DOCSLIB.ORG

Peering Into the Universe and Its Ele Mentary Particles from Underground

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text

Load more

A gigantic detector to explore elementary particle unification theories and the mysteries of the Universe’s evolution Peering into the Universe and its ele mentary particles from underground The planned Hyper-Kamiokande detector will consist of an Unified Theory and explain the evolution of the Universe Large-aperture photosensors order of magnitude larger tank than the predecessor, Super- through the investigation of proton decay, CP violation (the The photosensor for Hyper-Kamiokande has Kamiokande, and will be equipped with ultra high sensitivity difference between neutrinos and antineutrinos), and the a 50-cm-diameter detection area with twice improvements in sensitivity, resolutions and photosensors. The Hyper-Kamiokande detector is both a observation of neutrinos from supernova explosions. The safety as compared with Super-Kamiokande. “microscope,” used to observe elementary particles, and a Hyper-Kamiokande experiment is an international research Under international collaboration, we are “telescope”, used to study the Sun and supernovas through project aiming to become operational in 2027. developing a supplementary "compound eye" neutrinos. Hyper-Kamiokande aims to elucidate the Grand unit using multiple photosensors to detect light patterns and timing precisely with the combined use of these sensors. ↑The multi-photosensor unit ←World's largest Courtesy of Hamamatsu Photonics K.K. photomultiplier tube A megaton water tank The huge Hyper-Kamiokande tank will be used in order to obtain in only 10 years an amount of data corresponding to 100 years of data collection time using Super-Kamiokande. This Experimental Technique allows the observation of previously unrevealed The photosensors on the tank wall detect the very weak Cherenkov rare phenomena and small values of CP light emitted along its direction of travel by a charged particle violation. ejected in the collision between neutrinos and water in the tank. This Cherenkov light is emitted in the form of a cone shape or in most cases a ring as the charged particle is eventually absorbed. Cherenkov light 10 times The energy, direction and type ducial volume of neutrinos are determined neutrino using the information obtained from the photosensors, such Charged as the quantity of light and the particle in water 50,000 tons 260,000 tons ring shape. Photosensors Super-Kamiokande Hyper-Kamiokande Bringing Neutrino Research to the Next Level The discovery of neutrino oscillations in the Super- of neutrino research has opened up for further investigations detect the very weak Cherenkov light generated in the water. Kamiokande experiment in 1998, for which the 2015 Nobel and discoveries. Through the realization of the Hyper-Kamiokande experiment, Prize in Physics was awarded, led to the investigation and Based on the highly sensitive techniques for neutrino we will lead neutrino research into the future. measurement of the properties of the neutrino which observation developed by Super-Kamiokande over the years, indicate the need for an update of the Standard Model. In Hyper-Kamiokande represents a further improvement in 2001, the solar neutrino oscillation was discovered. In 2011, sensitivity. Hyper-Kamiokande consists of a cylindrical tank, Kamioka Observatory, ICRR, the T2K experiment, which used a neutrino beam from the with a height of 72m and a diameter of 68m. The fiducial The University of Tokyo high intensity accelerator J-PARC and the Super-Kamiokande volume of the tank is approximately 10 times larger than that Mail : [email protected] detector, confirmed the third neutrino oscillation. Now that of the Super-Kamiokande detector. On the tank wall, 40,000 URL : http://www.hyper-k.org/ 2021.07 all neutrino oscillation modes have been confirmed, the field ultra high sensitivity photosensors will be installed in order to The region that the present colliders can explore The origin, evolution, and future of The region that nucleon decay and neutrino experiments can explore the Universe and its particles 1016GeV 102GeV 1MeV 1keV 0.3eV 103eV Energy 2×104eV At the birth of the universe, it Baryon number Ination Remaining is thought that the four forces that production Dark Matter Electromagnetic force govern our world (the strong, weak, Weak force The Grand Mixing of neutrino Supersymmetry electromagnetic, and gravitational Unied Theory mass / the origin of theory Strong force The end of CP violation the Universe? forces) were unified in the form of a Gravity force Synthesis of single force. When temperatures fell Energy emission Human from xed stars heavy elements beings with the evolution of the universe, from supernova burst 38 this unified force separated to the four 10 sec forces. Synthesis of light elements Synthesis of heavy elements The birth of human beings Nucleon decay The Grand Unified Theory, which governed the universe 10 ©ESA and the Planck Collaboration until about 10-38 seconds after the Big Bang (1016 GeV, in 10 sec 5 10 sec 100 sec 380,000 