DOCSLIB.ORG

Microscopic Nucleon-Nucleus Optical Potentials for Neutron-Rich Systems

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Microscopic Nucleon-Nucleus Optical Potentials for Neutron-Rich Systems Microscopic nucleon-nucleus optical potentials for neutron-rich systems Jeremy W. Holt Department of Physics University of Washington INT workshop: Reactions and structure of exotic nuclei, 03/05/2015 OUTLINE Physics motivations Neutron-capture rates in r-process nucleosynthesis Neutron star structure (inner crust) Charged-current weak reactions in newly formed neutron stars Nucleon self energy in homogeneous matter Improvements in theory: perturbative chiral nuclear forces that reproduce saturation Benchmark to phenomenological potentials close to valley of stability Corrections to the Lane parametrizaton of the isospin asymmetry dependence Microscopic op)cal poten)al for neutron-rich systems J. W. Holt, University of Washington CHALLENGE 1: R-PROCESS NUCLEOSYNTHESIS Astrophysical Core-collapse Neutron-star site? supernovae mergers http://www.csm.ornl.gov http://numrel.aei.mpg.de Microscopic op)cal poten)al for neutron-rich systems J. W. Holt, University of Washington INPUTS FROM NUCLEAR STRUCTURE Masses of neutron-rich nuclei Determine elemental abundance patterns along isotopic chains during equilibrium Beta-decay lifetimes Set timescale for formation of heavy elements from seed nuclei Partly responsible for peaks at A = 130 and A = 195 Neutron-capture rates Relevant during late-time freeze-out phase of the r-process Sensitivity studies vary capture rates over 1–2 orders of magnitude Surman et al., PRC (2009) Microscopic op)cal poten)al for neutron-rich systems J. W. Holt, University of Washington CHALLENGE 2: EQUILIBRIUM STATE OF NEUTRON STAR INNER CRUSTS Outer crust is a lattice of nuclei with gas of electrons Inner crust contains lattice of neutron-rich nuclei together with “dripped” neutrons Neutron drip density: Dripped neutrons Bound neutrons Outer Crust Inner Crust Microscopic op)cal poten)al for neutron-rich systems J. W. Holt, University of Washington GLOBAL OPTICAL POTENTIALS (PHENOMENOLOGICAL) Koning & Delaroche, NPA (2003) Energy dependence Microscopic op)cal poten)al for neutron-rich systems J. W. Holt, University of Washington LANE PARAMETRIZATION Isovector part of optical potential linear in the isospin asymmetry 80 Model predictions 60 40 (MeV) I U 20 Empirical DBHF Gogny RMF 0 Skyrme SkLya BHF -20 0 0.5 1 1.5 2 2.5 -1 k (fm ) Much less is known/predicted about isovector imaginary part Microscopic op)cal poten)al for neutron-rich systems J. W. Holt, University of Washington MICROSCOPIC OPTICAL POTENTIALS (HOMOGENEOUS MATTER) Identified with the on-shell nucleon self-energy [Bell and Squires, PRL (1959)] Hartree-Fock contribution (real, energy-independent): Second-order perturbative contibutions (complex, energy-dependent): Benchmarks: Depth and energy dependence of phenomenological volume parts (including isospin dependence) Microscopic op)cal poten)al for neutron-rich systems J. W. Holt, University of Washington MICROSCOPIC NUCLEAR PHYSICS FROM “NEXT-TO-FIRST PRINCIPLES” Quark/gluon (high energy) dynamics Approximate chiral symmetry (left- and right- handed quarks transform independently) n Nucleon/pion (low energy) dynamics Compatible with explicit and spontaneous chiral p symmetry breaking Microscopic op)cal poten)al for neutron-rich systems J. W. Holt, University of Washington NUCLEAR FORCES IN CHIRAL EFFECTIVE FIELD THEORY SEPARATION OF SCALES + SYMMETRIES CHIRAL EFFECTIVE FIELD THEORY Energy Low-energy theory of nucleons and pions Heavy mesons (ρ, ω) Λ 0 π (q/Λ) N Systematic expansion Nucleon momenta Pion mass q (q/Λ)2 QCD chiral symmetry quarks (q/Λ)3 (q/Λ)4 Pions weakly-coupled at low momenta! Microscopic op)cal poten)al for neutron-rich systems J. W. Holt, University of Washington NUCLEAR FORCES IN CHIRAL EFFECTIVE FIELD THEORY SEPARATION OF SCALES + SYMMETRIES CHIRAL EFFECTIVE FIELD THEORY Energy Low-energy theory of nucleons and pions Heavy mesons (ρ, ω) Λ 0 π (q/Λ) N Systematic expansion Nucleon momenta q Pion mass Fit to NN scattering (q/Λ)2 (future: lattice QCD?) QCD chiral symmetry quarks (q/Λ)3 (q/Λ)4 Pions weakly-coupled at low momenta! Microscopic op)cal poten)al for neutron-rich systems J. W. Holt, University of Washington NUCLEAR FORCES IN CHIRAL EFFECTIVE FIELD THEORY SEPARATION OF SCALES + SYMMETRIES CHIRAL EFFECTIVE FIELD THEORY Energy Low-energy theory of nucleons and pions Heavy mesons (ρ, ω) Λ 0 π (q/Λ) N Systematic expansion Nucleon momenta q Pion mass Consistent vertices in 2N (q/Λ)2 & 3N forces (also πN) QCD chiral symmetry quarks (q/Λ)3 (q/Λ)4 Pions weakly-coupled at low momenta! Microscopic op)cal poten)al for neutron-rich systems J. W. Holt, University of Washington NUCLEAR FORCES IN CHIRAL EFFECTIVE FIELD THEORY SEPARATION OF SCALES + SYMMETRIES CHIRAL EFFECTIVE FIELD THEORY Energy Low-energy theory of nucleons and pions Heavy mesons (ρ, ω) Λ 0 π (q/Λ) N Systematic expansion Nucleon momenta q Pion mass Fit to 3H binding energy (q/Λ)2 and lifetime QCD chiral symmetry quarks (q/Λ)3 (q/Λ)4 Pions weakly-coupled at low momenta! Microscopic op)cal poten)al for neutron-rich systems J. W. Holt, University of Washington NUCLEAR FORCES IN CHIRAL EFFECTIVE FIELD THEORY SEPARATION OF SCALES + SYMMETRIES CHIRAL EFFECTIVE FIELD THEORY Energy Low-energy theory of nucleons and pions Heavy mesons (ρ, ω) Λ 0 π (q/Λ) N Systematic expansion Nucleon momenta q Pion mass Frontier in nuclear structure (q/Λ)2 QCD chiral symmetry quarks (q/Λ)3 (q/Λ)4 Pions weakly-coupled at low momenta! Microscopic op)cal poten)al for neutron-rich systems J. W. Holt, University of Washington STARTING POINT: MICROSCOPIC CHIRAL NUCLEAR FORCES Regulating function sets resolution scale Variations in regulator Estimate of theoretical uncertainty Coraggio, Holt, Itaco, Machleidt & Sammarruca, PRC (2013) Microscopic op)cal poten)al for neutron-rich systems J. W. Holt, University of Washington NEUTRON MATTER EoS (T=0): Perturbave Features Coraggio, Holt, Itaco, Machleidt & Sammarruca, PRC (2013) 40 N3LO 2NF + N2LO 3NF [500 MeV] N3LO 2NF + N2LO 3NF [414 MeV] 36 E1 1st order 1st 32 2nd order 3rd order 28 Pade’ [2|1] 2nd E3 E 24 3rd [2|1] E2 20 E/A [MeV] 16 12 8 4 0 0.00 0.05 0.10 0.15 0.20 0.25 –3-3 -3 n ρ (fm [fm ]) n (fm ) Low-momentum potentials: improved perturbative properties Microscopic op)cal poten)al for neutron-rich systems J. W. Holt, University of Washington SATURATION OF SYMMETRIC NUCLEAR MATTER Coraggio, Holt, Itaco, Machleidt, Marcucci & Sammarruca, PRC (2013) & (2014) Uncertainty esmate Empirical Fit to triton lifetime cD Saturation energy: Saturation density: Nontrivial without Asymmetry energy: extra tuning Compressibility: Microscopic op)cal poten)al for neutron-rich systems J. W. Holt, University of Washington LIQUID-GAS PHASE TRANSITION and THE CRITICAL POINT (CP) Wellenhofer, Holt, Kaiser & Weise, PRC (2014) Predicted critical endpoint * Empirical CP Critical temperature: gas Theorecal CP liquid Critical density: liquid-gas Critical pressure: Experiment (compound nucleus & multifragmentation) [J. B. Elliott et al., PRC (2013) Microscopic op)cal poten)al for neutron-rich systems J. W. Holt, University of Washington 1ST- AND 2ND-ORDER VOLUME CONTRIBUTIONS 3NF 2NF (1st) ReΣ 2NF (2nd) ImΣ 2NF (2nd) Holt, Kaiser, Miller & Weise, PRC (2013) Microscopic op)cal poten)al for neutron-rich systems J. W. Holt, University of Washington MOMENTUM DEPENDENCE OF 3NF TERMS Holt, Kaiser, Miller & Weise, PRC (2013) Nearly all momentum dependence comes from the two-pion-exchange 3NF Microscopic op)cal poten)al for neutron-rich systems J. W. Holt, University of Washington BENCHMARK: PHENOMENOLOGICAL OPTICAL POTENTIALS Holt, Kaiser, Miller & Weise, PRC (2013) Re Σ Self consistency: 56 Typical phenomenological potential: Fe n3lo500 Im Σ Microscopic op)cal poten)al for neutron-rich systems J. W. Holt, University of Washington INDIVIDUAL CONTRIBUTIONS IN ASYMMETRIC MATTER q (MeV) q (MeV) 0 0.5 1 1.5 2 2.5 0.5 1 1.5 2 2.5 20 20 = 0.0 0 np np = 0.1 0 -20 n (2) -20 p U2N+3N n MeV (1) MeV -40 p U3N -40 n U (1) -60 p 2N -60 = 0 -80 -80 20 20 0 np = 0.2 np = 0.4 0 -20 -20 MeV -40 -40 MeV -60 -60 -80 -80 0 0.5 1 1.5 2 2.5 0.5 1 1.5 2 2.5 q (MeV) q (MeV) Microscopic op)cal poten)al for neutron-rich systems J. W. Holt, University of Washington REAL AND IMAGINARY PROTON/NEUTRON POTENTIALS E (MeV) E (MeV) E (MeV) E (MeV) 0 20 40 60 80 100 20 40 60 80 100 0 20 40 60 80 100 20 40 60 80 100 -10 -10 = 0.6 0 = 0.2 0 0 0 Un = 0.6 0 W -20 -20 n = 0.2 0 -5 U U W (MeV) p n W n -30 -30 (MeV) (MeV) (MeV) p = 0.0 -10 -10 np = 0.0 U(E) np U(E) -40 = 0.2 -40 W(E) W(E) np = 0.2 -15 np W = 0.4 Up = 0.4 p -50 np -50 np 0 0 -20 -20 0 = 0.8 = 0 -10 = 0.8 -10 0 0 0 = 0 -20 -20 W W U U n n -30 n n -30 -10 -10 (MeV) (MeV) (MeV) -40 -40 (MeV) U(E) U(E) -50 -50 W(E) W(E) W W U U p p -60 p p -60 -20 -20 -70 -70 0 20 40 60 80 100 20 40 60 80 100 0 20 40 60 80 100 20 40 60 80 100 E (MeV) E (MeV) E (MeV) E (MeV) Microscopic op)cal poten)al for neutron-rich systems J. W. Holt, University of Washington CORRECTIONS TO LANE PARAMETRIZATION 15 -3 n = 0.13 fm , E = 10 MeV quadratic fit 10 n linear fit U = 25.1 + 13.3 2 5 I np np neutrons 0 (MeV) I U protons quadratic fit -5 p 2 UI = -21.0 np + 13.8 np -10 linear fit Holt, Kaiser & Miller, in prep.
