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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2015). Forward production of Upsilon mesons in pp collisions at root s=7 and 8 TeV. J. High Energy Phys., 11(11), 103–34pp.
Abstract: The production of Upsilon mesons in pp collisions at root s = 7 and 8 TeV is studied with the LHCb detector using data samples corresponding to an integrated luminosity of 1 fb(-1) and 2 fb(-1) respectively. The production cross-sections and ratios of cross-sections are measured as functions of the meson transverse momentum p and rapidity y, for p < 30 GeV/c and 2.0 < y < 4.5.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2016). Angular analysis of the B-0 -> K*(0) mu(+) mu(-) decay using 3 fb(-1) of integrated luminosity. J. High Energy Phys., 02(2), 104–79pp.
Abstract: An angular analysis of the B-0 -> K*(0) (-> K+pi(-))mu(+)mu(-) decay is presented. The dataset corresponds to an integrated luminosity of 3.0 fb(-1) of pp collision data collected at the LHCb experiment. The complete angular information from the decay is used to determine CP-averaged observables and CP asymmetries, taking account of possible contamination from decays with the K+pi(-) system in an S-wave configuration. The angular observables and their correlations are reported in bins of q(2), the invariant mass squared of the dimuon system. The observables are determined both from an unbinned maximum likelihood fit and by using the principal moments of the angular distribution. In addition, by fitting for q(2)-dependent decay amplitudes in the region 1.1 < q(2) < 6.0 GeV2/(c)4, the zero-crossing points of several angular observables are computed. A global fit is performed to the complete set of CP-averaged observables obtained from the maximum likelihood fit. This fit indicates differences with predictions based on the Standard Model at the level of 3.4 standard deviations. These differences could be explained by contributions from physics beyond the Standard Model, or by an unexpectedly large hadronic effect that is not accounted for in the Standard Model predictions.
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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 decay Lambda(0)(b) -> pK(-)mu(+)mu(-) and a search for CP violation. J. High Energy Phys., 06(6), 108–17pp.
Abstract: A search for CP violation in the decay Lambda(0)(b) -> pK(-)mu(+)mu(-) is presented. This decay is mediated by flavour-changing neutral-current transitions in the Standard Model and is potentially sensitive to new sources of CP violation. The study is based on a data sample of proton-proton collisions recorded with the LHCb experiment, corresponding to an integrated luminosity of 3 fb(-1). The Lambda(0)(b) -> pK(-)mu(+)mu(-) decay is observed for the first time, and two observables that are sensitive to different manifestations of CP violation are measured, Delta A(CP) equivalent to A(CP) (Lambda(0)(b) -> pK(-)mu(+)mu(-)) – A(CP) (Lambda(0)(b) -> pK(-)J/psi) and a(CP)((T) over cap -odd), where the latter is based on asymmetries in the angle between the mu(+)mu(-) and pK(-) decay planes. These are measured to be Delta A(CP) = (-3.5 +/- 5.0 (stat) +/- 0.2 (syst)) x 10(-2), a(CP)((T) over cap -odd) = (1.2 +/- 5.0 (stat) +/- 0.7 (syst)) x 10(-2), and no evidence for CP violation is found.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2015). Measurement of forward Z -> e(+)e(-) production at root s=8 TeV. J. High Energy Phys., 05(5), 109–21pp.
Abstract: A measurement of the cross-section for Z-boson production in the forward region of pp collisions at 8 TeV centre-of-mass energy is presented. The measurement is based on a sample of Z -> e(+)e(-) decays reconstructed using the LHCb detector, corresponding to an integrated luminosity of 2.0 fb(-1). The acceptance is defined by the requirements 2.0 < eta < 4.5 and p(T) > 20 GeV for the pseudorapidities and transverse momenta of the leptons. Their invariant mass is required to lie in the range 60-120 GeV. The cross-section is determined to be sigma(pp -> Z -> e(+)e(-)) = 93.81 +/- 0.41(stat) +/- 1.48(syst) +/- 1.14(lumi) pb, where the first uncertainty is statistical and the second reflects all systematic effects apart from that arising from the luminosity, which is given as the third uncertainty. Differential cross-sections are presented as functions of the Z-boson rapidity and of the angular variable phi*, which is related to the Z-boson transverse momentum.
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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). Measurement of forward t(t)over-bar, W + b(b)over-bar and W+ c(c)over-bar production in ppc ollisions at root s=8 TeV. Phys. Lett. B, 767, 110–120.
Abstract: The production of t (t) over bar, W + b (b) over bar and W+ c (c) over bar is studied in the forward region of proton-proton collisions collected at a centre-of-mass energy of 8 TeV by the LHCb experiment, corresponding to an integrated luminosity of 1.98 +/- 0.02 fb(-1). The Wbosons are reconstructed in the decays W -> lv, where l denotes muon or electron, while the b and cquarks are reconstructed as jets. All measured cross-sections are in agreement with next-to-leading-order Standard Model predictions.
