DOCSLIB.ORG

Introduction to Unified Theories of Weak, Electromagnetic and Strong Interactions - Su(5)

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Introduction to Unified Theories of Weak, Electromagnetic and Strong Interactions - Su(5) FR3looo?2. CEA-N-2175 Note CEA-N-2175 Centre d'Etudes Nucléaires de Saclay Division de la Physique Service de Physique Théorique INTRODUCTION TO UNIFIED THEORIES OF WEAK, ELECTROMAGNETIC AND STRONG INTERACTIONS - SU(5) - par Alain BILLOIRE, André MOREL -Novembre 1980- Note CEA':-2175 DESCRIPTION-MATIERE (mois clifs extraits du thesaurus SI DON MIS) an français an anglais MODELES DE JAUGE UNIFIES UNIFIED GAUGE MODELS INTERACTIONS FORTES STRONG INTERACTIONS INTERACTIONS FAIBLES WEAK INTERACTIONS INTERACTIONS ELECTROMAGNETIQUES ELECTROMAGNETIC INTERACTIONS GROUPES SU-5 SU-5 GROUPS COURS LECTURES H Note CEA-N-2175- Centre d'Etudes Nucléaires de Saclay Division de la Physique Service d? Physique Théorique INTRODUCTION TO UNIFIED THEORIES OF WEAK. ELECTROMAGNETIt AND STRONG INTERACTIONS - SU(5) - par Alain BILLOIRE. André MOREL ri CEA-N-Z175 - Alain BILLOIRE, André MOREL INTRODUCTION AUX THEORIES UNIFIEES DES INTERACTIONS FAIBLE, ELECTROMAGNETIQUE ET FORTE - SU(5) So—aire.- Ces notes constituent la version écrite d'une série de cours donnés au DPh-T a Saclay pendant l'hiver 1ï'9-19S0. L'intention est de fournir une introduction aux théories dites unifiées des interactions faible, électromagnétique et forte. Il ne s'agit en aucune façon d'une revue des travaux de recherche récents ou en cours ; nous avons plutôt cherché a présenter in» exposé aussi élémentaire que possible et renvoyant au minimum 5 d'autres ouvrages. En particulier, le* connaissances en théorie des champs e' en théorie des groupes nécessaires a la compréhension du texte ont été ramenées au minimum et nous nous sommes efforcés d'en rappeler les principaux éléments au moment d'en faire usage. La liste de références, loin d'être exhaustive, devrait être suffisante pour guider le lecteur souhaitant approfondir les bases de la théorie r.u trouver des détails concernant les progrès récents. Dan? une premier, partie, nous rap­ pelons le modèle SU(2) • U(1), en insistant sur les pro:.limes qui, laissés ouverts dans ce cadre, trouvent une solution dans celui des théories unifiées. Dans la deuxième partie, nous expliquons de façon systématique comment on peut construire des théories unifiées, et 1 CEA-N-2175 - Alain BILLOIRE, André MCREL INTRODUCTION TO UNIFIED THEORIES OF WEAK, ELECTROMAGNETIC AND STRONG INTERACTIONS - SU(5) Summary.- These notes correspond to a series of lectures given at Saclay during winter 1979-1980. They are meant to be an introduction to the so-called grand unified theories of weak, electromagnetic and strong interactions. By no means do they constitute s review of the current research work on the subject. We tried to be as elementary and self-contained as possible. In particular, tho required knowled­ ge in field and Lie group theory has been kept at the minimal level, and we made an effort to recall the basic theoretical tocls when they were needed. Our list of references, far from exhaustive, should be sufficient to guide the reader who is interested cither in lear­ ning more about fundamental topics or in finding d.-t.uls about recent progress reported in the literature. In a first pa^t, we recall in a very elementary way the standard SU(2) S U(11 mod.l of electroweak interactions, putting the emphasis on the questions «hich. arc left open by this model and which unified theoriss help to answer. In part II, we explain in a systematic way how unified theoi;rs can ht constructed, and develop the SU(5) model in great detail. Oth^r arc not models, like SO(10) and F0, presented, net bfnuse of any développons le modèle SU(5) en détails. D'autres modèles, comme S0(10) ou E0, ne sont pas présentés, non par préjugé mais parce que SU(5) est le plus simple et le plus étudié. 11 se trouve d'ailleurs que la plupart des concepts et résultat; généraux ne sont pas spéci­ fiques à un groupe de symétrie particulier. La préparation de ces notes doit beaucoup à d'utiles discussions avec nos collègues du DPh-T de Saclay ; nous remercions en particulier F. Hayot et R. Lacaze pour leur lecture critique d'une grande part du manuscrit. Nous sommes très reconnaissants envers D. Bunel et F, Lefèvre pour leur très grande efficacité et le soin apporté à la présentation de ces notes. 