LIGHT UNFLAVORED MESONS
($\boldsymbol S$ = $\boldsymbol C$ = $\boldsymbol B$ = 0)
For $\mathit I = 1$ (${{\mathit \pi}}$, ${{\mathit b}}$, ${{\mathit \rho}}$, ${{\mathit a}}$): ${\mathit {\mathit u}}$ ${\mathit {\overline{\mathit d}}}$, ( ${\mathit {\mathit u}}$ ${\mathit {\overline{\mathit u}}}−$ ${\mathit {\mathit d}}$ ${\mathit {\overline{\mathit d}}})/\sqrt {2 }$, ${\mathit {\mathit d}}$ ${\mathit {\overline{\mathit u}}}$;
for $\mathit I = 0$ (${{\mathit \eta}}$, ${{\mathit \eta}^{\,'}}$, ${{\mathit h}}$, ${{\mathit h}^{\,'}}$, ${{\mathit \omega}}$, ${{\mathit \phi}}$, ${{\mathit f}}$, ${{\mathit f}^{\,'}}$): ${\mathit {\mathit c}}_{{\mathrm {1}}}$( ${{\mathit u}}{{\overline{\mathit u}}}$ $+$ ${{\mathit d}}{{\overline{\mathit d}}}$ ) $+$ ${\mathit {\mathit c}}_{{\mathrm {2}}}$( ${{\mathit s}}{{\overline{\mathit s}}}$ )
INSPIRE search

${{\boldsymbol X}{(1835)}}$ $I^G(J^{PC})$ = $?^?(0^{- +})$ 

Could be a superposition of two states, one with small width appearing as threshold enhancement in ${{\mathit p}}{{\overline{\mathit p}}}$ , the other one with a larger width. For the former ABLIKIM 2012D determine $\mathit J{}^{PC} = 0{}^{-+}$.
${{\mathit X}{(1835)}}$ MASS   $1826.5 {}^{+13.0}_{-3.4}$ MeV 
${{\mathit X}{(1835)}}$ WIDTH   $242 {}^{+14}_{-15}$ MeV 
$\Gamma_{1}$ ${{\mathit p}}{{\overline{\mathit p}}}$ seen-1
$\Gamma_{2}$ ${{\mathit \eta}^{\,'}}{{\mathit \pi}^{+}}{{\mathit \pi}^{-}}$ seen624
$\Gamma_{3}$ ${{\mathit \gamma}}{{\mathit \gamma}}$ 913
$\Gamma_{4}$ ${{\mathit K}_S^0}$ ${{\mathit K}_S^0}$ ${{\mathit \eta}}$ seen474
$\Gamma_{5}$ ${{\mathit \gamma}}{{\mathit \phi}{(1020)}}$ possibly seen629
$\Gamma_{6}$ 3 ( ${{\mathit \pi}^{+}}{{\mathit \pi}^{-}}$) seen773