XI-PRODUCTION IN HEAVY-ION COLLISIONS AT THE AGS

We report the first observation of XI- in heavy ion collisions at the AGS. The lifetime of XI- measured agrees very well with the particle d ata group value. We present the observed XI- effective mass spectrum a nd the rapidity distribution after acceptance correction. In the measu red rapidity region (1.4-2.9) for 14.6 GeV/c Si on Pb, we obtained a y ield of 0.25 +/- 0.04 XI- per central event and a ratio of N(XI-)/N(LA MBDA) = 0.12 +/- 0.02 using a fireball+ model (a model which includes a fireball plus a term simulating a cascade) tor acceptance correction (see text for systematic error). This result is larger than any casca de model prediction so far.