Search for CP violation in ${D}_{(s)}^{+}\to {h}^{+}{\pi}^0$ and ${D}_{(s)}^{+}\to {h}^{+}\eta$ decays

Abstract

Searches for CP violation in the two-body decays ${D}_{(s)}^{+}\to {h}^{+}{\pi}^0$ and ${D}_{(s)}^{+}\to {h}^{+}\eta$ (where h⁺ denotes a π⁺ or K⁺ meson) are performed using pp collision data collected by the LHCb experiment corresponding to either 9 fb⁻¹ or 6 fb⁻¹ of integrated luminosity. The π⁰ and η mesons are reconstructed using the e⁺e⁻γ final state, which can proceed as three-body decays π⁰ → e⁺e⁻γ and η → e⁺e⁻γ, or via the two-body decays π⁰ → γγ and η → γγ followed by a photon conversion. The measurements are made relative to the control modes ${D}_{(s)}^{+}\to {K}_{\mathrm{S}}^0{h}^{+}$ to cancel the production and detection asymmetries. The CP asymmetries are measured to be

$$ {\displaystyle \begin{array}{c}{\mathcal{A}}_{CP}\left({D}^{+}\to {\pi}^{+}{\pi}^0\right)=\left(-1.3\pm 0.9\pm 0.6\right)\%,\\ {}{\mathcal{A}}_{CP}\left({D}^{+}\to {K}^{+}{\pi}^0\right)=\left(-3.2\pm 4.7\pm 2.1\right)\%,\\ {}\begin{array}{c}{\mathcal{A}}_{CP}\left({D}^{+}\to {\pi}^{+}\eta \right)=\left(-0.2\pm 0.8\pm 0.4\right)\%,\\ {}{\mathcal{A}}_{CP}\left({D}^{+}\to {K}^{+}\eta \right)=\left(-6\pm 10\pm 4\right)\%,\\ {}\begin{array}{c}{\mathcal{A}}_{CP}\left({D}_s^{+}\to {K}^{+}{\pi}^0\right)=\left(-0.8\pm 3.9\pm 1.2\right)\%,\\ {}\begin{array}{c}{\mathcal{A}}_{CP}\left({D}_s^{+}\to {\pi}^{+}\eta \right)=\left(0.8\pm 0.7\pm 0.5\right)\%,\\ {}{\mathcal{A}}_{CP}\left({D}_s^{+}\to {K}^{+}\eta \right)=\left(0.9\pm 3.7\pm 1.1\right)\%,\end{array}\end{array}\end{array}\end{array}} $$

where the first uncertainties are statistical and the second systematic. These results are consistent with no CP violation and mostly constitute the most precise measurements of ${\mathcal{A}}_{CP}$ in these decay modes to date.