Measurement of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>γ</mml:mi></mml:math>rays from antiproton-deuterium annihilation at rest

Using modularized NaI(T1) detectors, we have carried out a high-statistics measurement of inclusive $\ensuremath{\gamma}$-ray spectra from $\overline{p}d$ annihilation at rest separately for each charge multiplicity of the final state. We have not seen, at statistical significance above $4\ensuremath{\sigma}$, any monochromatic $\ensuremath{\gamma}$-ray peaks, which may be assigned to baryonium production $\overline{p}p or \overline{p}n\ensuremath{\rightarrow}\ensuremath{\gamma}B \mathrm{or}\mathrm{to} \overline{N}\mathrm{NN}$ bound-state production $\overline{p}d\ensuremath{\rightarrow}\ensuremath{\gamma}(\overline{N}NN)$. The $4\ensuremath{\sigma}$ upper limit for baryonium production per annihilation varied between ${10}^{\ensuremath{-}2}$ and ${10}^{\ensuremath{-}4}$ depending on baryonium mass of 1700 to 600 MeV/${\mathit{c}}^{2}$ and on the charge multiplicity. At $(2\ensuremath{-}3)\ensuremath{\sigma}$ levels, however, five peaks were observed and three of them are located at the same position with the similar $(2\ensuremath{-}3)\ensuremath{\sigma}$ peaks observed in $\overline{p}p\ensuremath{\rightarrow}\ensuremath{\gamma}B$ and $\overline{p}p\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}B$.