Search for Majoron-emitting modes of Xe136 double beta decay with the complete EXO-200 dataset

A search for Majoron-emitting modes of the neutrinoless double beta decay of $^{136}\mathrm{Xe}$ is performed with the full EXO-200 dataset. This dataset consists of a total $^{136}\mathrm{Xe}$ exposure of $234.1\text{ }\text{ }\mathrm{kg}\ifmmode\cdot\else\textperiodcentered\fi{}\mathrm{yr}$, and includes data with detector upgrades that have improved the energy threshold relative to previous searches. A lower limit of ${\mathrm{T}}_{1/2}^{^{136}\mathrm{Xe}}>4.3\ifmmode\times\else\texttimes\fi{}{10}^{24}\text{ }\text{ }\mathrm{yr}$ at 90% C.L. on the half-life of the spectral index $n=1$ Majoron decay was obtained, a factor of 3.6 more stringent than the previous limit from EXO-200 and a factor of 1.6 more stringent than the previous best limit from KamLAND-Zen. This limit corresponds to a constraint on the Majoron-neutrino coupling constant of $|⟨{g}_{ee}^{M}⟩|