Observation of the Bc+→J/ψπ+π0 {B}_c^{+}\to J/\psi {\pi}^{+}{\pi}^0 decay

Abstract The first observation of the $${B}_c^{+}\to J/\psi {\pi}^{+}{\pi}^0$$ B c + → J / ψ π + π 0 decay is reported with high significance using proton-proton collision data, corresponding to an integrated luminosity of 9 fb−1, collected with the LHCb detector at centre-of-mass energies of 7, 8, and 13 TeV. The ratio of its branching fraction relative to the $${B}_c^{+}\to J/\psi {\pi}^{+}$$ B c + → J / ψ π + channel is measured to be$$\frac{{\mathcal{B}}_{B_c^{+}\to J/\psi {\pi}^{+}{\pi}^0}}{{\mathcal{B}}_{B_c^{+}\to J/\psi {\pi}^{+}}}=2.80\pm 0.15\pm 0.11\pm 0.16,$$ B B c + → J / ψ π + π 0 B B c + → J / ψ π + = 2.80 ± 0.15 ± 0.11 ± 0.16 , where the first uncertainty is statistical, the second systematic and the third related to imprecise knowledge of the branching fractions for B+ → J/ψK*+ and $${B}_c^{+}\to J/\psi {\pi}^{+}$$ B c + → J / ψ π + decays, which are used to determine the π0 detection efficiency. The π+π0 mass spectrum is found to be consistent with the dominance of an intermediate ρ+ contribution in accordance with a model based on QCD factorisation.</jats:p

Prompt and nonprompt ψ(2S) production in pPb collisions at sNN \sqrt{s_{\textrm{NN}}} = 8.16 TeV

Abstract The production of ψ(2S) mesons in proton-lead collisions at a centre-of-mass energy per nucleon pair of $$\sqrt{s_{\textrm{NN}}}$$ s NN = 8.16 TeV is studied with the LHCb detector using data corresponding to an integrated luminosity of 34 nb−1. The prompt and nonprompt ψ(2S) production cross-sections and the ratio of the ψ(2S) to J/ψ cross-section are measured as a function of the meson transverse momentum and rapidity in the nucleon-nucleon centre-of-mass frame, together with forward-to-backward ratios and nuclear modification factors. The production of prompt ψ(2S) is observed to be more suppressed compared to pp collisions than the prompt J/ψ production, while the nonprompt productions have similar suppression factors.</jats:p

A model-independent measurement of the CKM angle γ in partially reconstructed B± → D*h± decays with D → KS0 {K}_S^0 h+h− (h = π, K)

Abstract A measurement of CP-violating observables in B± → D*K± and B± → D*π± decays is made where the photon or neutral pion from the D*→ Dγ or D*→ Dπ0 decay is not reconstructed. The D meson is reconstructed in the self-conjugate decay modes, D → $${K}_S^0$$ K S 0 π+π− or D → $${K}_S^0$$ K S 0 K+K−. The distribution of signal yields in the D decay phase space is analysed in a model-independent way. The measurement uses a data sample collected in proton-proton collisions at centre-of-mass energies of 7, 8, and 13 TeV, corresponding to a total integrated luminosity of approximately 9 fb−1. The B± → D*K± and B± → D*π±CP-violating observables are interpreted in terms of hadronic parameters and the CKM angle γ, resulting in a measurement of γ = ($${92}_{-17}^{+21}$$ 92 − 17 + 21 )°. The total uncertainty includes the statistical and systematic uncertainties, and the uncertainty due to external strong-phase inputs.</jats:p

Search for Bc+ ⁣→π+μ+μ−{{B} _{c} ^+} \!\rightarrow {{\pi } ^+} {\mu ^+\mu ^-} decays and measurement of the branching fraction ratio B(Bc+ ⁣→ψ(2S)π+)/B(Bc+ ⁣→J ⁣/ψπ+){\mathcal {B}} ({{B} _{c} ^+} \!\rightarrow {\psi {(2S)}} {{\pi } ^+} )/{\mathcal {B}} ({{B} _{c} ^+} \!\rightarrow {{J \hspace{-1.66656pt}/\hspace{-1.111pt}\psi }} {{\pi } ^+} )