1 billion Age of 13.8 billion terms of the energy of the universe), deals with energies too years years the Universe years 10 35 years high to inspect directly through collision experiments in an accelerator. However, the Hyper-Kamiokande experiment can A gigantic detector to confront elementary particle unification theories and directly investigate the Grand Unified Theory by exploring the mysteries of the Universe’s evolution Collaboration with the J-PARC Accelerator proton decay. If protons decaying into more light particles can be observed, it means that all matter, including human In addition to natural neutrinos such as atmospheric and beings, in the universe has a finite lifetime and will decay in solar neutrinos, a high intensity and high quality neutrino the future. Determining the Ordering CP Violation Measurement beam from the J-PARC accelerator in Tokai, Ibaraki, may be Hyper-Kamiokande will elucidate neutrino properties such as of the Neutrino Masses used for precisely studying the properties of neutrinos such the CP violation and approach the mysteries surrounding the Hyper-Kamiokande will investigate CP violation (i.e the difference Based on the observation of neutrinos oscillations, the differences as CP violation. evolution of the universe and the birth of life, through the between particles and anti-particles) by observation of oscillations between the three neutrino masses have been measured. However, Hyper-Kamiokande is expected to observe 30 times as many observation of solar and supernova neutrinos. using neutrino/anti-neutrino beam from J-PARC accelerator. it is not known whether the two masses that compose solar neutrinos as the T2K experiment after the increase of the The present universe is filled with "matter" such as stars and neutrinos are heavier or lighter than the third mass. Determining human beings, but "anti-matter" is not seen. This imbalance the ordering of the neutrino masses is an important line of J-PARC beam power. ©JAEA/KEK J-PARC Center between matter and antimatter might occur because of CP research not only because it increases the precision of CP violation violation in neutrinos. We will investigate this asymmetry. measurements, but also because it is an essential ingredient for Neutrinos and Neutrino oscillations determining whether the neutrino is a Majorana fermion, a type of particle which is indistinguishable from its antiparticle. The matter in the Universe consist of elementary particles called quarks and leptons. For example, one proton, made Kamioka-town, Hida-city, Gifu of three quarks, and one electron, which is a kind of lepton, Hyper-Kamiokande form a hydrogen atom. The neutrino is a kind of lepton Tokai-village, Naka-gun, Ibaraki without electric charge and exists in types; electron neutrino, J-PARC accelerator mu neutrino and tau neutrino. Uncover the mystery of The three types of neutrinos mix with each other and can neutrino oscillation change their type. This phenomenon is called “Neutrino oscillation” and was discovered by Super-Kamiokande in 1998. The detailed study of neutrino oscillation enables us to reveal the properties of neutrinos. Cosmic Neutrino Observation Proton Decay Searches The Standard Model, which describes the elementary Using cosmic neutrinos such as the neutrinos originating One of the important questions for the elementary International Collaboration particle system, seemed to be completed by the discovery in the Sun, our galactic center, or a supernova explosion, particle physics community is whether or not a proton we may study the stellar objects themselves. It is remains stable forever. The Grand Unified Theory, which of the Higgs boson particle. However, the information about The Hyper-Kamiokande is an international research project. expected that Hyper-Kamiokande will enable us to includes the Standard Model of particle physics, predicts neutrino mass and its mixing rate obtained by previous Many researchers from various countries are working elucidate the history that protons decay studies have a large difference from those of quarks. It is together to realize the experiment. As of April 2021, the the universe. into lighter particles. considered that a more fundamental framework is needed Hyper-Kamiokande collaboration consists of about 400 Hyper-Kamiokande will beyond the Standard Model. be the most sensitive researches from 19 countries; Armenia, Brazil, Canada, Czech, Neutrino oscillation experiments are expected to be a key detector in the world France, Germany, India, Italy, Japan, Korea, Mexico, Poland, to address what the fundamental framework of elementary for use in proton decay Russia, Spain, Sweden, Switzerland, UK, Ukraine, USA. particles is. searches. The aim of Hyper-Kamiokande muon neutrino is to explore new horizons beyond the ©NASA Standard Model. tau neutrino electron neutrino Revealing the mystery of Universe’s origin and evolution Verification of Grand Unified Theories.
Recommended publications
  • Realization of the Low Background Neutrino Detector Double Chooz: from the Development of a High-Purity Liquid & Gas Handling Concept to first Neutrino Data

