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Description
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. \red{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 with the charm quark mass, remains significant, highlighting the ongoing importance of the gluon in the realm of charmed baryon physics.