Search for Exotic S=-2 Baryons in proton-antiproton Collisions at sqrt(s) = 1.96 TeV

A search for a manifestly exotic S = -2 baryon state decaying to {Xi}{sup -}{pi}{sup -}, and its neutral partner decaying to {Xi}{sup -}{pi}{sup +}, has been performed using 220 pb{sup -1} of p{bar p} collisions at {radical}s = 1.96 TeV collected by the Collider Detector at Fermilab. The {Xi}{sup -} trajectories were measured in a silicon tracker before their decay, resulting in a sample with low background and excellent position resolution. No evidence was found for S = -2 pentaquark candidates in the invariant mass range of 1600-2100 MeV/c{sup 2}. Upper limits on the product of pentaquark production cross section times its branching fraction to {Xi}{sup -}{pi}{sup +,-}, relative to the cross section of the well established {Xi}(1530) resonance, are presented for neutral and doubly negative candidates with p{sub T} > 2 GeV/c and |y| < 1 as a function of pentaquark mass. At 1862 MeV/c{sup 2}, these upper limits for neutral and doubly negative final states were found to be 3.2% and 1.7% at the 90% confidence level, respectively.