    Realization of the Low Background Neutrino Detector Double Chooz: from the Development of a High-Purity Liquid & Gas Handling Concept to first Neutrino Data

    Realization of the low background neutrino detector Double Chooz: From the development of a high-purity liquid & gas handling concept to first neutrino data Dissertation of Patrick Pfahler TECHNISCHE UNIVERSITAT¨ MUNCHEN¨ Physik Department Lehrstuhl f¨urexperimentelle Astroteilchenphysik / E15 Univ.-Prof. Dr. Lothar Oberauer Realization of the low background neutrino detector Double Chooz: From the development of high-purity liquid- & gas handling concept to first neutrino data Dipl. Phys. (Univ.) Patrick Pfahler Vollst¨andigerAbdruck der von der Fakult¨atf¨urPhysik der Technischen Universit¨atM¨unchen zur Erlangung des akademischen Grades eines Doktors des Naturwissenschaften (Dr. rer. nat) genehmigten Dissertation. Vorsitzender: Univ.-Prof. Dr. Alejandro Ibarra Pr¨uferder Dissertation: 1. Univ.-Prof. Dr. Lothar Oberauer 2. Priv.-Doz. Dr. Andreas Ulrich Die Dissertation wurde am 3.12.2012 bei der Technischen Universit¨atM¨unchen eingereicht und durch die Fakult¨atf¨urPhysik am 17.12.2012 angenommen. 2 Contents Contents i Introduction 1 I The Neutrino Disappearance Experiment Double Chooz 5 1 Neutrino Oscillation and Flavor Mixing 6 1.1 PMNS Matrix . 6 1.2 Flavor Mixing and Neutrino Oscillations . 7 1.2.1 Survival Probability of Reactor Neutrinos . 9 1.2.2 Neutrino Masses and Mass Hierarchy . 12 2 Reactor Neutrinos 14 2.1 Neutrino Production in Nuclear Power Cores . 14 2.2 Energy Spectrum of Reactor neutrinos . 15 2.3 Neutrino Flux Approximation . 16 3 The Double Chooz Experiment 19 3.1 The Double Chooz Collaboration . 19 3.2 Experimental Site: Commercial Nuclear Power Plant in Chooz . 20 3.3 Physics Program and Experimental Concept . 21 3.4 Signal . 23 3.4.1 The Inverse Beta Decay (IBD) .
  • Abdus Salam United Nations Educational, Scientific and Cultural International XA0101583 Organization Centre

    Abdus Salam United Nations Educational, Scientific and Cultural International XA0101583 Organization Centre

    the 1(72001/34 abdus salam united nations educational, scientific and cultural international XA0101583 organization centre international atomic energy agency for theoretical physics NEW DIMENSIONS NEW HOPES Utpal Sarkar Available at: http://www.ictp.trieste.it/-pub-off IC/2001/34 United Nations Educational Scientific and Cultural Organization and International Atomic Energy Agency THE ABDUS SALAM INTERNATIONAL CENTRE FOR THEORETICAL PHYSICS NEW DIMENSIONS NEW HOPES Utpal Sarkar1 Physics Department, Visva Bharati University, Santiniketan 731235, India and The Abdus Salam Insternational Centre for Theoretical Physics, Trieste, Italy. Abstract We live in a four dimensional world. But the idea of unification of fundamental interactions lead us to higher dimensional theories. Recently a new theory with extra dimensions has emerged, where only gravity propagates in the extra dimension and all other interactions are confined in only four dimensions. This theory gives us many new hopes. In earlier theories unification of strong, weak and the electromagnetic forces was possible at around 1016 GeV in a grand unified theory (GUT) and it could get unified with gravity at around the Planck scale of 1019 GeV. With this new idea it is possible to bring down all unification scales within the reach of the next generation accelerators, i.e., around 104 GeV. MIRAMARE - TRIESTE May 2001 1 Regular Associate of the Abdus Salam ICTP. E-mail: [email protected] 1 Introduction In particle physics we try to find out what are the fundamental particles and how they interact. This is motivated from the belief that there must be some fundamental law that governs ev- erything.
  • Physics Beyond the Standard Model (BSM)