1980 130 p. Commissariat à l'Energie Atomique - France prejudice, but essentially because SU(5) is the simplest one and has been subject to the deepest investigations up to now. Also it appears that most concepts and general results are not specific to any parti­ cular symmetry group. We wish to acknowledge many helpful discussions with our Colleagues in Saclay during the preparation of these notes, and especially thank F. Hayot and R, Lacaze for their critical reading of a substantial part of the manuscript. Finally, we are grateful to D. Bunel and F. Lcfevre for their very efficient typing. 1980 130 p. Commissariat 3 l'Energie Atomique - France TABLE OF CONTENTS Part I 1. INTRODUCTION 2. THE ALGEBRAIC STRUCTURE OF THE SU(2) 9 U(l) MODEL 3. SPONTANEOUS SYMMETRY BREAKING AND THE HIGGS MECHANISM FOR SU(2) 8U(1) 4. ANOMALIES Part II 5. IN SEARCH OF THE UNIFICATION GROUP 6. DESCRIPTION OF THE SU(5) MOOEL 7. RELATIONS BETWEEN THE SU(3), SU(2), U(l) COUPLING CONSTANTS 3. HIGGS BOSONS, SU(5) BREAKING, MASSES a) .i.rsc stage breaking : SU(5) » SU(3) B SU(2) 9 U(l) b) Second stage breaking : SU(3) 9 SU(2) 9 U(l) - SU(3) 9 'J (1) e.n. c) Generation mixing d) 3-L invariance 9. RENORMALIZATION OF THE SU(5) PREDICTIONS a) Coupling constant renoraalization b) Fermion mass renormalization 10. THE PROTON LIFETWE APPENDIX A : YANG MILLS AND GROUP THEG.IY APPENDIX B : YOUNG TABLEAUX FOR SU(N) REFERENCES - 3 - 1. INTRODUCTION Our understanding of elementary interactions is mainly based on the observation chat they obey a number of symmetry laws. Some of these laws seem Co be exact. Such are Poincari (Lorentz + translational) or CPT inva­ riances. Also, in the field theoretical formulation of the interactions, exact local gauge symmetries are realized, such as che U (I) symmetry c.a. which generates electromagnetic phenomena (QED), or as far as we know, the SU(3) colour symmetry, responsible for strong interactions (QCD). Such symmetries, when exact, imply the existence of aassless, spin 1, gauge bosons. Particles can then be classified according to representations of the corres­ ponding (Lie) groups, their quantum numbers being the eigenvalues of the com­ muting generators. For example, che OED Lagrangian is invariant under the local transformations ? •» 0 '? , e.a. U (x) - exp {-iea(x)Q} , (I.I) e.a. of che feraion fields. The charge operator Q is the generator of the transfor­ mation, a(x) an arbitrary real function of space time. Local invariance implies the existence of a aassless gauge boson, the photon. Clearly only the produce eO is physically relevant. If Q is normalised so that its eigenvalue in the electron state 0 is -1, then e is the usual electron charge (e*/(4Ti) «a is che fine structure constant). But at this level, nothing guarantees chat another particle has, in units of e, a charge equal to a fraction or to a multiple of Q , as we chink it is the case. It is so because U(I), being abeiian, contains only I-dimensional irreducible representations, so that different particles, belonging co different irreducible represencations of U(I), have unrelated quantum numbers (here charges). Kere is che first question which any unification aims to answer : Question I : Why axt JUtt. chaxqte comneruuAate 1 In order to go ahead, we need to classify particles in representations of some larger group g, in such a way that non-trivial commutation relations between che generators imply relations between the O.N. of che particles(even if chese particles belong Co different represencations). SU(3) is another, apparently exact, symmetry of nature. The elementary fermions appear either as members of che fundamental representation (quarks q., i"l,2,3) or as singlets of SU(3) (leptons, e,.