Observation of the doubly Cabibbo-suppressed decay Ξ c+ → pϕ

Abstract

The doubly Cabibbo-suppressed decay Ξ +c → pϕ with ϕ → K+K− is observed for the first time, with a statistical significance of more than fifteen standard deviations. The data sample used in this analysis corresponds to an integrated luminosity of 2 fb−1 recorded with the LHCb detector in pp collisions at a centre-of-mass energy of 8 TeV. The ratio of branching fractions between the decay Ξ +c → pϕ and the singly Cabibbo-suppressed decay Ξ +c → pK−π+ is measured to be B(Ξ+c→pϕ)B(Ξ+c→pK−π+)=(19.8±0.7±0.9±0.2)×10−3, where the first uncertainty is statistical, the second systematic and the third due to the knowledge of the ϕ → K+K− branching fraction.