Post-experiment coincidence counting method for coincidence detection techniques

Recently, two coincidence detection techniques, the coincidence angle-resolved photoemission spectroscopy (cARPES) and the coincidence inelastic neutron scattering (cINS), have been proposed to detect directly the two-body correlations of strongly correlated electrons in particle-particle channel or two-spin channel. In the original proposals, a coincidence detector is introduced for the coincidence detection of two photoelectric processes or two neutron-scattering processes. In this article, we present a post-experiment coincidence counting method for the proposed coincidence detection techniques without a coincidence detector. It requires a pulse photon or neutron source. Consider one incident multiphoton or multineutron pulse that causes many photoelectric or neutron-scattering processes within one time window. I_d_1^(1) and I_d_2^(1) record the numbers of the emitted photoelectrons or the scattered neutrons which arrive at two detectors D_1 and D_2, respectively. The coincidence counting is defined by I_d^(2)=I_d_1^(1)× I_d_2^(1), which records the coincidence probability of two photoelectric processes or two neutron-scattering processes within this time window. Therefore, I_d^(2) involves the two-body correlations of the target electrons. The previously proposed cARPES and cINS can be implemented upon the pulse-resolved angle-resolved photoemission spectroscopy (ARPES) and inelastic neutron scattering (INS) experimental apparatuses with pulse sources.