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BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., Oyanguren, A., & Villanueva-Perez, P. (2014). Dalitz plot analysis of eta(c) -> K+K-eta and eta(c) -> K+K-pi(0) in two-photon interactions. Phys. Rev. D, 89(11), 112004–16pp.
Abstract: We study the processes gamma gamma -> K+K-eta and gamma gamma -> K+K-pi(0) using a data sample of 519 fb(-1) recorded with the BABAR detector operating at the SLAC PEP-II asymmetric-energy e(+)e(-) collider at center-of-mass energies at and near the Upsilon(nS) (n = 2, 3, 4) resonances. We observe eta(c) -> K+K-pi(0) and eta(c) -> K+K-eta decays, measure their relative branching fraction, and perform a Dalitz plot analysis for each decay. We observe the K*(0)(1430) -> K eta decay and measure its branching fraction relative to the K pi decay mode to be R(K*(0)(1430)) = B(K*(0)(1430)-> K eta)/B(K*(0)(1430)-> K pi) = 0.092 +/- 0.025(- 0.025)(+0.010). The eta(c) -> K+K-eta and K*(0)(1430) -> K eta results correspond to the first observations of these channels. The data also show evidence for eta(c)(2S) -> K+K-pi(0) and first evidence for eta(c)(2S) -> K+K-eta.
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BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., Oyanguren, A., & Villanueva-Perez, P. (2014). Measurement of the B -> X(s)l(+)l(-) Branching Fraction and Search for Direct CP Violation from a Sum of Exclusive Final States. Phys. Rev. Lett., 112(21), 211802–8pp.
Abstract: We measure the total branching fraction of the flavor-changing neutral-current process B -> X(s)l(+)l(-), along with partial branching fractions in bins of dilepton and hadronic system (X-s) mass, using a sample of 471 x 10(6)Upsilon(4S) -> B (B) over bar events recorded with the BABAR detector. The admixture of charged and neutral B mesons produced at PEP-II2 are reconstructed by combining a dilepton pair with 10 different X-s final states. Extrapolating from a sum over these exclusive modes, we measure a lepton-flavor-averaged inclusive branching fraction B(B -> X(s)l(+)l(-)) = [6.73(-0.64)(+0.70)(stat)(-0.25)(+0.34)(exp syst) +/- 0.50(model syst)] x 10(-6) for m(l+l-)(2) > 0.1 GeV2/c(4). Restricting our analysis exclusively to final states from which a decaying B meson's flavor can be inferred, we additionally report measurements of the direct CP asymmetry A(CP) in bins of dilepton mass; over the full dilepton mass range, we find A(CP) = 0.04 +/- 0.11 +/- 0.01 for a leptonflavor-averaged sample.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2014). Differential branching fractions and isospin asymmetries of B -> K ((*)) μ(+) μ(-) decays. J. High Energy Phys., 06(6), 133–22pp.
Abstract: The isospin asymmetries of B -> K μ(+) μ(-) and B -> K (*) μ(+) μ(-) decays and the partial branching fractions of the B (0) -> K (0) μ(+) μ(-), B (+) -> K (+) μ(+) μ(-) and B (+) -> K (*+) μ(+) μ(-) decays are measured as functions of the dimuon mass squared, q (2). The data used correspond to an integrated luminosity of 3 fb(-1) from proton-proton collisions collected with the LHCb detector at centre-of-mass energies of 7 TeV and 8 TeV in 2011 and 2012, respectively. The isospin asymmetries are both consistent with the Standard Model expectations. The three measured branching fractions favour lower values than their respective theoretical predictions, however they are all individually consistent with the Standard Model.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., & Ruiz Valls, P. (2014). Observation of Photon Polarization in the b -> s gamma Transition. Phys. Rev. Lett., 112(16), 161801–8pp.
