Search for CP violation in 𝐷+(𝑠)→ℎ+𝜋0 and 𝐷+(𝑠)→ℎ+𝜂 decays

Journal of High Energy Physics. 2021. Vol. 6. Article 19.

Aaij R., Arzymatov K., Belavin V., Boldyrev A., Borisyak M., Derkach D., Hushchyn M., Karpov M., Maevskiy A., Philippov A., Popov S., Ratnikov F., Ryzhikov A., Ustyuzhanin A., Zunica G.

Searches for CP violation in the two-body decays 𝐷+(𝑠)→ℎ+𝜋0D(s)+→h+π0 and 𝐷+(𝑠)→ℎ+𝜂D(s)+→h+η (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)→𝐾0Sℎ+D(s)+→KS0h+ to cancel the production and detection asymmetries. The CP asymmetries are measured to be

𝐶𝑃(𝐷+→𝜋+𝜋0)=(−1.3±0.9±0.6)%,𝐶𝑃(𝐷+→𝐾+𝜋0)=(−3.2±4.7±2.1)%,𝐶𝑃(𝐷+→𝜋+𝜂)=(−0.2±0.8±0.4)%,𝐶𝑃(𝐷+→𝐾+𝜂)=(−6±10±4)%,𝐶𝑃(𝐷+𝑠→𝐾+𝜋0)=(−0.8±3.9±1.2)%,𝐶𝑃(𝐷+𝑠→𝜋+𝜂)=(0.8±0.7±0.5)%,𝐶𝑃(𝐷+𝑠→𝐾+𝜂)=(0.9±3.7±1.1)%,ACP(D+→π+π0)=(−1.3±0.9±0.6)%,ACP(D+→K+π0)=(−3.2±4.7±2.1)%,ACP(D+→π+η)=(−0.2±0.8±0.4)%,ACP(D+→K+η)=(−6±10±4)%,ACP(Ds+→K+π0)=(−0.8±3.9±1.2)%,ACP(Ds+→π+η)=(0.8±0.7±0.5)%,ACP(Ds+→K+η)=(0.9±3.7±1.1)%,

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 𝐶𝑃ACP in these decay modes to date.

Keywords: LHC, Standard Model, стандартная модель, БАК, физика элементарных частиц, CP-нарушение, тяжёлые кварки, экзотические состояния, Physics of heavy quarks and leptons

Publication based on the results of: Machine learning to check and improve the quality of data collected at the Large Hadron Collider and other particle physics experiments (2021)