Confirmation Of The Doubly Charmed Baryon Ξcc +(3520) Via Its Decay To Pd+k-

Abstract We observe a signal for the doubly charmed baryon Ξ c c + in the decay mode Ξ c c + → p D + K − to complement the previous reported decay Ξ c c + → Λ c + K − π + in data from SELEX, the charm hadroproduction experiment at Fermilab. In this new decay mode we observe an excess of 5.62 events over a combinatoric background estimated by event mixing to be 1.38 ± 0.13 events. The mixed background has Gaussian statistics, giving a signal significance of 4.8σ. The Poisson probability that a background fluctuation can produce the apparent signal is less than 6.4 × 10 −4 . The observed mass of this state is 3518 ± 3 MeV / c 2 , consistent with the published result. Averaging the two results gives a mass of 3518.7 ± 1.7 MeV / c 2 . The observation of this new weak decay mode confirms the previous SELEX suggestion that this state is a double charm baryon. The relative branching ratio for these two modes is 0.36 ± 0.21 .