Search for Two-Photon Decay in ThermalnpCapture

An upper limit of ${10}^{-4\mathrm{}}$ has been obtained for the branching ratio for the emission of two photons ($E_{\gamma }>0.57\mathrm{}$ MeV) following thermal neutron capture in hydrogen. This limit was obtained with two Ge(Li) detectors shielded so as to reduce $\gamma$-ray scattering from one detector into the other and is a factor of 10 lower than has been recently reported.