The strangest lifetime: A bizarre story of $\tau(\Omega_c^0)$

Abstract

For a long time it has been established both experimentally and theoretically that $\Omega_c^0$ is shortest-lived among the four singly charmed baryons which decay weakly. The situation was dramatically changed in 2018 when LHCb reported a new measurement of the $\Omega_c^0$ lifetime using semileptonic $b$-hadron decays. The value is nearly four times larger than the previous world average of $\tau(\Omega_c^0)$ and it is confirmed by the most recent LHCb measurement with the prompt production. In this viewpoint article, we review the status and point out that heavy quark expansion (HQE) fails to apply to $\Omega_c^0$ to the order of $1/m_c^4$. By demanding a sensible HQE for $\Omega_c^0$ will lead to a lifetime of $\Omega_c^0$ longer than $\Lambda_c^+$.