Herwig Schopper Editor Particle Physics Reference Library Volume 1: Theory and Experiments Particle Physics Reference Library Herwig Schopper Editor Particle Physics Reference Library Volume 1: Theory and Experiments Editor HerwigSchopper CERN Geneva,Switzerland ISBN978-3-030-38206-3 ISBN978-3-030-38207-0 (eBook) https://doi.org/10.1007/978-3-030-38207-0 Thisbookisanopenaccesspublication. ©TheEditor(s)(ifapplicable)andTheAuthor(s)2008,2020 Open Access This bookis licensed under the terms of the Creative Commons Attribution 4.0Inter- nationalLicense(http://creativecommons.org/licenses/by/4.0/), whichpermitsuse,sharing,adaptation, distribution andreproduction inanymediumorformat,aslong asyougive appropriate credit tothe originalauthor(s)andthesource,providealinktotheCreativeCommonslicenseandindicateifchanges weremade. Theimages or other third party material in this book are included in the book’s Creative Commons license,unlessindicatedotherwiseinacreditlinetothematerial.Ifmaterialisnotincludedinthebook’s CreativeCommonslicenseandyourintendeduseisnotpermittedbystatutoryregulationorexceedsthe permitteduse,youwillneedtoobtainpermissiondirectlyfromthecopyrightholder. Theuseofgeneraldescriptivenames,registerednames,trademarks,servicemarks,etc.inthispublication doesnotimply,evenintheabsenceofaspecificstatement,thatsuchnamesareexemptfromtherelevant protectivelawsandregulationsandthereforefreeforgeneraluse. Thepublisher,theauthors,andtheeditorsaresafetoassumethattheadviceandinformationinthisbook arebelievedtobetrueandaccurateatthedateofpublication.Neitherthepublishernortheauthorsor theeditorsgiveawarranty,expressedorimplied,withrespecttothematerialcontainedhereinorforany errorsoromissionsthatmayhavebeenmade.Thepublisherremainsneutralwithregardtojurisdictional claimsinpublishedmapsandinstitutionalaffiliations. ThisSpringerimprintispublishedbytheregisteredcompanySpringerNatureSwitzerlandAG. Theregisteredcompanyaddressis:Gewerbestrasse11,6330Cham,Switzerland Preface Formanyyearsthe Landolt-Börnstein—GroupI Elementary Particles, Nucleiand Atoms:Vol.21A(PhysicsandMethodsTheoryandExperiments,2008),Vol.21B1 (Elementary Particles Detectors for Particles and Radiation. Part 1: Principles and Methods, 2011),Vol. 21B2 (ElementaryParticles Detectors for Particles and Radiation.Part 2: Systems and Applications),and Vol. 21C (Elementary Particles AcceleratorsandColliders,2013)hasservedasamajorreferenceworkinthefield ofhigh-energyphysics. When, not long after the publication of the last volume, open access (OA) becamearealityforHEPjournalsin2014,discussionsbetweenSpringerandCERN intensifiedtofindasolutionforthe“Labö”whichwouldmakethecontentavailable in the same spirit to readers worldwide. This was helped by the fact that many researchersinthefieldexpressedsimilarviewsandtheirreadinesstocontribute. Eventually,in 2016,on the initiative of Springer,CERN and the originalLabö volumeeditorsagreedintacklingtheissuebyproposingtothecontributingauthors a new OA edition of their work. From these discussions, a compromise emerged alongthefollowinglines:transferasmuchaspossibleoftheoriginalmaterialinto open access; add some new material reflecting new developments and important discoveries,suchastheHiggsboson;andadapttotheconditionsduetothechange fromcopyrighttoaCCBY4.0license. Some authorswereno longeravailablefor makingsuchchanges,havingeither retired or, in some cases, deceased. In most such cases, it was possible to find colleagueswillingtotakecareofthenecessaryrevisions.Afewmanuscriptscould notbeupdatedandarethereforenotincludedinthisedition. Weconsiderthatthisneweditionessentiallyfulfillsthemaingoalthatmotivated us in the first place—there are some gaps compared to the original edition, as explained, as there are some entirely new contributions. Many contributions have beenonlyminimallyrevisedinordertomaketheoriginalstatusofthefieldavailable as historical testimony. Others are in the form of the original contribution being supplementedwithadetailedappendixrelatingtorecentdevelopmentsinthefield. However, a substantial fraction of contributions has been thoroughly revisited by theirauthorsresultingintrueneweditionsoftheiroriginalmaterial. v vi Preface We would like to express our appreciation and gratitude to the contributing authors, to the colleagues at CERN involved in the project, and to the publisher, whohashelpedmakingthisveryspecialendeavorpossible. Vienna,Austria ChristianFabjan Geneva,Switzerland StephenMyers Geneva,Switzerland HerwigSchopper July2020 Contents 1 Introduction................................................................. 1 HerwigSchopper 2 GaugeTheoriesandtheStandardModel................................ 7 GuidoAltarelliandStefanoForte 3 TheStandardModelofElectroweakInteractions...................... 35 GuidoAltarelliandStefanoForte 4 QCD:TheTheoryofStrongInteractions................................ 83 GuidoAltarelliandStefanoForte 5 QCDontheLattice......................................................... 137 HartmutWittig 6 TheDiscoveryoftheHiggsBosonattheLHC.......................... 263 PeterJenniandTejinderS.Virdee 7 RelativisticNucleus-NucleusCollisionsandtheQCDMatter PhaseDiagram.............................................................. 311 ReinhardStock 8 BeyondtheStandardModel............................................... 455 EliezerRabinovici 9 SymmetryViolationsandQuarkFlavourPhysics...................... 519 KonradKleinknechtandUlrichUwer 10 TheFutureofParticlePhysics:TheLHCandBeyond................. 