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4735 results in Particle Physics and Nuclear Physics

Page 103 of 237

  • 12 - The Structure and Properties of Few-Body Nuclei

  • T. William Donnelly, Massachusetts Institute of Technology, Joseph A. Formaggio, Massachusetts Institute of Technology, Barry R. Holstein, University of Massachusetts, Amherst, Richard G. Milner, Massachusetts Institute of Technology, Bernd Surrow, Temple University, Philadelphia
  • Book:
    Foundations of Nuclear and Particle Physics
    Published online:
    28 May 2018
    Print publication:
    01 February 2017, pp 307-332

  • Summary

    Introduction

    In this chapter, few-body nuclei will be defined as those created through big bang nucleosynthesis, namely lithium, beryllium, and lighter elements. All elements heavier than beryllium and lithium were created much later, by stellar nucleosynthesis in evolving and exploding stars. This is discussed in detail in Chapter 20. In Chapter 11, the groundstate structure and properties of the deuteron have been discussed in detail. Here, the main focus will be on what can be learned from electroproduction from masses A = 2, 3, and 4. In addition, the topics of hypernuclei and fusion will be discussed.

    Big bang nucleosynthesis (BBN) began a few minutes after the big bang, when the universe had cooled down sufficiently to allow deuterium nuclei to survive photodisintegration by high-energy photons. At this temperature, nucleosynthesis can take place and protons and neutrons can interact to form deuterium. Most of the deuterium then collided with other protons and neutrons to produce helium and a small amount of tritium. Lithium-7 could also form via the coalescence of one tritium and two deuterium nuclei. The BBN produced the stable nuclei 2H, 3He, 4He, 6Li, and 7Li as well as the radioactive nuclei 3H, 7Be, and 8Be. No elements heavier than beryllium were produced due to the absence of stable nuclei with five or eight nucleons. Note that this bottleneck is overcome in stars by triple collisions of 4He nuclei, producing carbon. However, this process is very slow, taking tens of thousands of years to convert a significant amount of helium to carbon in stars. (See Chapter 20 for further discussion of the Big Bang and astrophysics.)

    The theory of BBN predicts that roughly 25% of the mass of the universe consists of helium, with about 0.01% deuterium and smaller quantities of lithium. This prediction depends critically on the density of baryons (neutrons and protons) at the time of nucleosynthesis. The observation that helium is nowhere seen to have an abundance below 23% is strong evidence that the universe went through an early, hot phase. Further support comes from the consistency of the light element abundances for a particular value of baryon density and an independent measurement of this quantity from the anisotropies in the cosmic microwave background (CMB).

  • 7 - Introduction to Lepton Scattering

  • T. William Donnelly, Massachusetts Institute of Technology, Joseph A. Formaggio, Massachusetts Institute of Technology, Barry R. Holstein, University of Massachusetts, Amherst, Richard G. Milner, Massachusetts Institute of Technology, Bernd Surrow, Temple University, Philadelphia
  • Book:
    Foundations of Nuclear and Particle Physics
    Published online:
    28 May 2018
    Print publication:
    01 February 2017, pp 151-187

  • Summary

    We now progress from focusing primarily on issues of the Standard Model and QCD. Since throughout much of the rest of the book a focus will be placed on lepton scattering, particularly on electron scattering, we collect in this chapter some of the basic ideas behind this subject. The emphasis will be placed on the general aspects of the leptonic and hadronic tensors which, when contracted together, yield the basic quantity that determines the semileptonic cross section. Furthermore, the detailed discussions will be limited to inclusive scattering, namely, to reactions where the scattered lepton is assumed to be detected, but where any outgoing particles other than this lepton are not detected; the latter reaction where the lepton and at least one other particle are detected is called semi-inclusive and will be treated in later chapters (Chapter 9 for particle physics and Chapter 16 for nuclear physics). In addition to the general formalism for parity-conserving and parity-violating electron scattering, an introduction to the development of electromagnetic (EM) multipole operators is presented, as this will be important for later chapters where discrete states in nuclei that have good angular momentum and parity quantum numbers are considered.

    After the formal developments in the present chapter we progress in Chapter 8 to elastic electron scattering from the proton and the insights that this gives us into the structure of the nucleon and its relevance for low-Q2, strong-coupling QCD. Chapter 9 goes on to treat inelastic ep scattering with its underlying partonic modeling. Then, after an insertion (Chapter 10) where high-energy hadronic reactions are discussed as the way one studies quark–quark, quark–gluon and gluon–gluon interactions, we continue with the succeeding chapters where the developments here are employed – in few-body nuclei in Chapters 11 and 12, and in many-body nuclei in Chapters 13–16.

