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LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Henry, L., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., et al. (2017). Observation of the Decays Alpha(0)(b) -> chi(c1)pK(-) and Alpha(0)(b) ->chi(c2)pK(-). Phys. Rev. Lett., 119(6), 062001–11pp.
Abstract: The first observation of the decays Lambda(b)(0) -> chi(c1)pK(-) and Lambda(0)(b) -> chi(c2)pK(-) is reported using a data sample corresponding to an integrated luminosity of 3.0 fb(-1), collected by the LHCb experiment in pp collisions at center-of-mass energies of 7 and 8 TeV The following ratios of branching fractions are measured: B(Lambda(0)(b) -> chi(c1)pK(-))/B(Lambda(0)(b) -> J/psi pK(-)) = 0.242 +/- 0.014 +/- 0.013 +/- 0.009, B(Lambda(0)(b) -> chi(c2)pK(-))/B(Lambda(0)(b) -> J/psi pK(-)) = 0.248 +/- 0.020 +/- 0.014 +/- 0.009, B(Lambda(0)(b) -> chi(c2)pK(-))/B(Lambda(0)(b) -> chi(c1)pK(-)) = 1.02 +/- 0.010 +/- 0.02 +/- 0.05, where the first uncertainty is statistical, the second systematic, and the third due to the uncertainty on the branching fractions of the x(c1) -> J/psi gamma and chi(c2) -> J/psi gamma decays. Using both decay modes, the mass of the Ab baryon is also measured to be m(Lambda b0) = 5619.44 +/- 0.28 +/- 0.26 MeV/c(2), where the first and second uncertainties are statistical and systematic, respectively.
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LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Henry, L., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., et al. (2017). Observation of the Doubly Charmed Baryon Xi(++)(cc). Phys. Rev. Lett., 119(11), 112001–10pp.
Abstract: A highly significant structure is observed in the Lambda K-+(c)-pi(+)pi(+) mass spectrum, where the Lambda(+)(c) baryon is reconstructed in the decay mode pK(-)pi(+). The structure is consistent with originating from a weakly decaying particle, identified as the doubly charmed baryon Xi(++)(cc). The difference between the masses of the Xi(++)(cc) and Lambda(+)(c) states is measured to be 1334.94 +/- 0.72(stat.) +/- 0.27(syst.) MeV/c(2), and the Xi(++)(cc) mass is then determined to be 3621.40 +/- 0.72(stat.) +/- 0.27(syst.) +/- 0.14(Lambda(+)(c)) MeV/c(2), where the last uncertainty is due to the limited knowledge of the Lambda(+)(c) mass. The state is observed in a sample of proton-proton collision data collected by the LHCb experiment at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 1.7 fb(-1), and confirmed in an additional sample of data collected at 8 TeV.
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LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Henry, L., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., et al. (2017). Measurement of B-s(0) and D-s(-) Meson Lifetimes. Phys. Rev. Lett., 119(10), 101801–10pp.
Abstract: We report on a measurement of the flavor-specific B-s(0) lifetime and of the D-s(-) lifetime using proton-proton collisions at center-of-mass energies of 7 and 8 TeV, collected by the LHCb experiment and corresponding to 3.0 fb(-1) of integrated luminosity. Approximately 407 000 B-s(0) -> D-s(()*()) -> D-s(()*()-) mu+v(mu) decays are partially reconstructed in the K+K-pi(-)mu(+) final state. The B-s(0) and D-s(-) natural widths are determined using, as a reference, kinematically similar B-0 -> Dd(*)(-) mu+v(mu) decays reconstructed in the same final state. The resulting differences between widths of B-s(0) and B-0 mesons and of D-s(-) and D- mesons are Delta(Gamma)(B) = -0.0115 +/- 0.0053(stat) +/- 0.0041 (syst) ps(-1) and Delta(Gamma)(D) = 1.0131 +/- 0.0117(stat) +/- 0.0065(syst) ps(-1), respectively. Combined with the known B-0 and D- lifetimes, these yield the flavor-specific B-s(0) lifetime, tau(fs)(Bs0) = 1.547 +/- 0.013 (stat) +/- 0.010 (syst) +/- 0.004(tau(B)) ps and the D-s(-) lifetime, tau(Ds-) = 0.5064 +/- 0.0030(stat) +/- 0.0017(syst) +/- 0.0017(sys) +/- 0.0017(tau(D)). The last uncertainties originate from the limited knowledge of the B-0 and D- lifetimes. The results improve upon current determinations.
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LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Henry, L., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., et al. (2017). Observation of charmless baryonic decays B-(s)(0) -> p(p)over-barh plus h '(-). Phys. Rev. D, 96(5), 051103–10pp.
Abstract: Decays of B-0 and B-s(0) mesons to the charmless baryonic final states p (p) over barh(+)h'(-), where h and h' each denote a kaon or a pion, are searched for using the LHCb detector. The analysis is based on a sample of proton-proton collision data collected at center-of-mass energies of 7 and 8 TeV, corresponding to an integrated luminosity of 3 fb(-1). Four-body charmless baryonic B-s(0) decays are observed for the first time. The decays B-s(0) -> p (p) over barK(+) K-, B-s(0) -> p (p) over barK(+/-) pi(inverted perpendicular), B-0 -> p (p) over barK(+) pi(inverted perpendicular) and B-0 -> p (p) over bar pi(+) pi(-) are observed with a significance greater than 5 standard deviations; evidence at 4.1 standard deviations is found for the B-0 -> p (p) over barK(+) K- decay and an upper limit is set on the branching fraction for B-s(0) -> p (p) over bar pi(+) pi(-). Branching fractions in the kinematic region m(p (p) over bar) < 2850 MeV/c(2) are measured relative to the B-0 -> J/psi(-> p<(p)over bar>) K* (892)(0) channel.
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LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Henry, L., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., et al. (2017). Search for Baryon-Number Violating Xi(0)(b) Oscillations. Phys. Rev. Lett., 119(18), 181807–9pp.
Abstract: A search for baryon-number violating Xi(0)(b) oscillations is performed with a sample of pp collision data recorded by the LHCb experiment, corresponding to an integrated luminosity of 3 fb(-1). The baryon number at the moment of production is identified by requiring that the Xi(0)(b) come from the decay of a resonance Xi(b)*(-) -> Xi(0)(b)pi(-) or Xi(b)'(-) -> Xi(0)(b)pi(-) and the baryon number at the moment of decay is identified from the final state using the decays Xi(0)(b) -> Xi(0)(c)pi(-) , Xi(+-)(c) -> pK(-)pi(+). No evidence of baryon-number violation is found, and an upper limit at the 95% confidence level is set on the oscillation rate of omega < 0.08 ps(-1), where. is the associated angular frequency.
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