Threshold $��^-$ Photoproduction on the Neutron

Recent data from the PIONS$@$MAX-lab Collaboration, measuring the total cross section of the pion incoherent photoproduction $��d\to��^-pp$ near threshold, have been used to extract the E$_{0+}$ multipole and total cross section of the reaction $��n\!\to\!��^-p$, also near threshold. These are the first measurements of the reaction $��d\to��^-pp$ in the threshold region. The value of E$_{0+}$ is extracted through a fit to the deuteron data in a photoproduction model accounting for final-state interactions. The model takes an $S$-wave approximation for the elementary reaction $��n\!\to\!��^-p$ with E$_{0+}\! = $ const in the threshold region. The obtained value E$_{0+} = -31.86\pm 0.8$ (in $10^{-3}/m_{��^+}$ units) is in agreement with other existing results. Model predictions for the total cross section $��(��n\!\to\!��^-p)$ are also given.
7 pages, 4 figures, 2 tables