Has Charge Symmetry Breaking Been Observed in thedd→απ0Reaction?

Abstract

Estimates are made of the $\mathrm{dd}\ensuremath{\rightarrow}\ensuremath{\alpha}\ensuremath{\gamma}\ensuremath{\gamma}$ production cross sections in a model where each neutron-proton pair in the beam and target initiates an $\mathrm{np}\ensuremath{\rightarrow}d\ensuremath{\gamma}$ reaction. This approach, which successfully reproduces observables in two-pion production at intermediate energies, suggests that direct two-photon production could provide a very significant background to the measurement of the charge-symmetry-breaking (CSB) reaction $\mathrm{dd}\ensuremath{\rightarrow}\ensuremath{\alpha}{\ensuremath{\pi}}^{0}$. A nonvanishing CSB cross section has been reported which might be confused with such two-photon production under the given experimental conditions.