arXiv subjects

F. Iachello

Publications and source records attributed to F. Iachello.

46 records · Page 3Linked to original sources

arXiv2002

The algebraic cluster model. Three-body clusters

A new method is introduced to study three-body clusters. Triangular configurations with ${\cal D}_{3h}$ point-group symmetry are analyzed. The spectrum, transition form factors and $B(Eλ)$ values of $^{12}$C are investigated. It is concluded that the low-lying spectrum of $^{12}$C can be described by three alpha-particles at the vertices of an equilateral triangle, but not as a rigid structure. Large rotation-vibration interactions, Coriolis forces and vibration-vibration interactions are needed. Other interpretations, such as the harmonic oscillator and a soft deformed oscillator with SO(6) hyperspherical symmetry, appear to be excluded by electron scattering data.

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arXiv2000

Algebraic Models of Hadron Structure II. Strange Baryons

The algebraic treatment of baryons is extended to strange resonances. Within this framework we study a collective string-like model in which the radial excitations are interpreted as rotations and vibrations of the strings. We derive a mass formula and closed expressions for strong and electromagnetic decay widths and use these to analyze the available experimental data.

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arXiv2000

Cluster states in nuclei as representations of a U(n+1) group

We propose a description of cluster states in nuclei in terms of representations of unitary algebras U(n+1), where n is the number of space degrees of freedom. Within this framework, a variety of situations including both vibrational and rotational spectra, soft and rigid configurations, identical and non-identical constituents can be described. As an example, we show how the method can be used to study alpha-clustering configurations in 12C with point group symmetry D(3h).

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arXiv1999

Sensitivity of tensor analyzing power in the process $d+p\to d+X$ to the longitudinal isoscalar form factor of the Roper resonance electroexcitation

The tensor analyzing power of the process $d + p \to d + X$, for forward deuteron scattering in the momentum interval 3.7 to 9 GeV/c, is studied in the framework of $ω$ exchange in an algebraic collective model for the electroexcitation of nucleon resonances. We point out a special sensitivity of the tensor analyzing power to the isoscalar longitudinal form factor of the Roper resonance excitation. The main argument is that the $S_{11}(1535)$, $D_{13}(1520)$ and $S_{11}(1650)$ resonances have only isovector longitudinal form factors. It is the longitudinal form factor of the Roper excitation, which plays an important role in the $t-$dependence of the tensor analyzing power. We discuss possible evidence of swelling of hadrons with increasing excitation energy.

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arXiv1998

Algebraic treatment of the hyper-Coulomb problem

A completely algebraic treatment of the six-dimensional hypercoulomb problem is discussed in terms of an oscillator realization of the dynamical algebra of SO(7,2). Closed expressions are derived for the energy spectrum and form factors.

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arXiv1996

Strong decays of qqq baryons

We study strong decays of nonstrange baryons by making use of the algebraic approach to hadron structure. Within this framework we derive closed expressions for decay widths in an elementary-meson emission model and use these to analyze the experimental data for N* -> N + pi, N* -> Delta + pi, N* -> N + eta, Delta* -> N + pi, Delta* -> Delta + pi and Delta* -> Delta + eta decays.

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arXiv1996

Electromagnetic Form Factors in a Collective Model of the Nucleon

We study the electromagnetic form factors of the nucleon in a collective model of baryons. Using the algebraic approach to hadron structure, we derive closed expressions for both elastic and transition form factors, and consequently for the helicity amplitudes that can be measured in electro- and photoproduction. Effects of spin-flavor symmetry breaking and of swelling of hadrons with increasing excitation energy are considered.

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arXiv1994

Algebraic models of hadron structure: I. Nonstrange baryons

We introduce an algebraic framework for the description of baryons. Within this framework we study a collective string-like model and show that this model gives a good overall description of the presently available data. We discuss in particular masses and electromagnetic couplings, including the transition form factors that can be measured at new electron facilities.

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arXiv1993

Strong Decays of $Q \bar Q$ Mesons

We present a detailed study of the two-body strong decays of light mesons. Both the space part and the spin-flavor-color part of the wave functions are generated algebraically and closed forms are obtained for all decays. Experimental deviations from our systematics are seen to be suggestive of both missing mesons and exotic QCD configurations.

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arXiv1993

A Collective Model of Baryons

We propose an algebraic description of the geometric structure of baryons in terms of the algebra $U(7)$. We construct a mass operator that preserves the threefold permutational symmetry and discuss a collective model of baryons with the geometry of an oblate top.

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