Abstract: This Letter presents a study of the flavor-changing neutral current radiative B-+/- -> K-+/-pi(-/+)pi(+/-)gamma decays performed using data collected in proton-proton collisions with the LHCb detector at 7 and 8 TeV center-of-mass energies. In this sample, corresponding to an integrated luminosity of 3 fb(-1), nearly 14 000 signal events are reconstructed and selected, containing all possible intermediate resonances with a K-+/-pi(-/+)pi(+/-) final state in the [1.1, 1.9] GeV/c(2) mass range. The distribution of the angle of the photon direction with respect to the plane defined by the final-state hadrons in their rest frame is studied in intervals of K-+/-pi(-/+)pi(+/-) mass and the asymmetry between the number of signal events found on each side of the plane is obtained. The first direct observation of the photon polarization in the b -> s(gamma) transition is reported with a significance of 5.2 sigma.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2014). Measurement of the resonant and CP components in (B)over-bar(0) -> J/psi pi(+)pi(-) decays. Phys. Rev. D, 90(1), 012003–21pp.
Abstract: The resonant structure of the reaction (B) over bar (0) --> J/psi pi(+)pi(-) is studied using data from 3 fb(-1) of integrated luminosity collected by the LHCb experiment, one third at 7 TeV center-of-mass energy and the remainder at 8 TeV. The invariant mass of the pi(+)pi(-) pair and three decay angular distributions are used to determine the fractions of the resonant and nonresonant components. Six interfering pi(+)pi(-) states, rho(770), f(0)(500), f(2)(1270), rho(1450), omega(782) and rho(1700), are required to give a good description of invariant mass spectra and decay angular distributions. The positive and negative charge parity fractions of each of the resonant final states are determined. The f(0)(980) meson is not seen and the upper limit on its presence, compared with the observed f(0)(500) rate, is inconsistent with a model where these scalar mesons are formed from two quarks and two antiquarks (tetraquarks) at the eight standard deviation level. In the q (q) over bar model, the absolute value of the mixing angle between the f(0)(980) and the f(0)(500) scalar mesons is limited to be less than 17 degrees at 90% confidence level.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2014). Measurement of CP asymmetry in D-0 -> K- K+ and D-0 -> pi(-) pi(+) decays. J. High Energy Phys., 07(7), 041–25pp.
Abstract: Time-integrated CP asymmetries in D-0 decays to the final states K- K+ and pi(-) pi(+) are measured using proton-proton collisions corresponding to 3 fb(-1) of integrated luminosity collected at centre-of-mass energies of 7 TeV and 8 TeV. The D-0 mesons are produced in semileptonic b-hadron decays, where the charge of the accompanying muon is used to determine the initial flavour of the charm meson. The difference in CP asymmetries between the two final states is measured to be Delta A(CP) = A(CP)(K- K+) – A(CP)(pi(-) pi(+)) = (+0.14 +/- 0.16 (stat) +/- 0.08 (syst))% . A measurement of A(CP)(K- K+) is obtained assuming negligible CP violation in charm mixing and in Cabibbo-favoured D decays. It is found to be A(CP)(K- K+) = (-0.06 +/- 0.15 (stat) +/- 0.10 (syst))% , where the correlation coefficient between Delta A(CP) and A(CP)(K- K+) is rho = 0.28. By combining these results, the CP asymmetry in the D-0 -> pi(-) pi(+) channel is A(CP)(pi(-) pi(+)) = (-0.20 +/- 0.19 (stat) +/- 0.10 (syst))%.
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BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., & Oyanguren, A. (2014). Study of the reaction e(+)e(-) -> psi(2S)pi(+)pi(-) via initial-state radiation at BABAR. Phys. Rev. D, 89(11), 111103–8pp.