>e ,u,u v etc.). Therefore, Ue.a . (1) cannot 'e identified co a U(l) subgroup of SU(3)^. Rather, we have as a symmetry group Che direct produce - 4 - gQ - SU(3)c« U<B (1) . (1.2) From this examole, we see chat the needed group g should not contain U (1) as a factor, if we are to explain that charges are commensurate, but ocmf cours. e it should contain g as a (non invariant) subgroup in order to accomodate in particular the colour and charge quantum numbers of the known elementary fields. Weak interactions (W.I.) are also considered as deriving from a gauge sym­ metry group, namely SU(2). But this symmetry cannot be an exact symmetry : at present energies, W.I. appear as short range interactions, (Fermi type interac­ tions), which cannot be described by zero mass vector boson exchange. Both their smallness and their short range nature may be accounted tor at the same cime if the gauge fields associated with the SU(2) symmetry have masses M large as com­ pared to the relevant energy scale (the proton mass). Their exchange in a 2 fermion •* 2 fermion transition leads co an effective Fermi interaction of 2 2 strength G_ of order g /M , where g is the dimensionless SU(2) coupling constant. gauge boson (M) | 2 <SCM2 Fig. f. 1 - Gauge, oo-ion zxchange. at ixani^eA. iouaxtd Q} and for a. baon ireu,i ,'.f <Kvej "u-Je to an z^icXiv?. fouA. Fzmi inttiaition oj i£re.ngth Gr~g2/$ io\ ]02\ « M*.
Load more

Recommended publications
  • Masse Des Neutrinos Et Physique Au-Delà Du Modèle Standard
    œa UNIVERSITE PARIS-SUD XI THESE Spécialité: PHYSIQUE THÉORIQUE Présentée pour obtenir le grade de Docteur de l'Université Paris XI par Pierre Hosteins Sujet: Masse des Neutrinos et Physique au-delà du Modèle Standard Soutenue le 10 Septembre 2007 devant la commission d'examen: MM. Asmaa Abada, Sacha Davidson, Emilian Dudas, rapporteur, Ulrich Ellwanger, président, Belen Gavela, Thomas Hambye, rapporteur, Stéphane Lavignac, directeur de thèse. 2 Remerciements : Un travail de thèse est un travail de longue haleine, au cours duquel se produisent inévitablement beaucoup de rencontres, de collaborations, d'échanges... Voila pourquoi, sans doute, il me semble que la liste des personnes a qui je suis redevable est devenue aussi longue ! Tâchons cependant de remercier chacun comme il le mérite. En relisant ce manuscrit je ne peux m'empêcher de penser a Stéphane Lavignac, que je me dois de remercier pour avoir accepté d'encadrer mon travail de thèse et qui m'a toujours apporté le soutien et les explications nécessaires, avec une patience admirable. Sa grande rigueur d'analyse et sa minutie m'offrent un exemple que je m'évertuerai à suivre avec la plus grande application. Ces travaux n'auraient pas pu voir le jour non plus sans mes autres collaborateurs que sont Carlos Savoy, Julien Welzel, Micaela Oertel, Aldo Deandrea, Asmâa Abada et François-Xavier Josse-Michaux, qui ont toujours été disponibles et avec qui j'ai eu un plaisir certain a travailler. C'est avec gratitude que je remercie Asmâa pour tous les conseils et recommandations qu'elle n'a cessé de me fournir tout au long de mes études au sein de l'Université Paris XL Au cours de ces trois années de travail dans le domaine de la Physique Au-delà de Modèle Standard, j'ai bénéficié du contact de toute la communauté des théoriciens de la région.
    [Show full text]
  • GRAND UNIFIED THEORIES Paul Langacker Department of Physics
    GRAND UNIFIED THEORIES Paul Langacker Department of Physics, University of Pennsylvania Philadelphia, Pennsylvania, 19104-3859, U.S.A. I. Introduction One of the most exciting advances in particle physics in recent years has been the develcpment of grand unified theories l of the strong, weak, and electro­ magnetic interactions. In this talk I discuss the present status of these theo­ 2 ries and of thei.r observational and experimenta1 implications. In section 11,1 briefly review the standard Su c x SU x U model of the 3 2 l strong and electroweak interactions. Although phenomenologically successful, the standard model leaves many questions unanswered. Some of these questions are ad­ dressed by grand unified theories, which are defined and discussed in Section III. 2 The Georgi-Glashow SU mode1 is described, as are theories based on larger groups 5 such as SOlO' E , or S016. It is emphasized that there are many possible grand 6 unified theories and that it is an experimental problem not onlv to test the basic ideas but to discriminate between models. Therefore, the experimental implications are described in Section IV. The topics discussed include: (a) the predictions for coupling constants, such as 2 sin sw, and for the neutral current strength parameter p. A large class of models involving an Su c x SU x U invariant desert are extremely successful in these 3 2 l predictions, while grand unified theories incorporating a low energy left-right symmetric weak interaction subgroup are most likely ruled out. (b) Predictions for baryon number violating processes, such as proton decay or neutron-antineutnon 3 oscillations.
