Evidence for a new meson: A quasinuclearNN¯bound state?

We report evidence for an isoscalar state X(1110), observed via p¯n→${\rho }^{\mathrm{-}}$+X (→${\pi }^{+}$ ${\pi }^{\mathrm{-}}$) in p¯d annihilations at rest, of mass and width 1107±4 MeV/$c^2$ and 111±8 (statistical)±15 (systematic) MeV/$c^2$, respectively. The product branching ratio B(p¯n→${\rho }^{\mathrm{-}}$X)B(X →2π)=(3.6±0.5)% and $J^{\mathrm{PC}}$($I^G$ ${)=0\mathrm{}}^{++}$ ${(0\mathrm{}}^{+}$), $2^{++}$ ${(0\mathrm{}}^{+}$),. . . . As a $0^{++}$ the X(1110) would be a candidate for the ground ${}_{}{}^{13}{}_{}{}^{}\mathrm{P}_0^{}{}_{}{}^{}$ state of the I=0 natural-parity band of quasinuclear NN¯ states with the ζ(1480) being the ${}_{}{}^{13}{}_{}{}^{}\mathrm{P}_2^{}{}_{}{}^{}$ ${\mathrm{-}}^{13}$ ${\mathrm{F}}_2$. This interpretation predicts masses for the member states ${}_{}{}^{13}{}_{}{}^{}\mathrm{S}_1^{}{}_{}{}^{}$ ${\mathrm{-}}^{13}$ ${\mathrm{D}}_1$ and ${}_{}{}^{13}{}_{}{}^{}\mathrm{D}_3^{}{}_{}{}^{}$ ${\mathrm{-}}^{13}$ ${\mathrm{G}}_3$ of 1240 and 1850 MeV/$c^2$, respectively. Evidence for the ${}_{}{}^{13}{}_{}{}^{}\mathrm{S}_1^{}{}_{}{}^{}$ ${\mathrm{-}}^{13}$ ${\mathrm{D}}_1$ is discussed.