LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., Ruiz Valls, P., et al. (2017). Measurement of B-0, B-s(0), B(+)and lambda(0)(b) production asymmetries in 7 and 8 TeV proton-proton collisions. Phys. Lett. B, 774, 139–158.
Abstract: The B-0, B-s(0), B+ and lambda(0)(b) hadron production asymmetries are measured using a data sample corresponding to an integrated luminosity of 3.0 fbc(-1), collected by the LHCb experiment in proton-proton collisions at centre-of-mass energies of 7 and 8 TeV. The measurements are performed as a function of transverse momentum and rapidity of the b hadrons within the LHCb detector acceptance. The overall production asymmetries, integrated over transverse momentum and rapidity, are also determined.
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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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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 D-0 meson decays to pi(+) pi(-) mu(+) mu(-) and K+ K- mu(+) mu(-) final states. Phys. Rev. Lett., 119(18), 181805–10pp.
Abstract: The first observation of the D-0 -> pi(+) pi(-) mu(+) mu(-) and D-0 -> K+ K- mu(+) mu(-) decays is reported using a sample of proton-proton collisions collected by LHCb at a center-of-mass energy of 8 TeV, and corresponding to 2 fb(-1) of integrated luminosity. The corresponding branching fractions are measured using as normalization the decay D-0 -> K- pi(+) [mu(+) mu(-)](rho 0/omega), where the two muons are consistent with coming from the decay of a rho(0) or omega meson. The results are B(D-0 -> pi(+) pi(-) mu(+) mu(-)) = (9.64 +/- 0.48 +/- 0.51 +/- 0.97) x 10(-7) and B(D-0 -> K+ K- mu(+) mu(-)) = (1.54 +/- 0.27 +/- 0.09 +/- 0.16) x 10(-7), where the uncertainties are statistical, systematic, and due to the limited knowledge of the normalization branching fraction. The dependence of the branching fraction on the dimuon mass is also investigated.
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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). Study of prompt D-0 meson production in pPb collisions at root(NN)-N-s=5 TeV. J. High Energy Phys., 10(10), 090–28pp.
Abstract: Production of prompt D-0 mesons is studied in proton-lead and lead-proton collisions recorded at the LHCb detector at the LHC. The data sample corresponds to an integrated luminosity of 1.58 +/- 0.02 nb(-1) recorded at a nucleon-nucleon centre-of-mass energy of root(NN)-N-s = 5 TeV. Measurements of the differential cross-section, the forward-backward production ratio and the nuclear modification factor are reported using D-0 candidates with transverse momenta less than 10 GeV/c and rapidities in the ranges 1.5 < y* < 4.0 and -5.0 < y* < -2.5 in the nucleon-nucleon centre-of-mass system.
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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). Improved limit on the branching fraction of the rare decay K-S(0) -> mu(+)mu(-). Eur. Phys. J. C, 77(10), 678–12pp.
Abstract: A search for the decay K-S(0) -> mu+ mu- is performed, based on a data sample of proton- proton collisions corresponding to an integrated luminosity of 3 fb(-1), collected by the LHCb experiment at centre-of- mass energies of 7 and 8 TeV. The observed yield is consistent with the background- only hypothesis, yielding a limit on the branching fraction of B( K-S(0) -> mu(+)mu(-)) < 0.8 (1.0) x 10(-9) at 90% ( 95%) confidence level. This result improves the previous upper limit on the branching fraction by an order of magnitude.
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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., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., Ruiz Valls, P., et al. (2017). Observation of the Xi(-)(b) -> J/psi Lambda K- decay. Phys. Lett. B, 772, 265–273.
Abstract: The observation of the decay Xi(-)(b)-> J/psi Lambda K- is reported, using a data sample corresponding to an integrated luminosity of 3 fb(-1), collected by the LHCb detector in pp collisions at centre-of-mass energies of 7 and 8 TeV. The production rate of Xi(-)(b) baryons detected in the decay Xi(-)(b) -> J/psi Lambda K- is measured relative to that of Lambda(0)(b) baryons using the decay Lambda(0)(b) -> J/psi Lambda. Integrated over the b-baryon transverse momentum p(T) < 25 GeV/c and rapidity 2.0 < y < 4.5, the measured ratio is f Xi(-)(b/) f Lambda(0)(b) B(Xi(-)(b)-> J/psi Lambda K-) / B(Lambda(0)(b)-> J/psi Lambda) = (4.19 +/- 0.29 (stat) +/- 0.15 (syst)) x 10(-2), where f(Xi)(b)(-) band f(Lambda)(b)(0)are the fragmentation fractions of b ->Xi(-)(b)and b ->Lambda(0)(b)transitions, and ss represents the branching fraction of the corresponding b- baryon decay. The mass difference between Xi(-)(b) and Lambda(0)(b) baryons is measured to be M(Xi(-)(b))-M(Lambda(0)(b)) = 177.08 +/- 0.47 (stat) +/- 0.16 (syst) MeV/c(2).
