Search for CP and $P$ violating pseudoscalar decays into $\pi \pi$

Using a sample of $(225.2\pm 2.8)\times {10}^6$ $J\mathrm{/}\psi$ events collected with the Beijing Spectrometer (BESIII) at the Beijing Electron-Positron Collider, CP and $P$ violating decays of $\eta$, ${\eta }^{\mathrm{\prime }}$ and $\text{etac}$ into ${\pi }^{+}{\pi }^{-}$ and ${\pi }^0{\pi }^0$ are searched for in $\text{jpsi}$ radiative decays. No significant $\eta$, ${\eta }^{\mathrm{\prime }}$ or $\text{etac}$ signal is observed, and 90% confidence level upper limits of $\text{BR}(\eta \to {\pi }^{+}{\pi }^{-})<3.9\times {10}^{-4}$, $\BR(\eta’ \to \pi^+\pi^-)<5.5\times 10^{-5}$,$\BR(\etac \to \pi^+\pi^-)<1.3\times 10^{-4}$,$\BR(\eta \to \pi^0 \pi^0)<6.9\times 10^{-4}$,$\BR(\eta’ \to \pi^0 \pi^0)<4.5\times 10^{-4}$and$\BR(\etac \to \pi^0 \pi^0)<4.2\times 10^{-5}$ are obtained.