    Physics Beyond the Standard Model (BSM)

    Vorlesung 10: Search for Physics Beyond the Standard Model (BSM) • Standard Model : success and problems • Grand Unified Theories (GUT) • Supersymmetrie (SUSY) – theory – direct searches • other models / ideas for physics BSM Tevatron and LHC WS17/18 TUM S.Bethke, F. Simon V10: BSM 1 The Standard Model of particle physics... • fundamental fermions: 3 pairs of quarks plus 3 pairs of leptons • fundamental interactions: through gauge fields, manifested in – W±, Z0 and γ (electroweak: SU(2)xU(1)), – gluons (g) (strong: SU(3)) … successfully describes all experiments and observations! … however ... the standard model is unsatisfactory: • it has conceptual problems • it is incomplete ( ∃ indications for BSM physics) Tevatron and LHC WS17/18 TUM S.Bethke, F. Simon V10: BSM 2 Conceptual Problems of the Standard Model: • too many free parameters (~18 masses, couplings, mixing angles) • no unification of elektroweak and strong interaction –> GUT ; E~1016 GeV • quantum gravity not included –> TOE ; E~1019 GeV • family replication (why are there 3 families of fundamental leptons?) • hierarchy problem: need for precise cancellation of –> SUSY ; E~103 GeV radiation corrections • why only 1/3-fractional electric quark charges? –> GUT indications for New Physics BSM: • Dark Matter (n.b.: known from astrophysical and “gravitational” effects) • Dark Energy / Cosmological Constant / Vacuum Energy (n.b.: see above) • neutrinos masses • matter / antimatter asymmetry Tevatron and LHC WS17/18 TUM S.Bethke, F. Simon V10: BSM 3 Grand Unified Theory (GUT): • simplest symmetry which contains U(1), SU(2) und SU(3): SU(5) (Georgi, Glashow 1974) • multiplets of (known) leptons and quarks which can transform between each other by exchange of heavy “leptoquark” bosons, X und Y, with -1/3 und -4/3 charges, ± 0 as well as through W , Z und γ.
  • The Grand Unified Theory of the Firm and Corporate Strategy: Measures to Build Corporate Competitiveness

    The Grand Unified Theory of the Firm and Corporate Strategy: Measures to Build Corporate Competitiveness

    THE GRAND UNIFIED THEORY OF THE FIRM AND CORPORATE STRATEGY: MEASURES TO BUILD CORPORATE COMPETITIVENESS by Hong Y. Park Professor of Economics Department of Economics College of Business and Management Saginaw Valley State University University Center, MI 48710 e-mail: [email protected] Geon-Cheol Shin Professor School of Business Kyung Hee University Seoul, Korea e-mail: [email protected] This study was funded by the Fulbright Foundation, the Korea Economic Research Institute (KERI), and Saginaw Valley State University. Abstract A good understanding of the nature of the firm is essential in developing corporate strategies, building corporate competitiveness, and establishing sound economic policy. Several theories have emerged on the nature of the firm: the neoclassical theory of the firm, the principal agency theory, the transaction cost theory, the property rights theory, the resource-based theory and the evolutionary theory. Each of these theories identify some elements that describe the nature of the firm, but no single theory is comprehensive enough to include all elements of the nature of the firm. Economists began to seek a theory capable of describing the nature of the firm within a single, all- encompassing, coherent framework. We propose a unified theory of the firm, which encompasses all elements of the firm. We then evaluate performances of Korean firms from the unified theory of the firm perspective. Empirical evidences are promising in support of the unified theory of the firm. Introduction A good understanding of the nature of the firm is essential in developing corporate strategies and building corporate competitiveness. Several theories have emerged on the nature of the firm: The neoclassical theory of the firm, the principal agency theory, the transaction cost theory, the property rights theory, the resource-based theory and the evolutionary theory.
  • Neutrinoless Double Beta Decay Searches

