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Lecture Notes in Physics 947 Samoil Bilenky Introduction to the Physics of Massive and Mixed Neutrinos Second Edition Lecture Notes in Physics Volume 947 FoundingEditors W.Beiglböck J.Ehlers K.Hepp H.Weidenmüller EditorialBoard M.Bartelmann,Heidelberg,Germany P.Hänggi,Augsburg,Germany M.Hjorth-Jensen,Oslo,Norway R.A.L.Jones,Sheffield,UK M.Lewenstein,Barcelona,Spain H.vonLöhneysen,Karlsruhe,Germany A.Rubio,Hamburg,Germany M.Salmhofer,Heidelberg,Germany W.Schleich,Ulm,Germany S.Theisen,Potsdam,Germany D.Vollhardt,Augsburg,Germany J.D.Wells,AnnArbor,USA G.P.Zank,Huntsville,USA The Lecture Notes in Physics The series Lecture Notes in Physics (LNP), founded in 1969, reports new devel- opmentsin physicsresearch and teaching-quicklyand informally,but with a high qualityand the explicitaim to summarizeand communicatecurrentknowledgein anaccessibleway.Bookspublishedinthisseriesareconceivedasbridgingmaterial between advanced graduate textbooks and the forefront of research and to serve threepurposes: (cid:129) to be a compact and modern up-to-date source of reference on a well-defined topic (cid:129) to serve as an accessible introduction to the field to postgraduate students and nonspecialistresearchersfromrelatedareas (cid:129) to be a source of advanced teaching material for specialized seminars, courses andschools Bothmonographsandmulti-authorvolumeswillbeconsideredforpublication. 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Proposalsshouldbe sent to a memberof the EditorialBoard, ordirectly to the managingeditoratSpringer: ChristianCaron SpringerHeidelberg PhysicsEditorialDepartmentI Tiergartenstrasse17 69121Heidelberg/Germany [email protected] Moreinformationaboutthisseriesathttp://www.springer.com/series/5304 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) https://doi.org/10.1007/978-3-319-74802-3 LibraryofCongressControlNumber:2018934708 ©SpringerInternationalPublishingAG,partofSpringerNature2018 ©Springer-VerlagBerlinHeidelberg2010 Thisworkissubjecttocopyright.AllrightsarereservedbythePublisher,whetherthewholeorpartof thematerialisconcerned,specificallytherightsoftranslation,reprinting,reuseofillustrations,recitation, broadcasting,reproductiononmicrofilmsorinanyotherphysicalway,andtransmissionorinformation storageandretrieval,electronicadaptation,computersoftware,orbysimilarordissimilarmethodology nowknownorhereafterdeveloped. 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Theregisteredcompanyaddressis:Gewerbestrasse11,6330Cham,Switzerland 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. xi