Hadron Structure

Total Page:16

File Type:pdf, Size:1020Kb

Hadron Structure Hadron Structure Proceedings Smolenice Czechoslovakia Physics and щ! Applications jjp^ Vol. 14 1 Hadron Structure '87 Proceedings Smolenice Czechoslovakia November 16-20, 1987 Physics and Applications Vol. 14 Present volume of Physics and Appli­ cations contains most of the contribu­ tions delivered at the 1987 Hadron Struc­ ture Conference held in Smolenice, Cze­ choslovakia. The conference was de­ voted mainly to the nonperturbative i methods in QCD, to the theory and experiment of high energy particle pro­ duction and to the hadron-nucleus and heavy ion collisions. The book is of interest to scientists wor­ king in the subnuclear physics research and to the senior research students. 7 С1Я23А%ЪЛ*~ЯЪ** INSTITUTE OF PHYSICS EPRC Slovak Academy of Sciences Slovak Academy of Sciences Institute of Physics of the Electro-Physical Research Centre Scientific Editor Š. Luby Distributed by: Institute of Physics EPRC SASc. 842 28 Bratislava Czechoslovakia Hadr on Structure '87 Proceedings of the Conference Smolenice November 16—20,1987 Physics and Applications Vol. 14 Edited by D. Krupa INSTITUTE OF PHYSICS EPRC Slovak Academy of Sciences Bratislava 1988 % ' © Institute of Physics, EPRC, Slovak Academy of Sciences, 1988 Contents Lectures W.Kummer: Status of Noncovariant Supergauges II C.Cronstrom: Rcgularization of the Yang-Mills Action and Energy *** P .Hnsrnfrntz : Sin^i'lir Kcnormal i znt ion Group Transformation *** G.Tripiccione: Mass Spectrum of Glueballs in Lattice SU(3) QCD *** J.Greensitc: Computer Measurements of the Yang-Mills Vacuum and String Havefunctionals 25 M.Campostrini: Monte Carlo Studies of Lattice QCD with Dynamical Quarks *** H.-C.Pauli: Discretized Light-Cone Quantization .... *** C.M.Bender: Nonperturbative Perturbation Theory .... 40 A.V.Turbiner: Quasi-Exactly-Solvable Problem"- in Quantum Mechanics 51 i e "To L.Ramello: Results on 0- and S- Nucleus Collisions from the HELIOS Collaboration 60 I.Derado: Results on Hadron Production in O+Au at 200 GeV/Nucleon from NA35 Experiment *** R.Haroutunian: Results on 3/f- Production in 0-U Interactions at 200 GeV/Nucleon from the NA38 Experiment *** N.N.Nikolaev: Matter and Energy Density in Central Heavy Ion Collisions *** N.Pišútová, J.Plšút: Space-Time Evolution of Proton- Proton, Proton-Nucleus and Nucleus-Nucleus Collisions and the Dilepton Production .... 70 S.Yu.Shmakov. V.V.Uzhinskii: New Realization of the Hadron-Hadron, Hadron-Nucleus and Nucleus- Nucleus Fragmentation Model 85 E.M.Levin, M.G.Ryskin: Hadron Interactions at High Energy in QCD 95 A.Bialas: Oscillations оГ the Qunrk-Gluon-Plasmn .... *** П.В.Levchonfco: Correlation Phenomena in Particle Production on Nuclei lie M.Kutchera: Particle Production in Ultrorclativis tic Proton-Proton and Proton-Nucleus Collisions in a Parton String Model 123 A.V.Efremov: Nuclear Structure Functions and Cumulative Processes 133 (i.Eckcr: Non-Leptonic Weak Interactions in Chiral Perturbation Theory 145 Short Communications V.K.Petrov. G.M.Zinoviev: Deconfincment Analysis in Exactly Solvable Model for Lattice QCD .... 158 C.B.Lang, M.Salmhofer: Optimization of Renormalization Group Transformations 166 M.L.Laurscn, M.Miiller-Preussker: Monopole Excitations in the 3D Gcorgi-Glushow Model on Lattice. , . 