Abstract: We study the process e(+)e(-) -> psi(2S)pi(+)pi(-) with initial-state-radiation events produced at the PEP-II asymmetric-energy collider. The data were recorded with the BABAR detector at center-of-mass energies at and near the (nS) (n = 2, 3, 4) resonances and correspond to an integrated luminosity of 520 fb(-1). We investigate the psi(2S)pi(+)pi(-) mass distribution from 3.95 to 5.95 GeV/c(2), and measure the center-of-mass energy dependence of the associated e(+)e(-) -> psi(2S)pi(+)pi(-) cross section. The mass distribution exhibits evidence of two resonant structures. A fit to the psi(2S)pi(+)pi(-) mass distribution corresponding to the decay mode psi(2S) -> J/psi pi(+)pi(-) yields a mass value of 4340 +/- 16 (stat) +/- 9 (syst) MeV/c(2) and a width of 94 +/- 32 (stat) +/- 13 (syst) MeV for the first resonance, and for the second a mass value of 4669 +/- 21 (stat) +/- 3 (syst) MeV/c(2) and a width of 104 +/- 48 (stat) +/- 10 (syst) MeV. In addition, we show the pi(+)pi(-) mass distributions for these resonant regions.
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BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., Oyanguren, A., & Villanueva-Perez, P. (2014). Antideuteron production in Upsilon(nS) decays and in e(+)e(-) -> q(q) over bar at root s approximate to 10.58 GeV. Phys. Rev. D, 89(11), 111102–8pp.
Abstract: We present measurements of the inclusive production of antideuterons in e(+)e(-) annihilation into hadrons at approximate to 10.58 GeV center-of-mass energy and in Upsilon(1S, 2S, 3S) decays. The results are obtained using data collected by the BABAR detector at the PEP-II electron-positron collider. Assuming a fireball spectral shape for the emitted antideuteron momentum, we find B(Upsilon(1S) -> (d) over barX) = (2.81 +/- 0.49(stat)-(+0.20)(0.24)(syst)) x 10(-5), B(Upsilon(2S) -> (d) over barX) = (2.64 +/- 0.11(stat)(-0.21)(+0.26)(syst)) x 10(-5), B(Upsilon(3S) -> (d) over barX) = (2.33 +/- 0.15(stat)(-0.28)(+0.31)(syst)) x 10(-5), and sigma(e(+)e(-) -> (d) over barX) = (9.63 +/- 0.41(stat)(-1.01)(+1.17)(syst) fb.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., & Ruiz Valls, P. (2014). Precision measurement of the ratio of the Lambda(0)(b) to (B)over-bar(0) lifetimes. Phys. Lett. B, 734, 122–130.
Abstract: The LHCb measurement of the lifetime ratio of the Lambda(0)(b) baryon to the (B) over bar (0) meson is updated using data corresponding to an integrated luminosity of 3.0 fb(-1) collected using 7 and 8 TeV centre-of-mass energy pp collisions at the LHC. The decay modes used are Lambda(0)(b) -> J/psi pK(-) and (B) over bar (0) -> J/psi pi K-+(-), where the pi K-+(-) mass is consistent with that of the (K) over bar*(0)(892) meson. The lifetime ratio is determined with unprecedented precision to be 0.974 +/- 0.006 +/- 0.004, where the first uncertainty is statistical and the second systematic. This result is in agreement with original theoretical predictions based on the heavy quark expansion. Using the current world average of the (B) over bar (0) lifetime, the Lambda(0)(b) lifetime is found to be 1.479 +/- 0.009 +/- 0.010 ps.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2014). Study of production and cold nuclear matter effects in pPb collisions at=5 TeV. J. High Energy Phys., 07(7), 094–19pp.
Abstract: Production of mesons in proton-lead collisions at a nucleon-nucleon centre-of-mass energy = 5 TeV is studied with the LHCb detector. The analysis is based on a data sample corresponding to an integrated luminosity of 1.6 nb(-1). The mesons of transverse momenta up to 15 GeV/c are reconstructed in the dimuon decay mode. The rapidity coverage in the centre-of-mass system is 1.5 < y < 4.0 (forward region) and -5.0 < y < -2.5 (backward region). The forward-backward production ratio and the nuclear modification factor for (1S) mesons are determined. The data are compatible with the predictions for a suppression of (1S) production with respect to proton-proton collisions in the forward region, and an enhancement in the backward region. The suppression is found to be smaller than in the case of prompt J/psi mesons.
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