Observation of Ξ− Production in Interactions at 540 GeV CMS Energy

We have made the first observations of Ξ− production in pp interactions at √s=540 GeV. In a sample of 6964 non single-diffractive events we observe 17 Ξ− decays with an estimated background of less than one event. This corresponds to 0.04 ± 0.01 Ξ− per event in the transverse momentum range pt>1.0 GeV/c and in the pseudorapidity range |η| < 3.5. Assuming an exponential pt distribution, we find 〈pt〉=1.1−0.2+0.3 GeV/c.