[Triumf-seminars] TRIUMF Seminar today at 15:00

Tue, 7 Sep 2004 05:00:00 -0700

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Date/Time: Tue 2004-09-07 at 15:00

Location:  Auditorium          

Speaker:   Ken Amos (School of Physics, University of Melbourne)

Title:     Probing the structure of radioactive ion beams (RIBS)

Abstract: Increasingly, exotic nuclei are being formed as RIBs with which their properties and reactions with other nuclei can be studied; properties and processes which are of import in cosmology and nuclear astrophysics. Of course they are inherently of interest with the possibilities of new forms of nuclear structure. Because the effective interactions between an external nucleon and one bound within nuclear matter now are reasonably established, and in the absence (as yet) of electron scattering from such exotic nuclei, the scattering of RIBs from hydrogen is a prime way to probe the matter profiles of those nuclei. But to do so credible scattering theory must be established. In this talk I will present two such with applications primarily to elastic scattering. 
1. MCAS, a multi-channel algebraic scattering theory which is suitable to analyze low energy scattering. This theory produces scattering that includes compound resonances on a smooth but energy dependent background and, as well, determines all sub-threshold bound states of the compound nucleus. The implementation ensures that all states and resonances within the chosen energy regime are found and that the Pauli exclusion principle is adequately taken into account. Examples of scattering of 12C and of 6He will be shown.
2. the g-folding optical potential for elastic scattering. With this approach, cross sections and spin observables for nucleon-nucleus scattering in the range 25 to 250 MeV have been predicted. Fits to data show a sensitivity to the matter profile of thhe nucleus, and in particular to the neutron matter distribution. Such data analysis is convincing evidence that the neutron skin thickness of 208Pb is 0.17+-0.02fm., and that 6He and 11Li have extended neutron distributions (halos) while 8He and 9Li do not.

Stimulants available 15 minutes before the talk.

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