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A<sc>bstract</sc> This paper presents a study of the charmless three-body decays$$ {B}_{(s)}^0\to {K}_{\mathrm{S}}^0{h}^{+}h{\prime}^{-} $$ $B_{\left(s\right)}^0\to K_S^0{h}^{+}h{\prime }^{-}$ (whereh⁽′⁾=π, K), using a sample ofppcollision data collected by the LHCb experiment during Runs 1 and 2 of the LHC, corresponding to an integrated luminosity of 9 fb⁻¹. The decay$$ {B}_s^0\to {K}_{\mathrm{S}}^0{K}^{+}{K}^{-} $$ $B_s^0\to K_S^0{K}^{+}{K}^{-}$ is observed for the first time, and the following ratios of branching fractions are measured:$$ {\displaystyle \begin{array}{l}\frac{\mathcal{B}\left({B}^0\to {K}_{\mathrm{S}}^0{K}^{+}{K}^{-}\right)}{\mathcal{B}\left({B}^0\to {K}_{\mathrm{S}}^0{\pi}^{+}{\pi}^{-}\right)}=0.578\pm 0.007\pm 0.017,\\ {}\frac{\mathcal{B}\left({B}^0\to {K}_{\mathrm{S}}^0{K}^{\pm }{K}^{\mp}\right)}{\mathcal{B}\left({B}^0\to {K}_{\mathrm{S}}^0{\pi}^{+}{\pi}^{-}\right)}=0.1363\pm 0.0035\pm 0.051,\\ {}\begin{array}{l}\frac{\mathcal{B}\left({B}_s^0\to {K}_{\mathrm{S}}^0{\pi}^{+}{\pi}^{-}\right)}{\mathcal{B}\left({B}^0\to {K}_{\mathrm{S}}^0{\pi}^{+}{\pi}^{-}\right)}=0.269\pm 0.011\pm 0.015\pm 0.008,\\ {}\frac{\mathcal{B}\left({B}_s^0\to {K}_{\mathrm{S}}^0{K}^{+}{K}^{-}\right)}{\mathcal{B}\left({B}^0\to {K}_{\mathrm{S}}^0{\pi}^{+}{\pi}^{-}\right)}=0.0303\pm 0.0041\pm 0.0025\pm 0.0009,\\ {}\frac{\mathcal{B}\left({B}_s^0\to {K}_{\mathrm{S}}^0{K}^{\pm }{\pi}^{\mp}\right)}{\mathcal{B}\left({B}^0\to {K}_{\mathrm{S}}^0{\pi}^{+}{\pi}^{-}\right)}=1.818\pm 0.021\pm 0.031\pm 0.056,\end{array}\end{array}} $$ $\begin{array}{c}\frac{B\left(B^0\to K_S^0{K}^{+}{K}^{-}\right)}{B\left(B^0\to K_S^0{\pi }^{+}{\pi }^{-}\right)}=0.578\pm 0.007\pm 0.017,\\ \frac{B\left(B^0\to K_S^0{K}^{\pm }{K}^{\mp }\right)}{B\left(B^0\to K_S^0{\pi }^{+}{\pi }^{-}\right)}=0.1363\pm 0.0035\pm 0.051,\\ \begin{array}{c}\frac{B\left(B_s^0\to K_S^0{\pi }^{+}{\pi }^{-}\right)}{B\left(B^0\to K_S^0{\pi }^{+}{\pi }^{-}\right)}=0.269\pm 0.011\pm 0.015\pm 0.008,\\ \frac{B\left(B_s^0\to K_S^0{K}^{+}{K}^{-}\right)}{B\left(B^0\to K_S^0{\pi }^{+}{\pi }^{-}\right)}=0.0303\pm 0.0041\pm 0.0025\pm 0.0009,\\ \frac{B\left(B_s^0\to K_S^0{K}^{\pm }{\pi }^{\mp }\right)}{B\left(B^0\to K_S^0{\pi }^{+}{\pi }^{-}\right)}=1.818\pm 0.021\pm 0.031\pm 0.056,\end{array}\end{array}$ where the uncertainties are statistical, systematic, and due to knowledge of the ratio of hadronisation fractions of the$$ {B}_s^0 $$ $B_s^0$ andB⁰mesons, respectively. 

An amplitude analysis of the ${\mathrm{\Xi }}_c^{+}\to p{K}^{-}{\pi }^{+}$ decay together with a measurement of the ${\mathrm{\Xi }}_c^{+}$ polarization vector in semileptonic beauty-hadron decays is presented. The analysis is performed using proton-proton collision data collected by the LHCb experiment, corresponding to an integrated luminosity of $9{\mathrm{fb}}^{-1}$ . An amplitude model is developed and the resonance fractions as well as two- and three-body decay parameters are reported. A sizeable ${\mathrm{\Xi }}_c^{+}$ polarization is found. A large sensitivity of the ${\mathrm{\Xi }}_c^{+}\to p{K}^{-}{\pi }^{+}$ decay to the polarization is seen, making the amplitude model suitable for ${\mathrm{\Xi }}_c^{+}$ polarization measurements in other systems. 

