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LHCb Collaboration(Aaij, R. et al), Henry, L., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., et al. (2021). Search for long-lived particles decaying to e(+/-)mu(-/+)nu. Eur. Phys. J. C, 81(3), 261–16pp.
Abstract: Long-lived particles decaying to e(+/-) mu(-/+)nu, with masses between 7 and 50 GeV/c(2) and lifetimes between 2 and 50 ps, are searched for by looking at displaced vertices containing electrons and muons of opposite charges. The search is performed using 5.4 fb(-1) of pp collisions collected with the LHCb detector at a centre-of-mass energy of root s = 13 TeV. 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 125 GeV/c(2), 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.
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LHCb Collaboration(Aaij, R. et al), Henry, L., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., et al. (2021). Observation of the Lambda(0)(b) -> Lambda+cK+K-pi(-) decay. Phys. Lett. B, 815, 136172–10pp.
Abstract: The Lambda(0)(b) -> Lambda+cK+K-pi(-) decay is observed for the first time using a data sample of proton-proton collisions at centre-of-mass energies of root s = 7 and 8 TeV collected by the LHCb detector, corresponding to an integrated luminosity of 3fb(-1). The ratio of branching fractions between the Lambda(0)(b) -> Lambda K-+(c)+ K-pi(-) and the Lambda(0)(b) -> Lambda D-+(c)s(-) decays is measured to be B(Lambda(0)(b) -> Lambda+cK+K-pi(-))/B(Lambda(0)(b) -> Lambda D-+(c)s(-)) = (9.26 +/- 0.29 +/- 0.46 +/- 0.26) x 10(-2), where the first uncertainty is statistical, the second systematic and the third is due to the knowledge of the D-s(-) -> K+K-pi(-) branching fraction. No structure on the invariant mass distribution of the Lambda K-+(c)+ system is found, consistent with no open-charm pentaquark signature.
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LHCb Collaboration(Aaij, R. et al), Henry, L., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., et al. (2021). Measurement of CP observables in B-+/- -> D-(*K-)(+/-) and B-+/- -> D-(*())pi(+/-) decays using two-body D final states. J. High Energy Phys., 04(4), 081–36pp.
Abstract: Measurements of CP observables in B-+/- -> D(*) K-+/- and B-+/- -> D(*) pi(+/-) decays are presented, where D(*) indicates a neutral D or D* meson that is an admixture of meson and anti-meson states. Decays of the D(*) meson to the D pi(0) and D gamma final states are partially reconstructed without inclusion of the neutral pion or photon. Decays of the D meson are reconstructed in the K-+/-pi(-/+), K+K-, and pi(+)pi(-) final states. The analysis uses a sample of charged B mesons produced in proton-proton collisions and collected with the LHCb experiment, corresponding to integrated luminosities of 2.0, 1.0, and 5.7 fb(-1) taken at centre-of-mass energies of 7, 8, and 13TeV, respectively. The measurements of partially reconstructed B-+/- -> D(*) K-+/- and B-+/- -> D(*)pi(+/-) with D -> K--/+pi(+/-) decays are the first of their kind, and a first observation of the B-+/- -> (D pi(0)) D*pi(+/-) decay is made with a significance of 6.1 standard deviations. All CP observables are measured with world-best precision, and in combination with other LHCb results will provide strong constraints on the CKM angle gamma.
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LHCb Collaboration(Aaij, R. et al), Henry, L., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., et al. (2021). Measurement of the branching fraction of the B0 -> Ds+ pi- decay. Eur. Phys. J. C, 81(4), 314–15pp.
Abstract: A branching fraction measurement of the B0 -> Ds+</mml:msubsup>pi- decay is presented using proton-proton collision data collected with the LHCb experiment, corresponding to an integrated luminosity of 5.0<mml:mspace width=“0.166667em”></mml:mspace>fb-1. The branching fraction is found to be B(B0 -> Ds+</mml:msubsup>pi-)=(19.4 +/- 1.8 +/- 1.3 +/- 1.2)x10-6, where the first uncertainty is statistical, the second systematic and the third is due to the uncertainty on the B0 -> D-pi+, Ds+</mml:msubsup>-> K+K-pi+ and D--> K+pi-pi- 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 <mml:msub>Vub. Additionally, the collision energy dependence of the hadronisation-fraction ratio <mml:msub>fs/<mml:msub>fd is measured through B<overbar></mml:mover>s0 -> Ds+pi- and B0 -> D-pi <mml:mo>+ decays.
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LHCb Collaboration(Aaij, R. et al), Henry, L., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., et al. (2021). Observation of a New Excited D-s(+) Meson in B-0 -> D- D+ K+ pi(-) Decays. Phys. Rev. Lett., 126(12), 122002–11pp.
Abstract: Using pp collision data corresponding to an integrated luminosity of 5.4 fb(-1) collected with the LHCb detector at a center-of-mass energy of 13 TeV, the B-0 -> D- D+ K+ pi(-) decay is studied. A new excited D-s(+) meson is observed decaying into the D+K+pi(-) final state with large statistical significance. The pole mass and width, and the spin parity of the new state are measured with an amplitude analysis to be m(R) = 2591 +/- 6 +/- 7 MeV, Gamma(R) = 89 +/- 16 +/- 12 MeV, and J(P) = 0(-), where the first uncertainty is statistical and the second systematic. Fit fractions for all components in the amplitude analysis are also reported. The new resonance, denoted as D-s0(2590)(+), is a strong candidate to be the D-s(2(1)S(0))(+) state, the radial excitation of the pseudoscalar ground-state D-s(+) meson.
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