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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 Violation in the Decay B plus -> K+ pi(0). Phys. Rev. Lett., 126(9), 091802–11pp.
Abstract: A measurement of CP violation in the decay B+ -> K+pi(0) is reported using data corresponding to an integrated luminosity of 5.4 fb- 1 collected with the LHCb experiment at a center-of-mass energy of root s = 13 TeV. The CP asymmetry is measured to be 0.025 +/- 0.015 +/- 0.006 +/- 0.003, where the uncertainties are statistical, systematic, and due to an external input. This is the most precise measurement of this quantity. It confirms and significantly enhances the observed anomalous difference between the direct CP asymmetries of the B-0 -> K+pi(-) and B+ -> K+pi 0 decays, known as the K pi puzzle.
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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 heavy neutral leptons in W plus . μplus μ+/- jet decays. Eur. Phys. J. C, 81(3), 248–15pp.
Abstract: A search is performed for heavy neutrinos in the decay of a W boson into two muons and a jet. The data set corresponds to an integrated luminosity of approximately 3.0 fb-1 of proton-proton collision data at centre-of-mass energies of 7 and 8 TeV collected with the LHCb experiment. Both same-sign and opposite-signmuons in the final state are considered. Data are found to be consistent with the expected background. Upper limits on the coupling of a heavy neutrino with the Standard Model neutrino are set at 95% confidence level in the heavy-neutrino mass range from 5 to 50GeV/c2. These are of the order of 10(-3) for lepton-number-conserving decays and of the order of 10(-4) for lepton-number-violating heavy-neutrino 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). 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 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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