Speaker
Description
In few-nucleon systems, the transition-density formalism is highly efficient
to compute interactions with perturbative probes. One- and two-body
transition densities that encode the nuclear structure of the target are
evaluated once and stored for one nucleus. They are then convoluted with an
interaction kernel to produce observables. The same densities can be used with
different kernels. This method exploits factorisation between nuclear
structure and interaction kernel in Chiral EFT. It takes full advantage of the
numerical power of modern few-nucleon methods, is markedly more computationally
efficient and applicable to a wide array of nuclei and reactions. In this
contribution, the formalism is first introduced and then applied to present
the first theory description of 4He Compton scattering. It uses the same
Compton kernels familiar from proton, deuteron and 3He Compton scattering in
Chiral Effective Field Theory with explicit Delta degrees of freedom,
applicable between about 50 and 130MeV. The result compares well to
data from HI$\gamma$S, MAXlab and Illinois. We also address the sensitivity
of cross section and beam asymmetry on the (static) scalar-isoscalar
polarisabilities of the nucleon which parametrise the stiffness of charge
distributions against deformations. The project is part of the synergetic
international effort of experimentalists and theorists in Compton scattering
on one- and few-nucleon systems.
Work in collaboration with J.~A.~McGovern (U.~of Manchester), A.~Nogga (FZ
J\"ulich) and D.~R.~Phillips (Ohio U.).
| Parallel Session | Few-Body Systems |
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