Energy levels of A = 21−44 nuclei (V)

New insights from studies of spontaneous fission with large detector arrays

We report a measurement of a new high spin Jπ=5- state at 22.4(2) MeV in 12C which fits very well to the predicted (ground state) rotational band of an oblate equilateral triangular spinning top with a D3h symmetry characterized by the sequence 0+, 2+, 3-, 4±, 5- with almost degenerate 4+ and 4- (parity doublet) states. Such a D3h symmetry was observed in triatomic molecules, and it is observed here for the first time in nuclear physics. We discuss a classification of other rotation-vibration bands in 12C such as the (0+) Hoyle band and the (1-) bending mode band and suggest measurements in search of the predicted ("missing") states that may shed new light on clustering in 12C and light nuclei. In particular, the observation (or nonobservation) of the predicted ("missing") states in the Hoyle band will allow us to conclude the geometrical arrangement of the three alpha particles composing the Hoyle state at 7.654 MeV in 12C.

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Evidence for triangular D3h symmetry in 12C.

The discovery of a new excited state in carbon-12 hints at this nucleus's triangular symmetry.

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Evidence for TriangularD3hSymmetry inC12

Solitons emerge in various non-linear systems as stable localized configurations, behaving in many ways like particles, from non-linear optics and condensed matter to nuclear physics, cosmology and supersymmetric theories This book provides an introduction to integrable and non-integrable scalar field models with topological and non-topological soliton solutions Focusing on both topological and non-topological solitons, it brings together debates around solitary waves and construction of soliton solutions in various models and provides a discussion of solitons using simple model examples These include the Kortenweg-de-Vries system, sine-Gordon model, kinks and oscillons, and skyrmions and hopfions The classical field theory of scalar field in various spatial dimensions is used throughout the book in presentation of related concepts, both at the technical and conceptual level Providing a comprehensive introduction to the description and construction of solitons, this book is ideal for researchers and graduate students in mathematics and theoretical physics

Topological and Non-Topological Solitons in Scalar Field Theories

Investigation of the alpha-particle model for light nuclei

MIT bag model with center-of-mass correction

Nucleon core size and nuclear forces

The cross section between a $c\overline{c}$ pair and a nucleon is small and sensitive to the $c$-$\overline{c}$ separation if the pair is in a color-singlet state, but very large and insensitive to the separation if it is in a color-octet state. We use this property in an absorption model involving both color components to deduce the color structure of $c\overline{c}$ pairs produced in $p\stackrel{\ensuremath{\rightarrow}}{A}\ensuremath{\psi}X$ reactions. Our analysis shows that the NA3, NA38, and E772 data are not inconsistent with the theoretical picture that color-octet and color-singlet precursors are produced in roughly equal proportions if the produced color-singlet precursors are pointlike and transparent. However, if the color-singlet precursors are not transparent but have a cross section of a few mb, these data do show a definite preference for a larger fraction of color-singlet precursors. In either case, the color-octet fraction increases with ${x}_{{}_{F}}$, approaching close to unity as ${x}_{{}_{F}}$ increases to about 0.5.

Color-octet fraction in J / ψ production and absorption

We examine the relation between two approaches to the quantum relativistic two-body problem: (1) the Breit equation, and (2) the two-body Dirac equations derived from constraint dynamics. In applications to quantum electrodynamics, the former equation becomes pathological if certain interaction terms are not treated as perturbations. The difficulty comes from singularities which appear at finite separations r in the reduced set of coupled equations for attractive potentials even when the potentials themselves are not singular there. They are known to give rise to unphysical bound states and resonances. In contrast, the two-body Dirac equations of constraint dynamics do not have these pathologies in many nonperturbative treatments. To understand these marked differences we first express these contraint equations, which have an “external potential” form, similar to coupled one-body Dirac equations, in a hyperbolic form. These coupled equations are then recast into two equivalent equations: (1) a covariant Breit-like equation with potentials that are exponential functions of certain “generator” functions, and (2) a covariant orthogonality constraint on the relative momentum. This reduction enables us to show in a transparent way that finite-r singularities do not appear as long as the exponential structure is not tampered with and the exponential generators of the interaction are themselves nonsingular for finite r. These Dirac or Breit equations, free of the structural singularities which plague the usual Breit equation, can then be used safely under all circumstances, encompassing numerous applications in the fields of particle, nuclear, and atomic physics which involve highly relativistic and strong binding configurations.

Chun Wa Wong

Papers

Investigation of the alpha-particle model for light nuclei

MIT bag model with center-of-mass correction

Nucleon core size and nuclear forces

Color-octet fraction in J / ψ production and absorption

Singularity-free breit equation from constraint two-body dirac equations