Cascade B

The cascade B baryon particle, also known as Ξ^-_b, was discovered by D0 and CDF experiments at Fermilab. The discovery was announced on June 12 2007. It was the first known particle made of quarks from all three quark families -- namely, a down quark, a strange quark, and a bottom quark. D0 experiment reported mass of the new state to be 5.774±0.019 GeV/c²; and CDF measured the mass at 5.7929±0.0030 GeV/c². The two results are consistent. An unofficial weighted mean mass is 5.792±0.003 GeV/c².