The Fermilab
HyperCP experiment has accumulated the world's largest sample of Ξ
− and
Ξ
+ hyperon decays within two running periods in 1997 and 1999. The primary goal of the experiment is to search ...for direct CP violation in the decay sequences Ξ
− → Λ π
− →
p π
− π
− and
Ξ
+ →
Λ
π
+ →
p
π
+ π
+. A violation of CP would manifest itself as a difference between the angular distribution of the proton and the antiproton in the Λ and
Λ
helicity frame. The amount of data is enough to reach a statistical sensitivity of 1.4 × 10
−4 in the CP violating asymmetry
A
ΞΛ = (α
Ξ α
Λ − α
Ξ
α
Λ
)/(α
Ξ α
Λ + α
Ξ
α
Λ
). We present an analysis method used to take into account the slight differences in the production of the Ξ
− and
Ξ
+ samples. A preliminary results on
A
ΞΛ at the level of a few 10
−3 and based on a few percent of the 1997 data will be presented.
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