[Triumf-seminars] TRIUMF Nuclear Physics Seminar today at 15:30

[TRIUMF Seminars]

Date/Time: Mon 2016-11-14 at 15:30

Location:  Auditorium          

Speaker:   S. Ragnar Stroberg + Jack Henderson (TRIUMF)

Title:     Ab initio treatment of collective observables  +  Mirror symmetry in the lower sd-shell studied through transition strengths

Abstract: One challenging aspect of low energy nuclear structure is the coexistence of single-particle and collective degrees of freedom. The connection between these two complimentary pictures is somewhat understood at a qualitative phenomenological level. However, a quantitative connection has thus far proved elusive. An important point of connection between collective/single-particle motion is that of electric quadrupole transitions, which can be highly collective (10-100 times the single-particle estimate). These collective transitions are reasonably well described in the phenomenological shell  model by the introduction of effective charges, suggesting that most of the effects of the collective excitation can be incorporated by the renormalization of the nucleon charge. I will discuss current efforts towards explicitly performing this renormalization ab initio, with no input parameters. As an example application, I will discuss results relevant to recent measurements made at TRIUMF. 
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The concept of isospin symmetry is rooted in the fact that, once Coulomb effects are accounted for, the nuclear force is broadly independent of the isospin of the particles involved, i.e. whether they are protons or neutrons. This effect can be seen in the symmetry between energy levels in mirror nuclei (nuclei in which the numbers of protons and neutrons are inverted). A more complete investigation of isospin symmetry requires the observation of reduced transition probabilities, in particular B(E2) values for transitions within mirror nuclei. I will present preliminary results from recent experiments performed at TRIUMF, utilizing Coulomb excitation reactions to determine reduced transition probabilities in neutron-deficient magnesium isotopes..

Theory+Experiment Progess Reports

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General TRIUMF seminar information available at http://www.triumf.ca/home/upcoming-events/about-seminars-lectures