    Neutrinoless Double Beta Decay Searches

    FLASY2019: 8th Workshop on Flavor Symmetries and Consequences in 2016 Symmetry Magazine Accelerators and Cosmology Neutrinoless Double Beta Decay Ke Han (韩柯) Shanghai Jiao Tong University Searches: Status and Prospects 07/18, 2019 Outline .General considerations for NLDBD experiments .Current status and plans for NLDBD searches worldwide .Opportunities at CJPL-II NLDBD proposals in China PandaX series experiments for NLDBD of 136Xe 07/22/19 KE HAN (SJTU), FLASY2019 2 Majorana neutrino and NLDBD From Physics World 1935, Goeppert-Mayer 1937, Majorana 1939, Furry Two-Neutrino double beta decay Majorana Neutrino Neutrinoless double beta decay NLDBD 1930, Pauli 1933, Fermi + 2 + (2 ) Idea of neutrino Beta decay theory 136 136 − 07/22/19 54 → KE56 HAN (SJTU), FLASY2019 3 ̅ NLDBD probes the nature of neutrinos . Majorana or Dirac . Lepton number violation . Measures effective Majorana mass: relate 0νββ to the neutrino oscillation physics Normal Inverted Phase space factor Current Experiments Nuclear matrix element Effective Majorana neutrino mass: 07/22/19 KE HAN (SJTU), FLASY2019 4 Detection of double beta decay . Examples: . Measure energies of emitted electrons + 2 + (2 ) . Electron tracks are a huge plus 136 136 − 54 → 56 + 2 + (2)̅ . Daughter nuclei identification 130 130 − 52 → 54 ̅ 2νββ 0νββ T-REX: arXiv:1512.07926 Sum of two electrons energy Simulated track of 0νββ in high pressure Xe 07/22/19 KE HAN (SJTU), FLASY2019 5 Impressive experimental progress . ~100 kg of isotopes . ~100-person collaborations . Deep underground . Shielding + clean detector 1E+27 1E+25 1E+23 1E+21 life limit (year) life - 1E+19 half 1E+17 Sn Ca νββ Ge Te 0 1E+15 Xe 1E+13 1940 1950 1960 1970 1980 1990 2000 2010 2020 Year .
  • Unified Equations of Boson and Fermion at High Energy and Some

    Unified Equations of Boson and Fermion at High Energy and Some

    Unified Equations of Boson and Fermion at High Energy and Some Unifications in Particle Physics Yi-Fang Chang Department of Physics, Yunnan University, Kunming, 650091, China (e-mail: [email protected]) Abstract: We suggest some possible approaches of the unified equations of boson and fermion, which correspond to the unified statistics at high energy. A. The spin terms of equations can be neglected. B. The mass terms of equations can be neglected. C. The known equations of formal unification change to the same. They can be combined each other. We derive the chaos solution of the nonlinear equation, in which the chaos point should be a unified scale. Moreover, various unifications in particle physics are discussed. It includes the unifications of interactions and the unified collision cross sections, which at high energy trend toward constant and rise as energy increases. Key words: particle, unification, equation, boson, fermion, high energy, collision, interaction PACS: 12.10.-g; 11.10.Lm; 12.90.+b; 12.10.Dm 1. Introduction Various unifications are all very important questions in particle physics. In 1930 Band discussed a new relativity unified field theory and wave mechanics [1,2]. Then Rojansky researched the possibility of a unified interpretation of electrons and protons [3]. By the extended Maxwell-Lorentz equations to five dimensions, Corben showed a simple unified field theory of gravitational and electromagnetic phenomena [4,5]. Hoffmann proposed the projective relativity, which is led to a formal unification of the gravitational and electromagnetic fields of the general relativity, and yields field equations unifying the gravitational and vector meson fields [6].
  • Supersymmetry Min Raj Lamsal Department of Physics, Prithvi Narayan Campus, Pokhara Min Lamsal@Yahoo.Com