171 M.Faber, IV.Feilmajr. H.Markům: Quark-Polarization Effects from Dynamical Quarks 175 J.Wosiek: On the Space Structure of Confining Strings. *** S.G.Gorishny, A.L.Kataev. S.A.Larin: Next-Next-to- Leading 0(ots ) QCD Correlations to T. (e+e *Hadrons): Analytical Calculations and Estimation оГ the Parameter Л гт-„ ,8° MS F.Schoberl: Influence of Strong Interactions on Electromasuetic Mass Differences I92 L.Turko: Condensation of Hadronic Matter 198 Z.Fodor: Infrared AFymptotics of the Quark Propagator in Gauge Theories 202 G.V.Efimov, M.A.Ivanov: Confinement and Quark Structure of Hadrons 210 P.Kolář: The QCD Sum Rules, their Validity and Applicability 218 M.Schepkin: Masses of High Spin Hadrons 223 A.N.Ivanov: Physics оГ Low Energy Hadronic Interactions in the Quark Model оГ Supercoductivity Type. *** M.Nagy. M.K.Volkov; Decay of Gluonium in the Gene­ ralized Quark Model of Superconductivity Type 235 H.J.Kaiser, K.Scharnhorst, E.Wieczorek: Yang-Mills Propagators in Background Fields 239 V.V.Bazhanov: Critical Exactly Solvable Models and Conformal Field Theory 244 J.Dittrich, P.Exner: A Non-Relativistic Model of Two- Particle Decoy: Resonance and Bound States • . 247 M.Zno.Ul. M.F.Fiyin, R.F.Bishop: The Triple Problem of Convergence in the Perturbation Expan­ sions with Non-Diagonal Propagators 252 M.Blažek: Remarks on Angular Distributions of Muon Pairs in High Energy Hadronic Collisions . 257 V.zimák. M.šumbera, I.Zborovský: Entropy in the Multiparticle Production ..... 264 M.Plutner. S.Raha, R.M.Weiner: Cohrernce, Chaos and Entropy Scaling in High Energy Collisions . 272 P.Malecki: Long-Range Correlations in Hadron-Nucleus Interactions 278 J.Ftáčnik: Transverse Energy Distribution in Hadron- Nucleus and Nucleus-Nucleus Collisions 284 O.Pavlenko: Quark-Hadron Phase Transition in High Energy Hadronic and Nuclear Collisions *** P.Závada: Nuclear Response and Hadron Formation Length • in Hadron-Nucleus Interactions *** B.Rsman: Charged Particle Multiplicity Distributions at 200 GeV and 900 GeV 289 W.Lohman: New Results on Proton Structure Functions from Deep Inelastic Muon Scattering at High Q2 294 D.Křupa. V.A.Mashcheryakov, Yu.S.Surovtsev: Scalar Glueball Indication in Pion Scattering .... 299 D.S.Bngdasarynn, G.B.Kazaryan, H.G.Mkrtchyan, I.A.Troshcnkova: Investigation of (e,e') Scattering on Electron Synchrotron at Yerevan Physics Institute 305 V.Kundrát. M.Lokaj íček, D.Křupa: High Energy Hadron Scattering in Forward Direction ЗЮ IV.Grimus: A Model of Massive Neutrinos with a Conservrd Lepton Number ... 3 i 7 H.Neufeld: Spontaneous CP Violation and Neutral Flavour Conservation in SUU^xUd)1 324 ll.Perlt: String Thermodynamics and Cosmology *** K.Lewin, G.B.Motz: On Quark Masses in (QQ) Potential Models 320 M."haichian, J.Fischer: Unitarity Bounds for High Energy Scattering in Many Dimensions 334 J.Szwed: The Square Root of the Dirac Equation within Supersynmetry ..... *** A.R.Kereseiidze, A.G.Liparteliaoi, G.G.Volkov: Superstring Inspired Left-Right Models .... 339 P.Miibius: Nonlinear Field Equations and Infinite Dimensional Lie Algebras ........... 342 H.Pcrez-Ro.ias. R.Gonzáles: Phase Transitions of W-Condensation in the Hot Universe 350 I.Lukác: On the Geometry of Group Space of Group of Motion of Three-Dimensionnl Quadratic Form . 