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A bstract This report details the capabilities of LHCb and its upgrades towards the study of kaons and hyperons. The analyses performed so far are reviewed, elaborating on the prospects for some key decay channels, while proposing some new measurements in LHCb to expand its strangeness research program.

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.

A bstract The production cross-section of J/ψ pairs is measured using a data sample of pp collisions collected by the LHCb experiment at a centre-of-mass energy of s = 13 TeV, corresponding to an integrated luminosity of 279 ±11 pb −1 . The measurement is performed for J/ψ mesons with a transverse momentum of less than 10 GeV/ c in the rapidity range 2 . 0 < y < 4 . 5. The production cross-section is measured to be 15 . 2 ± 1 . 0 ± 0 . 9 nb. The first uncertainty is statistical, and the second is systematic. The differential cross-sections as functions of several kinematic variables of the J/ψ pair are measured and compared to theoretical predictions.

The decay-time-dependent CP asymmetry in Bs0→J/ψK+K- decays is measured using proton–proton collision data, corresponding to an integrated luminosity of 1.9fb-1, collected with the LHCb detector at a centre-of-mass energy of 13TeV in 2015 and 2016. Using a sample of approximately 117 000 signal decays with an invariant K+K- mass in the vicinity of the ϕ(1020) resonance, the CP-violating phase ϕs is measured, along with the difference in decay widths of the light and heavy mass eigenstates of the Bs0-B¯s0 system, ΔΓs. The difference of the average Bs0 and B0 meson decay widths, Γs-Γd, is determined using in addition a sample of B0→J/ψK+π- decays. The values obtained are ϕs=-0.083±0.041±0.006rad, ΔΓs=0.077±0.008±0.003ps-1 and Γs-Γd=-0.0041±0.0024±0.0015ps-1, where the first uncertainty is statistical and the second systematic. These are the most precise single measurements of these quantities to date and are consistent with expectations based on the Standard Model and with a previous LHCb analysis of this decay using data recorded at centre-of-mass energies 7 and 8 TeV. Finally, the results are combined with recent results from Bs0→J/ψπ+π- decays obtained using the same dataset as this analysis, and with previous independent LHCb results.

A structure is observed in the B±K∓ mass spectrum in a sample of proton–proton collisions at centre-of-mass energies of 7, 8, and 13 TeV, collected with the LHCb detector and corresponding to a total integrated luminosity of 9fb-1. The structure is interpreted as the result of overlapping excited Bs0 states. With high significance, a two-peak hypothesis provides a better description of the data than a single resonance. Under this hypothesis the masses and widths of the two states, assuming they decay directly to B±K∓, are determined to be m1=6063.5±1.2(stat)±0.8(syst)Me,Γ1=26±4(stat)±4(syst)Me,m2=6114±3(stat)±5(syst)Me,Γ2=66±18(stat)±21(syst)Me.Alternative values assuming a decay through B∗±K∓, with a missing photon from the B∗±→B±γ decay, which are shifted by approximately 45MeV, are also determined. The possibility of a single state decaying in both channels is also considered. The ratio of the total production cross-section times branching fraction of the new states relative to the previously observed Bs2∗0 state is determined to be 0.87±0.15(stat)±0.19(syst).

Long-lived particles decaying to e±μ∓ν, with masses between 7 and 50GeV/c2 and lifetimes between 2 and 50ps, are searched for by looking at displaced vertices containing electrons and muons of opposite charges. The search is performed using 5.4fb-1 of pp collisions collected with the LHCb detector at a centre-of-mass energy of s=13TeV. Three mechanisms of production of long-lived particles are considered: the direct pair production from quark interactions, the pair production from the decay of a Standard-Model-like Higgs boson with a mass of 125GeV/c2, and the charged current production from an on-shell W boson with an additional lepton. No evidence of these long-lived states is obtained and upper limits on the production cross-section times branching fraction are set on the different production modes.

