Diquark properties from full QCD lattice simulations

Abstract

We study diquarks on the lattice in the background of a static quark, in a gauge-invariant formalism with quark masses down to almost physical mπ. We determine mass differences between diquark channels as well as diquark-quark mass differences. The lightest and next-to-lightest diquarks have “good” scalar, $$ {\overline{3}}_F $$ 3 ¯ F , $$ {\overline{3}}_c $$ 3 ¯ c , JP = 0+, and “bad” axial vector, 6F, $$ {\overline{3}}_c $$ 3 ¯ c , JP = 1+, quantum numbers, and a bad-good mass difference for ud flavors, 198(4) MeV, in excellent agreement with phenomenological determinations. Quark-quark attraction is found only in the “good” diquark channel. We extract a corresponding diquark size of ∼ 0.6 fm and perform a first exploration of the “good” diquark shape, which is shown to be spherical. Our results provide quantitative support for modeling the low-lying baryon spectrum using good light diquark effective degrees of freedom.

Good and bad diquark properties and spatial correlations in lattice QCD

“…Further details and supporting studies that go beyond the scope of this contribution can found in Ref. [16]. The results shown here were taken from this main reference.…”

“…not gauge-invariant, and the lattice cannot access them directly. In this contribution, based on the work of [16], we address this issue by forming gauge-invariant probes of diquark properties through embedding them in hadrons that contain in addition a single static quark. The mass of this infinitely heavy quark cancels exactly in mass differences.…”

Shapes and sizes of diquarks in lattice QCD

“…Further details and supporting studies that go beyond the scope of this contribution can found in [19]. The results shown here were taken from this main reference.…”

“…We also compare with new quenched simulations with a valence pion mass 𝑚 𝑣 𝜋 = 909 MeV. All reported results are based on [19].…”