357 M.Bonesini: Prompt Gamma Physics: New Experimental Results - 362 Author Index 369 List of Participants 371 *** Oral presentation only. The names of speakers are underlined. Preface It became a good tradition that Czechoslovak physicists interested in elementary particle physics meet together with their colleagues from abroad at the lladron Structure confe­ rences evry year. The present book represents the proceedings of the Hadron Structure '87 conference whirh was held in Smolenice Castle near Bratislava on November 16-20, this year The programme of the conference consisted of lectures and short communications. The main topics covered were: - nonperturbative calculations in field theory ( QCD in Particular ) - Particle production in hadron-nucleus and nucleus- nucleus collisions and the quark-gluon plasma - recent experimental results. The arrangement of papers follows closely chronology of talks us they were presented at the conference with the exception that lectures (presented during morning sessions) and short communications arc grouped together separately. ГП the coiiLv«.iL:s wc list all papers presented at the conference specifying those which were not made available for publication in the present volume. The editors would like to th&nk all authors submitting their papers for printing in the camera ready form. V»e are also grateful to the Vela Publishing Ho'ise for their interest to Publish this proceedings and for their assistance. F.d i tor STATUS OF NONCOVARIANT SUPERGAUGES* (Lecture at "Hadron Structure 1987" , 16. - 20,11.1987, Smolenice, CSSR) W. KUMMER Institut fur Theoretische Physik der Technischen Univereitat Wien Abstract» Supersynunetric gauge theories can be suitably quantized in non- supersymmetric gauges without abolishing the advantages of supergraph techniques. The state of the art now encompasses the proof of renormalization and of gauge-independence and super- symmetry for observable physical quantities. Karlsplatz 13, A-1040 Wien Supported by "Ponds zur wissenschaftlichen Forschung", Proj. Nr. 5485 It 1 • Introduction The general superfield treatment of renormalization problem in eupersymmetric gauge-theories £lj cannot evade the choice of a gauge which breaks super symmetry, at least softly Q2]. This suggests the study of general noncovariant supergaugee which, on the other hand, allow the inclusion of celebrated gauges like the Wess-Zumino gauge [3,4,5^ in a supergraph formalism. 2. Gauge-Superfield and Notation The ordinary gauge-field v in supersymmetry becomes a component of a hermitian superfield [6/73 V = V (2.1) which contains powers of the Lorentz 2-spinor Grassmann-varia- bles eQ and ?• (a, & =1,2). The basic anticommutatór for the Bplnor charges Q< and Q^ in supersymmetry reads (Pm is the generator of the translations) (2.2) Supereymmetric covarlant derivatives ( ^a УлВ* ' anticommute with QK and 5* , but obey the same relation (2.2) with Pm„ = 1Эm . The supergraph-renormalization problem [2] is a consequence of the (mass-) dimension zero of V which in turn follows from 12 the dimension 1 of the vector-fiold v_ and from the dimension 1 m - •£ for e. The scalar component of V has dimension zero too and, for purely dimensional reasons, the c-propagator must bo- have like 1/k . Thus a now type of infrared (IR) divergence appears, except the "unphysical" components of V are fixed appropriately. Only vm and one spinor-field are physical de­ grees of freedom. Fixing the gauge in a way which does not break supersymmetry will not provide a solution of this problem. Sufficient for such a solution is the choice of the Wess-Zumino gauge [ij which eliminates all fields except v, \ and £) Such a gauge clearly breaks supersymmetry.
