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

Abstract

Abstract

Searches for CP violation in the two-body decays

D

s

+

→

h +

π 0

$$ {D}_{(s)}^{+}\to {h}^{+}{\pi}^0 $$ and

D

s

+

→

h +

η

$$ {D}_{(s)}^{+}\to {h}^{+}\eta $$ (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

+

→

K S 0

h +

$$ {D}_{(s)}^{+}\to {K}_{\mathrm{S}}^0{h}^{+} $$ to cancel the production and detection asymmetries. The CP asymmetries are measured to be

A CP

D +

→

π +

π 0

=

− 1.3 ± 0.9 ± 0.6

% ,

A CP

D +

→

K +

π 0

=

− 3.2 ± 4.7 ± 2.1

% ,

A CP

D +

→

π +

η

=

− 0.2 ± 0.8 ± 0.4

% ,

A CP

D +

→

K +

η

=

− 6 ± 10 ± 4

% ,

A CP

D s +

→

K +

π 0

=

− 0.8 ± 3.9 ± 1.2

% ,

A CP

D s +

→

π +

η

=

0.8 ± 0.7 ± 0.5

% ,

A CP

D s +

→

K +

η

=

0.9 ± 3.7 ± 1.1

% ,

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

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

A CP

$$ {\mathcal{A}}_{CP} $$ in these decay modes to date.