Investigation on the $\Omega(2012)$ from QCD sum rules

Abstract

We study the recently observed $\Omega(2012)$ baryon in QCD sum rules. We construct the $P$-wave $\Omega$ baryon currents with a covariant derivative, and perform spin projection to obtain the currents with total spin 1/2 and 3/2. We then apply the parity-projected QCD sum rules to separate the contributions of the positive and negative parity states. We extract the masses of $J^P = 1/2^-$ and $3/2^-$ states to be $M_{1/2^-} = 2.07^{+0.07}_{-0.07}{\rm~GeV}$ and $M_{3/2^-} = 2.05^{+0.09}_{-0.10}{\rm~GeV}$. Both results are in good agreement with the experimental result. Therefore, it is likely that the $\Omega(2012)$ is a negative parity state, which is interpreted as a $P$-wave excited state in the quark model. However, its spin is not determined in the present analysis, which can be done by detailed study on its decay properties.