Load more

Recommended publications
  • Electron-Nucleon Scattering at LDMX for DUNE
    Snowmass Letter of Intent: Snowmass Topical Groups: NF6, RF6, TF11 Electron-Nucleon Scattering at LDMX for DUNE Torsten Akesson1, Artur Ankowski2, Nikita Blinov3, Lene Kristian Bryngemark4, Pierfrancesco Butti2, Caterina Doglioni1, Craig Dukes5, Valentina Dutta6, Bertrand Echenard7, Thomas Eichlersmith8, Ralf Ehrlich5, Andrew Furmanski∗8, Niramay Gogate9, Mathew Graham2, Craig Group5, Alexander Friedland2, David Hitlin7, Vinay Hegde9, Christian Herwig3, Joseph Incandela6, Wesley Ketchumy3, Gordan Krnjaic3, Amina Li6, Shirley Liz2,3, Dexu Lin7, Jeremiah Mans8, Cristina Mantilla Suarez3, Phillip Masterson6, Martin Meier8, Sophie Middleton7, Omar Moreno2, Geoffrey Mullier1, Tim Nelson2, James Oyang7, Gianluca Petrillo2, Ruth Pottgen1, Stefan Prestel1, Luis Sarmiento1, Philip Schuster2, Hirohisa Tanaka2, Lauren Tompkins4, Natalia Toro2, Nhan Tran§3, and Andrew Whitbeck9 1Lund University 2Stanford Linear Accelerator Laboratory 3Fermi National Accelerator Laboratory 4Stanford University 5University of Virginia 6University of California Santa Barbara 7California Institute of Technology 8University of Minnesota 9Texas Tech University ABSTRACT We point out that the LDMX (Light Dark Matter eXperiment) detector design, conceived to search for sub-GeV dark matter, will also have very advantageous characteristics to pursue electron-nucleus scattering measurements of direct relevance to the neutrino program at DUNE and elsewhere. These characteristics include a 4-GeV electron beam, a precision tracker, electromagnetic and hadronic calorimeters with near 2p azimuthal acceptance from the forward beam axis out to 40◦ angle, and low reconstruction energy threshold. LDMX thus could provide (semi)exclusive cross section measurements, with∼ detailed information about final-state electrons, pions, protons, and neutrons. We compare the predictions of two widely used neutrino generators (GENIE, GiBUU) in the LDMX region of acceptance to illustrate the large modeling discrepancies in electron-nucleus interactions at DUNE-like kinematics.
    [Show full text]
  • From Quark and Nucleon Correlations to Discrete Symmetry and Clustering
    From quark and nucleon correlations to discrete symmetry and clustering in nuclei G. Musulmanbekov JINR, Dubna, RU-141980, Russia E-mail: [email protected] Abstract Starting with a quark model of nucleon structure in which the valence quarks are strongly correlated within a nucleon, the light nu- clei are constructed by assuming similar correlations of the quarks of neighboring nucleons. Applying the model to larger collections of nucleons reveals the emergence of the face-centered cubic (FCC) sym- metry at the nuclear level. Nuclei with closed shells possess octahedral symmetry. Binding of nucleons are provided by quark loops formed by three and four nucleon correlations. Quark loops are responsible for formation of exotic (borromean) nuclei, as well. The model unifies independent particle (shell) model, liquid-drop and cluster models. 1 Introduction arXiv:1708.04437v2 [nucl-th] 19 Sep 2017 Historically there are three well known conventional nuclear models based on different assumption about the phase state of the nucleus: the liquid-drop, shell (independent particle), and cluster models. The liquid-drop model re- quires a dense liquid nuclear interior (short mean-free-path, local nucleon interactions and space-occupying nucleons) in order to predict nuclear bind- ing energies, radii, collective oscillations, etc. In contrast, in the shell model each point nucleon moves in mean-field potential created by other nucleons; the model predicts the existence of nucleon orbitals and shell-like orbital- filling. The cluster models require the assumption of strong local-clustering 1 of particularly the 4-nucleon alpha-particle within a liquid or gaseous nuclear interior in order to make predictions about the ground and excited states of cluster configurations.
