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Register a new userTwo- and three-alpha systems with nonlocal potential
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Two body data alone cannot determine the potential uniquely, one needs three-body data as well. A method is presented here which simultaneously fits local or nonlocal potentials to two-body and three-body observables. The interaction of composite particles, due to the Pauli effect and the indistinguishability of the constituent particles, is genuinely nonlocal. As an example, we use a Pauli-correct nonlocal fish-bone type optical model for the $alpha-alpha$ potential and derive the fitting parameters such that it reproduces the two-$alpha$ and three-$alpha$ experimental data.
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We elucidate the fate of neighboring two and three-$alpha$ particles in cold neutron matter by focusing on an analogy between such $alpha$ systems and Fermi polarons realized in ultracold atoms. We describe in-medium excitation properties of an $alpha$ particle and neutron-mediated two- and three-$alpha$ interactions using theoretical approaches developed for studies of cold atomic systems. We numerically solve the few-body Schrodinger equation of $alpha$ particles within standard $alpha$ cluster models combined with in-medium properties of $alpha$ particles. We point out that the resultant two-$alpha$ ground state and three-$alpha$ first excited state, which correspond to $^8$Be and the Hoyle state, respectively, known as main components in the triple-$alpha$ reaction, can become bound states in such a many-neutron background although these states are unstable in vacuum. Our results suggest a significance of these in-medium cluster states not only in astrophysical environments such as core-collapsed supernova explosions and neutron star mergers but also in neutron-rich nuclei.
The fishbone potential of composite particles simulates the Pauli effect by nonlocal terms. We determine the $alpha-alpha$ fishbone potential by simultaneously fitting to two-$alpha$ resonance energies, experimental phase shifts and three-$alpha$ binding energies. We found that essentially a simple gaussian can provide a good description of two-$alpha$ and three-$alpha$ experimental data without invoking three-body potentials.
In this talk we show recent developments on few body systems involving mesons. We report on an approach to Faddeev equations using chiral unitary dynamics, where an explicit cancellation of the two body off shell amplitude with three body forces stemming from the same chiral Lagrangians takes place. This removal of the unphysical off shell part of the amplitudes is most welcome and renders the approach unambiguous, showing that only on shell two body amplitudes need to be used. Within this approach, systems of two mesons and one baryon are studied, reproducing properties of the low lying $1/2^+$ states. On the other hand we also report on multirho and $K^*$ multirho states which can be associated to known meson resonances of high spin.
We present a complete calculation of nucleon-deuteron scattering as well as ground and low-lying excited states of light nuclei in the mass range A=3-16 up through next-to-next-to-leading order in chiral effective field theory using semilocal coordinate-space regularized two- and three-nucleon forces. It is shown that both of the low-energy constants entering the three-nucleon force at this order can be reliably determined from the triton binding energy and the differential cross section minimum in elastic nucleon-deuteron scattering. The inclusion of the three-nucleon force is found to improve the agreement with the data for most of the considered observables.
The fishbone potential of composite particles simulates the Pauli effect by nonlocal terms. We determine the $n-alpha$ and $p-alpha$ fish-bone potential by simultaneously fitting to the experimental phase shifts. We found that with a double Gaussian parametrization of the local potential can describe the $n-alpha$ and $p-alpha$ phase shifts for all partial waves.
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