Positronium oscillations to mirror world revisited.

We present a calculation of the branching ratio of orthopositronium decay into an invisible mode, which is done in the context of mirror world models, where ordinary positronium can disappear from our world due to oscillation into its mirror twin. In this revision we clarify some formulas and approximations used previously, correct them at some places, add new effects relevant for a feasible experiment, and finally perform a combined analysis. We include into consideration various effects due to external magnetic and electric fields, collisions with cavity walls, and scattering off gas atoms in the cavity. Oscillations of the Rydberg positroniums are also considered. To perform a numerical estimate in a realistic case we wrote computer code, which can be adopted in any experimental setup. Its work is illustrated with an example of a planned positronium experiment within the AEgIS project. [ABSTRACT FROM AUTHOR]