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The Υ (2 S ) and Υ (3 S ) production cross-sections are measured relative to that of the Υ (1 S ) meson, as a function of charged-particle multiplicity in proton-proton collisions at a centre-of-mass energy of 13 TeV. The measurement uses data collected by the LHCb experiment in 2018 corresponding to an integrated luminosity of 2 fb − 1 . Both the Υ (2 S )-to- Υ (1 S ) and Υ (3 S )-to- Υ (1 S ) cross-section ratios are found to decrease significantly as a function of event multiplicity, with the Υ (3 S )-to- Υ (1 S ) ratio showing a steeper decline towards high multiplicity. This hierarchy is qualitatively consistent with the comover model predictions, indicating that final-state interactions play an important role in bottomonia production in high-multiplicity events.

A time-integrated angular analysis of the decay$$ {B}_s^0\\to J/\\psi {\\overline{K}}^{\\ast }{(892)}^0 $$B s 0 → J / ψ K ¯ ∗ 892 0 , with J / ψ → μ + μ − and$$ {\\overline{K}}^{\\ast }{(892)}^0\\to {K}^{-}{\\pi}^{+} $$K ¯ ∗ 892 0 → K − π + , is presented. The analysis employs a sample of proton-proton collision data collected by the LHCb experiment during 2015–2018 at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 6 fb − 1 . A simultaneous maximum-likelihood fit is performed to the angular distributions in bins of the K − π + mass. This fit yields measurements of the CP -averaged polarisation fractions and CP asymmetries for the P-wave component of the K − π + system. The longitudinal and parallel polarisation fractions are determined to be f 0 = 0.534 ± 0.012 ± 0.009 and f || = 0.211 ± 0.014 ± 0.005, respectively, where the first uncertainty is statistical and the second is systematic. The CP asymmetries are measured with 3–7% precision and are found to be consistent with zero. These measurements, along with an updated determination of the branching fraction relative to the B 0 → J / ψK *0 decay, are combined with previous LHCb results, providing the most precise values for these observables to date.

Branching fraction ratios between the decays$$ {B}_{(s)}^0\\to J/\\psi {\\eta}^{\\left(\\prime \\right)} $$B s 0 → J / ψ η ′ are measured 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 measured ratios of these branching fractions are$$ {\\displaystyle \\begin{array}{c}\\frac{\\mathcal{B}\\left({B}^0\\to J/{\\psi \\eta}^{\\prime}\\right)}{\\mathcal{B}\\left({B}^0\\to J/\\psi \\eta \\right)}=0.48\\pm 0.06\\pm 0.02\\pm 0.01,\\\ {}\\frac{\\mathcal{B}\\left({B}_s^0\\to J/{\\psi \\eta}^{\\prime}\\right)}{\\mathcal{B}\\left({B}_s^0\\to J/\\psi \\eta \\right)}=0.80\\pm 0.02\\pm 0.02\\pm 0.01,\\end{array}} $$B B 0 → J / ψη ′ B B 0 → J / ψη = 0.48 ± 0.06 ± 0.02 ± 0.01 , B B s 0 → J / ψη ′ B B s 0 → J / ψη = 0.80 ± 0.02 ± 0.02 ± 0.01 , where the uncertainties are statistical, systematic and related to the precision of the η (′) branching fractions, respectively. They are used to constrain the η/η ′ mixing angle, ϕ P , and to probe the presence of a possible glueball component in the η ′ meson, described by the gluonic mixing angle ϕ G . The obtained results are$$ {\\displaystyle \\begin{array}{c}{\\phi}_{\\textrm{P}}={\\left({41.6}_{-1.2}^{+1.0}\\right)}^{\\circ },\\\ {}{\\phi}_{\\textrm{G}}={\\left({28.1}_{-4.0}^{+3.9}\\right)}^{\\circ },\\end{array}} $$ϕ P = 41.6 − 1.2 + 1.0 ∘ , ϕ G = 28.1 − 4.0 + 3.9 ∘ , where the uncertainties are statistically dominated. While the value of ϕ P is compatible with existing experimental determinations and theoretical calculations, the angle ϕ G differs from zero by more than four standard deviations, which points to a substantial glueball component in the η ′ meson and/or unexpectedly large contributions from gluon-mediated processes in these decays. The absolute branching fractions are also measured relative to that of the well-established$$ {B}_s^0\\to J/\\psi \\phi $$B s 0 → J / ψϕ decay, which serves as the normalisation channel. These results supersede the previous LHCb measurements and are the most precise to date.