Recommended publications
  • The Large Hadron Collider Lyndon Evans CERN – European Organization for Nuclear Research, Geneva, Switzerland
    34th SLAC Summer Institute On Particle Physics (SSI 2006), July 17-28, 2006 The Large Hadron Collider Lyndon Evans CERN – European Organization for Nuclear Research, Geneva, Switzerland 1. INTRODUCTION The Large Hadron Collider (LHC) at CERN is now in its final installation and commissioning phase. It is a two-ring superconducting proton-proton collider housed in the 27 km tunnel previously constructed for the Large Electron Positron collider (LEP). It is designed to provide proton-proton collisions with unprecedented luminosity (1034cm-2.s-1) and a centre-of-mass energy of 14 TeV for the study of rare events such as the production of the Higgs particle if it exists. In order to reach the required energy in the existing tunnel, the dipoles must operate at 1.9 K in superfluid helium. In addition to p-p operation, the LHC will be able to collide heavy nuclei (Pb-Pb) with a centre-of-mass energy of 1150 TeV (2.76 TeV/u and 7 TeV per charge). By modifying the existing obsolete antiproton ring (LEAR) into an ion accumulator (LEIR) in which electron cooling is applied, the luminosity can reach 1027cm-2.s-1. The LHC presents many innovative features and a number of challenges which push the art of safely manipulating intense proton beams to extreme limits. The beams are injected into the LHC from the existing Super Proton Synchrotron (SPS) at an energy of 450 GeV. After the two rings are filled, the machine is ramped to its nominal energy of 7 TeV over about 28 minutes. In order to reach this energy, the dipole field must reach the unprecedented level for accelerator magnets of 8.3 T.
    [Show full text]
  • MIT at the Large Hadron Collider—Illuminating the High-Energy Frontier
    Mit at the large hadron collider—Illuminating the high-energy frontier 40 ) roland | klute mit physics annual 2010 gunther roland and Markus Klute ver the last few decades, teams of physicists and engineers O all over the globe have worked on the components for one of the most complex machines ever built: the Large Hadron Collider (LHC) at the CERN laboratory in Geneva, Switzerland. Collaborations of thousands of scientists have assembled the giant particle detectors used to examine collisions of protons and nuclei at energies never before achieved in a labo- ratory. After initial tests proved successful in late 2009, the LHC physics program was launched in March 2010. Now the race is on to fulfill the LHC’s paradoxical mission: to complete the Stan- dard Model of particle physics by detecting its last missing piece, the Higgs boson, and to discover the building blocks of a more complete theory of nature to finally replace the Standard Model. The MIT team working on the Compact Muon Solenoid (CMS) experiment at the LHC stands at the forefront of this new era of particle and nuclear physics. The High Energy Frontier Our current understanding of the fundamental interactions of nature is encap- sulated in the Standard Model of particle physics. In this theory, the multitude of subatomic particles is explained in terms of just two kinds of basic building blocks: quarks, which form protons and neutrons, and leptons, including the electron and its heavier cousins. From the three basic interactions described by the Standard Model—the strong, electroweak and gravitational forces—arise much of our understanding of the world around us, from the formation of matter in the early universe, to the energy production in the Sun, and the stability of atoms and mit physics annual 2010 roland | klute ( 41 figure 1 A photograph of the interior, central molecules.
    [Show full text]
  • The Pion Cloud: Insights Into Hadron Structure
    614 Progress of Theoretical Physics Supplement No. 168, 2007 The Pion Cloud: Insights into Hadron Structure Anthony W. Thomas Jefferson Lab, 12000 Jefferson Ave., Newport News, VA 23606, USA and College of William and Mary, Williamsburg, VA 23187, USA Modern nuclear theory presents a fascinating study in contrasting approaches to the structure of hadrons and nuclei. Nowhere is this more apparent than in the treatment of the pion cloud. As this discussion really begins with Yukawa, it is entirely appropriate that this invited lecture at the Yukawa Institute in Kyoto should deal with the issue. §1. Introduction While the pion has been with us in theory since 1935 and in fact since 1947, chiral symmetry has provided important guidance in dealing with strong interaction phenomena since the 1960s. Well known work by Gell Mann and L´evy, Weinberg, Pagels and many others developed the consequences before the underlying origins in terms of QCD were discovered – for a review see Ref. 1). That early work was not only mathematically rigorous but was guided by sound physics insight. Since the early 1980s a great deal of work which exploits the chiral symmetry of QCD has been carried out within the framework of chiral perturbation theory. This work is usually described in language which equates it to QCD and talks about a systematic, rigorous description of the hadronic world in terms of a set of low energy constants. In a few outstanding examples this approach has proven very valuable indeed. For some low energy phenomena it has proven possible to make rigorous statements concerning cross sections that had previously seemed incurably model dependent.
