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Mesons comprising a beauty quark and strange quark can oscillate between particle ( B s 0 ) and antiparticle ( B ¯ s 0 ) flavour eigenstates, with a frequency given by the mass difference between heavy and light mass eigenstates, Δ m s . Here we present a measurement of Δ m s using B s 0 → D s − π + decays produced in proton–proton collisions collected with the LHCb detector at the Large Hadron Collider. The oscillation frequency is found to be Δ m s  = 17.7683 ± 0.0051 ± 0.0032 ps −1 , where the first uncertainty is statistical and the second is systematic. This measurement improves on the current Δ m s precision by a factor of two. We combine this result with previous LHCb measurements to determine Δ m s  = 17.7656 ± 0.0057 ps −1 , which is the legacy measurement of the original LHCb detector. The LHCb collaboration reports an improved measurement of the oscillation frequency of mesons consisting of a bottom quark and strange quark, which is then combined with previous results.

The Ξ b 0 → Ξ c + D s - and Ξ b - → Ξ c 0 D s - decays are observed for the first time using proton-proton collision data collected by the LHCb experiment at a centre-of-mass energy of s = 13 TeV , corresponding to an integrated luminosity of 5.1 fb - 1 . The branching fractions times the production cross-sections of Ξ b baryons relative to that of Λ b 0 baryon are measured to be R Ξ b 0 Λ b 0 ≡ σ Ξ b 0 σ Λ b 0 × B Ξ b 0 → Ξ c + D s - B Λ b 0 → Λ c 0 D s - = ( 15.8 ± 1.1 ± 0.6 ± 7.7 ) % , R Ξ b - Λ b 0 ≡ σ Ξ b - σ Λ b 0 × B Ξ b - → Ξ c 0 D s - B Λ b 0 → Λ c 0 D s - = ( 16.9 ± 1.3 ± 0.9 ± 4.3 ) % , where the first uncertainties are statistical, the second systematic, and the third due to the uncertainties on the decay branching fractions of relevant charmed baryons. The masses of Ξ b 0 and Ξ b - baryons are measured to be m Ξ b 0 = 5791.12 ± 0.60 ± 0.45 ± 0.24 MeV / c 2 and m Ξ b - = 5797.02 ± 0.63 ± 0.49 ± 0.29 MeV / c 2 , where the uncertainties are statistical, systematic, and those due to charmed-hadron masses, respectively.

The first observation of the Ξ b 0 → J / ψ Ξ - π + decay and the most precise measurement of the branching fraction of the Λ b 0 → J / ψ Ξ - K + decay are reported, using proton-proton collision data from the LHCb experiment collected in 2016–2018 at a centre-of-mass energy of 13 \\,Te V , corresponding to an integrated luminosity of 5.4 \\,fb - 1 . Using the Λ b 0 → J / ψ Λ and Ξ b - → J / ψ Ξ - decays as normalisation channels, the ratios of branching fractions are measured to be B ( Λ b 0 → J / ψ Ξ - K + ) B ( Λ b 0 → J / ψ Λ ) = ( 1.17 ± 0.14 ± 0.08 ) × 10 - 2 , B ( Ξ b 0 → J / ψ Ξ - π + ) B ( Ξ b - → J / ψ Ξ - ) = ( 11.9 ± 1.4 ± 0.6 ) × 10 - 2 , where the first uncertainty is statistical and the second systematic.

An angular analysis of the B-s(0)-> phi e(+)e(-) decay is performed using the proton-proton collision dataset collected between 2011 and 2018 by the LHCb experiment, corresponding to an integrated luminosity of 9 fb(-1) at centre-of-mass energies of 7, 8 and 13 TeV. The analysis is performed in the very low dielectron invariant mass-squared region between 0.0009 and 0.2615 GeV2/c(4). The longitudinal polarisation fraction of the phi meson is measured to be less than 11.5% at 90% confidence level. The A(T)(ReCP) observable, which is related to the lepton forward-backward asymmetry, is measured to be 0.116 +/- 0.155 +/- 0.006, where the first uncertainty is statistical and the second systematic. The transverse asymmetries, A(T)((2)) and A(T)(ImCP), which are sensitive to the virtual photon polarisation, are found to be -0.045 +/- 0.235 +/- 0.014 and 0.002 +/- 0.247 +/- 0.016, respectively. The results are consistent with Standard Model predictions.

