Threshold π − photoproduction on the neutron

Recent data from the PIONS@MAX-lab Collaboration, measuring the total cross section of the incoherent pion photoproduction reaction, γ d → π − pp , near threshold, have been used to extract the E 0 + multipole and total cross section of the reaction γ n → π − p , also near threshold. These are the first measurements of the reaction γ d → π − 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 γ n → π − p with E 0 + = const in the threshold region. The fit over all the 6 deuteron data points gives the value E 0 + = − 31 . 86 ± 0 . 8 (in units 10 − 3 / m π ). We explore the dependence of our results on the choice of data subsets included in the fit. The obtained values of E 0 + , for differ-ent subsets, have overlapping errors and agree with previous determinations.