Particle Physics Reference Library

631 Pages·2020·20.306 MB·English

by  Herwig Schopper

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
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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:[e-mail]
©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.