Di-nucleons do not form bound states at heavy pion mass

TL;DR

This study uses advanced lattice QCD techniques at a heavy pion mass to show that di-nucleons do not form bound states, challenging previous claims of bound di-nucleons in similar conditions.

Contribution

The paper provides the first high-statistics lattice QCD calculation at heavy pion mass that conclusively rules out bound di-nucleons, addressing discrepancies in earlier studies.

Findings

No bound di-nucleons in isospin 0 and 1 channels.

Hexaquark operators do not influence the spectrum.

HAL QCD potential aligns with no bound states.

Abstract

We perform a high-statistics lattice QCD calculation of the low-energy two-nucleon scattering amplitudes. In order to address discrepancies in the literature, the calculation is performed at a heavy pion mass in the limit that the light quark masses are equal to the physical strange quark mass, $m_\pi = m_K \simeq 714 $ MeV. Using a state-of-the-art momentum space method, we rule out the presence of a bound di-nucleon in both the isospin 0 (deuteron) and 1 (di-neutron) channels, in contrast with many previous results that made use of compact hexaquark creation operators. In order to diagnose the discrepancy, we add such hexaquark interpolating operators to our basis and find that they do not affect the determination of the two-nucleon finite volume spectrum, and thus they do not couple to deeply bound di-nucleons that are missed by the momentum-space operators. Further, we perform a high-statistics calculation of the HAL QCD potential on the same gauge ensembles and find qualitative agreement with our main results. We conclude that di-nucleons do not form bound states at heavy pion masses and that previous identification of deeply bound di-nucleons must have arisen from a misidentification of the spectrum from off-diagonal elements of a correlation function.