    [Show full text]
  • First Results of the Cosmic Ray NUCLEON Experiment
    Prepared for submission to JCAP First results of the cosmic ray NUCLEON experiment E. Atkin,a V. Bulatov,b V. Dorokhov,b N. Gorbunov,c;d S. Filippov,b V. Grebenyuk,c;d D. Karmanov,e I. Kovalev,e I. Kudryashov,e A. Kurganov,e M. Merkin,e A. Panov,e;1 D. Podorozhny,e D. Polkov,b S. Porokhovoy,c V. Shumikhin,a L. Sveshnikova,e A. Tkachenko,c;f L. Tkachev,c;d A. Turundaevskiy,e O. Vasiliev ande A. Voronine aNational Research Nuclear University “MEPhI”, Kashirskoe highway, 31. Moscow, 115409, Russia bSDB Automatika, Mamin-Sibiryak str, 145, Ekaterinburg, 620075, Russia cJoint Institute for Nuclear Research, Dubna, Joliot-Curie, 6, Moscow region, 141980, Russia d arXiv:1702.02352v2 [astro-ph.HE] 2 Jul 2018 “DUBNA” University, Universitetskaya str., 19, Dubna, Moscow region, 141980, Russia eSkobeltsyn Institute of Nuclear Physics, Moscow State University, 1(2), Leninskie gory, GSP-1, Moscow, 119991, Russia f Bogolyubov Institute for Theoretical Physics, 14-b Metrolohichna str., Kiev, 03143, Ukraine 1Corresponding author. E-mail: [email protected], [email protected], [email protected], [email protected], [email protected], [email protected], [email protected], [email protected], [email protected], [email protected], [email protected], [email protected], [email protected], [email protected], [email protected], [email protected], tfl[email protected], [email protected], [email protected], [email protected], [email protected], [email protected] Abstract.
    [Show full text]
  • 14. Structure of Nuclei Particle and Nuclear Physics
    14. Structure of Nuclei Particle and Nuclear Physics Dr. Tina Potter Dr. Tina Potter 14. Structure of Nuclei 1 In this section... Magic Numbers The Nuclear Shell Model Excited States Dr. Tina Potter 14. Structure of Nuclei 2 Magic Numbers Magic Numbers = 2; 8; 20; 28; 50; 82; 126... Nuclei with a magic number of Z and/or N are particularly stable, e.g. Binding energy per nucleon is large for magic numbers Doubly magic nuclei are especially stable. Dr. Tina Potter 14. Structure of Nuclei 3 Magic Numbers Other notable behaviour includes Greater abundance of isotopes and isotones for magic numbers e.g. Z = 20 has6 stable isotopes (average=2) Z = 50 has 10 stable isotopes (average=4) Odd A nuclei have small quadrupole moments when magic First excited states for magic nuclei higher than neighbours Large energy release in α, β decay when the daughter nucleus is magic Spontaneous neutron emitters have N = magic + 1 Nuclear radius shows only small change with Z, N at magic numbers. etc... etc... Dr. Tina Potter 14. Structure of Nuclei 4 Magic Numbers Analogy with atomic behaviour as electron shells fill. Atomic case - reminder Electrons move independently in central potential V (r) ∼ 1=r (Coulomb field of nucleus). Shells filled progressively according to Pauli exclusion principle. Chemical properties of an atom defined by valence (unpaired) electrons. Energy levels can be obtained (to first order) by solving Schr¨odinger equation for central potential. 1 E = n = principle quantum number n n2 Shell closure gives noble gas atoms. Are magic nuclei analogous to the noble gas atoms? Dr.
