Evidence for a Neutral Boson of Mass 953 MeV and Narrow Width

A 20-standard deviation peak is observed at a mass of ${953.4}_{-2.\mathrm{}5}^{+1\mathrm{}}$ MeV and with a physical width $\Gamma <15\mathrm{}$ MeV, produced with ${\left(\frac{d\sigma }{d\Omega }\right)}_{\mathrm{c}.\mathrm{m}.\mathrm{},{60}^{\circ }}=2\mathrm{}\times {10}^{-35}$ ${\mathrm{cm}}^2$/sr in the reaction $p+d\to {\mathrm{He}}^3+$ missing mass. The incident proton energy was 3 BeV and the proton-to-meson and proton-to-${\mathrm{He}}^3$ transfers $t=-1.74\mathrm{}$ and $u=-4\mathrm{}{\left(\frac{\mathrm{BeV}}{c}\right)}^2$, respectively. The ${\eta }_0\mathrm{}\left(958\right)\mathrm{}$, ${\delta }^0\mathrm{}\left(963\right)\mathrm{}$, and ${\varphi }^0\mathrm{}\left(1019\right)\mathrm{}$ are not observed and the ${\rho }^0\mathrm{}\left(765\right)\mathrm{}$ not apparent in our data.