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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2015). Observation of J/psi p Resonances Consistent with Pentaquark States in Lambda(0)(b) -> J/psi K(-)p Decays. Phys. Rev. Lett., 115(7), 072001–15pp.
Abstract: Observations of exotic structures in the J/psi p channel, which we refer to as charmonium-pentaquark states, in Lambda(0)(b) --> J/psi K(-)p decays are presented. The data sample corresponds to an integrated luminosity of 3 fb(-1) acquired with the LHCb detector from 7 and 8 TeV pp collisions. An amplitude analysis of the three-body final state reproduces the two-body mass and angular distributions. To obtain a satisfactory fit of the structures seen in the J/psi p mass spectrum, it is necessary to include two Breit-Wigner amplitudes that each describe a resonant state. The significance of each of these resonances is more than 9 standard deviations. One has a mass of 4380 +/- 8 +/- 29 MeV and a width of 205 +/- 18 +/- 86 MeV, while the second is narrower, with a mass of 4449.8 +/- 1.7 +/- 2.5 MeV and a width of 39 +/- 5 +/- 19 MeV. The preferred J(P) assignments are of opposite parity, with one state having spin 3/2 and the other 5/2.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2015). Determination of the quark coupling strength vertical bar V-ub vertical bar using baryonic decays. Nat. Phys., 11(9), 743–747.
Abstract: In the Standard Model of particle physics, the strength of the couplings of the b quark to the u and c quarks, vertical bar V-ub vertical bar and vertical bar V-ub vertical bar, are governed by the coupling of the quarks to the Higgs boson. Using data from the LHCb experiment at the Large Hadron Collider, the probability for the Lambda(0)(b) baryon to decay into the p mu(-)(nu) over bar (mu) final state relative to the Lambda(+)(c)mu(-)(nu) over bar (mu) final state is measured. Combined with theoretical calculations of the strong interaction and a previously measured value of vertical bar V-ub vertical bar, the first vertical bar V-ub vertical bar measurement to use a baryonic decay is performed. This measurement is consistent with previous determinations of vertical bar V-ub vertical bar using B meson decays to specific final states and confirms the existing incompatibility with those using an inclusive sample of final states.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2015). First measurement of the differential branching fraction and CP asymmetry of the B-+/- -> pi(+/-)mu(+/-)mu(-) decay. J. High Energy Phys., 10(10), 034–21pp.
Abstract: The differential branching fraction with respect to the dimuon invariant mass squared, and the CP asymmetry of the B-+/- -> pi(+/-)mu(+/-)mu(-) decay are measured for the first time. The CKM matrix elements vertical bar V-td vertical bar, and vertical bar V-ts vertical bar, and the ratio vertical bar V-td/V-ts vertical bar are determined. The analysis is performed using proton-proton 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. The total branching fraction and CP asymmetry of B-+/- -> pi(+/-)mu(+/-)mu(-) decays are measured to be B(B-+/- -> pi(+/-)mu(+/-)mu(-)) = (1.83 +/- 0.24 +/- 0.05) x 10(-8) and A(cp)(B-+/- -> pi(+/-)mu(+/-)mu(-)) = -0.11 +/- 0.12 +/- 0.01, where the first uncertainties are statistical and the second are systematic. These are the most precise measurements of these observables to date, and they are compatible with the predictions of the Standard Model.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2016). First Observation of D-0 – (D)over-bar(0) Oscillations in D-0 -> K+pi(-)pi(+)pi(-) Decays and Measurement of the Associated Coherence Parameters. Phys. Rev. Lett., 116(24), 241801–10pp.
Abstract: Charm meson oscillations are observed in a time-dependent analysis of the ratio of D-0 -> K+pi(-)pi(+)pi(-) to D-0 -> K-pi(+)pi(-)pi(+) decay rates, using data corresponding to an integrated luminosity of 3.0 fb(-1) recorded by the LHCb experiment. The measurements presented are sensitive to the phase-space averaged ratio of doubly Cabibbo-suppressed to Cabibbo-favored amplitudes r(D)(K3 pi) and the product of the coherence factor R-D(K3 pi) and a charm mixing parameter y'(K3 pi). The constraints measured are r(D)(K3 pi) = (5.67 +/- 0.12) x 10(-2), which is the most precise determination to date, and R-D(K3 pi) y'(K3 pi) = (0.3 +/- 1.8) x 10(-3), which provides useful input for determinations of the CP-violating phase gamma in B-+/- -> DK +/-, D -> K--/+pi(+/-)pi(-/+)pi(+/-) decays. The analysis also gives the most precise measurement of the D-0 -> K+pi(-)pi(+)pi(-) branching fraction, and the first observation of D-0-(D) over bar (0) oscillations in this decay mode, with a significance of 8.2 standard deviations.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2015). Measurement of the forward-backward asymmetry in Z/gamma* -> mu(+)mu(-) decays and determination of the effective weak mixing angle. J. High Energy Phys., 11(11), 190–19pp.