    [Show full text]
  • THE STANDARD MODEL and BEYOND: a Descriptive Account of Fundamental Particles and the Quest for the Unification of Their Interactions
    THE STANDARD MODEL AND BEYOND: A descriptive account of fundamental particles and the quest for the uni¯cation of their interactions. Mesgun Sebhatu ([email protected]) ¤ Department of Chemistry, Physics and Geology Winthrop University, Rock Hill SC 29733 Abstract fundamental interactions|gravity, electroweak, and the strong nuclear|into one. This will be In the last three decades, signi¯cant progress has equivalent to having a complete theory of every- been made in the identi¯cation of fundamental thing (TOE). Currently, a contender for a TOE particles and the uni¯cation of their interactions. is the so called superstring theory. The theoret- This remarkable result is summarized by what ical extensions of the Standard Model and the is con¯dently called the Standard Model (SM). experimental tests of their predictions is likely This paper presents a descriptive account of the to engage high energy physicists of the 21st cen- Standard Model and its possible extensions. Ac- tury. cording to SM, all matter in the universe is made up of a dozen fermions|six quarks and six lep- tons. The quarks and leptons interact by ex- 1 HISTORICAL INTRO- changing a dozen gauge (spin|one) bosons| DUCTION eight gluons and four electroweak bosons. The Standard Model provides a framework for the Our job in physics is to see things sim- uni¯cation of the electroweak and strong nu- ply, to understand a great many com- clear forces. A major de¯ciency of the Standard plicated phenomena in a uni¯ed way, in Model is its exclusion of gravity. The ultimate terms of a few simple principles.
    [Show full text]
  • Physics Beyond the Standard Model
    SM Generalities Symmetries Electroweak Yukawa Methodology BSM Unification SU(5) SO(10) Flavour Conclusions Physics beyond the Standard Model Ulrich Nierste Karlsruhe Institute of Technology KIT Center Elementary Particle and Astroparticle Physics LHCb Workshop Neckarzimmern 13-15 February 2013 SM Generalities Symmetries Electroweak Yukawa Methodology BSM Unification SU(5) SO(10) Flavour Conclusions Scope The lecture gives an introduction to physics beyond the Standard Model associated with new particles in the 100 GeV– 10 TeV range. The concept is bottom-up, starting from the Standard Model and its problems, with emphasis on the standard way beyond the Standard Model: Grand unification (and supersymmetry). SM Generalities Symmetries Electroweak Yukawa Methodology BSM Unification SU(5) SO(10) Flavour Conclusions Scope The lecture gives an introduction to physics beyond the Standard Model associated with new particles in the 100 GeV– 10 TeV range. The concept is bottom-up, starting from the Standard Model and its problems, with emphasis on the standard way beyond the Standard Model: Grand unification (and supersymmetry). Not covered: Search strategies for new particles at colliders, theories of gravitation, large extra dimensions, strongly interacting Higgs sectors, ... SM Generalities Symmetries Electroweak Yukawa Methodology BSM Unification SU(5) SO(10) Flavour Conclusions Contents Standard Model Generalities Symmetries Electroweak interaction Yukawa interaction Methodology of new physics searches Beyond the Standard Model Towards unification of forces SU(5) SO(10) Probing new physics with flavour Conclusions SM Generalities Symmetries Electroweak Yukawa Methodology BSM Unification SU(5) SO(10) Flavour Conclusions The theorist’s toolbox A theory’s particles and their interactions are encoded in the Lagrangian .