    [Show full text]
  • This Space Should Be Left Blank, Except for the Name of the First Author
    Hadron Colliders and Hadron Collider Physics Symposium Dmitri Denisov Fermi National Accelerator Laboratory, Batavia, Illinois 60510 USA Abstract. This article summarizes main developments of the hadron colliders and physics results obtained since their inception around forty years ago. The increase in the collision energy of over two orders of magnitude and even larger increases in luminosity provided experiments with unique data samples. Developments of full acceptance detectors, particle identification and analysis methods provided fundamental discoveries and ultra-precise measurements which culminated in the completion and in depth verification of the Standard Model. Hadron Collider Physics symposium provided opportunities for those working at hadron colliders to share results of their research since 1979 and helped greatly to develop the field of particle physics. 1 Hadron Colliders The idea of using colliding beams to increase center of mass energy was developed in 1960’s with e+e- colliders designed and constructed. This idea is based on the kinematics of the collision. In the case of head on collisions for colliding beams of the same mass particles the center of mass system and the laboratory system coincide and the total center of mass energy is twice the energy of the beams. In the case of fixed target experiments, which provided critical experimental information at the early stages of the Standard Model developments, for proton proton collisions the center of mass energy is ~ (2mpEbeam) in the approximation of beam energy Ebeam well above mass of proton mp. This square root dependence√ reduces the center of mass energy of the fixed target experiments substantially. For example, at 1 TeV beam energy fixed target center of mass energy is ~50 GeV, while two 1 TeV beams Fig.
    [Show full text]
  • The Application of the Quark-Hadron Chiral Parity-Doublet Model to Neutron Star Matter A
    A&A 608, A110 (2017) Astronomy DOI: 10.1051/0004-6361/201731505 & c ESO 2017 Astrophysics The application of the Quark-Hadron Chiral Parity-Doublet model to neutron star matter A. Mukherjee1, S. Schramm1, J. Steinheimer1, and V. Dexheimer2 1 Frankfurt Institute for Advanced Studies, 60438 Frankfurt am Main, Germany e-mail: [mukherjee;schramm;steinheimer]@fias.uni-frankfurt.de 2 Department of Physics, Kent State University, Kent, OH 44242, USA e-mail: [email protected] Received 4 July 2017 / Accepted 24 September 2017 ABSTRACT Aims. The Quark-Hadron Chiral Parity-Doublet model is applied to calculate compact star properties in the presence of a deconfine- ment phase transition. Methods. Within this model, a consistent description of nuclear matter properties, chiral symmetry restoration, and a transition from hadronic to quark and gluonic degrees of freedom is possible within one unified approach. Results. We find that the equation of state obtained is consistent with recent perturbative quantum chromodynamics results and is able to accommodate observational constraints of massive and small neutron stars. Furthermore, we show that important features of the equation of state, such as the symmetry energy and its slope, are well within their observational constraints. Key words. equation of state – stars: neutron 1. Introduction temperature. In order to theoretically investigate the properties of strongly interacting matter in all of these environments, one Understanding strong interaction physics at extreme conditions has to employ a model approach containing hadrons and quarks of temperature and/or density is a central topic of current theo- in a comprehensive manner. After having analyzed (isospin- retical and experimental nuclear research.
