30 research outputs found
Singlet Deuteron, Dineutron and Neutral Nuclei
The existence of the dineutron was predicted over 70 years ago. At present, a
number of experimental works confirm this assumption. By virtue of the
principle of isotopic invariance, a singlet deuteron must also exist. The
possibility of describing the neutron-proton interaction in the state at low
energies as the excitation of a quasi-stationary level (singlet deuteron) lying
below the deuteron decay threshold is discussed. The position, neutron and
radiative widths of the level are determined by the scattering length, the
effective radius, and the cross section for the radiative capture of neutrons
by protons. Experiments to search for this level are discussed. The discovery
of the singlet deuteron would be confirmation of the existence of the
dineutron
Precision Measurement of the n-3He Incoherent Scattering Length Using Neutron Interferometry
We report the first measurement of the low-energy neutron-He incoherent
scattering length using neutron interferometry: fm. This is in good agreement with a
recent calculation using the AV18+3N potential. The neutron-He scattering
lengths are important for testing and developing nuclear potential models that
include three nucleon forces, effective field theories for few-body nuclear
systems, and neutron scattering measurements of quantum excitations in liquid
helium. This work demonstrates the first use of a polarized nuclear target in a
neutron interferometer.Comment: 4 figure
Nuclear Reaction Network for Primordial Nucleosynthesis: a detailed analysis of rates, uncertainties and light nuclei yields
We analyze in details the standard Primordial Nucleosynthesis scenario. In
particular we discuss the key theoretical issues which are involved in a
detailed prediction of light nuclide abundances, as the weak reaction rates,
neutrino decoupling and nuclear rate modeling. We also perform a new analysis
of available data on the main nuclear processes entering the nucleosynthesis
reaction network, with particular stress on their uncertainties as well as on
their role in determining the corresponding uncertainties on light nuclide
theoretical estimates. The current status of theoretical versus experimental
results for 2H, 3He, 4He and 7Li is then discussed using the determination of
the baryon density as obtained from Cosmic Microwave Background anisotropies.Comment: LaTeX, 83 pages, 30 .pdf figures. Some typos in the units of
R-functions in appendix D and relative plots fixe