A<sc>bstract</sc> The invariant-mass distribution for the coherent photoproduction of dipions in ultraperipheral PbPb collisions is measured using data, corresponding to an integrated luminosity of 224.6 ± 9.6μb⁻¹, collected by the LHCb experiment in 2018 at a nucleon-nucleon centre-of-mass energy$$ \sqrt{{\textrm{s}}_{\textrm{NN}}}=5.02 $$ $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV. In the mass range from 400 to 1200 MeV, the results are consistent with previous experiments, with the spectrum dominated by theρ⁰meson, which interferes with a nonresonant component, together with a smallerωmeson contribution. In an extended mass range up to 2300 MeV, models previously used do not fit the data and a consistent description requires the introduction of two resonances at masses of 1350 ± 20 MeV and 1790 ± 20 MeV with widths of about 300 MeV. The cross-section for each meson is measured differentially in twelve bins of rapidity from 2.05 to 4.90. Theρ⁰cross-section increases with rapidity from about 400 to 600 mb and is measured with a typical precision of 8%, while the cross-section times branching fraction for theω,ρ′andρ′′, with the statistical precision of the data, do not have a pronounced rapidity dependence and are between 0.5 and 1.5mb, with uncertainties up to 30%. A large nuclear suppression is observed for theρ⁰meson compared to expectations based on photoproduction on the proton that use the impulse approximation. Significant suppression is also observed compared to that predicted by elastic scattering described in the Glauber approach, or with the addition of inelastic scattering in a Gribov-Glauber model. 

A<sc>bstract</sc> The elliptic and triangular flow of charged particles are measured using two-particle angular correlations inpPb collisions in the pseudorapidity range 2.0<|η|<4.8. The data sample was collected by the LHCb experiment in 2016 at a centre-of-mass energy per nucleon pair of$$ \sqrt{s_{\textrm{NN}}}=8.16 $$ $\sqrt{s_{\mathrm{NN}}}=8.16$ TeV, containing in total approximately 1.5 billion collision events. Non-flow contributions are obtained in low-multiplicity collisions and subtracted to extract the flow harmonics. The results are presented as a function of event multiplicity and hadron transverse momentum. Comparisons with a full (3+1)D dynamic model indicate that it overestimates the measured elliptic flow. A comparison between the forward and backward regions reveals no significant differences in flow parameters, suggesting that final-state effects may dominate over initial-state effects in the origin of flow in small systems. 

A<sc>bstract</sc> A search for the doubly-charmed-baryon decay$$ {\Xi}_{cc}^{++}\to {\Xi}_c^0{\pi}^{+}{\pi}^{+} $$ ${\Xi }_{\mathrm{cc}}^{++}\to {\Xi }_c^0{\pi }^{+}{\pi }^{+}$ is performed using proton-proton collision data collected by the LHCb experiment at a centre-of-mass energy of 13 TeV and corresponding to an integrated luminosity of 5.4 fb⁻¹. A significant structure consistent with the$$ {\Xi}_{cc}^{++} $$ ${\Xi }_{\mathrm{cc}}^{++}$ baryon is observed in the$$ {\Xi}_c^0{\pi}^{+}{\pi}^{+} $$ ${\Xi }_c^0{\pi }^{+}{\pi }^{+}$ invariant-mass spectrum. Using the$$ {\Xi}_{cc}^{++}\to {\Lambda}_c^{+}{K}^{-}{\pi}^{+}{\pi}^{+} $$ ${\Xi }_{\mathrm{cc}}^{++}\to {\Lambda }_c^{+}{K}^{-}{\pi }^{+}{\pi }^{+}$ decay as the normalisation channel, the branching fraction ratio,$$ \frac{\mathcal{B}\left({\Xi}_{cc}^{++}\to {\Xi}_c^0{\pi}^{+}{\pi}^{+}\right)}{\mathcal{B}\left({\Xi}_{cc}^{++}\to {\Lambda}_c^{+}{K}^{-}{\pi}^{+}{\pi}^{+}\right)} $$ $\frac{B\left({\Xi }_{\mathrm{cc}}^{++}\to {\Xi }_c^0{\pi }^{+}{\pi }^{+}\right)}{B\left({\Xi }_{\mathrm{cc}}^{++}\to {\Lambda }_c^{+}{K}^{-}{\pi }^{+}{\pi }^{+}\right)}$ , is measured to be 1.37±0.18 (stat)±0.09 (syst)±0.35 (ext). This measurement provides critical input for testing QCD factorisation methods in the weak decays of doubly-heavy baryons, particularly in quantifying nonperturbative effects such as final-state interactions and resonance contributions to the hadronisation process. 

