Measurement of $CP$ asymmetries in $D_{(s)}^{+}\to \eta {\pi }^{+}$ and $D_{(s)}^{+}\to {\eta }^{\prime }{\pi }^{+}$ decays

Abstract

Searches for $CP$ violation in the decays $D_{(s)}^{+}\to \eta {\pi }^{+}$ and $D_{(s)}^{+}\to {\eta }^{\prime }{\pi }^{+}$ are performed using $pp$ collision data corresponding to 6 fb${}^{-1}$ of integrated luminosity collected by the LHCb experiment. The calibration channels $D_{(s)}^{+}\to \varphi {\pi }^{+}$ are used to remove production and detection asymmetries. The resulting $CP$-violating asymmetries are $A^{CP}(D^{+}\to \eta {\pi }^{+})=(0.34\pm 0.66\pm 0.16\pm 0.05)\%$, $A^{CP}(D_s^{+}\to \eta {\pi }^{+})=(0.32\pm 0.51\pm 0.12)\%$, $A^{CP}(D^{+}\to {\eta }^{\prime }{\pi }^{+})=(0.49\pm 0.18\pm 0.06\pm 0.05)\%$, $A^{CP}(D_s^{+}\to {\eta }^{\prime }{\pi }^{+})=(0.01\pm 0.12\pm 0.08)\%$, where the first uncertainty is statistical, the second is systematic and the third, relevant for the $D^{+}$ channels, is due to the uncertainty on $A^{CP}(D^{+}\to \varphi {\pi }^{+})$. These measurements, currently the most precise for three of the four channels considered, are consistent with the absence of $CP$ violation. A combination of these results with previous LHCb measurements is presented.

All figures and tables, along with machine-readable versions and any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2021-051.html (LHCb public pages)

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