Towards a Hyperon \Super-CP" Experiment: Report of the Hyperon-CP -Violation Working Group

The Hyperon-CP-Violation working group at the p2000 Workshop met together with the Beta-Decay working group. After brie y introducing the physics, I summarize the workinggroup discussions relevent to CP violation. The working group sketched issues that need to be explored in designing a hyperon CP-violation experiment that might achieve 10 5 sensitivity for the CP asymmetry A , one order of magnitude beyond that of the current HyperCP experiment and in the range at which an e ect is predicted by the Standard model. 1 Hyperon CP Violation In addition to CP violation in kaon decays [1], the Standard Model predicts a slight CP asymmetry in decays of hyperons [2, 3, 4]. The most accessible signals involve comparison of the (nonuniform) angular distributions of the decay products of polarized hyperons with those of the corresponding antihyperons [3]. For a precision measurement, it is necessary to know the polarizations of the initial hyperons and antihyperons to high accuracy. By angular-momentum conservation, in the decay of a spin-1/2 hyperon to a spin-1/2 baryon plus a pion, the nal state must be either S-wave or P-wave. As is well known, the interference term between the Sand P-wave decay amplitudes gives rise to parity violation, parametrized by Lee and Yang [5] in terms of two independent parameters and : is proportional to the real and to the imaginary part of this interference term. CP violation can be sought as a di erence in j j or j j for a hyperon decay and its CP-conjugate antihyperon decay or as a particle-antiparticle di erence in the partial widths for such decays [3, 6]. E-mail: [email protected] Members of the Hyperon-CP-Violation Working Group: R. A. Burnstein, A. Chakravorty, D. Hertzog, D. M. Kaplan, D. Rajaram, H. A. Rubin, N. Solomey, G. Valencia, C. G. White.