The treatment of data from a neutral meson spectrometer

Simple analytic formulae are presented for reconstructing the momentum of a neutral meson from the measured energies and directions of its two decay photons. These formulae, obtained from a maximum likelihood treatment, can produce a more accurate result for the momentum than the method usually used to analyse such data. The results are used to investigate the dependence of the momentum resolution of a neutral meson spectrometer on the energy and angular resolution of its photon detecting elements.