    [Show full text]
  • Electron- Vs Neutrino-Nucleus Scattering
    Electron- vs Neutrino-Nucleus Scattering Omar Benhar INFN and Department of Physics Universita` “La Sapienza” I-00185 Roma, Italy NUFACT11 University of Geneva, August 2nd, 2011 Neutrino-nucleus scattering . impact of the flux average . flux-averaged electron scattering x-section: a numerical experiment . contributions of reaction mechanisms other than quasi elastic single nucleon knock out to the MiniBooNE CCQE data sample Summary & Outlook Outline Electron scattering . standard data representation . theoretical description: the impulse approximation Omar Benhar (INFN, Roma) NUFACT11 Geneva 02/08/2011 2 / 24 Summary & Outlook Outline Electron scattering . standard data representation . theoretical description: the impulse approximation Neutrino-nucleus scattering . impact of the flux average . flux-averaged electron scattering x-section: a numerical experiment . contributions of reaction mechanisms other than quasi elastic single nucleon knock out to the MiniBooNE CCQE data sample Omar Benhar (INFN, Roma) NUFACT11 Geneva 02/08/2011 2 / 24 Outline Electron scattering . standard data representation . theoretical description: the impulse approximation Neutrino-nucleus scattering . impact of the flux average . flux-averaged electron scattering x-section: a numerical experiment . contributions of reaction mechanisms other than quasi elastic single nucleon knock out to the MiniBooNE CCQE data sample Summary & Outlook Omar Benhar (INFN, Roma) NUFACT11 Geneva 02/08/2011 2 / 24 The inclusive electron-nucleus x-section The x-section of the process e
    [Show full text]
  • In-Medium QCD Sum Rules for Ω Meson, Nucleon and D Meson QCD-Summenregeln F ¨Ur Im Medium Modifizierte Ω-Mesonen, Nukleonen Und D-Mesonen
    Institut f¨ur Theoretische Physik Fakult¨at Mathematik und Naturwissenschaften Technische Universit¨at Dresden In-Medium QCD Sum Rules for ω Meson, Nucleon and D Meson QCD-Summenregeln f ¨ur im Medium modifizierte ω-Mesonen, Nukleonen und D-Mesonen Dissertation zur Erlangung des akademischen Grades Doctor rerum naturalium vorgelegt von Ronny Thomas geboren am 7. Februar 1978 in Dresden C Dresden 2008 To Andrea and Maximilian Eingereicht am 07. Oktober 2008 1. Gutachter: Prof. Dr. Burkhard K¨ampfer 2. Gutachter: Prof. Dr. Christian Fuchs 3. Gutachter: PD Dr. Stefan Leupold Verteidigt am 28. Januar 2009 Abstract The modifications of hadronic properties caused by an ambient nuclear medium are investigated within the scope of QCD sum rules. This is exemplified for the cases of the ω meson, the nucleon and the D meson. By virtue of the sum rules, integrated spectral densities of these hadrons are linked to properties of the QCD ground state, quantified in condensates. For the cases of the ω meson and the nucleon it is discussed how the sum rules allow a restriction of the parameter range of poorly known four-quark condensates by a comparison of experimental and theoretical knowledge. The catalog of independent four-quark condensates is covered and relations among these condensates are revealed. The behavior of four-quark condensates under the chiral symmetry group and the relation to order parameters of spontaneous chiral symmetry breaking are outlined. In this respect, also the QCD condensates appearing in differences of sum rules of chiral partners are investigated. Finally, the effects of an ambient nuclear medium on the D meson are discussed and relevant condensates are identified.
    [Show full text]
  • Inclusive Nucleon Decay Searches As a Frontier of Baryon Number Violation
    UCI-TR-2019-24 Inclusive Nucleon Decay Searches as a Frontier of Baryon Number Violation Julian Heeck1, ∗ and Volodymyr Takhistov2, y 1Department of Physics and Astronomy, University of California, Irvine Irvine, California, 92697-4575, USA 2Department of Physics and Astronomy, University of California, Los Angeles Los Angeles, California, 90095-1547, USA Proton decay, and the decay of nucleons in general, constitutes one of the most sensitive probes of high-scale physics beyond the Standard Model. Most of the existing nucleon decay searches have focused primarily on two-body decay channels, motivated by Grand Unified Theories and supersymmetry. However, many higher-dimensional operators violating baryon number by one unit, ∆B = 1, induce multi-body nucleon decay channels, which have been only weakly constrained thus far. While direct searches for all such possible channels are desirable, they are highly impractical. In light of this, we argue that inclusive nucleon decay searches, N ! X+anything (where X is a light Standard Model particle with an unknown energy distribution), are particularly valuable, as are model-independent and invisible nucleon decay searches such as n ! invisible. We comment on complementarity and opportunities for such searches in the current as well as upcoming large- scale experiments Super-Kamiokande, Hyper-Kamiokande, JUNO, and DUNE. Similar arguments apply to ∆B > 1 processes, which kinematically allow for even more involved final states and are essentially unexplored experimentally. CONTENTS I. INTRODUCTION I. Introduction 1 Baryon number B and lepton number L are seem- ingly accidentally conserved in the Standard Model (SM), II. Nucleon decay operators 2 which makes searches for their violation extremely impor- A.
