Abstract A search for the fully reconstructed B s 0 $$ {B}_s^0 $$ → μ + μ − γ decay is performed at the LHCb experiment using proton-proton collisions at s $$ \sqrt{s} $$ = 13 TeV corresponding to an ...integrated luminosity of 5.4 fb −1. No significant signal is found and upper limits on the branching fraction in intervals of the dimuon mass are set B B s 0 → μ + μ − γ < 4.2 × 10 − 8 , m μ + μ − ∈ 2 m μ 1.70 GeV / c 2 , B B s 0 → μ + μ − γ < 7.7 × 10 − 8 , m μ + μ − ∈ 1.70, 2.88 GeV / c 2 , B B s 0 → μ + μ − γ < 4.2 × 10 − 8 , m μ + μ − ∈ 3.92 m B s 0 GeV / c 2 , $$ {\displaystyle \begin{array}{cc}\mathcal{B}\left({B}_s^0\to {\mu}^{+}{\mu}^{-}\gamma \right)<4.2\times {10}^{-8},& m\left({\mu}^{+}{\mu}^{-}\right)\in \left2{m}_{\mu },1.70\right\textrm{GeV}/{c}^2,\\ {}\mathcal{B}\left({B}_s^0\to {\mu}^{+}{\mu}^{-}\gamma \right)<7.7\times {10}^{-8},&\ m\left({\mu}^{+}{\mu}^{-}\right)\in \left\textrm{1.70,2.88}\right\textrm{GeV}/{c}^2,\\ {}\mathcal{B}\left({B}_s^0\to {\mu}^{+}{\mu}^{-}\gamma \right)<4.2\times {10}^{-8},& m\left({\mu}^{+}{\mu}^{-}\right)\in \left3.92,{m}_{B_s^0}\right\textrm{GeV}/{c}^2,\end{array}} $$ at 95% confidence level. Additionally, upper limits are set on the branching fraction in the 2m μ , 1.70 GeV/c 2 dimuon mass region excluding the contribution from the intermediate ϕ(1020) meson, and in the region combining all dimuon-mass intervals.
Abstract The Λ b 0 $$ {\Lambda}_b^0 $$ → D + D − Λ decay is observed for the first time using proton-proton collision data collected by the LHCb experiment at a center-of-mass energy of 13 TeV, ...corresponding to an integrated luminosity of 5.3 fb −1. Using the B 0 → D + D − K S 0 $$ {D}^{+}{D}^{-}{K}_S^0 $$ decay as a reference channel, the product of the relative production cross-section and decay branching fractions is measured to be R = σ Λ b 0 σ B 0 = B Λ b 0 → D + D − Λ B B 0 → D + D − K S 0 = 0.179 ± 0.022 ± 0.014 , $$ \mathcal{R}=\frac{\sigma_{\Lambda_b^0}}{\sigma_{B^0}}=\frac{\mathcal{B}\left({\Lambda}_b^0\to {D}^{+}{D}^{-}\Lambda \right)}{\mathcal{B}\left({B}^0\to {D}^{+}{D}^{-}{K}_{\textrm{S}}^0\right)}=0.179\pm 0.022\pm 0.014, $$ where the first uncertainty is statistical and the second is systematic. The known branching fraction of the reference channel, B B 0 → D + D − K S 0 $$ \mathcal{B}\left({B}^0\to {D}^{+}{D}^{-}{K}_{\textrm{S}}^0\right) $$ , and the cross-section ratio, σ Λ b 0 / σ B 0 $$ {\sigma}_{\Lambda_b^0}/{\sigma}_{B^0} $$ , previously measured by LHCb are used to derive the branching fraction of the Λ b 0 $$ {\Lambda}_b^0 $$ → D + D − Λ decay B Λ b 0 → D + D − Λ = 1.24 ± 0.15 ± 0.10 ± 0.28 ± 0.11 × 10 − 4 , $$ \mathcal{B}\left({\Lambda}_b^0\to {D}^{+}{D}^{-}\Lambda \right)=\left(1.24\pm 0.15\pm 0.10\pm 0.28\pm 0.11\right)\times {10}^{-4}, $$ where the third and fourth contributions are due to uncertainties of B B 0 → D + D − K S 0 $$ \mathcal{B}\left({B}^0\to {D}^{+}{D}^{-}{K}_{\textrm{S}}^0\right) $$ and σ Λ b 0 / σ B 0 $$ {\sigma}_{\Lambda_b^0}/{\sigma}_{B^0} $$ , respectively. Inspection of the D +Λ and D + D − invariant-mass distributions suggests a rich presence of intermediate resonances in the decay. The Λ b 0 $$ {\Lambda}_b^0 $$ → D *+ D − Λ decay is also observed for the first time as a partially reconstructed component in the D + D − Λ invariant mass spectrum.
Abstract The resonant structure of the radiative decay Λ b 0 → pK − γ $$ {\Lambda}_b^0\to {pK}^{-}\gamma $$ in the region of proton-kaon invariant-mass up to 2.5 GeV/c 2 is studied using ...proton-proton collision data recorded at centre-of-mass energies of 7, 8, and 13 TeV collected with the LHCb detector, corresponding to a total integrated luminosity of 9 fb −1. Results are given in terms of fit and interference fractions between the different components contributing to this final state. Only Λ resonances decaying to pK − are found to be relevant, where the largest contributions stem from the Λ(1520), Λ(1600), Λ(1800), and Λ(1890) states.
