Measurement of CP observables in B± → D(*)K± and B± → D(*)π± decays using two-body D final states

Measurements of CP observables in B± → D(*)K± and B± → D(*)π± decays are presented, where D(∗) indicates a neutral D or D∗ meson that is an admixture of meson and anti-meson states. Decays of the D(∗) meson to the Dπ0 and Dγ final states are partially reconstructed without inclusion of the neutral pion or photon. Decays of the D meson are reconstructed in the K±π∓, K+K−, and π+π− final states. The analysis uses a sample of charged B mesons produced in proton-proton collisions and collected with the LHCb experiment, corresponding to integrated luminosities of 2.0, 1.0, and 5.7 fb−1 taken at centre-of-mass energies of 7, 8, and 13 TeV, respectively. The measurements of partially reconstructed B± → D(*)K± and B± → D(∗)π± with D → K∓π± decays are the first of their kind, and a first observation of the B± → $$ {\left(D{\pi}^0\right)}_{D^{\ast }}{\pi}^{\pm } $$ D π 0 D ∗ π ± decay is made with a significance of 6.1 standard deviations. All CP observables are measured with world-best precision, and in combination with other LHCb results will provide strong constraints on the CKM angle γ.

Measurement of the CKM angle γ and $$ {B}_s^0\hbox{-} {\overline{B}}_s^0 $$ mixing frequency with $$ {B}_s^0\to {D}_s^{\mp }{h}^{\pm }{\pi}^{\pm }{\pi}^{\mp } $$ decays

The CKM angle γ is measured for the first time from mixing-induced CP violation between $$ {B}_s^0\to {D}_s^{\mp }{K}^{\pm }{\pi}^{\pm }{\pi}^{\mp } $$ B s 0 → D s ∓ K ± π ± π ∓ and $$ {\overline{B}}_s^0\to {D}_s^{\pm }{K}^{\mp }{\pi}^{\mp }{\pi}^{\pm } $$ B ¯ s 0 → D s ± K ∓ π ∓ π ± decays reconstructed in proton-proton collision data corresponding to an integrated luminosity of 9 fb−1 recorded with the LHCb detector. A time-dependent amplitude analysis is performed to extract the CP-violating weak phase γ − 2βs and, subsequently, γ by taking the $$ {B}_s^0\hbox{-} {\overline{B}}_s^0 $$ B s 0 ‐ B ¯ s 0 mixing phase βs as an external input. The measurement yields γ = (44 ± 12)° modulo 180°, where statistical and systematic uncertainties are combined. An alternative model-independent measurement, integrating over the five-dimensional phase space of the decay, yields $$ \gamma =\left({44}_{-13}^{+20}\right){}^{\circ} $$ γ = 44 − 13 + 20 ° modulo 180°. Moreover, the $$ {B}_s^0\hbox{-} {\overline{B}}_s^0 $$ B s 0 ‐ B ¯ s 0 oscillation frequency is measured from the flavour-specific control channel $$ {B}_s^0\to {D}_s^{-}{\pi}^{+}{\pi}^{+}{\pi}^{-} $$ B s 0 → D s − π + π + π − to be ∆ms = (17.757 ± 0.007(stat) ± 0.008(syst)) ps−1, consistent with and more precise than the current world-average value.

Measurement of the CKM angle γ in B± → DK± and B± → Dπ± decays with D → $$ {K}_{\mathrm{S}}^0 $$h+h−

A measurement of CP-violating observables is performed using the decays B± → DK± and B± → Dπ±, where the D meson is reconstructed in one of the self-conjugate three-body final states $$ {K}_{\mathrm{S}}^0 $$ K S 0 π+π− and $$ {K}_{\mathrm{S}}^0 $$ K S 0 K+K− (commonly denoted $$ {K}_{\mathrm{S}}^0 $$ K S 0 h+h−). The decays are analysed in bins of the D-decay phase space, leading to a measurement that is independent of the modelling of the D-decay amplitude. The observables are inter- preted in terms of the CKM angle γ. Using a data sample corresponding to an integrated luminosity of 9 fb−1 collected in proton-proton collisions at centre-of mass energies of 7, 8, and 13 TeV with the LHCb experiment, γ is measured to be $$ \left({68.7}_{-5.1}^{+5.2}\right){}^{\circ} $$ 68.7 − 5.1 + 5.2 ° . The hadronic parameters $$ {r}_B^{D K},{r}_B^{D\pi},{\delta}_B^{D K},\kern0.5em \mathrm{and}\kern0.5em {\delta}_B^{D\pi} $$ r B DK , r B Dπ , δ B DK , and δ B Dπ , which are the ratios and strong-phase differences of the suppressed and favoured B± decays, are also reported.