  A conversion-reconversion experimental scheme is proposed where photons
stored in a Fabry-Perot cavity (FP) embracing a dipole conversion magnet
generate two beams of ultralight bosons emitted in opposite directions.
Fractions of the bosons convert in dipole magnets aligned along the two boson
beam lines and generate photons of the same energy and directions of the FP
grandparent photons. The reconversion photons are detected individually by
means of single photon detectors. Such an experiment can determine the bosons
parity by measurements with different angles between the polarization vector of
linearly polarized light injected into the FP and the direction of the magnetic
field Bc of the conversion magnets. It can establish both the bosons mass m and
the coupling constant to two photons gmgg by measurements with different
lengths Lr of the string of powered regeneration magnets of one boson beam
line, while the second boson beam line is left unchanged and used for
normalization. The optimal total length Lc of the string of conversion magnets
depends on m2 and on the energy E of the laser photons. For E=2.4eV Lc is of
the order of 3m if m=10-3eV and of the order of 300m if m=10-4eV. If the
signals observed by the PVLAS experiment are due to the existence of ultralight
bosons with m=10-3eV and gmgg=10-6GeV-1, these regeneration measurements are
feasible with existing tachnology on a site of length below 100m in relatively
short periods of data taking time.
