A study of semileptonic and 2-body decays of charm strange baryons, a search for CP violation in Xi hyperon decays and a study of surface-treated planar microstrip gas chambers
Using the CLEO II detector at the Cornell Electron Storage Ring we search for evidence of W0c production at e+e - machines in the decay mode Oc O e+nue. We find 10.4 +/- 3.8 candidate events. The probability that the background accounts for all events in the signal region as a statistical fluctuation is 7.7 x 10-4. Our result is B( W0c O-e+nu e) sigma(e+ e- W0c X) = 0.22 +/- 0.08pb. We have measured the product of the decay asymmetry parameters, alphaalpha xi, in the decay chain xi- pi -, p+pi -. We find alphaalphaxi = -0.293 +/- 0.021+0.019-0.014 which is in good agreement with the current world average alpha alphaxi = -0.293 +/- 0.007. Using our reconstructed sample of 4204 +/- 75 xi- and similar number of xi+, we search for evidence of direct CP violation by measuring the asymmetry, A , in the angular distribution of xi pi charge conjugate states. In the Standard Model, direct CP violation in hyperons is expected to occur at the 10-4--10-5 level. The observation of CP violation at a higher level may indicate the presence of new physics. We find no evidence of CP violation: A Axi + A = -0.057 +/- 0.064 +/- 0.028. Given the world average A = -0.03 +/- 0.06, we find Axi = -0.03 +/- 0.06 +/- 0.07. The systematic error is dominated by the A measurement. We have measured the X0c decay asymmetry parameter in the decay X0c xi-pi+. We find aX0c alphaxi = 0.26 +/- 0.18+0.05-0.04, , using the world average of alphaxi = -0.456 +/- 0.014 we obtain aX0c = -0.56 +/- 0.39+0.10-0.09 where aX0c is <0.1 at the 90% CL. The central value occupies the middle of the theoretically expected range but is not yet precise enough to choose between models
Downloadable Article, English, 1999