Amplitude analysis of the Λb0→pK−γ decay

The resonant structure of the radiative decay Λb0→pK−γ in the region of proton-kaon invariant-mass up to 2.5 GeV/c2 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

Search for the Bs0 → μ+μ−γ decay

A search for the fully reconstructed B0 s → µ +µ −γ decay is performed at the LHCb experiment using proton-proton collisions at √ s = 13 TeV corresponding to an integrated luminosity of 5.4 fb−1 . No signifcant signal is found and upper limits on the branching fraction in intervals of the dimuon mass are set B(B 0 s → µ +µ −γ) < 4.2 × 10−8 , m(µ +µ −) ∈ [2mµ, 1.70] GeV/c2 , B(B 0 s → µ +µ −γ) < 7.7 × 10−8 , m(µ +µ −) ∈ [1.70, 2.88] GeV/c2 , B(B 0 s → µ +µ −γ) < 4.2 × 10−8 , m(µ +µ −) ∈ [3.92, mB0 s ] GeV/c2 , at 95% confdence level. Additionally, upper limits are set on the branching fraction in the [2mµ, 1.70] GeV/c2 dimuon mass region excluding the contribution from the intermediate ϕ(1020) meson, and in the region combining all dimuon-mass intervals

Observation of the Bc+ → J/ψπ+π0 decay

The first observation of the Bc+→J/ψπ+π0 decay is reported with high significance using proton-proton collision data, corresponding to an integrated luminosity of 9 fb−1, collected with the LHCb detector at centre-of-mass energies of 7, 8, and 13 TeV. The ratio of its branching fraction relative to the Bc+→J/ψπ+ channel is measured to beBBc+→J/ψπ+π0BBc+→J/ψπ+=2.80±0.15±0.11±0.16, where the first uncertainty is statistical, the second systematic and the third related to imprecise knowledge of the branching fractions for B+ → J/ψK*+ and Bc+→J/ψπ+ decays, which are used to determine the π0 detection efficiency. The π+π0 mass spectrum is found to be consistent with the dominance of an intermediate ρ+ contribution in accordance with a model based on QCD factorisation

Amplitude analysis of the Λ0b→pK−γ decay

The resonant structure of the radiative decay Λ0b→pK−γ in the region of proton-kaon invariant-mass up to 2.5 GeV/c2 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

Search for Bc+ → π+μ+μ- decays and measurement of the branching fraction ratio B(Bc+ → ψ (2S)π+) / B(Bc+ → J/ψπ+)

The first search for nonresonant Bc+ → 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 9fb-1. No evidence for an excess of signal events over background is observed and an upper limit is set on the branching fraction ratio B(Bc+→π+μ+μ-)/B(Bc+→J/ψπ+)<2.1×10-4 at 90% confidence level. Additionally, an updated measurement of the ratio of the Bc+→ψ(2S)π+ and Bc+→J/ψπ+ branching fractions is reported. The ratio B(Bc+→ψ(2S)π+)/B(Bc+→J/ψπ+) is measured to be 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/ψ and ψ(2S) decays. This measurement is the most precise to date and is consistent with previous LHCb results

Search for the lepton-flavor violating decay Bs0 → ϕμ±τ∓

A search for the lepton-flavor violating decays B0 s → ϕμ±τ∓ is presented, using a sample of proton-proton collisions at center-of-mass energies of 7, 8, and 13 TeV, collected with the LHCb detector and corresponding to a total integrated luminosity of 9 fb−1. The τ leptons are selected using decays with three charged pions. No significant excess is observed, and an upper limit on the branching fraction is determined to be B(B0 s → ϕμ±τ∓) < 1.0 × 10−5 at 90% confidence level

Transverse polarization measurement of Λ hyperons in pNe collisions at √sNN = 68.4 GeV with the LHCb detector

A measurement of the transverse polarization of the Λ andΛ hyperons in pNe fixed-target collisions at √ sNN = 68.4 GeV is presented using data collected by the LHCb detector. The polarization is studied using the decay Λ → pπ− together with its charge conjugated process, the integrated values measured are PΛ = 0.029 ± 0.019 (stat) ± 0.012 (syst), PΛ = 0.003 ± 0.023 (stat) ± 0.014 (syst). Furthermore, the results are shown as a function of the Feynman x variable, transverse momentum, pseudorapidity and rapidity of the hyperons, and are compared with previous measurements

Multiplicity dependence of σψ(2S) /σJ/ψ in pp collisions at √s = 13 TeV

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 = 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

First observation of the Λb0 → D+D−Λ decay

The Λ 0 b → 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 B0 → D+D−K0 S decay as a reference channel, the product of the relative production cross-section and decay branching fractions is measured to be R = σΛ0 b σB0 × B(Λ0 b → D+D−Λ) B(B0 → D+D−K0 S ) = 0.179 ± 0.022 ± 0.014 , where the first uncertainty is statistical and the second is systematic. The known branching fraction of the reference channel, B(B0 → D+D−K0 S ), and the cross-section ratio, σΛ0 b /σB0 , previously measured by LHCb are used to derive the branching fraction of the Λ 0 b → D+D−Λ decay B(Λ0 b → D+D−Λ) = (1.24 ± 0.15 ± 0.10 ± 0.28 ± 0.11) × 10−4 , where the third and fourth contributions are due to uncertainties of B(B0 → D+D−K0 S ) and σΛ0 b /σB0 , respectively. Inspection of the D+Λ and D+D− invariant-mass distributions suggests a rich presence of intermediate resonances in the decay. The Λ 0 b → D∗+D−Λ decay is also observed for the first time as a partially reconstructed component in the D+D−Λ invariant mass spectrum

Amplitude analysis of the radiative decay Bs0 → K+K−γ

A search for radiative decay of B0 s mesons to orbitally excited K+K− states is performed using proton proton collisions recorded by the LHCb experiment, corresponding to an integrated luminosity of 9 fb−1 . The dikaon spectrum in the mass range mKK < 2400 MeV/c 2 is dominated by the ϕ(1020) resonance that accounts for almost 70% of the decay rate. Considering the possible contributions of f2(1270), f ′ 2 (1525) and f2(2010) meson states, the overall tensor contribution to the amplitude is measured to be F{f2} = 16.8 ± 0.5 (stat.) ± 0.7 (syst.)%, mostly dominated by the f ′ 2 (1525) state. Several statistically equivalent solutions are obtained for the detailed resonant structure depending on whether the smaller amplitudes interfere destructively or constructively with the dominant amplitude. The preferred solution that corresponds to the lowest values of the ft fractions along with constructive interference leads to the relative branching ratio measurement B(B0 s → f ′ 2γ) B(B0 s → ϕγ) = 19.4 +0.9 −0.8 (stat.) +1.4 −0.5 (syst.) ± 0.5 (B)%, where the last uncertainty is due to the ratio of measured branching fractions to the K+K− final state. This result represents the first observation of the radiative B0 s → f ′ 2 (1525)γ decay, which is the second radiative transition observed in the B0 s sector