The decays Λ b 0 → Λ c + D ¯ ( ∗ ) 0 K - and Λ b 0 → Λ c + D s ∗ - are observed for the first time, in proton-proton collision data at s = 13 Te V , corresponding to an integrated luminosity of 5.4 fb - 1 collected with the LHCb detector. Their ratios of branching fractions with respect to the Λ b 0 → Λ c + D s - mode are measured to be B Λ b 0 → Λ c + D ¯ 0 K - B Λ b 0 → Λ c + D s - = 0.1908 - 0.0034 + 0.0036 - 0.0018 + 0.0016 ± 0.0038 , B Λ b 0 → Λ c + D ¯ ∗ 0 K - B Λ b 0 → Λ c + D s - = 0.589 - 0.017 + 0.018 - 0.018 + 0.017 ± 0.012 , B Λ b 0 → Λ c + D s ∗ - B Λ b 0 → Λ c + D s - = 1.668 ± 0.022 - 0.055 + 0.061 , where the first uncertainties are statistical, the second systematic, and the third, for the Λ b 0 → Λ c + D ¯ ( ∗ ) 0 K - decays, are due to the uncertainties on the branching fractions of the D s - → K - K + π - and D ¯ 0 → K + π - decay modes. The measured branching fractions probe factorization assumptions in effective theories and provide the normalization for future pentaquark searches in Λ b 0 → Λ c + D ¯ ( ∗ ) 0 K - decay channels.

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 $π$^{+}$π$^{−}$ and $ {K}_{\\mathrm{S}}^0 $K$^{+}$K$^{−}$ (commonly denoted $ {K}_{\\mathrm{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} $. 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} $, which are the ratios and strong-phase differences of the suppressed and favoured B$^{±}$ decays, are also reported.[graphic not available: see fulltext]

A measurement of CP asymmetry in D0→KS0KS0 decays is reported, based on a data sample of proton-proton collisions collected with the LHCb detector in 2024 at a centre-of-mass energy of 13.6 TeV, corresponding to an integrated luminosity of 6.2 fb−1. The D0→KS0π+π− decay is used as calibration channel to cancel residual detection and production asymmetries. The time-integrated CP asymmetry for the D0→KS0KS0 mode is measured to be ACPD0→KS0KS0=1.86±1.04±0.41%, where the first uncertainty is statistical, and the second is systematic. This measurement represents the most precise single-experiment determination of this quantity to date.

This paper describes a measurement of the Λb0→J/ψΛ branching fraction using data collected with the LHCb experiment in proton-proton collisions from 2016 to 2018. The dataset corresponds to an integrated luminosity of 5.4 fb−1. The branching fraction is determined relative to that of B0→J/ψKS0 decays, BΛb0→J/ψΛBB0→J/ψKS0=0.750±0.005±0.022±0.005±0.062, yielding BΛb0→J/ψΛ=3.34±0.02±0.10±0.08±0.28×10−4 , where the first uncertainty is statistical, the second systematic, the third due to external inputs on branching fractions and the fourth due to the ratio of Λb0 baryon and B0 meson hadronisation fractions. In addition, the isospin asymmetry between the rates of B0→J/ψKS0 and B+→ J/ψK+ decays is measured to be AI=−0.0135±0.0004±0.0133, where the first uncertainty is statistical and the second systematic.

Kinematic correlations for pairs of beauty hadrons, produced in high energy proton-proton collisions, are studied. The data sample used was collected with the LHCb experiment at centre-of-mass energies of 7 and 8 TeV and corresponds to an integrated luminosity of 3 fb−1. The measurement is performed using inclusive b → J/ψX decays in the rapidity range 2 < yJ/ψ < 4.5. The observed correlations are in good agreement with theoretical predictions.

A time-dependent, flavour-tagged measurement of CP violation is performed with B0→ D+D− and Bs0 → Ds+Ds− decays, using data collected by the LHCb detector in proton-proton collisions at a centre-of-mass energy of 13 TeV corresponding to an integrated luminosity of 6 fb−1. In B0→ D+D− decays the CP-violation parameters are measured to be SD+D−=−0.552±0.100stat±0.010syst,CD+D−=0.128±0.103stat±0.010syst. In Bs0 → Ds+Ds− decays the CP-violating parameter formulation in terms of ϕs and |λ| results in ϕs=−0.086±0.106stat±0.028systrad,∣λDs+Ds−∣=1.145±0.126stat±0.031syst. These results represent the most precise single measurement of the CP-violation parameters in their respective channels. For the first time in a single measurement, CP symmetry is observed to be violated in B0→ D+D− decays with a significance exceeding six standard deviations.