    [Show full text]
  • 10. Other Extensions of the Standard Model
    10. Other Extensions of the Standard Model 10.1 Introduction to Grand Unified Theories 10.2 Leptoquarks 10.3 Additional Gauge bosons, W’ and Z’ searches 10.4 Compositeness and excited quarks 10.5 Extra Space dimensions Why Physics Beyond the Standard Model ? 1. Gravity is not yet incorporated in the Standard Model 2. Dark Matter not accomodated 3. Many open questions in the Standard Model 19 - Hierarchy problem: mW (100 GeV) → mPlanck (10 GeV) - Unification of couplings - Flavour / family problem - ….. All this calls for a more fundamental theory of which the Standard Model is a low energy approximation → New Physics Candidate theories: Supersymmetry Many extensions predict new Extra Dimensions physics at the TeV scale !! New gauge bosons ……. Strong motivation for LHC, mass reach ~ 3 TeV 10.1 Introduction to Grand Unified Theories (GUT) • The SU(3) x SU(2) x U(1) gauge theory is in impressive agreement with experiment. • However, there are still three gauge couplings (g, g’, and αs) and the strong interaction is not unified with the electroweak interaction • Is a unification possible ? Is there a larger gauge group G, which contains the SU(3) x SU(2) x U(1) ? Gauge transformations in G would then relate the electroweak couplings g and g’ to the strong coupling αs. For energy scales beyond MGUT, all interactions would then be described by a grand unified gauge theory (GUT) with a single coupling gG, to which the other couplings are related in a specific way. • Gauge couplings are energy-dependent, g2 and g3 are asymptotically free, i.e.
    [Show full text]
  • Download Download
    Proceedings of the 2017 CERN–Latin-American School of High-Energy Physics, San Juan del Rio, Mexico 8-21 March 2017, edited by M. Mulders and G. Zanderighi, CYR: School Proceedings, Vol. 4/2018, CERN-2018-007-SP (CERN, Geneva, 2018) Beyond the Standard Model M. Mondragon Instituto de Fisica, Universidad Nacional Autonoma de Mexico UNAM, CD MX 01000, Mexico Abstract I present a brief outline of some of the different paths for extending the Stan- dard Model. These include supersymmetry, Grand Unified Theories, extra dimensions, and multi-Higgs models. The aim is to give graduate students an overview of some of the theoretical motivations to go into a specific extension, and a few examples of how the experimental searches go hand in hand with these efforts. Supersymmetry, Grand Unified Theories, Extra dimensions, Multi-Higgs models 1 Introduction The Standard Model is an extremely successful description of the elementary particles and its interac- tions around the Fermi scale, but it leaves a number of unanswered questions that lead naturally to the conclusion that it is the low energy limit of a more fundamental theory. Along with these unanswered question comes a large number of free parameters whose value can only be determined experimentally. Among the unanswered questions in the Standard Model are: – Are there more than three generations of particles? – Why are the fundamental particles masses so different? – How is the Higgs mass stablilized, i.e. what solves the hierarchy problem? – Is there more than one Higgs? – What is the nature of the neutrinos, are they Dirac or Majorana? – What is dark matter? – Why is there more matter than anti-matter? – Is there more CP violation? – Why only left-handed particles feel the electroweak interaction? – Is it possible to unify quantum mechanics with gravity? The collection of models and theories that make the research that extends the Standard Model to answer some of these, and many more, questions is known as physics Beyond the Standard Model (BSM).
    [Show full text]
  • Grand Unification
    Grand Unification The present status of grnnd unified theories (GUTs) are described. Topics include the problems of the standard model that are or arc not solved by grand unification, experimental implications, and features that are likely to survive extensions of the simplest GUTs. INTRODUCTION 2 The nonobservation of proton decay' · into e + 'TTo has almost cer­ 3 tainly ruled out the minimal SU5 modeJ .4 as well as many other similar models with only two mass scales. However, such models are only the simplest examples of a large class of theories, many of which have longer proton lifetimes or dominant decays into other modes. Grand unified theories have many very attractive features, in­ cluding the unification of the basic microscopic interactions, the elegant explanation of the equality of the proton and positron electric charges, the dynamical generation of the baryon-antibar­ yon asymmetry of the Universe, and the prediction of sin2 0w. On the negative side GUTs have shed little light on the fermion masses, mixing angles, or family structure, have not explained the ex­ tremely small value of the weak interaction mass scale relative to the Planck mass (the problem is rephrased as the gauge hierarchy 24 problem, which refers to the tiny ratio (Mw1Mx)2 < 10- ), and Commems Nud Part. Phys (t) 1985 Gordon and Breach, 1985. Vol 15. No 2. pp 41 - 67 Science Publishers. Inc. and OPA Ltd. 01110-2709 /85 i I 51l~-IXl41 /$25 ,011 /ll 1'1 intcd in Great Britain 41 do not incorporate gravity in any fundamental way. On balance it seems unlikely and even naive (and always did) that a model as simple as SU_, could be the ultimate theory of nature below the Planck scale.
