Measurement of the Asymmetry in the Decay ${\overline{\Omega }}^{+}\to \overline{\Lambda }{K}^{+}\to \overline{p}{\pi }^{+}{K}^{+}$

The asymmetry in the $\overline{p}$ angular distribution in the sequential decay ${\overline{\Omega }}^{+}\to \overline{\Lambda }{K}^{+}\to \overline{p}{\pi }^{+}{K}^{+}$ has been measured to be ${\overline{\alpha }}_{\Omega }{\overline{\alpha }}_{\Lambda }=[+1.16\pm 0.18(\mathrm{stat})\pm 0.17(\mathrm{syst})]\times {10}^{-2}$ using $1.89\times {10}^6$ unpolarized ${\overline{\Omega }}^{+}$ decays recorded by the HyperCP (E871) experiment at Fermilab. Using the known value of ${\alpha }_{\Lambda }$, and assuming that ${\overline{\alpha }}_{\Lambda }=-{\alpha }_{\Lambda }$, ${\overline{\alpha }}_{\Omega }=[-1.81\pm 0.28(\mathrm{stat})\pm 0.26(\mathrm{syst})]\times {10}^{-2}$. A comparison between this measurement of ${\overline{\alpha }}_{\Omega }{\overline{\alpha }}_{\Lambda }$ and recent measurements of ${\alpha }_{\Omega }{\alpha }_{\Lambda }$ made by HyperCP shows no evidence of a violation of $CP$ symmetry.

Figure 1

The $\overline{p}{\pi }^{+}{K}^{+}$ and $\overline{p}{\pi }^{+}$ invariant-mass distributions, after all cuts, with fits to signal and background. Arrows delimit the extent of the good event sample.

Figure 2

The real (lines) and weighted HMC (points) $\cos \theta$ distributions of the $\overline{p}$. The total number of HMC events has been reduced by a factor of 10 to equal the number of real events.

Figure 3

The differences between the real (${\mathsf{N}}_{\mathsf{r}}$) and HMC (${\mathsf{N}}_{\mathsf{m}\mathsf{c}}$) $\cos \theta$ distributions of the $\overline{p}$, for unweighted (top) and weighted (bottom) HMC events. The total number of HMC events has been reduced by a factor of 10 to equal the number of real events.