AbstractThe first search for nonresonant $${{B} _{c} ^+} \!\rightarrow {{\pi } ^+} {\mu ^+\mu ^-}$$ B c + → π + μ + μ - decays is reported. The analysis uses proton–proton collision data collected with the LHCb detector between 2011 and 2018, corresponding to an integrated luminosity of 9$$\,\text {fb} ^{-1}$$ fb - 1 . No evidence for an excess of signal events over background is observed and an upper limit is set on the branching fraction ratio {\mathcal {B}} ({{B} _{c} ^+} \!\rightarrow {{\pi } ^+} {\mu ^+\mu ^-} )/{\mathcal {B}} ({{B} _{c} ^+} \!\rightarrow {{J \hspace{-1.66656pt}/\hspace{-1.111pt}\psi }} {{\pi } ^+} ) < 2.1\times 10^{-4} B ( B c + → π + μ + μ - ) / B ( B c + → J / ψ π + ) &lt; 2.1 × 10 - 4 at $$90\%$$ 90 % confidence level. Additionally, an updated measurement of the ratio of the $${{B} _{c} ^+} \!\rightarrow {\psi {(2S)}} {{\pi } ^+}$$ B c + → ψ ( 2 S ) π + and $${{B} _{c} ^+} \!\rightarrow {{J \hspace{-1.66656pt}/\hspace{-1.111pt}\psi }} {{\pi } ^+}$$ B c + → J / ψ π + branching fractions is reported. The ratio $${\mathcal {B}} ({{B} _{c} ^+} \!\rightarrow {\psi {(2S)}} {{\pi } ^+} )/{\mathcal {B}} ({{B} _{c} ^+} \!\rightarrow {{J \hspace{-1.66656pt}/\hspace{-1.111pt}\psi }} {{\pi } ^+} )$$ B ( B c + → ψ ( 2 S ) π + ) / B ( B c + → J / ψ π + ) is measured to be $$0.254\pm 0.018 \pm 0.003 \pm 0.005$$ 0.254 ± 0.018 ± 0.003 ± 0.005 , where the first uncertainty is statistical, the second systematic, and the third is due to the uncertainties on the branching fractions of the leptonic $${J \hspace{-1.66656pt}/\hspace{-1.111pt}\psi }$$ J / ψ  and $$\psi {(2S)}$$ ψ ( 2 S )  decays. This measurement is the most precise to date and is consistent with previous LHCb results.</jats:p

Study of Bc+→χcπ+ {B}_c^{+}\to {\chi}_c{\pi}^{+} decays

Abstract A study of $${B}_c^{+}\to {\chi}_c{\pi}^{+}$$ B c + → χ c π + decays is reported using proton-proton collision data, collected with the LHCb detector at centre-of-mass energies of 7, 8, and 13 TeV, corresponding to an integrated luminosity of 9 fb−1. The decay $${B}_c^{+}\to {\chi}_{c2}{\pi}^{+}$$ B c + → χ c 2 π + is observed for the first time, with a significance exceeding seven standard deviations. The relative branching fraction with respect to the $${B}_c^{+}\to J/\psi {\pi}^{+}$$ B c + → J / ψ π + decay is measured to be$$\frac{{\mathcal{B}}_{B_c^{+}\to {\chi}_{c2}{\pi}^{+}}}{{\mathcal{B}}_{B_c^{+}\to J/\psi {\pi}^{+}}}=0.37\pm 0.06\pm 0.02\pm 0.01,$$ B B c + → χ c 2 π + B B c + → J / ψ π + = 0.37 ± 0.06 ± 0.02 ± 0.01 , where the first uncertainty is statistical, the second is systematic, and the third is due to the knowledge of the χc2→ J/ψγ branching fraction. No significant $${B}_c^{+}\to {\chi}_{c1}{\pi}^{+}$$ B c + → χ c 1 π + signal is observed and an upper limit for the relative branching fraction for the $${B}_c^{+}\to {\chi}_{c1}{\pi}^{+}$$ B c + → χ c 1 π + and $${B}_c^{+}\to {\chi}_{c2}{\pi}^{+}$$ B c + → χ c 2 π + decays of \frac{{\mathcal{B}}_{B_c^{+}\to {\chi}_{c1}{\pi}^{+}}}{{\mathcal{B}}_{B_c^{+}\to {\chi}_{c2}{\pi}^{+}}}=<0.49 B B c + → χ c 1 π + B B c + → χ c 2 π + = &lt; 0.49 is set at the 90% confidence level.</jats:p

Study of CP violation in B0 → DK⋆(892)0 decays with D → Kπ(ππ), ππ(ππ), and KK final states

Abstract A measurement of CP-violating observables associated with the interference of B0→ D0K⋆(892)0 and $${B}^0\to {\overline{D}}^0{K}^{\star }{(892)}^0$$ B 0 → D ¯ 0 K ⋆ 892 0 decay amplitudes is performed in the D0→ K∓π±(π+π−), D0→ π+π−(π+π−), and D0→ K+K− final states using data collected by the LHCb experiment corresponding to an integrated luminosity of 9 fb−1. CP-violating observables related to the interference of $${B}_s^0\to {D}^0{\overline{K}}^{\star }{(892)}^0$$ B s 0 → D 0 K ¯ ⋆ 892 0 and $${B}_s^0\to {\overline{D}}^0{\overline{K}}^{\star }{(892)}^0$$ B s 0 → D ¯ 0 K ¯ ⋆ 892 0 are also measured, but no evidence for interference is found. The B0 observables are used to constrain the parameter space of the CKM angle γ and the hadronic parameters $${r}_{B^0}^{DK\star }$$ r B 0 DK ⋆ and $${\delta}_{B^0}^{DK\star }$$ δ B 0 DK ⋆ with inputs from other measurements. In a combined analysis, these measurements allow for four solutions in the parameter space, only one of which is consistent with the world average.</jats:p