    [Show full text]
  • Chapter 2 the Atomic Nucleus
    Nuclear Science—A Guide to the Nuclear Science Wall Chart ©2018 Contemporary Physics Education Project (CPEP) Chapter 2 The Atomic Nucleus Searching for the ultimate building blocks of the physical world has always been a central theme in the history of scientific research. Many acclaimed ancient philosophers from very different cultures have pondered the consequences of subdividing regular, tangible objects into their smaller and smaller, invisible constituents. Many of them believed that eventually there would exist a final, inseparable fundamental entity of matter, as emphasized by the use of the ancient Greek word, atoos (atom), which means “not divisible.” Were these atoms really the long sought-after, indivisible, structureless building blocks of the physical world? The Atom By the early 20th century, there was rather compelling evidence that matter could be described by an atomic theory. That is, matter is composed of relatively few building blocks that we refer to as atoms. This theory provided a consistent and unified picture for all known chemical processes at that time. However, some mysteries could not be explained by this atomic theory. In 1896, A.H. Becquerel discovered penetrating radiation. In 1897, J.J. Thomson showed that electrons have negative electric charge and come from ordinary matter. For matter to be electrically neutral, there must also be positive charges lurking somewhere. Where are and what carries these positive charges? A monumental breakthrough came in 1911 when Ernest Rutherford and his coworkers conducted an experiment intended to determine the angles through which a beam of alpha particles (helium nuclei) would scatter after passing through a thin foil of gold.
    [Show full text]
  • The 21St-Century Electron Microscope for the Study of the Fundamental Structure of Matter
    The Electron-Ion Collider The 21st-Century Electron Microscope for the Study of the Fundamental Structure of Matter 60 ) milner mit physics annual 2020 by Richard G. Milner The Electron-Ion Collider he Fundamental Structure of Matter T Fundamental, curiosity-driven science is funded by developed societies in large part because it is one of the best investments in the future. For example, the study of the fundamental structure of matter over about two centuries underpins modern human civilization. There is a continual cycle of discovery, understanding and application leading to further discovery. The timescales can be long. For example, Maxwell’s equations developed in the mid-nineteenth century to describe simple electrical and magnetic laboratory experiments of that time are the basis for twenty-first century communications. Fundamental experiments by nuclear physicists in the mid-twentieth century to understand spin gave rise to the common medical diagnostic tool, magnetic resonance imaging (MRI). Quantum mechanics, developed about a century ago to describe atomic systems, now is viewed as having great potential for realizing more effective twenty-first century computers. mit physics annual 2020 milner ( 61 u c t g up quark charm quark top quark gluon d s b γ down quark strange quark bottom quark photon ve vμ vτ W electron neutrino muon neutrino tau neutrino W boson e μ τ Z electron muon tau Z boson Einstein H + Gravity Higgs boson figure 1 THE STANDARD MODEL (SM) , whose fundamental constituents are shown sche- Left: Schematic illustration [1] of the fundamental matically in Figure 1, represents an enormous intellectual human achievement.