The cross-sections of ψ ( 2 S ) meson production in proton-proton collisions at s = 13 TeV are measured with a data sample collected by the LHCb detector corresponding to an integrated luminosity of 275 pb - 1 . The production cross-sections for prompt ψ ( 2 S ) mesons and those for ψ ( 2 S ) mesons from b -hadron decays ( ψ ( 2 S ) -from- b ) are determined as functions of the transverse momentum, p T , and the rapidity, y , of the ψ ( 2 S ) meson in the kinematic range 2 < p T < 20 GeV/ c and 2.0 < y < 4.5 . The production cross-sections integrated over this kinematic region are σ ( prompt ψ ( 2 S ) , 13 TeV ) = 1.430 ± 0.005 (stat) ± 0.099 (syst) μ b , σ ( ψ ( 2 S ) -from- b , 13 TeV ) = 0.426 ± 0.002 (stat) ± 0.030 (syst) μ b . A new measurement of ψ ( 2 S ) production cross-sections in pp collisions at s = 7 TeV is also performed using data collected in 2011, corresponding to an integrated luminosity of 614 pb - 1 . The integrated production cross-sections in the kinematic range 3.5 < p T < 14 GeV/ c and 2.0 < y < 4.5 are σ ( prompt ψ ( 2 S ) , 7 TeV ) = 0.471 ± 0.001 (stat) ± 0.025 (syst) μ b , σ ( ψ ( 2 S ) -from- b , 7 TeV ) = 0.126 ± 0.001 (stat) ± 0.008 (syst) μ b . All results show reasonable agreement with theoretical calculations.

A search is performed for massive long-lived particles (LLPs) decaying semileptonically into a muon and two quarks. Two kinds of LLP production processes were considered. In the first, a Higgs-like boson with mass from 30 to 200\\,GeV\\!/c2 is produced by gluon fusion and decays into two LLPs. The analysis covers LLP mass values from 10\\,GeV\\!/c2 up to about one half the Higgs-like boson mass. The second LLP production mode is directly from quark interactions, with LLP masses from 10 to 90\\,GeV\\!/c2. The LLP lifetimes considered range from 5 to 200 ps. This study uses LHCb data collected from proton-proton collisions at s=13\\,TeV, corresponding to an integrated luminosity of 5.4\\,fb-1. No evidence of these long-lived states has been observed, and upper limits on the production cross-section times branching ratio have been set for each model considered.

A branching fraction measurement of the B0→Ds+π- decay is presented using proton–proton collision data collected with the LHCb experiment, corresponding to an integrated luminosity of 5.0fb-1. The branching fraction is found to be B(B0→Ds+π-)=(19.4±1.8±1.3±1.2)×10-6, where the first uncertainty is statistical, the second systematic and the third is due to the uncertainty on the B0→D-π+, Ds+→K+K-π+ and D-→K+π-π- branching fractions. This is the most precise single measurement of this quantity to date. As this decay proceeds through a single amplitude involving a b→u charged-current transition, the result provides information on non-factorisable strong interaction effects and the magnitude of the Cabibbo–Kobayashi–Maskawa matrix element Vub. Additionally, the collision energy dependence of the hadronisation-fraction ratio fs/fd is measured through B¯s0→Ds+π- and B0→D-π+ decays.

A bstract A search for the rare two-body charmless baryonic decay B + → p Λ ¯ is performed with pp collision data, corresponding to an integrated luminosity of 3 fb −1 , collected by the LHCb experiment at centre-of-mass energies of 7 and 8 TeV. An excess of B + → p Λ ¯ candidates with respect to background expectations is seen with a statistical significance of 4.1 standard deviations, and constitutes the first evidence for this decay. The branching fraction, measured using the B +  →  K S 0 π + decay for normalisation, is ℬ B + → p Λ ¯ = 2 . 4 − 0.8 + 1.0 ± 0.3 × 1 0 − 7 , where the first uncertainty is statistical and the second systematic.