We report results from a study of the spin and parity of ${\mathrm{\Xi }}_c(2970{)}^{+}$ using a $980{\mathrm{fb}}^{-1}$ data sample collected by the Belle detector at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider. The decay angle distributions in the chain ${\mathrm{\Xi }}_c(2970{)}^{+}\to {\mathrm{\Xi }}_c(2645{)}^0{\pi }^{+}\to {\mathrm{\Xi }}_c^{+}{\pi }^{-}{\pi }^{+}$ are analyzed to determine the spin of this charmed-strange baryon. The angular distributions strongly favor the ${\mathrm{\Xi }}_c(2970{)}^{+}$ spin $J=1/2$ over $3/2$ or $5/2$, under an assumption that the lowest partial wave dominates in the decay. We also measure the ratio of ${\mathrm{\Xi }}_c(2970{)}^{+}$ decay branching fractions $R=\mathcal{B}[{\mathrm{\Xi }}_c(2970{)}^{+}\to {\mathrm{\Xi }}_c(2645{)}^0{\pi }^{+}]/\mathcal{B}[{\mathrm{\Xi }}_c(2970{)}^{+}\to {\mathrm{\Xi }}_c^{\prime 0}{\pi }^{+}]=1.67\pm 0.29{(\mathrm{stat})}_{-0.09}^{+0.15}(\mathrm{syst})\pm 0.25(\mathrm{IS})$, where the last uncertainty is due to possible isospin-symmetry-breaking effects. This $R$ value favors the spin-parity $J^P=1/2^{+}$ with the spin of the light-quark degrees of freedom $s_l=0$. This is the first determination of the spin and parity of a charmed-strange baryon.

• Received 2 August 2020
• Accepted 12 May 2021

DOI:https://doi.org/10.1103/PhysRevD.103.L111101

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Published by the American Physical Society