Speaker
Dr
Lorenzo Contessi
(Racah Institute of Physics, The Hebrew University, Jerusalem, Israel)
Description
We present an effective field theory (EFT) at leading order to describe light single-$\Lambda$ hypernuclei [1].
Owing to the weak $\Lambda$ binding and to the $\Lambda$-n short interaction range, meson exchange forces are approximated by contact interactions within a pion-less EFT where the only degrees of freedom are baryons.
At leading order the theory contains both 2-body (singlet and triplet) and three 3-body interactions, a total of 5 terms associated with 5 coupling strengths or low energy constants (LECs).
We adjust the 2-body LECs from available data that constrain the $\Lambda$-n scattering lengths.
Because of the limited 3-body data, both 3-body and 4-body hypernuclear binding energies and excitation energies are used to adjust the 3-body LECs.
To calculate the binding energies for the A-body systems with A>2, we have expanded the wave-function using a Gaussian basis. The stochastic variational method was employed to select the non-linear parameters.
The resulting EFT is then applied to calculate the $\Lambda$ binding energy in
$ ^5 \Lambda $He, where the adjusted 3-body interactions largely resolve the known overbinding problem of $ ^5 _\Lambda $He [2].
[1] L. Contessi, N. Barnea, A. Gal (in preparation).
[2] R.H. Dalitz, R.C. Herndon, Y.C. Tang, Nucl. Phys. B 47 (1972) 109.
Primary author
Dr
Lorenzo Contessi
(Racah Institute of Physics, The Hebrew University, Jerusalem, Israel)
Co-authors
Prof.
Avraham Gal
(Racah Institute of Physics, The Hebrew University, Jerusalem, Israel)
Prof.
Nir Barnea
(Racah Institute of Physics, The Hebrew University, Jerusalem, Israel)