    [Show full text]
  • Hadron–Quark Phase Transition in the SU (3) Local Nambu–Jona-Lasinio (NJL) Model with Vector Interaction
    S S symmetry Article Hadron–Quark Phase Transition in the SU (3) Local Nambu–Jona-Lasinio (NJL) Model with Vector Interaction Grigor Alaverdyan Department of Radio Physics, Yerevan State University, 1 Alex Manoogian Street, Yerevan 0025, Armenia; [email protected] Abstract: We study the hadron–quark hybrid equation of state (EOS) of compact-star matter. The Nambu–Jona-Lasinio (NJL) local SU (3) model with vector-type interaction is used to describe the quark matter phase, while the relativistic mean field (RMF) theory with the scalar-isovector d-meson effective field is adopted to describe the hadronic matter phase. It is shown that the larger the vector coupling constant GV, the lower the threshold density for the appearance of strange quarks. For a sufficiently small value of the vector coupling constant, the functions of the mass dependence on the baryonic chemical potential have regions of ambiguity that lead to a phase transition in nonstrange quark matter with an abrupt change in the baryon number density. We show that within the framework of the NJL model, the hypothesis on the absolute stability of strange quark matter is not realized. In order to describe the phase transition from hadronic matter to quark matter, Maxwell’s construction is applied. It is shown that the greater the vector coupling, the greater the stiffness of the EOS for quark matter and the phase transition pressure. Our results indicate that the infinitesimal core of the quark phase, formed in the center of the neutron star, is stable. Keywords: quark matter; NJL model; RMF theory; deconfinement phase transition; Maxwell con- struction Citation: Alaverdyan, G.
    [Show full text]
  • Hadron-Nucleus Interactions
    Hadron-Nucleus Interactions Beginners’ FLUKA Course Hadronic showers: many particle species, wide energy range 100 GeV p in a Fe absorber: 100 GeV p on Pb space-averaged particle spectra shower longitudinal development 2 Hadronic showers: we want to simulate also what is left ! The MC should be able to Residual nuclei distribution reproduce this complexity, Following 15 GeV proton maintaining correlations and interactions on Lead cross-talks among the shower components Hadronic interactions have to be simulated over a wide energy range with an high degree of accuracy Nuclear effects are essential => need detailed nuclear interaction models => need checks on simple data (thin target) A summary of the hadronic interaction models used in FLUKA is given in the following 3 The FLUKA hadronic Models Hadron-nucleus: PEANUT Sophisticated Elastic,exchange P<3-5GeV/c G-Intranuclear Cascade Phase shifts Resonance prod data, eikonal and decay Gradual onset of Glauber-Gribov multiple hadron interactions hadron Preequilibrium low E π,K High Energy Coalescence Special DPM hadronization Evaporation/Fission/Fermi break-up deexcitation 4 Hadron-nucleon interaction models Particle production interactions: p-p and p-n cross section two kinds of models FLUKA and data total Those based on “resonance” production and decays, cover the energy range up to 3–5 GeV Those based on quark/parton elastic string models, which provide reliable results up to several tens of TeV Elastic, charge exchange and strangeness exchange reactions: • Available phase-shift analysis and/or fits of experimental differential data • At high energies, standard eikonal approximations are used 5 Nonelastic hN interactions at intermediate energies ’ ‘ ’ ‘ • N1 + N2 → N 1 + N 2 + π threshold at 290 MeV, important above 700 MeV, • π + N → π ‘+ π” + N ‘ opens at 170 MeV.
    [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]
  • What Is a Higgs Boson?