The ${\mathrm{\Xi }}_c^{+}{\pi }^{-}{\pi }^{+}$ spectrum is investigated using proton-proton collisions at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of $5.4{\mathrm{fb}}^{-1}$ , collected by the LHCb experiment during 2016–2018. Four states are observed with high significance, and their masses and widths are measured to be $m\left[{\mathrm{\Xi }}_c\right(2815{)}^{+}]=2816.65\pm 0.03\pm 0.03\pm 0.23\mathrm{MeV}$ , $\mathrm{\Gamma }\left[{\mathrm{\Xi }}_c\right(2815{)}^{+}]=2.07\pm 0.08\pm 0.12\mathrm{MeV}$ , $m\left[{\mathrm{\Xi }}_c\right(2923{)}^{+}]=2922.8\pm 0.3\pm 0.5\pm 0.2\mathrm{MeV}$ , $\mathrm{\Gamma }\left[{\mathrm{\Xi }}_c\right(2923{)}^{+}]=5.3\pm 0.9\pm 1.4\mathrm{MeV}$ , $m\left[{\mathrm{\Xi }}_c\right(2970{)}^{+}]=2968.6\pm 0.5\pm 0.5\pm 0.2\mathrm{MeV}$ , $\mathrm{\Gamma }\left[{\mathrm{\Xi }}_c\right(2970{)}^{+}]=31.7\pm 1.7\pm 1.9\mathrm{MeV}$ , $m\left[{\mathrm{\Xi }}_c\right(3080{)}^{+}]=3076.8\pm 0.7\pm 1.3\pm 0.2\mathrm{MeV}$ , $\mathrm{\Gamma }\left[{\mathrm{\Xi }}_c\right(3080{)}^{+}]=6.8\pm 2.3\pm 0.9\mathrm{MeV}$ , where the uncertainties are statistical, systematic, and due to the limited precision on the ${\mathrm{\Xi }}_c^{+}$ mass, respectively. The ${\mathrm{\Xi }}_c(2923{)}^{+}$ baryon is observed for the first time, and is consistent with being the isospin partner of the previously observed ${\mathrm{\Xi }}_c(2923{)}^0$ state. Most of the measured parameters are more precise than existing world averages. 

A<sc>bstract</sc> This article presents doubly differential measurements of the asymmetries in production rates between mesons containing a charm quark and those containing an anti-charm quark in proton-proton collisions at a centre-of-mass energy of$$ \sqrt{s}=13.6 $$ $\sqrt{s}=13.6$ TeV using data recorded by the LHCb experiment. The asymmetries ofD⁰,D⁺and$$ {D}_s^{+} $$ $D_s^{+}$ mesons are measured for two-dimensional intervals in transverse momentum and pseudorapidity, within the range 2.5< p_T<25.0 GeV/cand 2.0< η <4.5. No significant production asymmetries are observed. Comparisons to the Pythia8 and Herwig 7 event generators are also presented, and their agreement with the data is evaluated. These measurements constitute the first measurements of production asymmetries at this centre-of-mass energy of colliding beams, and the first measurements with the LHCb Run 3 detector. 

A<sc>bstract</sc> An angular analysis ofB⁰→ K^*0e⁺e⁻decays is presented using proton-proton collision data collected by the LHCb experiment at centre-of-mass energies of 7, 8 and 13 TeV, corresponding to an integrated luminosity of 9 fb⁻¹. The analysis is performed in the region of the dilepton invariant mass squared of 1.1–6.0 GeV²/c⁴. In addition, a test of lepton flavour universality is performed by comparing the obtained angular observables with those measured inB⁰→ K^*0μ⁺μ⁻decays. In general, the angular observables are found to be consistent with the Standard Model expectations as well as with global analyses of otherb → sℓ⁺ℓ⁻processes, whereℓis either a muon or an electron. No sign of lepton-flavour-violating effects is observed. 

A<sc>bstract</sc> A search for the decay$$ {B}_c^{+} $$ $B_c^{+}$ → χ_c1(3872)π⁺is reported using proton-proton collision data collected with the LHCb detector between 2011 and 2018 at centre-of-mass energies of 7, 8, and 13 TeV, corresponding to an integrated luminosity of 9 fb⁻¹. No significant signal is observed. Using the decay$$ {B}_c^{+} $$ $B_c^{+}$ →ψ(2S)π⁺as a normalisation channel, an upper limit for the ratio of branching fractions$$ {\mathcal{R}}_{\psi (2S)}^{\chi_{c1}(3872)}=\frac{{\mathcal{B}}_{B_c^{+}\to {\chi}_{c1}(3872){\pi}^{+}}}{{\mathcal{B}}_{B_c^{+}\to \psi (2S){\pi}^{+}}}\times \frac{{\mathcal{B}}_{\chi_{c1}(3872)\to J/\psi {\pi}^{+}{\pi}^{-}}}{{\mathcal{B}}_{\psi (2S)\to J/\psi {\pi}^{+}{\pi}^{-}}}<0.05(0.06), $$ $R_{\psi \left(2S\right)}^{{\chi }_{c1}\left(3872\right)}=\frac{B_{B_c^{+}\to {\chi }_{c1}\left(3872\right){\pi }^{+}}}{B_{B_c^{+}\to \psi \left(2S\right){\pi }^{+}}}\times \frac{B_{{\chi }_{c1}\left(3872\right)\to J/\psi {\pi }^{+}{\pi }^{-}}}{B_{\psi \left(2S\right)\to J/\psi {\pi }^{+}{\pi }^{-}}}<0.05\left(0.06\right),$ is set at the 90 (95)% confidence level.