625 KenPeach vii About the Editor Herwig Schopper joined as a research associate at CERN since 1966 and returned in 1970 as leader of the Nuclear Physics Division and went on to become a member of the directorate responsible for the coordination of CERN’s experimental program. He was chairman of the ISR Committee at CERN from 1973 to 1976 and was elected as member of the Scientific Policy Committee in 1979. Following LéonVanHove’sandJohnAdams’yearsasDirector- General for research and executive Director-General, SchopperbecamethesoleDirector-GeneralofCERN in1981. Schopper’syearsasCERN’sDirector-Generalsaw theconstructionandinstallationoftheLargeElectron- Positron Collider (LEP) and the first tests of four detectors for the LEP experiments. Several facilities (includingISR, BEBC, andEHS)hadto beclosedto freeupresourcesforLEP. ix Chapter 1 Introduction HerwigSchopper Sinceoldagesithasbeenoneofthenobleaspirationsofhumankindtounderstand theworldinwhichweareliving.Inadditiontoourimmediateenvironment,planet earth, two more remote frontiers have attracted interest: the infinitely small and the infinitely large. A flood of new experimental and theoretical results obtained during the past decades has provideda completely new picture of the micro- and macrocosm and surprisingly intimate relations have been discovered between the two. It turned out that the understanding of elementary particles and the forces acting between them is extremely relevantfor our perceptionof the cosmological development. Quite often scientific research is supported because it is the basis for technicalprogressand for the materialwell-beingof humans. The exploration of the microcosm and the universe contributes to this goal only indirectly by the developmentofbetterinstrumentsandnewtechniques.However,ittriestoanswer some fundamental questions which are essential to understand the origins, the environment and the conditions for the existence of humankind and thus is an essentialpartoftheculturalheritage. One of the fundamentalquestions concerns the nature of matter, the substance ofwhichthestars,theplanetsandlivingcreaturesaremade,ortoputitinanother way—can the many phenomena which we observe in nature be explained on the basisofafewelementarybuildingblocksandforceswhichactbetweenthem.The first attempts go back 2000 years when the Greek philosophers speculated about indestructibleatoms, like Democritus,or the fourelementsand the regularbodies ofPlato. H.Schopper((cid:2)) CERN,Geneva,Switzerland e-mail:[email protected] ©TheAuthor(s)2020 1 H.Schopper(ed.),ParticlePhysicsReferenceLibrary, https://doi.org/10.1007/978-3-030-38207-0_1 2 H.Schopper Since Newton who introduced infinitely hard smooth balls as constituents of matter1 and who described gravitation as the first force acting between them, the conceptofunderstandingnatureintermsof‘eternal’buildingblocksholdtogether by forces has not changed during the past 200 years. What has changed was the nature of the elementary building blocks and new forces were discovered. The chemistsdiscoveredtheatomsofthe92elementswhich,however,contrarytotheir name,werefoundtobedivisibleconsistingofanucleussurroundedbyanelectron cloud. Then it was found that the atomic nuclei contain protons and neutrons. Around1930the world appearedsimple with everythingconsisting of these three particles:protons,neutronsandelectrons. Thencamethe‘annusmirabilis’1931with thediscoveryofthepositronasthe firstrepresentativeofantimatterandthemysteriousneutrinoinnuclearbeta-decay indicatinganewforce,theweakinteraction.Inthefollowingdecadesthe‘particle zoo’withallitsnewlydiscoveredmesons,pionsand‘strange’particleswasleading togreatconfusion.Simplicitywasrestoredwhenallthesehundredsof‘elementary ‘particlescould be understoodin terms of a new kind of elementaryparticles, the quarksandtheirantiquarks.Thesystematicsoftheseparticlesismainlydetermined bythestrongnuclearforce,welldescribedtodaybythequantumchromodynamics QCD. Whether quarksand gluons(the bindingparticles of the strong interaction) existonlyinsidetheatomicnucleiorwhetheraphasetransitionintoaquark-gluon plasmaispossible,isonetheintriguingquestionswhichstillneedsananswer. Impressive progress was made in another domain, in the understanding of the weaknuclearforceresponsibleforradioactivebeta-decayandtheenergyproduction in the sun. Three kinds of neutrinos (with their associated antiparticles) were found and recently it could be shown that the neutrinos are not massless as had been originally assumed. The mechanism of the weak interaction could be clarified to a large extent by the discovery of its carriers, the W- and Z-particles. All the experimental results obtained so far will be summarized in this volume and the beautiful theoretical developments will be presented. The climax is the establishmentofthe‘StandardModelofParticlePhysics’SMwhichhasbeenshown to be a renormalizable gauge theory mainly by the LEP precision experiments. TheLEPexperimentshavealsoshownthatthereareonlythreefamiliesofquarks and leptons (electron, muon, tau-particle and associated neutrinos), a fact not yet understood. AlltheattemptstofindexperimentaldeviationsfromtheSMhavefailedsofar. However,theSMcannotbethefinaltheoryfortheunderstandingofthemicrocosm. Its main fault is that it has too many arbitrary parameters (e.g. masses of the particles,valuesofthecouplingconstantsoftheforces,numberofquarkandlepton families) which have to be determined empirically by experiment. An underlying theorybasedonfirstprinciplesisstillmissingandpossiblewaysintothefuturewill bediscussedbelow. 1IsaacNewton,Optics,Query31,London1718.