    Supersymmetry Min Raj Lamsal Department of Physics, Prithvi Narayan Campus, Pokhara Min [email protected]

    Supersymmetry Min Raj Lamsal Department of Physics, Prithvi Narayan Campus, Pokhara [email protected] Abstract : This article deals with the introduction of supersymmetry as the latest and most emerging burning issue for the explanation of nature including elementary particles as well as the universe. Supersymmetry is a conjectured symmetry of space and time. It has been a very popular idea among theoretical physicists. It is nearly an article of faith among elementary-particle physicists that the four fundamental physical forces in nature ultimately derive from a single force. For years scientists have tried to construct a Grand Unified Theory showing this basic unity. Physicists have already unified the electron-magnetic and weak forces in an 'electroweak' theory, and recent work has focused on trying to include the strong force. Gravity is much harder to handle, but work continues on that, as well. In the world of everyday experience, the strengths of the forces are very different, leading physicists to conclude that their convergence could occur only at very high energies, such as those existing in the earliest moments of the universe, just after the Big Bang. Keywords: standard model, grand unified theories, theory of everything, superpartner, higgs boson, neutrino oscillation. 1. INTRODUCTION unifies the weak and electromagnetic forces. The What is the world made of? What are the most basic idea is that the mass difference between photons fundamental constituents of matter? We still do not having zero mass and the weak bosons makes the have anything that could be a final answer, but we electromagnetic and weak interactions behave quite have come a long way.
  • Super Symmetry

    Super Symmetry

    MILESTONES DOI: 10.1038/nphys868 M iles Tone 1 3 Super symmetry The way that spin is woven into the in 1015. However, a form of symmetry very fabric of the Universe is writ between fermions and bosons called large in the standard model of supersymmetry offers a much more particle physics. In this model, which elegant solution because the took shape in the 1970s and can quantum fluctuations caused by explain the results of all particle- bosons are naturally cancelled physics experiments to date, matter out by those caused by fermions and (and antimatter) is made of three vice versa. families of quarks and leptons, which Symmetry plays a central role in are all fermions, whereas the physics. The fact that the laws of electromagnetic, strong physics are, for instance, symmetric in and weak forces that act on these time (that is, they do not change with particles are carried by other time) leads to the conservation of particles, such as photons and gluons, energy. These laws are also symmetric The ATLAS experiment under construction at the which are all bosons. with respect to space, rotation and Large Hadron Collider. Image courtesy of CERN. Despite its success, the standard relative motion. Initially explored in model is unsatisfactory for a number the early 1970s, supersymmetry is a of reasons. First, although the less obvious kind of symmetry, which, graviton. Searching for electromagnetic and weak forces if it exists in nature, would mean that supersymmetric particles will be a have been unified into a single force, the laws of physics do not change priority when the Large Hadron a ‘grand unified theory’ that brings when bosons are replaced by Collider comes into operation at the strong interaction into the fold fermions, and fermions are replaced CERN, the European particle-physics remains elusive.
  • Neutrino Oscillations: the Rise of the PMNS Paradigm Arxiv:1710.00715

    Neutrino Oscillations: the Rise of the PMNS Paradigm Arxiv:1710.00715

    Neutrino oscillations: the rise of the PMNS paradigm C. Giganti1, S. Lavignac2, M. Zito3 1 LPNHE, CNRS/IN2P3, UPMC, Universit´eParis Diderot, Paris 75252, France 2Institut de Physique Th´eorique,Universit´eParis Saclay, CNRS, CEA, Gif-sur-Yvette, France∗ 3IRFU/SPP, CEA, Universit´eParis-Saclay, F-91191 Gif-sur-Yvette, France November 17, 2017 Abstract Since the discovery of neutrino oscillations, the experimental progress in the last two decades has been very fast, with the precision measurements of the neutrino squared-mass differences and of the mixing angles, including the last unknown mixing angle θ13. Today a very large set of oscillation results obtained with a variety of experimental config- urations and techniques can be interpreted in the framework of three active massive neutrinos, whose mass and flavour eigenstates are related by a 3 3 unitary mixing matrix, the Pontecorvo- × Maki-Nakagawa-Sakata (PMNS) matrix, parameterized by three mixing angles θ12, θ23, θ13 and a CP-violating phase δCP. The additional parameters governing neutrino oscillations are the squared- mass differences ∆m2 = m2 m2, where m is the mass of the ith neutrino mass eigenstate. This ji j − i i review covers the rise of the PMNS three-neutrino mixing paradigm and the current status of the experimental determination of its parameters. The next years will continue to see a rich program of experimental endeavour coming to fruition and addressing the three missing pieces of the puzzle, namely the determination of the octant and precise value of the mixing angle θ23, the unveiling of the neutrino mass ordering (whether m1 < m2 < m3 or m3 < m1 < m2) and the measurement of the CP-violating phase δCP.
  • GRAND UNIFIED THEORIES Paul Langacker Department of Physics

