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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. (2018). Test of lepton flavor universality by the measurement of the B-0 -> D*(-) tau(+) nu(tau) branching fraction using three-prong tau decays. Phys. Rev. D, 97(7), 072013–26pp.
Abstract: The ratio of branching fractions R(D*(-)) = B(B-0 -> D*(-) tau(+)nu(tau))/(B-0 -> D*(-) mu(+)nu(mu)) is measured using a data sample of proton-proton collisions collected with the LHCb detector at center-of-mass energies of 7 and 8 TeV, corresponding to an integrated luminosity of 3 fb(-1). The tau lepton is reconstructed with three charged pions in the final state. A novel method is used that exploits the different vertex topologies of signal and backgrounds to isolate samples of semitauonic decays of b hadrons with high purity. Using the B-0 -> D*(-) pi(+)pi(-)pi(+) decay as the normalization channel, the ratio B(B-0 -> D*(-) tau(+)nu(tau))/B(B-0 -> D* pi(+)pi(-)pi(+)) is measured to be 1.97 +/- 0.13 +/- 0.18, where the first uncertainty is statistical and the second systematic. An average of branching fraction measurements for the normalization channel is used to derive B(B-0 -> D*(-) tau(+)nu(tau))(_)= (1.42 +/- 0.094 +/- 0.129 +/- 0.054)%, where the third uncertainty is due to the limited knowledge of B(B-0 -> D*(-) pi(+)pi(-)pi(+)). A test of lepton flavor universality is performed using the well- measured branching fraction B(B-0 -> D*(-) mu(+)nu(mu)) to compute R(D*(-))0 = 0.291 +/- 0.019 +/- 0.026 +/- 0.013, where the third uncertainty originates from the uncertainties on B(B-0 -> D*(-) pi(+)pi(-)pi(+)) and B(B-0 -> D*(-) mu(+)nu(mu)) This measurement is in agreement with the Standard Model prediction and with previous measurements.
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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. (2018). Search for the rare decay Lambda(+)(c) -> p mu(+ )mu(-). Phys. Rev. D, 97(9), 091101–10pp.
Abstract: A search for the flavor-changing neutral-current decay Lambda(+)(c) -> p mu(+)mu(-) is reported using a data set corresponding to an integrated luminosity of 3.0 fb(-1) collected by the LHCb Collaboration. No significant signal is observed outside of the dimuon mass regions around the phi and omega resonances, and an upper limit is placed on the branching fraction of B(Lambda(+ )(c)-> p mu(+)mu(-)) < 7.7(9.6) x 10(-8) at 90%(95%) confidence level. A significant signal is observed in the omega dimuon mass region for the first time.
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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. (2018). Measurement of CP asymmetries in two-body B-(s)(0)-meson decays to charged pions and kaons. Phys. Rev. D, 98(3), 032004–23pp.
Abstract: The time-dependent CP asymmetries in B-0 -> pi(+)pi(-) and B-(s)(0) -> K+K- decays are measured using a data sample of p p collisions corresponding to an integrated luminosity of 3.0 fb(-1), collected with the LHCb detector at center-of-mass energies of 7 and 8 TeV. The same data sample is used to measure the time-integrated CP asymmetries in B-0 -> K+pi(-) and B-(s)(0) -> pi K-+(-) decays. The results are C pi+pi- = -0.34 +/- 0.06 +/- 0.01, S pi+pi- = -0.63 +/- 0.05 +/- 0.01, CK+K- = 0.20 +/- 0.06 +/- 0.02, SK+K- = 0.18 +/- 0.06 +/- 0.02, A(K+K-)(Delta Gamma) = -0.79 +/- 0.07 +/- 0.10, A(CP)(B0) = -0.084 +/- 0.004 +/- 0.003, and A(CP)(B0s) = 0.213 +/- 0.015 +/- 0.007, where the first uncertainties are statistical and the second systematic. Evidence for CP violation is found in the B-s(0) -> K+K- decay for the first time.
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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. (2018). Observation of B-s(0) -> (D)over-bar*(0)phi and search for B-0 -> (D)over-bar(0)phi decays. Phys. Rev. D, 98(7), 071103–10pp.
Abstract: The first observation of the B-s(0) -> (D) over bar*(0)phi decay is reported, with a significance of more than seven standard deviations, from an analysis of pp collision data corresponding to an integrated luminosity of 3 fb -1 , collected with the LHCb detector at center-of-mass energies of 7 and 8 TeV. The branching fraction is measured relative to that of the topologically similar decay B-0 -> (D) over bar (0)pi(+)pi(-) and is found to be B(B-s(0) -> (D) over bar*(0)phi) = (3.7 +/- 05 +/- 0.3 +/- 0.2) x 10(-5), where the first uncertainty is statistical, the second systematic, and the third from the branching fraction of the B-0 -> (D) over bar (0)pi(+)pi(-) decay. The fraction of longitudinal polarization in this decay is measured to be f(L) = (73 +/- 15 +/- 4)%. The most precise determination of the branching fraction for the B-s(0) -> (D) over bar (0)phi decay is also obtained, B(B-s(0) -> (D) over bar (0)phi) = (3.0 +/- 0.3 +/- 0.2 +/- 0.2) x 10(-5). An upper limit, B(B-s(0) -> (D) over bar (0)phi) < 2.0 (2.3) x 10(-6) at 90% (95%) confidence level is set. A constraint on the omega – phi mixing angle delta is set at vertical bar delta vertical bar < 5.2 degrees (5.5 degrees) at 90% (95%) confidence level.
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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. (2018). Observation of the decay B-s(0) -> (D)over-bar(0)K (+) K-. Phys. Rev. D, 98(7), 072006–19pp.
Abstract: The first observation of the B-s(0) -> (D) over bar K-0 (+) K- decay is reported, together with the most precise branching fraction measurement of the mode B-0 -> (D) over bar K-0 (+) K- The results are obtained from an analysis of pp collision data corresponding to an integrated luminosity of 3.0 fb(-1). The data were collected with the LHCb detector at center-of-mass energies of 7 and 8 TeV, The branching fraction of the B-0 -> (D) over bar K-0 (+) K- decay is measured relative to that of the decay B-0 -> (D) over bar (0)pi (+) pi(-) to be B(B-0 -> (D) over bar K-0 (+) K-)/B(B-0 -> (D) over bar (0)pi (+) pi(-)) =(69 +/- 0.4 +/- 0.3)%, where the first uncertainty is statistical and the second is systematic. The measured branching fraction of the B-s(0) -> (D) over bar K-0 (+) K- decay mode relative to that of the corresponding B-0 decay is B(B-0 -> (D) over bar K-0 (+) K-)/B(B-0 -> (D) over bar K-0 (+) K-) = (93.0 +/- 809 +/- 6.9)%. Using the known branching fraction of B-0 -> (D) over bar (0)pi (+) pi(-), the values of B-0 -> (D) over bar K-0 (+) K- = (6.1 +/- 0.4 +/- 0.3 +/- 0.3) x 10(-5) and B(B-s(0) -> (D) over bar K-0 (+) K- = (5.7 +/- 0.5 +/- 0.4 +/- 0.5) x 10(-5) are obtained, where the third uncertainties arise from the branching fraction of the decay modes B-0 -> (D) over bar (0)pi (+) pi(-) and B-0 -> (D) over bar K-0 (+) K-, respectively.
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