Lambda Zero

As a followup to the stability-island comment, leading up to the neutron-star level:

I had a thought that the Island might not exist, due to (recently-observed) neutron repulsion from the Argonne V18 model. Argonne are still in the news for testing magic-number nucleus collisions; there may not be a number past 126.

This assumed our fermions are all protons and neutrons, made up of Up- and Down-quarks and only these. But, as of 1947, we know of other quarks, starting with the Strange. A Strange-quark among the other two creates another sort of particle: the hyperon. These don't last long on their own, namely in the 10^-10 second range. But then neutrons don't last on their own either. In a nucleus the Strong Force might keep them longer.

A hyperon positively charged, and attached to some neutrons, can take on an electron and congratulations, you've now got an atom without a proton. Mostly the experiments are around a proton with a neutral hyperon − the Λ⁰ being stable-est here − and a neutron too, I guess to keep it all together. This enhanced deuterium is called Hypertriton.

Hypertriton is a project of current research in that, even if it's unstable in of itself, it might be like a miniature neutron star. Everything is so dense in those, that hyperons can last longer.

I presume that the Argonne team has already taken this into account. If neutrons repel each other in Strong interactions, the Λ⁰s will mutually repel harder. I assume a balancing-game here.