Origin of hadron spin based on Lattice QCD study on the charmed hadrons

TL;DR

This study uses lattice QCD to analyze the spin decomposition of charmed hadrons, revealing the roles of quark spins and gluon contributions, and providing insights into the relativistic effects in proton-like states.

Contribution

First lattice QCD calculation of charmed hadron spin decomposition using overlap fermions on 2+1 flavor configurations, highlighting relativistic effects and gluon contributions.

Findings

Quark spin contributions are comparable to non-relativistic quark model expectations.

Relativistic effects mainly cause the non-trivial proton spin decomposition.

Gluon angular momentum remains significant in triple heavy quark states.

Abstract

We perform the first Lattice calculation about the charmed hadron spin decomposition using overlap fermions on a 2+1 flavor RBC/UKQCD domain-wall gauge configurations at 0.083 fm with 300 MeV pion mass. It is found that the contributions of quark spin to the spin of 1S, 1P charmonia and also proton-like triple heavy quark state are comparable with the expectation of non-relativistic quark model. Such an observation provides evidence that the non-triviality of proton spin decomposition mainly arises from the relativistic effects of the light quark. Conversely, the substantial gluon angular momentum contribution in the spin $(1/2)^+$ state with triple heavy quarks at the charm quark mass, remains significant, highlighting the ongoing importance of the gluon in the realm of charmed baryon physics.