The Xi double-charm baryon, denoted as Ξ c c + + {\displaystyle \Xi _{\rm {cc}}^{++}}, is a Xi baryon composed of two charm quarks and one up quark.

Its discovery by the LHCb Collaboration was announced on 6 July 2017 in Venice, Italy, at the European Physical Society Conference on High Energy Physics. Ξ c c + + {\displaystyle \Xi _{\rm {cc}}^{++}} is the first baryon discovered with two heavy quarks (charm and/or bottom) and a light quark. Its mass is 3621 MeV/c2, nearly four times that of the proton.

It was identified when it disintegrated into a Λ c + {\displaystyle \Lambda _{\rm {c}}^{+}} baryon and three lighter mesons, K–, π+ and π+.

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