    The lepton scattering process from a nucleon target provides a detailed “snapshot” of the target structure at a particular level of resolution. The highest resolution is provided by energetic, charged leptons, which interact with individual quarks and antiquarks inside a proton or neutron. These interactions, being sensitive to the motion of the struck quarks, can map the probability for finding the various constituents as a function of the fraction they carry of the nucleon's overall momentum.

  • Preface

  • T. William Donnelly, Massachusetts Institute of Technology, Joseph A. Formaggio, Massachusetts Institute of Technology, Barry R. Holstein, University of Massachusetts, Amherst, Richard G. Milner, Massachusetts Institute of Technology, Bernd Surrow, Temple University, Philadelphia
  • Book:
    Foundations of Nuclear and Particle Physics
    Published online:
    28 May 2018
    Print publication:
    01 February 2017, pp xi-xiv

  • Summary

    The first question one might ask about this book is: Why do we need another text on the subject of nuclear and particle physics when excellent texts already exist in both of these areas? Indeed, it is true that each sub-discipline has texts that range from elementary to very advanced and cover specific topics in varying degrees of depth that can be used for the appropriate types of courses. For instance, there are fine books on quantum field theory [Bjo64, Pes95, Wei05, Sch14], on the constituent quark model [Clo79], on highenergy physics [Gri08, Hal84], on hadron scattering [Col84], and on nuclear structure [Des74, Wal95, Won98, Pov08, Row10]. However, there are relatively few textbooks that cover several sub-disciplines in a coherent and balanced way, and those that do exist are either more elementary, e.g., Povh et al. [Pov08] than the present book, or are cast at a more theoretical level and are too advanced for the goals we as authors have set for ourselves. Having a book that stresses the interconnections between the two areas of subatomic physics is crucial, since increasingly one finds that the two fields overlap and that it is essential for a graduate student conducting frontier research and preparing for a career in the field to have an understanding of both. An example of this overlap occurs, for instance, in modern neutrino physics wherein experiments utilizing several-GeV neutrinos as probes almost always involve targets/detectors constructed from nuclei and specifics of nuclear structure are unavoidably required to properly interpret such data.

    One specific decision we have made in designing this book is to assume that the reader is familiar with the basics of quantum field theory. More elementary texts typically do not make this assumption and thus much of the discussion, for instance, of lepton scattering from hadrons and nuclei, or of the foundations of chiral symmetry and effective field theory is limited and not at the frontier of the field.We realize that many students today do have at least an introductory course in quantum field theory, or are taking one simultaneously with a course that this book covers, and thus we have followed a somewhat more advanced approach than has been customary.

  • 10 - High-Energy QCD

  • T. William Donnelly, Massachusetts Institute of Technology, Joseph A. Formaggio, Massachusetts Institute of Technology, Barry R. Holstein, University of Massachusetts, Amherst, Richard G. Milner, Massachusetts Institute of Technology, Bernd Surrow, Temple University, Philadelphia
  • Book:
    Foundations of Nuclear and Particle Physics
    Published online:
    28 May 2018
    Print publication:
    01 February 2017, pp 240-274

  • Summary

    Introduction

    In Chapter 5, the non-Abelian SU(3)color gauge theory, QCD, was developed as the fundamental theory of the strong force in the Standard Model. Quantum chromodynamics describes hadrons as consisting of pointlike electrically charged quarks bound via color forces by the exchange of gluons. In Chapters 7, 8, and 9, lepton scattering has been used to great effect to image the nucleon at distance scales from several fm to 0.001 fm. We have interpreted these data in terms of QCD and have come to understand that the nucleon is a highly relativistic system of light quarks and massless gluons with tremendously strong forces at play. The measured momentum distributions of the quarks and gluons in the nucleon are characterized by a large rise at low x which reflects the fact that the virtual particles of QCD are playing a dominant role. By contrast, the virtual particles of QED play only a minor role in understanding the structure of the atom. Thus, understanding the structure and properties of the nucleon in terms of QCD drives experiments to high energies where the dominant, virtual particles at low x can be accessed and studied.