    [Show full text]
  • ELEMENTARY PARTICLES in PHYSICS 1 Elementary Particles in Physics S
    ELEMENTARY PARTICLES IN PHYSICS 1 Elementary Particles in Physics S. Gasiorowicz and P. Langacker Elementary-particle physics deals with the fundamental constituents of mat- ter and their interactions. In the past several decades an enormous amount of experimental information has been accumulated, and many patterns and sys- tematic features have been observed. Highly successful mathematical theories of the electromagnetic, weak, and strong interactions have been devised and tested. These theories, which are collectively known as the standard model, are almost certainly the correct description of Nature, to first approximation, down to a distance scale 1/1000th the size of the atomic nucleus. There are also spec- ulative but encouraging developments in the attempt to unify these interactions into a simple underlying framework, and even to incorporate quantum gravity in a parameter-free “theory of everything.” In this article we shall attempt to highlight the ways in which information has been organized, and to sketch the outlines of the standard model and its possible extensions. Classification of Particles The particles that have been identified in high-energy experiments fall into dis- tinct classes. There are the leptons (see Electron, Leptons, Neutrino, Muonium), 1 all of which have spin 2 . They may be charged or neutral. The charged lep- tons have electromagnetic as well as weak interactions; the neutral ones only interact weakly. There are three well-defined lepton pairs, the electron (e−) and − the electron neutrino (νe), the muon (µ ) and the muon neutrino (νµ), and the (much heavier) charged lepton, the tau (τ), and its tau neutrino (ντ ). These particles all have antiparticles, in accordance with the predictions of relativistic quantum mechanics (see CPT Theorem).
    [Show full text]
  • The Quark Model and Deep Inelastic Scattering
    The quark model and deep inelastic scattering Contents 1 Introduction 2 1.1 Pions . 2 1.2 Baryon number conservation . 3 1.3 Delta baryons . 3 2 Linear Accelerators 4 3 Symmetries 5 3.1 Baryons . 5 3.2 Mesons . 6 3.3 Quark flow diagrams . 7 3.4 Strangeness . 8 3.5 Pseudoscalar octet . 9 3.6 Baryon octet . 9 4 Colour 10 5 Heavier quarks 13 6 Charmonium 14 7 Hadron decays 16 Appendices 18 .A Isospin x 18 .B Discovery of the Omega x 19 1 The quark model and deep inelastic scattering 1 Symmetry, patterns and substructure The proton and the neutron have rather similar masses. They are distinguished from 2 one another by at least their different electromagnetic interactions, since the proton mp = 938:3 MeV=c is charged, while the neutron is electrically neutral, but they have identical properties 2 mn = 939:6 MeV=c under the strong interaction. This provokes the question as to whether the proton and neutron might have some sort of common substructure. The substructure hypothesis can be investigated by searching for other similar patterns of multiplets of particles. There exists a zoo of other strongly-interacting particles. Exotic particles are ob- served coming from the upper atmosphere in cosmic rays. They can also be created in the labortatory, provided that we can create beams of sufficient energy. The Quark Model allows us to apply a classification to those many strongly interacting states, and to understand the constituents from which they are made. 1.1 Pions The lightest strongly interacting particles are the pions (π).
    [Show full text]
  • The Quark Model
    The Quark Model • Isospin Symmetry • Quark model and eightfold way • Baryon decuplet • Baryon octet • Quark spin and color • Baryon magnetic moments • Pseudoscalar mesons • Vector mesons • Other tests of the quark model • Mass relations and hyperfine splitting • EM mass differences and isospin symmetry • Heavy quark mesons • The top quarks • EXTRA – Group Theory of Multiplets J. Brau Physics 661, The Quark Model 1 Isospin Symmetry • The nuclear force of the neutron is nearly the same as the nuclear force of the proton • 1932 - Heisenberg - think of the proton and the neutron as two charge states of the nucleon • In analogy to spin, the nucleon has isospin 1/2 I3 = 1/2 proton I3 = -1/2 neutron Q = (I3 + 1/2) e • Isospin turns out to be a conserved quantity of the strong interaction J. Brau Physics 661, Space-Time Symmetries 2 Isospin Symmetry • The notion that the neutron and the proton might be two different states of the same particle (the nucleon) came from the near equality of the n-p, n-n, and p-p nuclear forces (once Coulomb effects were subtracted) • Within the quark model, we can think of this symmetry as being a symmetry between the u and d quarks: p = d u u I3 (u) = ½ n = d d u I3 (d) = -1/2 J. Brau Physics 661, Space-Time Symmetries 3 Isospin Symmetry • Example from the meson sector: – the pion (an isospin triplet, I=1) + π = ud (I3 = +1) - π = du (I3 = -1) 0 π = (dd - uu)/√2 (I3 = 0) The masses of the pions are similar, M (π±) = 140 MeV M (π0) = 135 MeV, reflecting the similar masses of the u and d quark J.
    [Show full text]