A study of$$ {\\Lambda}_b^0 $$Λ b 0 and$$ {\\Xi}_b^0 $$Ξ b 0 baryon decays to the final states$$ p{K}_{\\textrm{S}}^0{\\pi}^{-} $$p K S 0 π − and$$ p{K}_{\\textrm{S}}^0{K}^{-} $$p K S 0 K − is performed using pp collision data collected by the LHCb experiment, corresponding to an integrated luminosity of 9 fb − 1 . The decays$$ {\\Lambda}_b^0\\to p{K}_{\\textrm{S}}^0{K}^{-} $$Λ b 0 → p K S 0 K − and$$ {\\Xi}_b^0\\to p{K}_{\\textrm{S}}^0{K}^{-} $$Ξ b 0 → p K S 0 K − are observed for the first time, with significances reaching eight standard deviations. The branching fractions and integrated CP asymmetries are measured for the$$ {\\Lambda}_b^0\\to p{K}_{\\textrm{S}}^0{\\pi}^{-} $$Λ b 0 → p K S 0 π − ,$$ {\\Lambda}_b^0\\to p{K}_{\\textrm{S}}^0{K}^{-} $$Λ b 0 → p K S 0 K − , and$$ {\\Xi}_b^0\\to p{K}_{\\textrm{S}}^0{K}^{-} $$Ξ b 0 → p K S 0 K − decays. For the decay$$ {\\Lambda}_b^0\\to p{K}_{\\textrm{S}}^0{\\pi}^{-} $$Λ b 0 → p K S 0 π − , the CP asymmetries are measured in different regions of the Dalitz plot. No evidence of CP violation is observed.

A search for the doubly-charmed-baryon decay$$ {\\Xi}_{cc}^{++}\\to {\\Xi}_c^0{\\pi}^{+}{\\pi}^{+} $$Ξ cc + + → Ξ c 0 π + π + 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$$ {\\Xi}_{cc}^{++} $$Ξ cc + + baryon is observed in the$$ {\\Xi}_c^0{\\pi}^{+}{\\pi}^{+} $$Ξ c 0 π + π + invariant-mass spectrum. Using the$$ {\\Xi}_{cc}^{++}\\to {\\Lambda}_c^{+}{K}^{-}{\\pi}^{+}{\\pi}^{+} $$Ξ cc + + → Λ c + K − π + π + decay as the normalisation channel, the branching fraction ratio,$$ \\frac{\\mathcal{B}\\left({\\Xi}_{cc}^{++}\\to {\\Xi}_c^0{\\pi}^{+}{\\pi}^{+}\\right)}{\\mathcal{B}\\left({\\Xi}_{cc}^{++}\\to {\\Lambda}_c^{+}{K}^{-}{\\pi}^{+}{\\pi}^{+}\\right)} $$B Ξ cc + + → Ξ c 0 π + π + B Ξ cc + + → Λ c + K − π + π + , 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 elliptic and triangular flow of charged particles are measured using two-particle angular correlations in p Pb 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$$ \\sqrt{s_{\\textrm{NN}}}=8.16 $$s 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.

