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First Determination of the Spin-Parity of Ξ𝑐(3055)+,0 Baryons
The Ξ0(−)𝑏→Ξ𝑐(3055)+(0)(→𝐷+(0)Λ)𝜋− decay chains are observed, and the spin-parity of Ξ𝑐(3055)+(0) baryons is determined for the first time. The measurement is performed using proton-proton collision data at a center-of-mass energy of √𝑠 =13 TeV, corresponding to an integrated luminosity of 5.4 fb−1, recorded by the LHCb experiment between 2016 and 2018. The spin-parity of the Ξ𝑐(3055)+(0) baryons is determined to be 3/2+ with a significance of more than 6.5𝜎 (3.5𝜎) compared to all other tested hypotheses. The up-down asymmetries of the Ξ0(−)𝑏→Ξ𝑐(3055)+(0)𝜋− transitions are measured to be −0.92±0.10±0.05 (−0.92±0.16±0.22), consistent with maximal parity violation, where the first uncertainty is statistical and the second is systematic. These results support the hypothesis that the Ξ𝑐(3055)+(0) baryons correspond to the first 𝐷-wave 𝜆-mode excitation of the Ξ𝑐 flavor triplet.