Physics
of Massive and
Mixed Neutrinos
Second Edition
Lecture Notes in Physics
Volume 947
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Samoil Bilenky
Introduction to the Physics
of Massive and Mixed
Neutrinos
Second Edition
123
SamoilBilenky
TRIUMF
Vancouver,BC
Canada
ISSN0075-8450 ISSN1616-6361 (electronic)
LectureNotesinPhysics
ISBN978-3-319-74801-6 ISBN978-3-319-74802-3 (eBook)
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Dedicatedtothememoryofthegreat
neutrinophysicistBrunoPontecorvo
Preface to the Second Edition
Thediscoveryofneutrinooscillationsandtheproofthatneutrinomassesdifferfrom
zero and are much smaller than the masses of leptons and quarks is the first (and
up to now the only) signature of physics beyond the Standard Model revealed in
particle physics experiments. Further investigations of neutrino oscillations have
continued in many experiments. The next generation of these investigations, and
other experiments now in preparation, will include the search for neutrinoless
doubleβ-decay.
After the first edition of this book was published it was found that the mixing
◦
angleθ wasdifferentfromzeroandwasrelativelylarge(about8 ).Thisfinding
13
opened the way to the investigation of such fundamental problems of neutrino
mixing as the characteristics of the neutrino mass spectrum (normal or inverted
ordering)andchargeconjugationparity(CP)violationintheleptonsector.
The important problem of sterile neutrinos will be solved soon; many reactor,
accelerator, and source short-baseline experimentsinvestigating evidence in favor
ofthetransitionofflavorneutrinosintosterilestates,foundinLosAlamosNeutrino
Detector (LSND) and other experiments, are now ongoing (or in preparation).
After the discovery of the Higgs boson at the Large Hadron Collider (LHC) and
the establishment of the Standard Model as the theory of elementary particles
in the electroweak region, belief in the minimal effective Lagrangian (Weinberg)
mechanismofthe generationof Majorananeutrinomassesincreasedsignificantly.
The search for neutrinoless double β-decay is now a top priority. In the second
editionofthebookIhavepresenteddataonthelatestneutrinooscillationandother
neutrinodata.Ihavekeptthesamestyleofthedetailedderivationofmajorresults,
butIhavealsotriedtoimproveandsimplifydifferentderivations.
Vancouver,BC,Canada SamoilBilenky
December2017
vii
Preface to the First Edition
For many years the neutrino was considered a massless particle. The theory of a
two-componentneutrino,which playeda crucialrole in the creation of the theory
ofweakinteraction,isbasedontheassumptionthatthemassofaneutrinoisequal
to zero. Now we know that neutrinos have nonzero, small masses. In numerous
experiments with solar, atmospheric, reactor, and accelerator neutrinos, a new
phenomenon, neutrino oscillations, was observed. Neutrino oscillations (periodic
transitionsbetweendifferentflavorneutrinosν ,ν ,ν )arepossibleonlyifneutrino
e μ τ
mass-squareddifferencesare differentfromzeroand the states of flavor neutrinos
are“mixed”.
The discovery of neutrino oscillations opened a new era in neutrino physics:
an era of investigation of neutrino masses, mixing, magnetic moments, and other
neutrinoproperties.After theestablishmentoftheStandardModelof electroweak
interaction at the end of the 1970s, the discovery of neutrino masses was the
most important discovery in particle physics. The small neutrino masses cannot
be explained by the standard Higgs mechanism of mass generation. For their
explanationa new mechanismis needed.Thus, in particle physics, small neutrino
massisthefirstsignatureofanewphysicsbeyondtheStandardModel.
It took many years of heroic efforts by many physicists to discover neutrino
oscillations. After the first period of the discovery and investigation of neutrino
oscillations, many challenging problems remained unsolved. One of the most
important is the problem of the nature of neutrinos with definite masses. Are
they Dirac neutrinos possessing a conserved lepton number which distinguishes
neutrinosandantineutrinos,oraretheyMajorananeutrinoswithidenticalneutrinos
andantineutrinos?Manynewexperimentsarenowongoingorinpreparation.There
isnodoubtthatexcitingresultslieahead.
This book is intended as an introduction to the physics of massive and mixed
neutrinos.ItisbasedonnumerouslecturesthatIhavegivenatdifferentuniversities
andschools.Ihavetriedtoexplainhowmanyofthemainresultswerederived.The
detailsofthederivationcanbeeasilyfollowedbythereader.Ihopethatthisbook
willbeusefulforphysicistswhoareworkinginneutrinophysics,forstudents,for
ix
x PrefacetotheFirstEdition
youngphysicistswhoplantoenterthisexcitingfield,andformanyscientistswho
areinterestedinthehistoryofneutrinophysicsanditspresentstatus.
Dubna,Russia/Vancouver,BC,Canada SamoilBilenky
December2016
Acknowledgments
I am very happyto expressmy deep gratitudeto my colleaguesand collaborators
W. Alberico, J. Bernabeu, A. Bottino, A. Faessler, F. von Feilitzsch, C. Giunti,
A. Grifols, W. Grimus, J. Hosek, C.W. Kim, M. Lindner, M. Mateev, T. Ohlsson,
S.Pascoli,S.Petcov,W.Potzel,F.Simkovic,andT.Schwetzfornumerousfruitful
discussionsofdifferentaspectsofneutrinophysics.Iamthankfultothetheoretical
departmentofTRIUMFforhospitality.
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