217 research outputs found
Momentum Distributions of Particles from Three--Body Halo Fragmentation: Final State Interactions
Momentum distributions of particles from nuclear break-up of fast three-body
halos are calculated consistently, and applied to Li. The same two-body
interactions between the three particles are used to calculate the ground state
structure and the final state of the reaction processes. We reproduce the
available momentum distributions from Li fragmentation, together with
the size and energy of Li, with a neutron-core relative state containing
a -state admixture of 20\%-30\%. The available fragmentation data strongly
suggest an -state in Li at about 50 keV, and indicate a -state
around 500 keV.Comment: 11 pages (RevTeX), 3 Postscript figures (uuencoded postscript file
attached at the end of the LaTeX file). To be published in Phys. Rev.
Resonances in three-body systems with short and long-range interactions
The complex scaling method permits calculations of few-body resonances with
the correct asymptotic behaviour using a simple box boundary condition at a
sufficiently large distance. This is also valid for systems involving more than
one charged particle. We first apply the method on two-body systems. Three-body
systems are then investigated by use of the (complex scaled) hyperspheric
adiabatic expansion method. The case of the 2 resonance in Be and
Li is considered. Radial wave functions are obtained showing the correct
asymptotic behaviour at intermediate values of the hyperradii, where wave
functions can be computed fully numerically.Comment: invited talk at the 18th International Conference on Few-Body
Problems in Physics, Santos-S.Paulo, August 21-26, 200
Momentum distributions of particles from three-body halo fragmentation: Final state interactions
4 págs.; 3 figs.; 1 tab. ; PACS number (s): 25.60.2t, 21.45.1v, 21.60.Gx, 27.20.1nMomentum distributions of particles from nuclear breakup of fast three-body halos are calculated consistently, and applied to Li-11. The same two-body interactions between the three particles are used to calculate the ground state structure and the final state of the reaction processes. We reproduce the available momentum distributions from Li-11 fragmentation, together with the size and energy of Li-11, with a neutron-core relative state containing ap-state admixture of 20%-30%. The available fragmentation data strongly suggest an s state in Li-10 at about 50 keV and indicate a p state around 500 keV. ©1996 American Physical SocietyOne of us (E.G.) acknowledges support from the European
Union through the Human Capital and Mobility program
Contract No. ERBCHBGCT930320Peer Reviewe
Anatomy of three-body decay I. Schematic models
Sequential three-body decay proceeds via spatially confined quasi-stationary
two-body configurations. Direct three-body decay populates the three-body
continuum without intermediate steps. The relative importance of these decay
modes is discussed in a schematic model employing only Coulomb or centrifugal
barrier potentials. Decisive dimensionless charge, mass and energy ratios are
derived. Sequential decay is usually favored for charged particles. Small
charge and small mass of high energy is preferably emitted first. Without
Coulomb potential the sequential decay is favored except when both resonance
energy and intermediate two-body energy are large.Comment: To be published in Nuclear Physics
Three-body bremsstrahlung and the rotational character of the 12C spectrum
22 págs.; 11 figs.; 6 tabs.; PACS number(s): 23.20.−g, 21.60.Gx, 21.45.−v, 27.20.+nThe electric quadrupole transitions between 0+,2+, and 4+ states in C12 are investigated in a 3α model. The three-body wave functions are obtained by means of the hyperspherical adiabatic expansion method, and the continuum is discretized by imposing a box boundary condition. Corresponding expressions for the continuum three-body (3α) bremsstrahlung and photon dissociation cross sections are derived and computed for two different α−α potentials. The available experimental energy dependence is reproduced and a series of other cross sections are predicted. The transition strengths are defined and derived from the cross sections, and compared to schematic rotational model predictions. The computed properties of the C12 resonances suggest that the two lowest bands are made, respectively, by the states {0+1,2+1,4+2} and {0+2,2+2,4+1}. The transitions between the states in the first band are consistent with the rotational pattern corresponding to three alphas in an equilateral triangular structure. For the second band, the transitions are also consistent with a rotational pattern, but with the three alphas in an aligned arrangement. ©2015 American Physical SocietyThis work was partly supported by funds provided by DGI
of MINECO (Spain) under Contract No. FIS2011-23565.Peer Reviewe
Three-boson relativistic bound states with zero-range interaction
For the zero-range interaction providing a given mass M_2 of the two-body
bound state, the mass M_3 of the relativistic three-boson state is calculated.
We have found that the three-body system exists only when M_2 is greater than a
critical value M_c approximately 1.43 m (m is the constituent mass). For
M_2=M_c the mass M_3 turns into zero and for M_2<M_c there is no solution with
real value of M_3.Comment: 7 pages, 4 figure
Anatomy of three-body decay III. Energy distributions
We address the problem of calculating momentum distributions of particles
emerging from the three-body decay of a many-body resonance. We show that these
distributions are determined by the asymptotics of the coordinate-space
complex-energy wave-function of the resonance. We use the hyperspherical
adiabatic expansion method where all lengths are proportional to the
hyperradius. The structures of the resonances are related to different decay
mechanisms. For direct decay all inter-particle distances increase proportional
to the hyperradius at intermediate and large distances. Sequential three-body
decay proceeds via spatially confined quasi-stationary two-body configurations.
Then two particles remain close while the third moves away. The wave function
may contain mixtures which produce coherence effects at small distances, but
the energy distributions can still be added incoherently. Two-neutron halos are
discussed in details and illustrated by the resonance in He. The
dynamic evolution of the decay process is discussed.Comment: 30 pages, 8 figures, to be published in Nuclear Physics
Three-Body Halos. II. from Two- to Three-Body Asymptotics
The large distance behavior of weakly bound three-body systems is
investigated. The Schr\"{o}dinger equation and the Faddeev equations are
reformulated by an expansion in eigenfunctions of the angular part of a
corresponding operator. The resulting coupled set of effective radial equations
are then derived. Both two- and three-body asymptotic behavior are possible and
their relative importance is studied for systems where subsystems may be bound.
The system of two nucleons outside a core is studied numerically in detail and
the character of possible halo structure is pointed out and investigated.Comment: 16 pages, compressed and uuencoded PosrScript file, IFA-94/3
Three-body halos. V. Computations of continuum spectra for Borromean nuclei
We solve the coordinate space Faddeev equations in the continuum. We employ
hyperspherical coordinates and provide analytical expressions allowing easy
computation of the effective potentials at distances much larger than the
ranges of the interactions where only s-waves in the different Jacobi
coordinates couple. Realistic computations are carried out for the Borromean
halo nuclei 6He (n+n+\alpha) for J\pi = 0+-, 1+-, 2+- and 11Li (n+n+9Li) for
(1/2)+-, (3/2)+-, (5/2)+-. Ground state properties, strength functions, Coulomb
dissociation cross sections, phase shifts, complex S-matrix poles are computed
and compared to available experimental data. We find enhancements of the
strength functions at low energies and a number of low-lying S-matrix poles.Comment: 35 pages, 14 figure
Comment on "New modes of halo excitations in the 6He nucleus"
We try to explain the differences in the 6He dipole strength function in
refs. [1] and [2]. We perform the full basis calculation of the strength
function with the same renormalized interaction as in [1] and show that the
size of the basis, needed for converged calculations of the 6He continuum
spectrum, is much larger than that for the discrete spectrum. The renormalized
interaction of [1] therefore cannot be used for the continuum spectrum
calculations with the same basis as for the ground state.Comment: 2 pages, 3 figure
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