Abstract: The forward-backward charge asymmetry for the process q (q) over bar -> Z/gamma* -> mu(+)mu(-) is measured as a function of the invariant mass of the dimuon system. Measurements are performed using proton proton collision data collected with the LHCb detector at root s = 7 and 8 TeV, corresponding to integrated luminosities of 1 fb(-1) and 2 fb(-2) respectively. Within the Standard Model the results constrain the effective electroweak mixing angle to be
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2014). Angular analysis of charged and neutral B -> K mu(+) mu(-) decays. J. High Energy Phys., 05(5), 082–25pp.
Abstract: The angular distributions of the rare decays B+ -> K+mu(+)mu(-) and B-0 -> K-S(0)mu(+)mu(-) are studied with data corresponding to 3 fb(-1) of integrated luminosity, collected in proton-proton collisions at 7 and 8 TeV centre-of-mass energies with the LHCb detector. The angular distribution is described by two parameters, F-H and the forward-backward asymmetry of the dimuon system A(FB), which are determined in bins of the dimuon mass squared. The parameter F-H is a measure of the contribution from (pseudo)scalar and tensor amplitudes to the decay width. The measurements of A(FB) and F-H reported here are the most precise to date and are compatible with predictions from the Standard Model.
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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). Measurement of the effective B-S(0) -> J/psi K-S(0) lifetime. Nucl. Phys. B, 873(2), 275–292.
Abstract: This paper reports the first measurement of the effective B-S(0) -> J/psi K-S(0) lifetime and an updated measurement of its time-integrated branching fraction. Both measurements are performed with a data sample, corresponding to an integrated luminosity of 1.0 fb(-1) of pp collisions, recorded by the LHCb experiment in 2011 at a centre-of-mass energy of 7 TeV. The results are: tau(eff)(J/psi KS0) = 1.75 +/- 0.12 (stat) +/- 0.07 (syst) ps and B(B-S(0) -> J/psi K-S(0)) = (1.97 +/- 0.23) x 10(-5). For the latter measurement, the uncertainty includes both statistical and systematic sources.
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LHCb Collaboration(Aaij, R. et al), Oyanguren, A., & Ruiz Valls, P. (2013). Observation of B-c(+) -> J/ psi D-s(+) and B-c(+) -> J/ psi D-s*(+) decays. Phys. Rev. D, 87(11), 112012–10pp.
Abstract: The decays B-c(+) -> J/ psi D-s(+) and B-c(+) -> J/ psi D-s*(+) are observed for the first time using a dataset, corresponding to an integrated luminosity of 3 fb(-1), collected by the LHCb experiment in proton-proton collisions at center-of-mass energies of root s = 7 and 8 TeV. The statistical significance for both signals is in excess of 9 standard deviations. The following ratios of branching fractions are measured to be 'B(B-c(+) -> J/ psi D-s(+))/B(B-c(+) -> J/ psi pi(+)) = 2.90 +/- 0.57 +/- 0.24, B(B-c(+) -> J/psi D-s*(+))/B(B-c(+) -> J/ psi D-s(+)) = 2.37 +/- 0.56 +/- 0.10, where the first uncertainties are statistical and the second systematic. The mass of the B-c(+) meson is measured to be m(Bc+) = 6276.28 +/- 1.44(stat) +/- 0.36(syst) MeV/c(2), using the B-c(+) -> J/ psi D-s(+) decay mode.
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LHCb Collaboration(Aaij, R. et al), Oyanguren, A., & Ruiz Valls, P. (2013). Measurement of CP violation and the B-s(0) meson decay width difference with B-s(0) -> J/psi K+K- and B-s(0) -> J/psi pi(+) pi(-)decays. Phys. Rev. D, 87(11), 112010–21pp.
Abstract: The time-dependent CP asymmetry in B-s(0) -> J/psi K+ K- decays is measured using pp collision data at root s = 7 TeV, corresponding to an integrated luminosity of 1: 0 fb(-1), collected with the LHCb detector. The decay-time distribution is characterized by the decay widths Gamma(L) and Gamma(H) of the light and heavy mass eigenstates of the B-s(0) – (B) over barB(s)(0) system and by a CP-violating phase s. In a sample of 27 617 B-s(0) -> J/psi K+ K- decays, where the dominant contribution comes from B-s(0) -> J/psi K+ K- decays, these parameters are measured to be phi(s) = 0. 07 +/- 0.09(stat) +/- 0. 01(syst) rad, Gamma(s) equivalent to (Gamma(L) + Gamma(L))/2 = 0.663 +/- 0.005(stat) +/- 0.006(syst) ps(-1), and 0.006(syst) ps(-1), and Delta Gamma(s) equivalent to Gamma(L) – Gamma(L) = 0.100 +/- 0.016(stat) +/- 0.003(syst) ps(-1), corresponding to the single most precise determination of phi(s), Delta Gamma(s), and Gamma(s.). The result of performing a combined analysis with B-s(0) -> J/psi pi(+) pi(-) decays gives phi(s) = 0.01 +/- 0.07(stat) +/- 0.01(syst)rad, Gamma(s) = 0.661 +/- 0.004(stat) +/- 0.006(syst) ps(-1), and Delta Gamma(s) = 0.106 +/- 0.011(stat) +/- 0.007(syst) ps(-1). All measurements are in agreement with the Standard Model predictions.
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