    [Show full text]
  • Jhep02(2013)085
    Published for SISSA by Springer Received: November 11, 2012 Accepted: January 18, 2013 Published: February 14, 2013 Search in leptonic channels for heavy resonances JHEP02(2013)085 decaying to long-lived neutral particles The CMS collaboration E-mail: [email protected] Abstract: A search is performed for heavy resonances decaying to two long-lived massive neutral particles, each decaying to leptons. The experimental signature is a distinctive topology consisting of a pair of oppositely charged leptons originating at a separated sec- ondary vertex. Events were collected by the CMS detector at the LHC during pp collisions p at s = 7 TeV, and selected from data samples corresponding to 4.1 (5.1) fb−1 of integrated luminosity in the electron (muon) channel. No significant excess is observed above standard model expectations, and an upper limit is set with 95% confidence level on the production cross section times the branching fraction to leptons, as a function of the long-lived massive neutral particle lifetime. Keywords: Hadron-Hadron Scattering ArXiv ePrint: 1211.2472 Open Access, Copyright CERN, doi:10.1007/JHEP02(2013)085 for the benefit of the CMS collaboration Contents 1 Introduction1 2 The CMS detector2 3 Data and Monte Carlo simulation samples3 4 Event reconstruction and selection3 JHEP02(2013)085 4.1 Selection efficiency4 5 Background estimation and modelling5 5.1 Background normalisation5 5.2 Background shape5 6 Systematic uncertainties6 6.1 Track-finding efficiency7 6.2 Trigger efficiency measurement8 6.3 Effect of higher-order QCD corrections9 6.4 Background uncertainty9 7 Results 9 8 Summary 14 The CMS collaboration 16 1 Introduction Several models of new physics predict the existence of massive, long-lived particles which could manifest themselves through their delayed decays to leptons.
    [Show full text]
  • Phenomenology
    Phenomenology Lectures given at the 2012 RAL Summer School P. Richardson, IPPP, Durham University. 1 Introduction Historically the lecture notes for the phenomenology course have consisted of the slides presented in the lectures. These notes are intended to provide additional information, and more mathematical detail, on the more theoretical aspects of the course which don’t change from year to year. The recent experimental results, which as the LHC experiments take more and more data change from day-to-day, will continue to be presented solely on the slides used in the lectures. The course will focus primarily, and unapologetically, on hadron collider, and specifi- cally LHC, phenomenology. In order to study hadron collisions we need to understand the basics of cross section calculations, Quantum Chromodynamics (QCD) and jets which we + will first consider in the simpler environment of e e− and lepton-hadron collisions before we go on to study hadron–hadron collisions. This occupies the first three lectures of the course. The next two lectures consider the electroweak and Higgs sector of the Standard Model. Lectures six and seven consider possible physics beyond the Standard Model. The final lecture looks at the physics of Monte Carlo event generators which are now an essential tool in all aspects of modern collider physics. Unfortunately there is no single good book on modern phenomenology. Two old classics but now a bit dated are: Quarks and Leptons Halzen and Martin [1]; • Collider Physics Barger and Phillips [2]. • Two good books, although mainly focused on QCD and probably at a bit too high a level for this course, are: QCD and Collider Physics Ellis, Stirling and Webber [3]; • Quantum Chromodynamics Dissertori, Knowles and Schmelling [4]; • and of course the classic on Higgs physics The Higgs Hunter’s Guide Gunion, Haber, Kane and Dawson [5].