The lifetimes of the$$ {\\varOmega}_c^0 $$Ω c 0 and$$ {\\Xi}_c^0 $$Ξ c 0 baryons are measured using a pp collision dataset collected by the LHCb experiment, corresponding to an integrated luminosity of 9 fb − 1 . The charm baryons are produced in the fully reconstructed decay chains$$ {\\varOmega}_b^{-}\\to {\\varOmega}_c^0\\left(\\to p{K}^{-}{K}^{-}{\\pi}^{+}\\right){\\pi}^{-} $$Ω b − → Ω c 0 → p K − K − π + π − and$$ {\\Xi}_b^{-}\\to {\\Xi}_c^0\\left(\\to p{K}^{-}{K}^{-}{\\pi}^{+}\\right){\\pi}^{-} $$Ξ b − → Ξ c 0 → p K − K − π + π − . The measurement uses topologically and kinematically similar B − → D 0 (→ K − K + π − π + ) π − decays for normalisation. The measured lifetimes are$$ {\\displaystyle \\begin{array}{c}{\\tau}_{\\varOmega_c^0}=276.3\\pm 19.4\\left(\\textrm{stat}\\right)\\pm 1.8\\left(\\textrm{syst}\\right)\\pm 0.7\\left({\\tau}_{D^0}\\right)\\textrm{fs},\\\ {}{\\tau}_{\\Xi_c^0}=149.2\\pm 2.5\\left(\\textrm{stat}\\right)\\pm 0.9\\left(\\textrm{syst}\\right)\\pm 0.4\\ \\left({\\tau}_{D^0}\\right)\\textrm{fs},\\end{array}} $$τ Ω c 0 = 276.3 ± 19.4 stat ± 1.8 syst ± 0.7 τ D 0 fs , τ Ξ c 0 = 149.2 ± 2.5 stat ± 0.9 syst ± 0.4 τ D 0 fs , where the first uncertainty is statistical, the second systematic and the third due to the uncertainty of the D 0 lifetime. These results are consistent with previous measurements performed by the LHCb experiment.

This paper presents the first measurement of$$\\psi {(2S)}$$ψ ( 2 S ) and$$\\chi _{c1}(3872)$$χ c 1 ( 3872 ) meson production within fully reconstructed jets. Each quarkonium state (tag) is reconstructed via its decay to the$${{J \\hspace{-1.66656pt}/\\hspace{-1.111pt}\\psi }} $$J / ψ ($$\\rightarrow $$→$$\\mu ^+\\mu ^-$$μ + μ - )$$\\pi ^+\\pi ^-$$π + π - final state in the forward region using proton-proton collision data collected by the LHCb experiment at the center-of-mass-energy of$$13\\text {TeV} $$13 TeV in 2016, corresponding to an integrated luminosity of$$1.64\\,\\text {\\,fb} ^{-1} $$1.64 \\,fb - 1 . The fragmentation function, presented as the ratio of the quarkonium-tag transverse momentum to the full jet transverse momentum ($$p_{\\textrm{T}} (\\text {tag})/p_{\\textrm{T}} (\\text {jet})$$p T ( tag ) / p T ( jet ) ), is measured differentially in$$p_{\\textrm{T}} (\\text {jet})$$p T ( jet ) and$$p_{\\textrm{T}} (\\text {tag})$$p T ( tag ) bins. The distributions are separated into promptly produced quarkonia from proton-proton collisions and quarkonia produced from displaced b -hadron decays. While the displaced quarkonia fragmentation functions are in general well described by parton-shower predictions, the prompt quarkonium distributions differ significantly from fixed-order non-relativistic QCD (NRQCD) predictions followed by a QCD parton shower.

A study of the charmless baryonic decays$$ {B}_{(s)}^0\\to {K}^0p\\overline{p} $$B s 0 → K 0 p p ¯ is presented, where$$ {B}_{(s)}^0 $$B s 0 denotes either a B 0 or a$$ {B}_s^0 $$B s 0 meson. The analysis is based on 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 decay$$ {B}_s^0\\to {K}^0p\\overline{p} $$B s 0 → K 0 p p ¯ is observed for the first time, with a measured branching fraction of (9 . 14 ± 1 . 69 ± 0 . 90 ± 0 . 33 ± 0 . 20) × 10 − 7 and a significance of 5.6 σ . The uncertainties respectively account for statistical and systematic contributions, the precision of the branching fraction of the normalisation channel B 0 → K 0 π + π − and the fragmentation fraction ratio f s /f d . The branching fraction determined for$$ {B}^0\\to {K}^0p\\overline{p} $$B 0 → K 0 p p ¯ is (2 . 82 ± 0 . 08 ± 0 . 12 ± 0 . 10) × 10 − 6 , which is the most precise measurement to date.

An angular analysis of the decay$$ {B}_s^0 $$B s 0 → ϕe + e − is presented, 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. The combined dataset corresponds to an integrated luminosity of 9 fb − 1 . Observables are determined by fitting time-integrated projections of the angular distribution in three bins of dielectron mass squared, q 2 , corresponding to [0 . 1 , 1 . 1], [1 . 1 , 6 . 0] and [15 . 0 , 19 . 0] GeV 2 /c 4 . The results are compatible with predictions based on the Standard Model of particle physics.