Evidence of a New Excited Charmed Baryon Decaying to Sigma(c) (2455)(0,+ +) pi(+/-)

Abstract

We present the study of B¯0→ςc(2455)0,++π±p¯ decays based on 772×106 BB¯ events collected with the Belle detector at the KEKB asymmetric-energy e+e- collider. The ςc(2455)0,++ candidates are reconstructed via their decay to Λc+π and Λc+ decays to pK-π+, pKS0, and Λπ+ final states. The corresponding branching fractions are measured to be B(B¯0→ςc(2455)0π+p¯)=(1.09±0.06±0.07)×10-4 and B(B¯0→ςc(2455)++π-p¯)=(1.84±0.11±0.12)×10-4, which are consistent with the world average values with improved precision. A new structure is found in the Mςc(2455)0,++π± spectrum with a significance of 4.2σ including systematic uncertainty. The structure is possibly an excited Λc+ and is tentatively named Λc(2910)+. Its mass and width are measured to be (2913.8±5.6±3.8) MeV/c2 and (51.8±20.0±18.8) MeV, respectively. The products of branching fractions for the Λc(2910)+ are measured to be B(B¯0→Λc(2910)+p¯)×B(Λc(2910)+→ςc(2455)0π+)=(9.5±3.6±1.6)×10-6 and B(B¯0→Λc(2910)+p¯)×B(Λc(2910)+→ςc(2455)++π-)=(1.24±0.35±0.10)×10-5. Here, the first and second uncertainties are statistical and systematic, respectively.