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LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., Ruiz Valls, P., et al. (2017). Search for massive long-lived particles decaying semileptonically in the LHCb detector. Eur. Phys. J. C, 77(4), 224–16pp.
Abstract: A search is presented formassive long-lived particles decaying into a muon and two quarks. The dataset consists of proton-proton interactions at centre-of-mass energies of 7 and 8TeV, corresponding to integrated luminosities of 1 and 2fb(-1), respectively. The analysis is performed assuming a set of production mechanisms with simple topologies, including the production of a Higgs-like particle decaying into two long-lived particles. The mass range from 20 to 80GeV/c(2) and lifetimes from 5 to 100 ps are explored. Results are also interpreted in terms of neutralino production in different R-Parity violating supersymmetric models, with masses in the 23-198 GeV/c(2) range. No excess above the background expectation is observed and upper limits are set on the production cross-section for various points in the parameter space of theoretical models.
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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). Study of charmonium production in b-hadron decays and first evidence for the decay B-s(0) -> phi phi phi. Eur. Phys. J. C, 77(9), 609–18pp.
Abstract: Using decays to f-meson pairs, the inclusive production of charmonium states in b-hadron decays is studied with pp collision data corresponding to an integrated luminosity of 3.0 fb(-1), collected by the LHCb experiment at centre-of-mass energies of 7 and 8 TeV. Denoting by B-C = B(b -> CX) x B(C -> phi phi) the inclusive branching fraction of a b hadron to a charmonium state C that decays into a pair of phi mesons, ratios R-C2(C1) = B-C1/B-C2 are determined as R-eta c(1S)(chi c0) = 0.147 +/- 0.023 +/- 0.011, R-eta c(1S)(chi c1) = 0.073 +/- 0.016 +/- 0.006, R-eta c(1S)(chi c2) = 0.081 +/- 0.013 +/- 0.005, R-chi c0(chi c1) = 0.50 +/- 0.11 +/- 0.01, R-chi c0(chi c2) = 0.56 +/- 0.10 +/- 0.01 and R-eta c(1S)(eta c(2S)) = 0.040 +/- 0.011 +/- 0.004. Here and below the first uncertainties are statistical and the second systematic. Upper limits at 90% confidence level for the inclusive production of X(3872), X(3915) and.c2(2P) states are obtained as R-chi c1(X(3872)) < 0.34, R-chi c0(X(3915)) < 0.12 and R-chi c2(chi c2(2P)) < 0.16. Differential cross-sections as a function of transverse momentum are measured for the eta(c)(1S) and chi(c) states. The branching fraction of the decay B-s(0). phi phi phi is measured for the first time, B(B-s(0) -> phi phi phi) = (2.15 +/- 0.54 +/- 0.28 +/- 0.21 B) x10(-6). Here the third uncertainty is due to the branching fraction of the decay B-s(0) -> phi phi, which is used for normalization. No evidence for intermediate resonances is seen. A preferentially transverse phi polarization is observed. Themeasurements allow the determination of the ratio of the branching fractions for the eta(c)(1S) decays to ff and p (p) over bar as B(eta(c)(1S) -> phi phi)/B(eta(c)(1S) -> p (p) over bar) = 1.79 +/- 0.14 +/- 0.32.
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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). Test of lepton universality with B-0 -> K*(0)l(+)l(-) decays. J. High Energy Phys., 08(8), 055–31pp.
Abstract: A test of lepton universality, performed by measuring the ratio of the branching fractions of the B-0 -> K*(0)mu(+) mu(-) and B-0 -> K*e(+)e(-) decays, R-K*0, is presented. The K*(0) meson is reconstructed in the final state K+pi(-), which is required to have an invariant mass within 100 MeV/c(2) of the known K*(892)(0) mass. The analysis is performed using proton-proton collision data, corresponding to an integrated luminosity of about 3 fb(-1), collected by the LHCb experiment at centre-of-mass energies of 7 and 8 TeV. The ratio is measured in two regions of the dilepton invariant mass squared, q(2), to be R-K*0 – {0.66(-0.007)(+0.11)(stat) +/- 0.03(syst) for 0.045 < q(2) < GeV2/c(4), 0.69(-0.07)(+0.11)(stat) +/- 0.05(syst) for 1.1 < q(2) < 6.0 GeV2/c(4). The corresponding 95.4% confidence level intervals are [0.52, 0.89] and [0.53, 0.94]. The results, which represent the most precise measurements of R-K*0 to date, are compatible with the Standard Model expectations at the level of 2.1-2.3 and 2.4-2.5 standard deviations in the two q(2) regions, respectively.
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