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LPHE - Research - E871 at LPHE
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E871 at LPHE

The HyperCP collaboration (E871 experiment at the Fermilab) propose to perform a sensitive search for CP violation in the hyperons decays. The HyperCP spectrometer consist of a hyperon magnet which select hyperons at the momentum range 160 GeV/c, a tracking system of proportional multiwires chambers with high rate capability, an analysis magnet, hodoscopes, a hadron calorimeter and a muon station.

The main study of CP violation is done on the Xi hyperons. The decay sequence (see figure) Xi -> Lambda + Pi and Lambda -> Proton + Pi is fully reconstructed.

A Xi event fully reconstructed Event Display

By studying the angular disribution of the (anti-)proton in the (anti-)Lambda rest frame, the product of the decay parameters of the Xi and of the Lambda could be extracted. Any difference between in the product of these parameters between the Xi decay sequence and the anti-Xi decay sequence is evidence of CP violation.

Analysis frameAngular measurement


The data were collected during the 1997 fixed target run. These data should yield 1.2 x 10^9 Xi and 0.3 x 10^9 anti-Xi. An accuracy of 2 x 10^-4 is expected. HyperCP experiment will accumulate more data during the 1999 run and should achieve an accuracy down to 1 x 10^-4.



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