123 research outputs found
Resonances and final state interactions in the reaction pp->pK^+Lambda
A study of the strangeness production reaction pp->pK^+Lambda for excess
energies of epsilon \le 150 MeV, accessible at high-luminosity accelerator
facilities like COSY, is presented. Methods to analyze the Dalitz plot
distribution and angular spectra in the Jackson and helicity frames are worked
out and suitable observables for extracting information on low lying resonances
that couple to the K-Lambda system and for determining the Lambda-p
effective-range parameters from the final state interaction are identified and
discussed. Furthermore, the chances for identifying the reaction mechanism of
strangeness production are investigated.Comment: 16 pages, 16 figure
Implications for (d,p) reaction theory from nonlocal dispersive optical model analysis of Ca(d,p)Ca
The nonlocal dispersive optical model (NLDOM) nucleon potentials are used for
the first time in the adiabatic analysis of a (d,p) reaction to generate
distorted waves both in the entrance and exit channels. These potentials were
designed and fitted by Mahzoon [Phys. Rev. Lett. 112, 162502
(2014)] to constrain relevant single-particle physics in a consistent way by
imposing the fundamental properties, such as nonlocality, energy-dependence and
dispersive relations, that follow from the complex nature of nuclei. However,
the NLDOM prediction for the Ca(d,p)Ca cross sections at low
energy, typical for some modern radioactive beam ISOL facilities, is about
70 higher than the experimental data despite being reduced by the NLDOM
spectroscopic factor of 0.73. This overestimation comes most likely either from
insufficient absorption or due to constructive interference between ingoing and
outgoing waves. This indicates strongly that additional physics arising from
many-body effects is missing in the widely used current versions of (d,p)
reaction theories.Comment: 14 pages, 15 figure
Hyperspherical cluster model for bosons: application to sub-threshold halo states in helium drops
To describe long-range behaviour of one particle removed from a few- or a
many-body system, a hyperspherical cluster model has been developed. It has
been applied to the ground and first excited states of helium drops with five,
six, eight and ten atoms interacting via a two-body soft gaussian potential.
Convergence of the hyperspherical cluster harmonics expansion is studied for
binding energies, root-mean-squared radii and overlaps of the wave functions of
two helium drops differing by one atom. It was shown that with increasing model
space the functional form of such overlaps at large distances converges to the
correct asymptotic behaviour. The asymptotic normalization coefficients that
quantify the overlaps' amplitudes in this region are calculated. It was also
shown that in the first excited state one helium atom stays far apart from the
rest forming a two-body molecule, or a halo. The probability of finding the
halo atom in the classically-forbidden region of space depends on the
definition of the latter and on the number of atoms in the drop. The total norm
of the overlap integrals, the spectroscopic factor, represents the number of
partitions of a many-body state into a chosen state of the system with one
particle removed. The spectroscopic factors have been calculated and their sum
rules are discussed giving a further insight into the structure of helium
drops.Comment: Accepted for publication in Few-Body System
Modelling overlap functions for one-nucleon removal: role of the effective three-nucleon force
One-nucleon overlap functions, needed for nucleon-removal reaction
calculations, are solutions of an inhomogeneous equation with the source term
defined by the wave functions of the initial and final nuclear states and
interaction between the removed nucleon with the rest. The source term approach
(STA) allows the overlaps with correct asymptotic decrease to be modelled while
using nuclear many-body functions calculated in minimal model spaces. By
properly choosing the removed nucleon interaction the minimum-model-space STA
can reproduce reduced values of spectroscopic factors extracted from
nucleon-removal reactions and predicts isospin asymmetry in the spectroscopic
factor reduction. It is well-known that model space truncation leads to the
appearance of higher-order induced forces, with three-nucleon force being the
most important. In this paper the role of such a force on the source term
calculation is studied. Applications to one-nucleon removal from double-magic
nuclei show that three-nucleon force improves the description of available
phenomenological overlap functions and reduces isospin asymmetry in
spectroscopic factors.Comment: Accepted for publication in Journal of Physics
- …