1,553 research outputs found
Renormalized QCD-inspired model for the pion and mesons
We apply the subtraction method to an effective QCD-inspired model, which
includes the Coulomb plus a zero-range hyperfine interactions, to define a
renormalized Hamiltonian for mesons. The spectrum of the renormalized
Hamiltonian agrees with the one obtained with a smeared hyperfine interaction.
The masses of the low-lying pseudo scalar and vector mesons are reasonably
described within the model.Comment: 5 pages, 3 figures, 5 references. To be published in Nucl. Phys. B
(Proc. Suppl.) Talk presented at the Workshop "Light-cone Physics: Particles
and Strings" at ECT* in Trento, Sep 3-11, 200
Absence of Cooper-type bound states in three- and few-electron systems
It is shown that the appearance of a fixed-point singularity in the kernel of
the two-electron Cooper problem is responsible for the formation of the Cooper
pair for an arbitrarily weak attractive interaction between two electrons. This
singularity is absent in the problem of three and few superconducting electrons
at zero temperature on the full Fermi sea. Consequently, such three- and
few-electron systems on the full Fermi sea do not form Cooper-type bound states
for an arbitrarily weak attractive pair interaction.Comment: 10 pages. Accepted in European Physical Journal
Radii in weakly-bound light halo nuclei
A systematic study of the root-mean-square distance between the constituents
of weakly-bound nuclei consisting of two halo neutrons and a core is performed
using a renormalized zero-range model. The radii are obtained from a universal
scaling function that depends on the mass ratio of the neutron and the core, as
well as on the nature of the subsystems, bound or virtual. Our calculations are
qualitatively consistent with recent data for the neutron-neutron
root-mean-square distance in the halo of Li and Be nuclei
Comment on "Efimov States and their Fano Resonances in a Neutron-Rich Nucleus"
By introducing a mass asymmetry in a non-Borromean three-body system, without
changing the energy relations, the virtual state pole cannot move from the
negative real axis of the complex energy plane (with nonzero width) and become
a resonance, because the analytical structure of the unitarity cuts remains the
same.Comment: To be published in PR
Solving the inhomogeneous Bethe-Salpeter Equation in Minkowski space: the zero-energy limit
For the first time, the inhomogeneous Bethe-Salpeter Equation for an
interacting system, composed by two massive scalars exchanging a massive
scalar, is numerically investigated in ladder approximation, directly in
Minkowski space, by using an approach based on the Nakanishi integral
representation. In this paper, the limiting case of zero-energy states is
considered, extending the approach successfully applied to bound states. The
numerical values of scattering lengths, are calculated for several values of
the Yukawa coupling constant, by using two different integral equations that
stem within the Nakanishi framework. Those low-energy observables are compared
with (i) the analogous quantities recently obtained in literature, within a
totally different framework and (ii) the non relativistic evaluations, for
illustrating the relevance of a non perturbative, genuine field theoretical
treatment in Minkowski space, even in the low-energy regime. Moreover,
dynamical functions, like the Nakanishi weight functions and the distorted part
of the zero-energy Light-front wave functions are also presented.
Interestingly, a highly non trivial issue related to the abrupt change in the
width of the support of the Nakanishi weight function, when the zero-energy
limit is approached, is elucidated, ensuring a sound basis to the forthcoming
evaluation of phase-shifts.Comment: 23 pages and 4 figures. Minor changes in the abstract, typos fixed
and added a figure. Submitted for publicatio
Charged three-body system with arbitrary masses near conformal invariance
Within an adiabatic approximation to the three-body Coulomb system, we study
the strength of the leading order conformaly invariant attractive dipole
interaction produced when a slow charged particle (with mass ) is
captured by the first excited state of a dimer [with individual masses and
charges ) and ()]. The approach leads to a universal
mass-charge critical condition for the existence of three-body level
condensation, , as well as the ratio between the geometrically scaled energy levels.
The resulting expressions can be relevant in the analysis of recent
experimental setups with charged three-body systems, such as the interactions
of excitons, or other matter-antimatter dimers, with a slow charged particle.Comment: 5 pages, 1 figure, to appear in Physical Review
Universal description of S-wave meson spectra in a renormalized light-cone QCD-inspired model
A light-cone QCD-inspired model, with the mass squared operator consisting of
a harmonic oscillator potential as confinement and a Dirac-delta interaction,
is used to study the S-wave meson spectra. The two parameters of the harmonic
potential and quark masses are fixed by masses of rho(770), rho(1450), J/psi,
psi(2S), K*(892) and B*. We apply a renormalization method to define the model,
in which the pseudo-scalar ground state mass fixes the renormalized strength of
the Dirac-delta interaction. The model presents an universal and satisfactory
description of both singlet and triplet states of S-wave mesons and the
corresponding radial excitations.Comment: RevTeX, 17 pages, 7 eps figures, to be published in Phys. Rev.
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