75 research outputs found
ARIEL experiments and theory
I present an overview of experiments at TRIUMF ARIEL and ISAC facilities
covering both the current and the future envisioned programs. I also briefly
review theory program at TRIUMF that relates to the ARIEL experimental program.
I highlight several recent experimental results from the nuclear astrophysics,
nuclear structure, fundamental symmetries, and the sterile neutrino search.
Finally, I mention ongoing theoretical ab initio calculations of the proton
capture on 7Li related to the X17 boson observation.Comment: Contribution to proceedings of the workshop New Scientific
Opportunities with the TRIUMF ARIEL e-linac, 10 pages, 5 figure
Ab initio description of the exotic unbound 7He nucleus
The neutron rich exotic unbound 7He nucleus has been the subject of many
experimental investigations. While the ground-state 3/2- resonance is well
established, there is a controversy concerning the excited 1/2- resonance
reported in some experiments as low-lying and narrow (E_R ~ 1 MeV, Gamma < 1
MeV) while in others as very broad and located at a higher energy. This issue
cannot be addressed by ab initio theoretical calculations based on traditional
bound-state methods. We introduce a new unified approach to nuclear bound and
continuum states based on the coupling of the no-core shell model, a
bound-state technique, with the no-core shell model/resonating group method, a
nuclear scattering technique. Our calculations describe the ground-state
resonance in agreement with experiment and, at the same time, predict a broad
1/2- resonance above 2 MeV.Comment: 5 pages, 3 figure
Unified ab initio approach to bound and unbound states: no-core shell model with continuum and its application to 7He
We introduce a unified approach to nuclear bound and continuum states based
on the coupling of the no-core shell model (NCSM), a bound-state technique,
with the no-core shell model/resonating group method (NCSM/RGM), a nuclear
scattering technique. This new ab initio method, no-core shell model with
continuum (NCSMC), leads to convergence properties superior to either NCSM or
NCSM/RGM while providing a balanced approach to different classes of states. In
the NCSMC, the ansatz for the many-nucleon wave function includes: i) a
square-integrable A-nucleon component expanded in a complete harmonic
oscillator basis; ii) a binary-cluster component with asymptotic boundary
conditions that can properly describe weakly-bound states, resonances and
scattering; and, in principle, iii) a three-cluster component suitable for the
description of, e.g., Borromean halo nuclei and reactions with final three-body
states. The Schroedinger equation is transformed into a system of
coupled-channel integral-differential equations that we solve using a modified
microscopic R-matrix formalism within a Lagrange mesh basis. We demonstrate the
usefulness of the approach by investigating the unbound 7He nucleus.Comment: 16 pages, 10 figure
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