Measurement of masses of the Ξc(2645) and Ξc(2815) baryons and observation of Ξc(2980)→Ξc(2645)π

We report a precise measurement of the masses of the Xi(c)(2645) and Xi(c)(2815) baryons using a data sample of 414 fb(-1) collected by the Belle Collaboration at the KEKB e(+)e(-) collider. The states Xi(c)(2645)(0,+) are observed in the Xi(+.0)(c)pi(-.+) decay modes, while the Xi(c)(2815)(0.+) are reconstructed in the Xi(c)(2645)(+.0)pi(-.+) decay modes. The following mass splittings are determined: m(Xi c(2645)+) - m(Xi c(2645)0) = (-0.1 +/- 0.3(stat) +/- 0.6(syst)) MeV/c(2) and m(Xi c(2815)+) - m(Xi c(2815)0) (-3.4 +/- 1.9(stat) +/- 0.9(syst)) MeV/c(2) with a much better precision than the current world averages. We also observe a new decay mode, Xi(c)(2980)(0.+) -> Xi(c)(2645)(+.0)pi(-.+). (C) 2008 Elsevier B.V. All rights reserved.