13 research outputs found
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
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
Computation of the winding number diffusion rate due to the cosmological sphaleron
A detailed quantitative analysis of the transition process mediated by a
sphaleron type non-Abelian gauge field configuration in a static Einstein
universe is carried out. By examining spectra of the fluctuation operators and
applying the zeta function regularization scheme, a closed analytical
expression for the transition rate at the one-loop level is derived. This is a
unique example of an exact solution for a sphaleron model in spacetime
dimensions.Comment: Some style corrections suggested by the referee are introduced
(mainly in Sec.II), one reference added. To appear in Phys.Rev.D 29 pages,
LaTeX, 3 Postscript figures, uses epsf.st