CHARGE CONJUGATION ($\mathit C$) INVARIANCE
 $\Gamma\mathrm {( {{\mathit \pi}^{0}} \rightarrow 3 {{\mathit \gamma}} )}$ $/$ $\Gamma\mathrm {(total)}$ $<3.1\times 10^{-8}$ CL=90.0%
 $\Gamma\mathrm {(( {{\mathit e}^{+}} {{\mathit e}^{-}} )_{\mathit J = 0} \rightarrow 3 {{\mathit \gamma}} )}/\Gamma\mathrm {(( {{\mathit e}^{+}} {{\mathit e}^{-}} )_{\mathit J = 0} \rightarrow 2 {{\mathit \gamma}} )}$ $<1 \times 10^{-5}$ CL=90.0%
 $\Gamma\mathrm {(( {{\mathit e}^{+}} {{\mathit e}^{-}} )_{\mathit J = 1} \rightarrow 4 {{\mathit \gamma}} )}/\Gamma\mathrm {(( {{\mathit e}^{+}} {{\mathit e}^{-}} )_{\mathit J = 1} \rightarrow 3 {{\mathit \gamma}} )}$ $<1 \times 10^{-5}$ CL=90.0%
${{\mathit \eta}}$ $\mathit C$-nonconserving decay parameters
 ${{\mathit \pi}^{+}}{{\mathit \pi}^{-}}{{\mathit \pi}^{0}}$ left-right asymmetry $0.0009$ ${}^{+0.0011}_{-0.0012}$
 ${{\mathit \pi}^{+}}{{\mathit \pi}^{-}}{{\mathit \pi}^{0}}$ sextant asymmetry $0.0012$ ${}^{+0.0010}_{-0.0011}$
 ${{\mathit \pi}^{+}}{{\mathit \pi}^{-}}{{\mathit \pi}^{0}}$ quadrant asymmetry ($-9$ $\pm9$) $\times 10^{-4}$
 ${{\mathit \pi}^{+}}{{\mathit \pi}^{-}}{{\mathit \gamma}}$ left-right asymmetry $0.009$ $\pm0.004$
 ${{\mathit \pi}^{+}}{{\mathit \pi}^{-}}{{\mathit \gamma}}$ parameter $\beta$ (${\mathit D}{\mathrm -wave}$) $-0.02$ $\pm0.07$      (S = 1.3)
 $\Gamma\mathrm {( {{\mathit \eta}} \rightarrow 3 {{\mathit \pi}^{0}} {{\mathit \gamma}} )}$ $/$ $\Gamma\mathrm {(total)}$ $<6\times 10^{-5}$ CL=90.0%
 $\Gamma\mathrm {( {{\mathit \eta}} \rightarrow {{\mathit \pi}^{0}} {{\mathit \gamma}} )}$ $/$ $\Gamma\mathrm {(total)}$ [1] $<9\times 10^{-5}$ CL=90.0%
 $\Gamma\mathrm {( {{\mathit \eta}} \rightarrow 2 {{\mathit \pi}^{0}} {{\mathit \gamma}} )}$ $/$ $\Gamma\mathrm {(total)}$ $<5\times 10^{-4}$ CL=90.0%
 $\Gamma\mathrm {( {{\mathit \eta}} \rightarrow 3 {{\mathit \gamma}} )}$ $/$ $\Gamma\mathrm {(total)}$ $<1.6\times 10^{-5}$ CL=90.0%
 $\Gamma\mathrm {( {{\mathit \eta}} \rightarrow {{\mathit \pi}^{0}} {{\mathit \mu}^{+}} {{\mathit \mu}^{-}} )}$ $/$ $\Gamma\mathrm {(total)}$ [2] $<5\times 10^{-6}$ CL=90.0%
 $\Gamma\mathrm {( {{\mathit \eta}} \rightarrow {{\mathit \pi}^{0}} {{\mathit e}^{+}} {{\mathit e}^{-}} )}$ $/$ $\Gamma\mathrm {(total)}$ [2] $<8\times 10^{-6}$ CL=90.0%
 $\Gamma\mathrm {( {{\mathit \omega}{(782)}} \rightarrow 2 {{\mathit \pi}^{0}} )}$ $/$ $\Gamma\mathrm {(total)}$ $<2.2\times 10^{-4}$ CL=90.0%
 $\Gamma\mathrm {( {{\mathit \omega}{(782)}} \rightarrow 3 {{\mathit \pi}^{0}} )}$ $/$ $\Gamma\mathrm {(total)}$ $<2.3\times 10^{-4}$ CL=90.0%
 $\Gamma\mathrm {( {{\mathit \omega}{(782)}} \rightarrow {{\mathit \eta}} {{\mathit \pi}^{0}} )}$ $/$ $\Gamma\mathrm {(total)}$ $<2.1\times 10^{-4}$ CL=90.0%
 ${{\mathit \eta}^{\,'}{(958)}}$ $\rightarrow$ ${{\mathit \pi}^{+}}{{\mathit \pi}^{-}}{{\mathit \gamma}}$ decay asymmetry parameter $-0.03$ $\pm0.04$
 $\Gamma\mathrm {( {{\mathit \eta}^{\,'}{(958)}} \rightarrow 3 {{\mathit \gamma}} )}$ $/$ $\Gamma\mathrm {(total)}$ $<1.0\times 10^{-4}$ CL=90.0%
 $\Gamma\mathrm {( {{\mathit \eta}^{\,'}{(958)}} \rightarrow {{\mathit \mu}^{+}} {{\mathit \mu}^{-}} {{\mathit \pi}^{0}} )}$ $/$ $\Gamma\mathrm {(total)}$ [2] $<6.0\times 10^{-5}$ CL=90.0%
 $\Gamma\mathrm {( {{\mathit \eta}^{\,'}{(958)}} \rightarrow {{\mathit \mu}^{+}} {{\mathit \mu}^{-}} {{\mathit \eta}} )}$ $/$ $\Gamma\mathrm {(total)}$ [2] $<1.5\times 10^{-5}$ CL=90.0%
 $\Gamma\mathrm {( {{\mathit \eta}^{\,'}{(958)}} \rightarrow {{\mathit \eta}} {{\mathit e}^{+}} {{\mathit e}^{-}} )}$ $/$ $\Gamma\mathrm {(total)}$ [2] $<2.4\times 10^{-3}$ CL=90.0%
 $\Gamma\mathrm {( {{\mathit \eta}^{\,'}{(958)}} \rightarrow {{\mathit \pi}^{0}} {{\mathit e}^{+}} {{\mathit e}^{-}} )}$ $/$ $\Gamma\mathrm {(total)}$ [2] $<1.4\times 10^{-3}$ CL=90.0%
 $\Gamma\mathrm {( {{\mathit J / \psi}{(1S)}} \rightarrow {{\mathit \gamma}} {{\mathit \phi}} )}$ $/$ $\Gamma\mathrm {(total)}$ $<1.4\times 10^{-6}$ CL=90.0%
 $\Gamma\mathrm {( {{\mathit J / \psi}{(1S)}} \rightarrow {{\mathit \gamma}} {{\mathit \gamma}} )}$ $/$ $\Gamma\mathrm {(total)}$ $<2.7\times 10^{-7}$ CL=90.0%

 [1] Forbidden by angular momentum conservation.
 [2] $\mathit C$ parity forbids this to occur as a single-photon process.