    Fermi National Accelerator Laboratory August 2015 What is a Higgs boson? In 2012 at the Large Hadron Collider, scientists discovered the long-sought Higgs boson. Now the question is: Are there more types of Higgs bosons? The Higgs field provides mass to quarks and other elementary particles that are the building blocks of matter. The photon and the gluon do not interact with the Higgs field, and hence they have no mass. Whether the Higgs field is the origin of the mass of dark matter or the tiny mass of the three known types of neutrinos is not yet known. What is a Higgs field? What is a Higgs boson? When did scientists discover the Higgs boson? The Higgs field is a force field that acts like a giant vat of molasses Scientists searched for the Higgs boson for more than two decades, spread throughout the universe. Most of the known types of particles starting with the LEP experiments at CERN in the 1990s and the that travel through it stick to the molasses, which slows them down Tevatron experiments at Fermilab in the 2000s. Years’ worth of LEP and makes them heavier. The Higgs boson is a particle that helps and Tevatron data narrowed the search for the Higgs particle. Then, transmit the mass-giving Higgs field, similar to the way a particle of in 2012 at CERN’s Large Hadron Collider (LHC), two experiments, light, the photon, transmits the electromagnetic field. ATLAS and CMS, reported the observation of a Higgs-like particle. With further analysis the new particle was confirmed as the Higgs boson in 2013.
    [Show full text]
  • Read Frequently Asked Questions About the Higgs Boson
    Frequently Asked Questions About the Higgs Boson What is a Higgs field? What is a Higgs boson? The Higgs field is like a giant vat of molasses spread throughout the universe. Most of the known types of particles that travel through it stick to the molasses, which slows them down and makes them heavier. The Higgs boson is a particle that helps transmit the mass-giving Higgs force field, similar to the way a particle of light, the photon, transmits the electromagnetic field. How long have physicists been looking for the Higgs boson? More than two decades. It started with the LEP experiments at CERN in the 1990s, continued with the Tevatron experiments at Fermilab and now continues with the Large Hadron Collider (LHC) experiments at CERN. A discovery of the Higgs boson would be just the beginning of a new era of particle physics research. Scientists would then focus on understanding in detail the interactions of the Higgs boson with other particles, testing the predictions made by theorists and looking for unexpected phenomena. What would the world look like without the Higgs boson or a similar particle? You wouldn’t recognize the world. Without the Higgs boson or something like it giving mass to the basic building blocks of matter, electrons would zip about at the speed of light. They would not form unions with protons or other would-be nuclei to make atoms. No atoms means no chemical reactions, no molecules, no ordinary matter as we know it, no template for life. We would not exist. How do physicists create a Higgs boson? A high-energy particle accelerator such as the Tevatron or LHC can recreate the extreme energies of the very early universe, generated shortly after the Big Bang.
    [Show full text]
  • Chapter 16 Constituent Quark Model
    Chapter 16 Constituent Quark Model 1 Quarks are fundamental spin- 2 particles from which all hadrons are made up. Baryons consist of three quarks, whereas mesons consist of a quark and an anti-quark. There are six 2 types of quarks called “flavours”. The electric charges of the quarks take the value + 3 or 1 (in units of the magnitude of the electron charge). − 3 2 Symbol Flavour Electric charge (e) Isospin I3 Mass Gev /c 2 1 1 u up + 3 2 + 2 0.33 1 1 1 ≈ d down 3 2 2 0.33 − 2 − ≈ c charm + 3 0 0 1.5 1 ≈ s strange 3 0 0 0.5 − 2 ≈ t top + 3 0 0 172 1 ≈ b bottom 0 0 4.5 − 3 ≈ These quarks all have antiparticles which have the same mass but opposite I3, electric charge and flavour (e.g. anti-strange, anti-charm, etc.) 16.1 Hadrons from u,d quarks and anti-quarks Baryons: 2 Baryon Quark content Spin Isospin I3 Mass Mev /c 1 1 1 p uud 2 2 + 2 938 n udd 1 1 1 940 2 2 − 2 ++ 3 3 3 ∆ uuu 2 2 + 2 1230 + 3 3 1 ∆ uud 2 2 + 2 1230 0 3 3 1 ∆ udd 2 2 2 1230 3 3 − 3 ∆− ddd 1230 2 2 − 2 113 1 1 3 Three spin- 2 quarks can give a total spin of either 2 or 2 and these are the spins of the • baryons (for these ‘low-mass’ particles the orbital angular momentum of the quarks is zero - excited states of quarks with non-zero orbital angular momenta are also possible and in these cases the determination of the spins of the baryons is more complicated).
    [Show full text]