We present a calculation of the giant dipole resonance in 16O based on a nucleon-nucleon (NN) interaction from chiral e ective eld theory that reproduces NN scattering data with high accuracy. By ...merging the Lorentz integral transform and the coupled-cluster methods, we extend the previous theoretical limits for break-up observables in light nuclei with mass numbers (A ≤ 7), and address the collective giant dipole resonance of 16O. We successfully benchmark the new approach against virtually exact results from the hyperspherical harmonics method in 4He. Our results for 16O reproduce the position and the total strength (bremsstrahlung sum rule) of the dipole response very well. When compared to the cross section from photo-absorption experiments the theoretical curve exhibits a smeared form of the peak. The tail region between 40 and 100 MeV is reproduced within uncertainties.
Full text
Available for:
CMK, CTK, FMFMET, IJS, NUK, PNG, UM
What is the size of the atomic nucleus? This deceivably simple question is difficult to answer. Although the electric charge distributions in atomic nuclei were measured accurately already half a ...century ago, our knowledge of the distribution of neutrons is still deficient. In addition to constraining the size of atomic nuclei, the neutron distribution also impacts the number of nuclei that can exist and the size of neutron stars. We present an ab initio calculation of the neutron distribution of the neutron-rich nucleus Ca-48. We show that the neutron skin (difference between the radii of the neutron and proton distributions) is significantly smaller than previously thought. We also make predictions for the electric dipole polarizability and the weak form factor; both quantities that are at present targeted by precision measurements. Based on ab initio results for Ca-48, we provide a constraint on the size of a neutron star.
Full text
Available for:
IJS, NUK, SBMB, UL, UM, UPUK
A three-body force acting between the η-meson and two nucleons was overlooked inadvertently in the model description and discussion in the published version of our paper “Onset of η-nuclear binding ...in a pionless EFT approach” Phys. Lett. B 771 (2017) 297–302 while present in the actual numerical calculations. The stated conclusion that a stabilizing ηNN contact term was not needed is therefore incorrect. Such a three-body force, associated with a new low energy constant dηNNΛ, must be introduced at leading order to stabilize η-nucleus systems.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
.
Using the zero-range model, it was demonstrated recently that Levinger’s quasi-deuteron model can be utilized to extract the nuclear neutron-proton contact. Going beyond the zero-range ...approximation and considering the full nuclear contact formalism, we rederive here the quasi-deuteron model for the nuclear photoabsorption cross-section and utilize it to establish relations and constraints for the general contact matrix. We also define and demonstrate the importance of the diagonalized nuclear contacts, which can be also relevant to further applications of the nuclear contacts.
Full text
Available for:
DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Integral transform approaches are numerous in many fields of physics, but in most cases limited to the use of the Laplace kernel. However, it is well known that the inversion of the Laplace transform ...is very problematic, so that the function related to the physical observable is in most cases unaccessible. The great advantage of kernels of the bell-shaped form has been demonstrated in few-body nuclear systems. In fact the use of the Lorentz kernel has allowed us to overcome the stumbling block of the ab initio description of reactions to the full continuum of systems of more than three particles. The problem of finding kernels of similar form, applicable to many-body problems, deserves particular attention. If this search were successful, the integral transform approach might represent the only viable ab initio access to many observables that are not calculable directly.
OBJECTIVE: Velocardiofacial syndrome, caused by a deletion on chromosome 22q11.2, is often accompanied by cognitive, behavioral, and psychiatric impairments. Specifically, velocardiofacial syndrome ...has been proposed as a disease model for a genetically mediated subtype of schizophrenia. Velocardiofacial syndrome is also known to affect brain structure. The most prominent structural findings in velocardiofacial syndrome are reduced white matter volumes. However, the structure of white matter and extent of specific regional involvement in this syndrome have never been investigated. The current study used diffusion tensor imaging to investigate white matter structure in children and young adults with velocardiofacial syndrome. METHOD: Nineteen participants with velocardiofacial syndrome and 19 age- and gender-matched comparison subjects underwent diffusion-weighted magnetic resonance imaging scans. Whole brain voxel-by-voxel analyses were conducted to investigate white matter fractional anisotropy differences between the groups. RESULTS: Relative to the comparison group, the velocardiofacial syndrome group had reduced white matter anisotropy in the frontal, parietal, and temporal regions as well as in tracts connecting the frontal and temporal lobes. CONCLUSIONS: This study demonstrates that alterations of white matter tract structure occur in velocardiofacial syndrome. Reduced white matter anisotropy was observed in individuals with velocardiofacial syndrome in areas previously implicated in the neurocognitive phenotype of velocardiofacial syndrome. The finding of aberrant parietal white matter tracts as well as aberrant frontotemporal connectivity in velocardiofacial syndrome and in previous schizophrenia studies may be associated with increased vulnerability for development of psychotic symptoms.
PDF
