LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2015). Search for Hidden-Sector Bosons in B-0 -> K*(0)mu(+)mu(-) Decays. Phys. Rev. Lett., 115(16), 161802–10pp.
Abstract: A search is presented for hidden-sector bosons, chi, produced in the decay B-0 -> K*(892)(0)chi, with K*(892)(0) -> K+pi(-) and chi -> mu(+)mu(-). The search is performed using pp-collision data corresponding to 3.0 fb(-1) collected with the LHCb detector. No significant signal is observed in the accessible mass range 214 <= m(chi) <= 4350 MeV, and upper limits are placed on the branching fraction product B(B-0 -> K*(892)(0)chi) X B(chi -> mu(+)mu(-)) as a function of the mass and lifetime of the chi boson. These limits are of the order of 10(-9) for chi lifetimes less than 100 ps over most of the m(chi) range, and place the most stringent constraints to date on many theories that predict the existence of additional low-mass bosons.
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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 time-integrated CP asymmetry in D-0 -> (KSKS0)-K-0 decays. J. High Energy Phys., 10(10), 055–15pp.
Abstract: The time-integrated CP asymmetry in the decay D-0 -> (KSKS0)-K-0 is measured using 3 fb(-1) of proton-proton collision data collected by the LHCb experiment at centreof- mass energies of 7 and 8TeV. The flavour of the D-0 meson is determined by use of the decay D*(+) -> D-0 pi(+) and its charge conjugate mode. The result is A(CP) = -0.029 +/- 0.052 +/- 0.022, where the first uncertainty is statistical and the second systematic. The result is consistent with Standard Model expectations and improves the uncertainty with respect to the only previous measurement of this quantity by more than a factor of three.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2016). Study of the production of A(b)(0) and (B)over-bar(0) hadrons in pp collisions and first measurement of the A(b)(0)-> J/psi pK(-) branching fraction. Chin. Phys. C, 40(1), 011001–16pp.
Abstract: The product of the A(b)(0) ((B) over bar (0)) differential production cross-section and the branching fraction of the decay A(b)(0)-> J/psi pK(-) ((B) over bar (0)-> J/psi p (K) over bar*(892)(0)) is measured as a function of the beauty hadron transverse momentum, p(T), and rapidity, y. The kinematic region of the measurements is p(T) <20 GeV/c and 2.0 < y < 4.5. The measurements use a data sample corresponding to an integrated luminosity of 3fb(-1) collected by the LHCb detector in pp collisions at centre-of-mass energies root s=7 TeV in 2011 and root s=8 TeV in 2012. Based on previous LHCb results of the fragmentation fraction ratio, f(Ab0)/f(d), the branching fraction of the decay A(b)(0)-> J/psi pK(-) is measured to be B(A(b)(0)-> J/psi pK(-))=(3.17 +/- 0.04 +/- 0.07 +/- 0.34(-0.28)(+0.45))x10(-4) where the first uncertainty is statistical, the second is systematic, the third is due to the uncertainty on the branching fraction of the decay (B) over bar (0)-> J/psi p (K) over bar*(892)(0), and the fourth is due to the knowledge of f(Ab0)/f(d). The sum of the asymmetries in the production and decay between A(b)(0) and (A) over bar (0)(b) is also measured as a function of p(T) and y. The previously published branching fraction of A(b)(0)-> J/psi p pi(-), relative to that of A(b)(0)-> J/psi pK(-), is updated. The branching fractions of A(b)(0)-> P-c(+)(-> J/psi p)K- are determined.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2015). Measurement of CP violation parameters and polarisation fractions in B-s(0) -> J/psi(K)over-bar*(0) decays. J. High Energy Phys., 11(11), 082–38pp.
Abstract: The first measurement of CP asymmetries in the decay B-s(0) -> J/psi(K) over bar*(892)(0) and an updated measurement of its branching fraction and polarisation fractions are presented. The results are obtained using data corresponding to an integrated luminosity of 3.0 fb (-1) of proton-proton collisions recorded with the LHCb detector at centre-of-mass energies of 7 and 8 TeV. Together with constraints from B-0 -> J/psi rho(0), the results are used to constrain additional contributions due to penguin diagrams in the CP-violating phase phi(s), measured through B-s(0) decays to charmonium.
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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. (2015). Measurement of forward J/psi production cross-sections in pp collisions at root s=13 TeV. J. High Energy Phys., 10(10), 172–29pp.
Abstract: The production of J/psi mesons in proton-proton collisions at a centre-of-mass energy of root s = 13 TeV is studied with the LHCb detector. Cross-section measurements are performed as a function of the transverse momentum p(T) and the rapidity y of the J/psi meson in the region p(T) < 14 GeV/c and 2.0 < y < 4.5, for both prompt J/psi mesons and J/psi mesons from b-hadron decays. The production cross-sections integrated over the kinematic coverage are 15.30 +/- 0.03 +/- 0.86 μb for prompt J/psi and 2.34 +/- 0.01 +/- 0.13 μb for J/psi from b-hadron decays, assuming zero polarization of the J/psi meson. The first uncertainties are statistical and the second systematic. The cross-section reported for J/psi mesons from b-hadron decays is used to extrapolate to a total b<(b)over bar> cross-section. The ratios of the cross-sections with respect to root s = 8 TeV are also determined.
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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. (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. (2015). Model-independent confirmation of the Z(4430)(-) state. Phys. Rev. D, 92(11), 112009–15pp.
Abstract: The decay B-0 -> psi(2S)K+pi(-) is analyzed using 3 fb(-1) of pp collision data collected with the LHCb detector. A model-independent description of the psi(2S)pi mass spectrum is obtained, using as input the K pi mass spectrum and angular distribution derived directly from data, without requiring a theoretical description of resonance shapes or their interference. The hypothesis that the psi(2S)pi mass spectrum can be described in terms of K pi reflections alone is rejected with more than 8 sigma significance. This provides confirmation, in a model-independent way, of the need for an additional resonant component in the mass region of the Z(4430)(-) exotic state.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2015). Evidence for the Strangeness-Changing Weak Decay Xi(-)(b) -> Lambda(0)(b)pi(-). Phys. Rev. Lett., 115(24), 241801–10pp.
Abstract: Using a pp collision data sample corresponding to an integrated luminosity of 3.0 fb(-1), collected by the LHCb detector, we present the first search for the strangeness-changing weak decay Xi(-)(b) -> Delta(0)(b)pi(-). No b hadron decay of this type has been seen before. A signal for this decay, corresponding to a significance of 3.2 standard deviations, is reported. The relative rate is measured to be f Xi(-)(b)/f Lambda B-0(b)(Xi(-)(b) -> Lambda(0)(b)pi(-)) = (5.7 +/- 1.8(-0.9)(+0.8)) x 10(-4) where f Xi(-)(b) and f Lambda(0)(b) are the b -> Xi(-)(b) and b -> Lambda(0)(b) fragmentation fractions, and B(Xi(-)(b) -> Lambda(0)(b)pi(-)) is the branching fraction. Assuming f Xi(-)(b)/f Lambda(0)(b) is bounded between 0.1 and 0.3, the branching fraction B(Xi(-)(b) -> Lambda(0)(b)pi(-)) would lie in the range from (0.57 +/- 0.21)% to (0.19 +/- 0.07)%.
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