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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 the Y(nS) polarizations in pp collisions at root s=7 and 8 TeV. J. High Energy Phys., 12(12), 110–60pp.
Abstract: The polarization of the (sic) (1S), (sic) (2S) and (sic) (3S) mesons, produced in pp collisions at centre-of-mass energies root s = 7 and 8TeV, is measured using data samples collected by the LHCb experiment, corresponding to integrated luminosities of 1 and 2 fb(-1), respectively. The measurements are performed in three polarization frames, using (sic) -> μμdecays in the kinematic region of the transverse momentum p(T)((sic)) < 30 GeV/c and rapidity 2.2 < y((sic)) < 4.5. No large polarization is observed.
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LHCb Collaboration(Aaij, R. et al), Oyanguren, A., & Ruiz Valls, P. (2013). Search for CP violation in D+ -> phi pi(+) and D-s(+) -> K-S(0)pi(+) decays. J. High Energy Phys., 06(6), 112–20pp.
Abstract: A search for C P violation in D+ -> phi pi(+) decays is performed using data collected in 2011 by the LHCb experiment corresponding to an integrated luminosity of 1.0 fb(-1) at a centre of mass energy of 7 TeV. The CP-violating asymmetry is measured to be (-0.04 +/- 0.14 +/- 0.14)% for candidates with K-K+ mass within 20 MeV/c(2) of the phi meson mass. A search for a CP-violating asymmetry that varies across the phi mass region of the D+ -> K-K+pi(+) Dalitz plot is also performed, and no evidence for CP violation is found. In addition, the CP asymmetry in the D-s(+) -> K-S(0)pi(+) decay is measured to be (0.61 +/- 0.83 +/- 0.14)%.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2015). Differential branching fraction and angular analysis of Lambda(0)(b) -> Lambda mu(+)mu(-) decays. J. High Energy Phys., 06(6), 115–29pp.
Abstract: The differential branching fraction of the rare decay Lambda(0)(b) -> Lambda mu(+)mu(-) is measured as a function of q(2), the square of the dimuon invariant mass. The analysis is performed using proton-proton collision data, corresponding to an integrated luminosity of 3.0 fb(-1), collected by the LHCb experiment. Evidence of signal is observed in the q(2) region below the square of the J/psi mass. Integrating over 15 < q(2) < 20 GeV2/c(4) the differential branching fraction is measured as dB(Lambda(0)(b) -> Lambda mu(+)mu(-))/dq(2) = (1.18(-0.08)(+0.09) +/- 0.03 +/- 0.27) x 10(-7) (GeV2/c(4))(-1) where the uncertainties are statistical, systematic and due to the normalisation mode Lambda(0)(b) -> J/psi Lambda , respectively. In the q(2) intervals where the signal is observed, angular distributions are studied and the forward-backward asymmetries in the dimuon (A(FB)(l)) and hadron (A(FB)(h)) systems are measured for the first time. In the range 15 < q(2) < 20GeV(2)/c(4) they are found to be A(FB)(l) = -0.05 +/- 0.09 (stat) +/- 0.03 (syst) and A(FB)(h) = -0.29 +/- 0.07 (stat) +/- 0.03 (syst).
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2016). Measurement of CP observables in B +/- -> DK +/- and B +/- -> D pi +/- with two- and four-body D decays. Phys. Lett. B, 760, 117–131.
Abstract: Measurements of CP observables in B-+/- -> DK +/- and B-+/- -> D pi(+/-) decays are presented where the D meson is reconstructed in the final states K-+/-pi(-/+), pi K-+/-(-/+), K+K-, pi(+)pi(-), K-+/-pi(-/+)pi(+)pi(-), pi K-+/-(-/+)pi(+)pi(-) and pi(+)pi(-)pi(+)pi(-). This analysis uses a sample of charged B mesons from pp collisions collected by the LHCb experiment in 2011 and 2012, corresponding to an integrated luminosity of 3.0 fb(-1). Various CP-violating effects are reported and together these measurements provide important input for the determination of the unitarity triangle angle gamma. The analysis of the four-pion D decay mode is the first of its kind.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2015). Search for the lepton flavour violating decay tau(-) -> mu(-)mu(+)mu(-). J. High Energy Phys., 02(2), 121–20pp.
Abstract: A search for the lepton flavour violating decay tau(-) -> mu(-)mu(+)mu(-) is performed with the LHCb experiment. The data sample corresponds to an integrated luminosity of 1.0 fb(-1) of proton-proton collisions at a centre-of-mass energy of 7 TeV and 2.0 fb(-1) at 8 TeV. No evidence is found for a signal, and a limit is set at 90% confidence level on the branching fraction, B(tau(-) -> mu(-)mu(+)mu(-)) < 4.6 x 10(-8).
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