We perform a systematic study of the α-particle excitation from its ground state 0_{1}^{+} to the 0_{2}^{+} resonance. The so-called monopole transition form factor is investigated via an electron ...scattering experiment in a broad Q^{2} range (from 0.5 to 5.0 fm^{-2}). The precision of the new data dramatically supersedes that of older sets of data, each covering only a portion of the Q^{2} range. The new data allow the determination of two coefficients in a low-momentum expansion, leading to a new puzzle. By confronting experiment to state-of-the-art theoretical calculations, we observe that modern nuclear forces, including those derived within chiral effective field theory that are well tested on a variety of observables, fail to reproduce the excitation of the α particle.
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CMK, CTK, FMFMET, IJS, NUK, PNG, UL, UM
The possibility to resolve narrow structures in reaction cross sections in calculations with the Lorentz integral-transform (LIT) method is studied. To this end we consider a fictitious two-nucleon ...problem with a low-lying and narrow resonance in the
3
P
1
nucleon-nucleon partial wave and calculate the corresponding “deuteron photoabsorption cross section”. In the LIT method the use of continuum wave functions is avoided and one works instead with a localized function
. In this case study it is investigated how far into the asymptotic region
has to be determined in order to obtain a precise resolution of the artificially introduced
E
1 resonance. Comparing with the results of a conventional calculation with explicit neutron-proton continuum wave functions it is shown that the LIT approach leads to an excellent reproduction of the cross section in the resonance region and of further finer cross-section details at higher energies. To this end, however, for
one has to take into account two-nucleon distances up to at least 30 fm.
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The Non-Symmetrized Hyperspherical Harmonics method (NSHH) is introduced in the hypernuclear sector and benchmarked with three different ab-initio methods, namely the Auxiliary Field Diffusion Monte ...Carlo method, the Faddeev–Yakubovsky approach and the Gaussian Expansion Method. Binding energies and hyperon separation energies of three- to five-body hypernuclei are calculated by employing the two-body
Λ
N
component of the phenomenological Bodmer–Usmani potential (Bodmer and Usmani in Nucl Phys A 477:621,
1988
; Usmani and Khanna in J Phys G 35:025105,
2008
), and a hyperon-nucleon interaction (Hiyama et al. in Phus Rev C 65:011301,
2001
) simulating the scattering phase shifts given by NSC97f (Rijken et al. in Phys Rev C 59:21,
1999
). The range of applicability of the NSHH method is briefly discussed.
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In the Standard Solar Model a central role in the nucleosynthesis is played by reactions of the kind , which enter the proton-proton chains. These reactions can also be studied through the inverse ...photodisintegration reaction. One option is to use the Lorentz Integral Transform approach, which transforms the continuum problem into a bound state-like one. A way to check the reliability of such methods is a direct calculation, for example using the Kohn Variational Principle to obtain the scattering wave function and then directly calculate the response function of the reaction.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
We have adapted the non-symmetrized hyperspherical harmonics method (NSHH) in order to treat light hypernuclei. In the past the method has been applied in the atomic and nuclear context dealing with ...identical particle systems exclusively. We have generalized and optimized the formalism in presence of two different species of particles, namely nucleons and hyperons. Preliminary benchmark results with a modern realistic 2-body nucleon-hyperon interaction are provided.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
A different formulation of the effective interaction hyperspherical harmonics (EIHH) method, suitable for non-local potentials, is presented. The EIHH method for local interactions is first shortly ...reviewed to point out the problems of an extension to non-local potentials. A viable solution is proposed and, as an application, results on the ground-state properties of 4- and 6-nucleon systems are presented. One finds a substantial acceleration in the convergence rate of the hyperspherical harmonics series. Perspectives for an application to scattering cross sections, via the Lorentz transform method are discussed.
The Lorentz integral transform method is briefly reviewed. The issue of the inversion of the transform, and in particular its ill-posedness, is addressed. It is pointed out that the mathematical term
...ill-posed
is misleading and merely due to a historical misconception. In this connection standard regularization procedures for the solution of the integral transform problem are presented. In particular a recent one is considered in detail and critical comments on it are provided. In addition a general remark concerning the concept of the Lorentz integral transform as a method with a
controlled resolution
is made.
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