Light Boson (${{\boldsymbol X}^{0}}$) Search in Nonresonant ${{\boldsymbol e}^{+}}{{\boldsymbol e}^{-}}$ Annihilation at Rest
INSPIRE search
Limits are for the ratio of ${{\mathit n}}{{\mathit \gamma}}{+}$ ${{\mathit X}^{0}}$ production relative to ${{\mathit \gamma}}{{\mathit \gamma}}$ .