    As the collision energy increases, regions of progressively higher gluon and sea quark density are probed. However, the density of gluons inside a nucleon, which dominate over the sea quarks, must eventually saturate to avoid untamed growth in the strength of the nucleon–nucleon cross section, which would violate the principle of unitarity. Thus far, this saturated gluon density regime has not been observed. In addition, the understanding of basic properties of the nucleon, e.g., the origin of its spin-1/2, as well as fundamental processes or hadronization that connects the experimental world of hadrons with the quarks and gluons of QCD, demand measurements at high energies. Further, it should be noted that high-energy DIS data on nuclei are sparse and characterized typically by low precision.

    To frame the discussion in this chapter, a number of important questions can be formulated [EIC12]:

  • • How are the sea quarks and gluons, and their spins, distributed in space and momentum inside the nucleon? How are these quark and gluon distributions correlated with overall nucleon properties, such as spin direction?

Supersymmetry, Supergravity, and Unification
  • Pran Nath
  • Published online:
    30 December 2016
    Print publication:
    15 December 2016
  • This unique book gives a modern account of particle physics and gravity based on supersymmetry and supergravity, two of the most significant developments in theoretical physics since general relativity. The book begins with a brief overview of the history of unification and then goes into a detailed exposition of both fundamental and phenomenological topics. The topics in fundamental physics include Einstein gravity, Yang–Mills theory, anomalies, the standard model, supersymmetry and supergravity, and the construction of supergravity couplings with matter and gauge fields, as well as computational techniques for SO(10) couplings. The topics of phenomenological interest include implications of supergravity models at colliders, CP violation, and proton stability, as well as topics in cosmology such as inflation, leptogenesis, baryogenesis, and dark matter. The book is intended for graduate students and researchers seeking to master the techniques for building grand unified models.

  • 24 - Further Reading

  • Pran Nath, Northeastern University, Boston
  • Book:
    Supersymmetry, Supergravity, and Unification
    Published online:
    30 December 2016
    Print publication:
    15 December 2016, pp 502-505

  • Summary

    The following is a list of books and review articles which the reader may find useful for cross-referencing the material discussed in this book and for further reading.

    Field Theory and Gauge Theories

    1. E. S. Abers and B. W. Lee, “Gauge theories,” Phys. Rep. 9, 1 (1973).

    2. T.-P. Cheng and L.-F. Li, Gauge Theory of Elementary Particle Physics, Oxford University Press (1984).

    3. P. H. Frampton, Gauge Field Theories, Benjamin-Cummings (1987).

    4. M. E. Peskin and D. V. Schroeder, An Introduction to Quantum Field Theory, Addison-Wesley (1995).

    5. C. Quigg, Gauge Theories of the Strong, Weak, and Electromagnetic Interactions, 2nd edn, Princeton University Press (2013).

    6. M. D. Schwartz, Quantum Field Theory and the Standard Model, Cambridge University Press (2013).

    7. M. Srednicki, Quantum Field Theory, Cambridge University Press (2007).

    8. S. Weinberg, The Quantum Theory of Fields, vols I and II, Cambridge University Press (2000).

    9. A. Zee, Quantum Field Theory in a Nutshell, Princeton University Press (2010).

    Supersymmetry and Supergravity

    1. R. Arnowitt, A. Chamseddine, and P. Nath, Applied N=1 Supergravity, World Scientific (1984).

    2. H. Baer and X. Tata, Weak Scale Supersymmetry, Cambridge University Press (2006).

    3. D. Bailin and A. Love, Supersymmetric Gauge Field Theory and String Theory, Institute of Physics (1994).

    4. P. Binetruy, Supersymmetry: Theory, Experiment and Cosmology, Oxford University Press (2006).

    5. I. L. Buchbinder and S. M. Kuzenko, Ideas and Methods of Supersymmetry and Supergravity: A Walk Through Superspace, Institute of Physics (1995).

    6. D. J. H. Chung, L. L. Everett, G. L. Kane, S. F. King, J. D. Lykken, and L. T. Wang, Phys. Rep. 407, 1 (2005).

    7. B. S. Dewitt, Supermanifiolds, Cambridge University Press (1992).

    8. M. Dine, Supersymmetry and String Theory: Beyond the Standard Model, Cambridge University Press (2007).

    9. M. Drees, R. Godbole, and P. Roy, Theory and Phenomenology of Sparticles, World Scientific (2004).

    10. D. Z. Freedman and A. Van Proeyen, Supergravity, Cambridge University Press (2012).

    11. S. J. Gates, M. T. Grisaru, M. Rocek, and W. Siegel, “Superspace or one thousand and one lessons in supersymmetry,” Front. Phys. 58, 1 (1983).

Page 103 of 237