    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.
  • The Quantum Vacuum and the Cosmological Constant Problem

    The Quantum Vacuum and the Cosmological Constant Problem

    The Quantum Vacuum and the Cosmological Constant Problem S.E. Rugh∗and H. Zinkernagely To appear in Studies in History and Philosophy of Modern Physics Abstract - The cosmological constant problem arises at the intersection be- tween general relativity and quantum field theory, and is regarded as a fun- damental problem in modern physics. In this paper we describe the historical and conceptual origin of the cosmological constant problem which is intimately connected to the vacuum concept in quantum field theory. We critically dis- cuss how the problem rests on the notion of physically real vacuum energy, and which relations between general relativity and quantum field theory are assumed in order to make the problem well-defined. 1. Introduction Is empty space really empty? In the quantum field theories (QFT’s) which underlie modern particle physics, the notion of empty space has been replaced with that of a vacuum state, defined to be the ground (lowest energy density) state of a collection of quantum fields. A peculiar and truly quantum mechanical feature of the quantum fields is that they exhibit zero-point fluctuations everywhere in space, even in regions which are otherwise ‘empty’ (i.e. devoid of matter and radiation). These zero-point fluctuations of the quantum fields, as well as other ‘vacuum phenomena’ of quantum field theory, give rise to an enormous vacuum energy density ρvac. As we shall see, this vacuum energy density is believed to act as a contribution to the cosmological constant Λ appearing in Einstein’s field equations from 1917, 1 8πG R g R Λg = T (1) µν − 2 µν − µν c4 µν where Rµν and R refer to the curvature of spacetime, gµν is the metric, Tµν the energy-momentum tensor, G the gravitational constant, and c the speed of light.
  • Grand Unified Theory

    Grand Unified Theory

    Grand Unified Theory Manuel Br¨andli [email protected] ETH Z¨urich May 29, 2018 Contents 1 Introduction 2 2 Gauge symmetries 2 2.1 Abelian gauge group U(1) . .2 2.2 Non-Abelian gauge group SU(N) . .3 3 The Standard Model of particle physics 4 3.1 Electroweak interaction . .6 3.2 Strong interaction and color symmetry . .7 3.3 General transformation of matter fields . .8 4 Unification of Standard Model Forces: GUT 8 4.1 Motivation of Unification . .8 4.2 Finding the Subgroups . .9 4.2.1 Example: SU(2) U(1) SU(3) . .9 4.3 Branching rules . .× . .⊂ . 10 4.3.1 Example: 3 representation of SU(3) . 11 4.4 Georgi-Glashow model with gauge group SU(5) . 14 4.5 SO(10) . 15 5 Implications of unification 16 5.1 Advantages of Grand Unified Theories . 16 5.2 Proton decay . 16 6 Conclusion 17 Abstract In this article we show how matter fields transform under gauge group symmetries and motivate the idea of Grand Unified Theories. We discuss the implications of Grand Unified Theories in particular for proton decay, which gives us a tool to test Grand Unified Theories. 1 1 Introduction In the 50s and 60s a lot of new particles were discovered. The quark model was a first successful attempt to categorize this particle zoo. It was based on the so-called flavor symmetry, which is an approximate symmetry. This motivated the use of group theory in particle physics [10]. In this article we will make use of gauge symmetries, which are local symmetries, to explain the existence of interaction particles and show how the matter fields transform under these symmetries, section 2.