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High Energy / Nuclear Theory / RIKEN seminars

[NT/RIKEN seminar] Two-baryon interactions from lattice QCD

by Andrew Hanlon

US/Eastern
Description

It has been over three decades since the first two-baryon
studies from lattice QCD were performed. Despite algorithmic
improvements and increases in computational resources since then,
there remains disagreement on results from various groups in the
lattice community. A major barrier in resolving these discrepancies is
the poor signal-to-noise ratio for baryons, which needs to be overcome
with modern methods. In this seminar, I will begin by covering various
techniques and formalism that have become standard in lattice
spectroscopy. This will include the use of distillation (and its
stochastic variant) to treat all-to-all quark propagation; a
variational method, which can help to reduce unwanted excited states
while allowing for several desired states to be extracted; and the
L\"uscher two-particle formalism, which relates finite-volume energies
to infinite-volume scattering amplitudes. I will then present our
recent results for two nucleon S-wave interactions in both isospin
channels, computed at the SU(3)-flavor-symmetric point corresponding
to $m_\pi \approx 714$ MeV. These results strongly disfavor the
presence of any bound states at this pion mass, which contradicts some
of the calculations in the literature. Further, our recent results for
the $H$ dibaryon---also using an SU(3)-symmetric setup, but
corresponding to $m_\pi \approx 420$ MeV---show appreciable dependence
on the lattice spacing. This could explain some of the discrepancies
in the literature. However, I will discuss other possibilities, as
well as future directions for spectroscopy.