Abstract Measurements of the branching fraction ratio B ϕ → μ + μ − / B ϕ → e + e − $$ \mathcal{B}\left(\phi \to {\mu}^{+}{\mu}^{-}\right)/\mathcal{B}\left(\phi \to {e}^{+}{e}^{-}\right) $$ with D s ...+ → π + ϕ $$ {D}_s^{+}\to {\pi}^{+}\phi $$ and D + → π + ϕ decays, denoted R ϕπ s $$ {R}_{\phi \pi}^s $$ and R ϕπ d $$ {R}_{\phi \pi}^d $$ , are presented. The analysis is performed using a dataset corresponding to an integrated luminosity of 5.4 fb −1 of pp collision data collected with the LHCb experiment. The branching fractions are normalised with respect to the B + → K + J/ψ(→ e + e − ) and B + → K + J/ψ(→ μ + μ − ) decay modes. The combination of the results yields R ϕπ = 1.022 ± 0.012 stat ± 0.048 syst . $$ {R}_{\phi \pi}=1.022\pm 0.012\left(\textrm{stat}\right)\pm 0.048\left(\textrm{syst}\right). $$ The result is compatible with previous measurements of the ϕ → ℓ + ℓ − branching fractions and predictions based on the Standard Model.
Abstract The ratio of branching fractions between B 0 → J/ψπ 0 and B + → J/ψK *+ decays is measured with proton-proton collision data collected by the LHCb experiment, corresponding to an integrated ...luminosity of 9 fb −1. The measured value is B B 0 → J / ψ π 0 B B + → J / ψ K ∗ + = 1.153 ± 0.053 ± 0.048 × 10 − 2 , $$ \frac{{\mathcal{B}}_{B^0\to J/\psi {\pi}^0}}{{\mathcal{B}}_{B^{+}\to J/\psi {K}^{\ast +}}}=\left(1.153\pm 0.053\pm 0.048\right)\times {10}^{-2}, $$ where the first uncertainty is statistical and the second is systematic. The branching fraction for B 0 → J/ψπ 0 decays is determined using the branching fraction of the normalisation channel, resulting in B B 0 → J / ψ π 0 = 1.670 ± 0.077 ± 0.069 ± 0.095 × 10 − 5 , $$ {\mathcal{B}}_{B^0\to J/\psi {\pi}^0}=\left(1.670\pm 0.077\pm 0.069\pm 0.095\right)\times {10}^{-5}, $$ where the last uncertainty corresponds to that of the external input. This result is consistent with the current world average value and competitive with the most precise single measurement to date.
Abstract A measurement of CP-violating observables associated with the interference of B 0 → D 0 K ⋆(892)0 and B 0 → D ¯ 0 K ⋆ 892 0 $$ {B}^0\to {\overline{D}}^0{K}^{\star }{(892)}^0 $$ decay ...amplitudes is performed in the D 0 → K ∓ π ± (π + π − ), D 0 → π + π − (π + π − ), and D 0 → 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 → D 0 K ¯ ⋆ 892 0 $$ {B}_s^0\to {D}^0{\overline{K}}^{\star }{(892)}^0 $$ and B s 0 → D ¯ 0 K ¯ ⋆ 892 0 $$ {B}_s^0\to {\overline{D}}^0{\overline{K}}^{\star }{(892)}^0 $$ are also measured, but no evidence for interference is found. The B 0 observables are used to constrain the parameter space of the CKM angle γ and the hadronic parameters r B 0 DK ⋆ $$ {r}_{B^0}^{DK\star } $$ and δ B 0 DK ⋆ $$ {\delta}_{B^0}^{DK\star } $$ 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.
Abstract The 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 + ) < 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.
Abstract The cross-section of associated J/ψ-ψ(2S) production in proton-proton collisions at a centre-of-mass energy of s $$ \sqrt{s} $$ = 13 TeV is measured using a data sample corresponding to an ...integrated luminosity of 4.2 fb −1, collected by the LHCb experiment. The measurement is performed for both J/ψ and ψ(2S) mesons having transverse momentum p T < 14 GeV/c and rapidity 2.0 < y < 4.5, assuming negligible polarisation of the J/ψ and ψ(2S) mesons. The production cross-section is measured to be 4.5 ± 0.7 ± 0.3 nb, where the first uncertainty is statistical and the second systematic. The differential cross-sections are measured as functions of several kinematic variables of the J/ψ-ψ(2S) candidates. The results are combined with a measurement of J/ψ-J/ψ production, giving a cross-section ratio between J/ψ-ψ(2S) and J/ψ-J/ψ production of 0.274 ± 0.044 ± 0.008, where the first uncertainty is statistical and the second systematic.
Abstract The ratio of production cross-sections of ψ(2S) over J/ψ mesons as a function of charged-particle multiplicity in proton-proton collisions at a centre-of-mass energy s $$ \sqrt{s} $$ = 13 ...TeV is measured with a data sample collected by the LHCb detector, corresponding to an integrated luminosity of 658 pb −1. The ratio is measured for both prompt and non-prompt ψ(2S) and J/ψ mesons. When there is an overlap between the rapidity ranges over which multiplicity and charmonia production are measured, a multiplicity-dependent modification of the ratio is observed for prompt mesons. No significant multiplicity dependence is found when the ranges do not overlap. For non-prompt production, the ψ(2S)-to-J/ψ production ratio is roughly independent of multiplicity, irrespective of the rapidity range over which the multiplicity is measured. The results are compared to predictions of the co-mover model and agree well except in the low multiplicity region. The ratio of production cross-sections of ψ(2S) over J/ψ mesons are cross-checked with other measurements in di-lepton channels and found to be compatible.
