First determination of the spin and parity of the charmed-strange baryon ?c (2970)+

Abstract

We report results from a study of the spin and parity of ?c(2970)+ using a 980 fb-1 data sample collected by the Belle detector at the KEKB asymmetric-energy e+e- collider. The decay angle distributions in the chain ?c(2970)+??c(2645)0?+??c+?-?+ are analyzed to determine the spin of this charmed-strange baryon. The angular distributions strongly favor the ?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 ?c(2970)+ decay branching fractions R=B[?c(2970)+??c(2645)0?+]/B[?c(2970)+??c?0?+]=1.67�0.29(stat)-0.09+0.15(syst)�0.25(IS), where the last uncertainty is due to possible isospin-symmetry-breaking effects. This R value favors the spin-parity JP=1/2+ with the spin of the light-quark degrees of freedom sl=0. This is the first determination of the spin and parity of a charmed-strange baryon. � 2021 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the "https://creativecommons.org/licenses/by/4.0/"Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by SCOAP3.