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LHCb Collaboration(Aaij, R. et al), Oyanguren, A., & Ruiz Valls, P. (2013). Searches for violation of lepton flavour and baryon number in tau lepton decays at LHCb. Phys. Lett. B, 724(1-3), 36–45.
Abstract: Searches for the lepton flavour violating decay tau(-) -> mu(-)mu(+)mu(-) and the lepton flavour and baryon number violating decays tau(-) -> (p) over bar mu(+)mu(-) and tau(-) -> p mu(-)mu(-) have been carried out using proton-proton collision data, corresponding to an integrated luminosity of 1.0 fb(-1), taken by the LHCb experiment at root s = 7 TeV. No evidence has been found for any signal, and limits have been set at 90% confidence level on the branching fractions: B(tau(-) -> mu(-)mu(+)mu(-) < 8.0 x 10(-8), B(tau(-) -> <(p)over bar>mu(+)mu(-)) < 3.3 x 10(-7) and B(tau(-) -> p mu(-)mu(-)) < 4.4 x 10(-7). The results for the tau(-) -> (p) over bar mu(+)mu(-) and tau(-) -> p mu(-)mu(-) decay modes represent the first direct experimental limits on these channels.
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LHCb Collaboration(Aaij, R. et al), Oyanguren, A., & Ruiz Valls, P. (2013). Search for D-(s)(+) -> pi(+)mu(+)mu(-) and D-(s)(+) -> pi(-)mu(+)mu(+) decays. Phys. Lett. B, 724(4-5), 203–212.
Abstract: A search for non-resonant D-(s)(+) -> pi(+)mu(+)mu(-) and D-(s)(+) -> pi(-)mu(+)mu(+) decays is performed using protonproton collision data, corresponding to an integrated luminosity of 1.0 fb(-1), at root s = 7 TeV recorded by the LHCb experiment in 2011. No signals are observed and the 90% (95%) confidence level (CL) limits on the branching fractions are found to be B(D+ -> pi(+)mu(+)mu(-)) < 7.3 (8.3) x 10(-8), B(D-s(+) -> pi(+)mu(+)mu(-)) < 4.1 (4.8) x 10(-7), B(D-s(+) -> pi(+)mu(+)mu(-)) < 2.2 (2.5) x 10(-8), B(D-s(+) -> pi(+)mu(+)mu(-)) < 1.2 (1.4) x 10(-7). These limits are the most stringent to date.
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LHCb Collaboration(Aaij, R. et al), Oyanguren, A., & Ruiz Valls, P. (2013). Differential branching fraction and angular analysis of the decay B-s(0) -> phi mu(+)mu(-). J. High Energy Phys., 07(7), 084–18pp.
Abstract: The determination of the differential branching fraction and the first angular analysis of the decay B-s(0) -> phi mu(+)mu(-) are presented using data, corresponding to an integrated luminosity of 1.0 fb(-1), collected by the LHCb experiment at root s = 7 TeV. The differential branching fraction is determined in bins of q(2), the invariant dimuon mass squared. Integration over the full q2 range yields a total branching fraction of B(B-s(0) -> phi mu(+)mu(-)) = (7.07(-0.59)(+0.64) +/- 0.17 +/- 0.71) x 10(-7), where the first uncertainty is statistical, the second systematic, and the third originates from the branching fraction of the normalisation channel. An angular analysis is performed to determine the angular observables F-L, S-3, A(6), and A(9). The observables are consistent with Standard Model expectations.
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LHCb Collaboration(Aaij, R. et al), Oyanguren, A., & Ruiz Valls, P. (2013). Differential branching fraction and angular analysis of the decay B-0 -> K*(0)mu(+)mu(-). J. High Energy Phys., 08(8), 131–31pp.
Abstract: The angular distribution and differential branching fraction of the decay B-0 -> K*(0)mu(+)mu(-) are studied using a data sample, collected by the LHCb experiment in pp collisions at root s = 7 TeV, corresponding to an integrated luminosity of 1.0 fb(-1). Several angular observables are measured in bins of the dimuon invariant mass squared, q(2). A first measurement of the zero-crossing point of the forward-backward asymmetry of the dimuon system is also presented. The zero-crossing point is measured to be q(0)(2) = 4.9 +/- 0.9 GeV2/c(4), where the uncertainty is the sum of statistical and systematic uncertainties. The results are consistent with the Standard Model predictions.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., & Ruiz Valls, P. (2014). Measurement of Upsilon production in collisions at root s=2.76 TeV. Eur. Phys. J. C, 74(4), 2835–11pp.
Abstract: The production of , and mesons decaying into the dimuon final state is studied with the LHCb detector using a data sample corresponding to an integrated luminosity of collected in proton-proton collisions at a centre-of-mass energy of TeV. The differential production cross-sections times dimuon branching fractions are measured as functions of the transverse momentum and rapidity, over the ranges GeV/ and . The total cross-sections in this kinematic region, assuming unpolarised production, are measured to be sigma (pp -> Upsilon(1S)X) x B(Upsilon(1S) -> mu(+)mu(-)) = 1.111 +/- 0.043 +/- 0.044 nb, sigma (pp -> Upsilon(2S)X) x B(Upsilon(2S) -> mu(+)mu(-)) = 0.264 +/- 0.023 +/- 0.011 nb, sigma (pp -> Upsilon(3S)X) x B(Upsilon(3S) -> mu(+)mu(-))s = 0.159 +/- 0.020 +/- 0.007 nb, where the first uncertainty is statistical and the second systematic.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., & Ruiz Valls, P. (2014). Measurement of resonant and CP components in (B)over-bar(s)(0) -> J/psi pi(+)pi(-) decays. Phys. Rev. D, 89(9), 092006–21pp.