    [Show full text]
  • Phenomenology Lecture 8
    Phenomenology Lecture 8: BSM Daniel Maître IPPP, Durham Phenomenology – Daniel Maître Why BSM? ● Despite the success of the Standard model, there are some puzzles left: – Why is the top so much heavier than the electron? – Why is Θ so small? – Is there enough CP violation? ● We need masses for the neutrinos ● What is dark matter? ● What is dark energy? ● What about gravity? Phenomenology – Daniel Maître BSM ● New models usually include more particles ● We can find them – Direct production: By directly producing them in the colliders if they are light enough and they interact (enough) with the standard model – Precision observables: By measuring their effect on precision observables through loop correction (where they can be off-shell if the energy is not sufficient to produce them) examples: g-2, EW precision measurements – Rare decays: If there is a new interaction, even a weak one, new processes become allowed that are not allowed in the standard model, or are highly suppressed. Examples: Proton decay, neutrino mixing, rare B and Kaon decays... Phenomenology – Daniel Maître BSM models ● There are a large number of BSM models ● This may be due to the fact that it is easier to “cook up” a model that it is to test it. ● Since there is no (direct) experimental evidence for BSM particles the game is to find models that are most undistinguishable from the SM. ● We can only cover a limited number of models and look at their experimental implications ● It is much better, when possible, to have model independent searches, so that they can be used for several models not just the one that is trendy at the moment of the measurement Phenomenology – Daniel Maître BSM models ● Here are some models – GUT theories – Technicolor – SUSY – Large extra dimensions – Small extra dimensions – Little Higgs Models – ..
    [Show full text]
  • Beyond the Standard Model
    Special Topics in Particle Physics Beyond the Standard Model Jonghee Yoo Korea Advanced Institute of Science and Technology 2018 Fall Physics Course Lecture Series PH489 Note 04 PH489 Contact Professor Yoo, Jonghee E-mail: [email protected] - E-mail is the easiest way to reach me Classes: E11-208 (2:30PM - 4:00PM, Monday and Wednesday) Office hours: There will be no regular office hours Email me ([email protected]) to organize meeting time - Office#1: KAIST Main Campus, E6-2, room 2306 (2nd floor) - Office#2: KAIST Munji Campus, Creation Hall, room C307-A (3rd floor) Web-page: yoo.kaist.ac.kr/lectures/ - course materials, corrections, useful links etc. KAIST-PH489-Yoo-2018-Note04: Beyond the Standard Model !2 PH489 Make up Classes? S M T W T F S ! 24 regular lecture opportunities 9 26 27 28 29 30 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 10 30 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 11 28 29 30 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 12 25 26 27 28 29 30 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 KAIST-PH489-Yoo-2018-Note04: Beyond the Standard Model !3 Standard Model of Particle Physics KAIST-PH489-Yoo-2018-Note04: Beyond the Standard Model !4 Standard Model of Particle Physics Particle Physics What are the fundamental constituents of the Universe? How do they interact each other? Standard Model of Particle Physics Matter Particles: Fermions Leptons and quarks Force Carrier Particles: Bosons Electromagnetic force (photon) Strong force (gluons)
    [Show full text]
  • Beyond the Standard Model
    Beyond the Standard Model V. Hedberg Beyond the Standard Model 1 The Standard Model What is the standard model ? The standard model describes the electromagnetic, strong and weak interactions. It is based on the principle of gauge invariance. The model has lots of free parameters: lepton and quark masses, coupling constants, quark and neutrino mixing parameters, W, Z and H masses... H It uses a basic set of fermions and gauge bosons: W Z g V. Hedberg Beyond the Standard Model 2 The Standard Model The Standard Model agrees very well with all experimental data. The model has been tested down to 10-18 m. It has been tested to a precision better than 0.1% . Problems with the standard model: Does the Higgs exist ? If neutrinos have mass, are there right-handed neutrinos ? Why are there 3 generations ? What about gravity ? V. Hedberg Beyond the Standard Model 3 The Standard Model Why are the masses so different (the hierarchy problem) ? Can the strong and electroweak interaction be described by a unified theory ? What happened with the anti-matter in the Big Bang ? What is dark matter ? What is dark energy ? V. Hedberg Beyond the Standard Model 4 Grand Unified Theories (GUTs) The Georgi-Glashow model Weak and electromagnetic interactions are unified, why not to add the strong one ? g2 g 2 s ’ W W= =8 =8 W We know that coupling 4 4 g’2 g 2 constants are not truely ’ = =8 Z =8 Z 4 4 Z constant but that they g 2 = s depend on energy (or Q2) ’ s 4 W g 2 in the interaction.
    [Show full text]