# HEP/Astro Seminar, Thursday 22nd January 1998

## Christopher White (Fermilab)




### Abstract

A sensitive search for direct CP violation in $\Xi^-$ ($\bar{\Xi}^+$)
and $\Lambda$ ($\bar{\Lambda}$) decays is underway at FNAL.
Experiment E871 (HyperCP) intends to perform a precision measurement of
the angular distribution of protons (anti-protons) with respect to the
helicity axis in the rest frame of the $\Lambda \; (\bar{\Lambda})$.
The slopes of these distributions give the decay parameters
$\alpha_{\Xi}\alpha_{\Lambda}$ and $\alpha_{\bar{\Xi}}\alpha_{\bar{\Lambda}}$.
An asymmetry parameter $\mathcal{A}$ in terms of these decay parameters
has been defined for which a non-zero value would be unambiguous evidence
for direct CP violation.  Theoretical predictions for $\mathcal{A}$
range from no asymmetry up to $\sim 10^{-3}$.  HyperCP expects
to measure $\mathcal{A}$ with an uncertainty of $\sim 2\times 10^{-4}$.



## Thursday 1:00pm, Smith Lab 4079

Francesco Antonuccio ( anton@pacific.mps.ohio-state.edu), last updated 15-SEP-97.