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LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Henry, L., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., et al. (2019). Observation of Two Resonances in the Lambda(0)(b)pi(+/-) Systems and Precise Measurement of Sigma(+/-)(b) and Sigma(*+/-)(b) Properties. Phys. Rev. Lett., 122(1), 012001–9pp.
Abstract: The first observation of two structures consistent with resonances in the final states Lambda(0)(b)pi(-) and Lambda(0)(b)pi(+) thorn is reported using samples of pp collision data collected by the LHCb experiment at root s = 7 and 8 TeV, corresponding to an integrated luminosity of 3 fb(-1). The ground states Sigma(+/-)(b) and Sigma(*+/-)(b) are also confirmed and their masses and widths are precisely measured.
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LHCb Collaboration(Aaij, R. et al), Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., & Ruiz Vidal, J. (2022). Observation of two new excited Ξ0b states decaying to Λ0bK−π+. Phys. Rev. Lett., 128(16), 162001–12pp.
Abstract: Two narrow resonant states are observed in the Λ0bK−π+ mass spectrum using a data sample of proton-proton collisions at a center-of-mass energy of 13 TeV, collected by the LHCb experiment and corresponding to an integrated luminosity of 6 fb−1. The minimal quark content of the Λ0bK−π+ system indicates that these are excited Ξ0b baryons. The masses of the Ξb(6327)0 and Ξb(6333)0 states are m(Ξb(6327)0)=6327.28+0.23−0.21±0.12±0.24 MeV and m(Ξb(6333)0)=6332.69+0.17−0.18±0.03±0.22 MeV, respectively, with a mass splitting of Δm=5.41+0.26−0.27±0.12 MeV, where the uncertainties are statistical, systematic and due to the Λ0b mass measurement. The measured natural widths of these states are consistent with zero, with upper limits of Γ(Ξb(6327)0)<2.20 (2.56) MeV and Γ(Ξb(6333)0)<1.60 (1.92) MeV at a 90% (95%) credibility level. The significance of the two-peak hypothesis is larger than nine (five) Gaussian standard deviations compared to the no-peak (one-peak) hypothesis. The masses, widths and resonant structure of the new states are in good agreement with the expectations for a doublet of 1D Ξ0b resonances.
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LHCb Collaboration(Aaij, R. et al), Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., & Ruiz Vidal, J. (2021). Observation of the suppressed Lambda(0)(b) -> DpK(-) decay with D -> K+ pi(-) and measurement of its CP asymmetry. Phys. Rev. D, 104(11), 112008–14pp.
Abstract: A study of A(b)(0) baryon decays to the DpK(-) final state is presented based on a proton-proton collision data sample corresponding to an integrated luminosity of 9 fb(-1) collected with the LHCb detector. Two A(b)(0) decays are considered, A(b)(0) -> DpK(-) with D -> K-pi(+) and D -> K+pi(-), where D represents a superposition of D-0 and over bar D-0 states. The latter process is expected to be suppressed relative to the former, and is observed for the first time. The ratio of branching fractions of the two decays is measured, and the CP asymmetry of the suppressed mode, which is sensitive to the Cabibbo-Kobayashi-Maskawa angle gamma, is also reported.
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LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Henry, L., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., et al. (2020). Observation of the semileptonic decay B+-> p(p)over-bar mu(+)nu(mu). J. High Energy Phys., 03(3), 146–22pp.
Abstract: The Cabibbo-suppressed semileptonic decay B+-> pp over bar mu+nu μis observed for the first time using a sample of pp collisions corresponding to an integrated luminosity of 1.0, 2.0 and 1.7 fb at centre-of-mass energies of 7, 8 and 13TeV, respectively. The differential branching fraction is measured as a function of the pp invariant mass using the decay mode B+ ! J= K+ for normalisation. The total branching fraction is measured to be B (B+ ! pp+) = (5:27+0:23 0:21 0:15) 10 where the first uncertainty is statistical, the second systematic and the third is from the uncertainty on the branching fraction of the normalisation channel.
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LHCb Collaboration(Aaij, R. et al), Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., & Ruiz Vidal, J. (2021). Observation of the Mass Difference Between Neutral Charm-Meson Eigenstates. Phys. Rev. Lett., 127(11), 111801–12pp.
Abstract: A measurement of mixing and CP violation in neutral charm mesons is performed using data reconstructed in proton-proton collisions collected by the LHCb experiment from 2016 to 2018, corresponding to an integrated luminosity of 5.4 fb(-1). A total of 30.6 million D0 -> K-s(0)pi(+)pi(-) decays are analyzed using a method optimized for the measurement of the mass difference between neutral charmmeson eigenstates. Allowing for CP violation in mixing and in the interference between mixing and decay, the mass and decay-width differences are measured to be x(CP) = [3.97 +/- 0.46(stat) +/- 0.29(syst)] x 10(-3) and y(CP) = [4.59 +/- 1.20(stat) +/- 0.85(syst)] x 10(-3), respectively. The CP-violating parameters are measured as Delta x= [-0.27 +/- 0.18(stat)+/- 0.01(syst)] x 10 (-3) and Delta y = [0.20 +/- 0.36(stat) +/- 0.13(syst)] x 10(-3). This is the first observation of a nonzero mass difference in the D-0 meson system, with a significance exceeding seven standard deviations. The data are consistent with CP symmetry and improve existing constraints on the associated parameters.
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