Search for CP Violation in Hyperon Decays at Fermilab

The HyperCP collaboration is performing a precision search for CP violation in hyperon decays. Hyperon decays are sensitive to exotic sources of CP violation that kaon decays, for example, are not. The measured CP observable is AΞΛ=(αΞαΛ−αΞ¯αΛ¯)/(αΞαΛ+αΞ¯αΛ¯), where αΞ and αΛ are decay parameters for Ξ−→Λπ−→pπ−π−, and αΞ¯ and αΛ¯ are decay parameters for Ξ¯+→Λ¯π+→p¯π+π+. We report on an analysis of 118 million Ξ− decays and 42 million Ξ¯+ decays from the 1999 Fermilab fixed-target run, about 10% of the total HyperCP data set, giving a preliminary result of AΞΛ=[0.0±5.1(stat)±4.4(syst)]×10−4.