Abstract: Structure of the decay B0s. J=.pp- is studied using data corresponding to 3 fb- 1 of integrated luminosity from pp collisions produced by the LHC and collected by the LHCb detector. Five interfering pp- states are required to describe the decay: F-0(980), F-0(1500), F-0(1790), F-2 (1270) and F-2(1525) An alternative model including these states and a nonresonant J=.pp- component also provides a good description of the data. Based on the different transversity components measured for the spin- 2 intermediate states, the final state is found to be compatible with being entirely CP odd. The CP- even part is found to be < 2.3% at a 95% confidence level. The f 0d500 state is not observed, allowing a limit to be set on the absolute value of the mixing angle with the f 0d980 of < 7.7 at a 90% confidence level, consistent with a tetraquark interpretation of the f(0)(980) substructure.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2014). Study of Beauty Hadron Decays into Pairs of Charm Hadrons. Phys. Rev. Lett., 112(20), 202001–9pp.
Abstract: First observations of the decays A(b)(0) -> A(c)(+)D((s))(-) are reported using data corresponding to an integrated luminosity of 3 fb(-1) collected at 7 and 8 TeV center-of- ass energies in proton-proton collisions with the LHCb detector. In addition, the most precise measurement of the branching fraction B(B-s(0) -> D+Ds-) is made and a search is performed for the decays B-0((s)) -> A(c)(+)A(c)(-). The results obtained are B(A(b)(0) -> A(c)(+)D(-))/B(A(b)(0) -> A(c)(+)D(s)(-)) = 0.042 +/- 0.003 (stat) +/- 0.003 (syst), [B(A(b)(0) -> A(c)(+)D(s)(-))/B((B) over bar (0) -> D+Ds-)]/[B(A(b)(0) -> A(c)(+)pi(-))/B((B) over bar (0) -> D+pi(-))] = 0.96 +/- 0.02 (stat) +/- 0.06 (syst), B(B-s(0) -> D+Ds-)/B((B) over bar (0) -> D+Ds-) = 0.038 +/- 0.004 (stat) +/- (syst), B((B) over bar (0) -> A(c)(+)A(c)(-))/B((B) over bar (0) -> D+Ds-) < 0.0022[95% C.L.], B(B-s(0) -> A(c)(+)A(c)(-)) /B(B-s(0) -> D+Ds-) < 0.30[95% C.L.]. Measurement of the mass of the A(b)(0) baryon relative to the (B) over bar (0) meson gives M(A(b)(0)) – M((B) over bar (0)) = 339.72 +/- 0.24 (stat) +/- 0.18 (syst) MeV/c(2). This result provides the most precise measurement of the mass of the A(b)(0) baryon to date.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., & Ruiz Valls, P. (2014). Measurement of charged particle multiplicities and densities in pp collisions root s=7 TeV in the forward region. Eur. Phys. J. C, 74(5), 2888–17pp.
Abstract: Charged particle multiplicities are studied in proton-proton collisions in the forward region at a centre-of-mass energy of TeV with data collected by the LHCb detector. The forward spectrometer allows access to a kinematic range of in pseudorapidity, momenta greater than and transverse momenta greater than . The measurements are performed using events with at least one charged particle in the kinematic acceptance. The results are presented as functions of pseudorapidity and transverse momentum and are compared to predictions from several Monte Carlo event generators.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2014). Measurement of polarization amplitudes and CP asymmetries in B-0 -> phi K*(892)(0). J. High Energy Phys., 05(5), 069–24pp.
Abstract: An angular analysis of the decay B (0) -> phi K (*)(892)(0) is reported based on a pp collision data sample, corresponding to an integrated luminosity of 1.0 fb(-1), collected at a centre-of-mass energy of root S = 7 TeV with the LHCb detector. The P-wave amplitudes and phases are measured with a greater precision than by previous experiments, and confirm about equal amounts of longitudinal and transverse polarization. The S-wave K+ pi(-) and K+ K- contributions are taken into account and found to be significant. A comparison of the B (0) -> phi K (*)(892)(0) and results shows no evidence for direct CP violation in the rate asymmetry, in the triple-product asymmetries or in the polarization amplitudes and phases.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., & Ruiz Valls, P. (2014). A study of CP violation in B-+/- -> DK +/- and B-+/- -> D pi(+/-) decays with D -> (KSK +/-)-K-0 pi(-/+) final states. Phys. Lett. B, 733, 36–45.
Abstract: A first study of CP violation in the decay modes B-+/- -> [(KSK +/-)-K-0 pi(-/+)](D)h(+/-) and B-+/- -> [(KSK +/-)-K-0 pi(-/+)](D)h(+/-), where h labels a K or pi meson and D labels a D-0 or (D) over bar (0) meson, is performed. The analysis uses the LHCb data set collected in pp collisions, corresponding to an integrated luminosity of 3 fb(-1). The analysis is sensitive to the CP-violating CKM phase gamma through seven observables: one charge asymmetry in each of the four modes and three ratios of the charge-integrated yields. The results are consistent with measurements of gamma using other decay modes. (C) 2014 The Authors. Published by Elsevier B.V.
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