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BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., & Oyanguren, A. (2013). Branching fraction measurement of B+ -> omega l(+)nu decays. Phys. Rev. D, 87(3), 032004–11pp.
Abstract: We present a measurement of the B+ -> omega l(+)nu branching fraction based on a sample of 467 million B (B) over bar pairs recorded by the BABAR detector at the SLAC PEP-II e(+)e(-) collider. We observe 1125 +/- 131 signal decays, corresponding to a branching fraction of B(B+ -> omega l(+)nu) = (1.21 +/- 0.14 +/- 0.08) x 10(-4), where the first error is statistical and the second is systematic. The dependence of the decay rate on q(2), the invariant mass squared of the leptons, is compared to QCD predictions of the form factors based on a quark model and light-cone sum rules.
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ATLAS Collaboration(Aad, G. et al), Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Ferrer, A., Fiorini, L., et al. (2013). Measurement of the Lambda(0)(b) lifetime and mass in the ATLAS experiment. Phys. Rev. D, 87(3), 032002–19pp.
Abstract: A measurement of the Lambda(0)(b) lifetime and mass in the decay channel Lambda(0)(b) -> J/psi (mu(+) mu(-))Lambda(0)(p pi(-)) is presented. The analysis uses a signal sample of about 2200 Lambda(0)(b) and (Lambda) over bar (0)(b) decays that are reconstructed in 4.9 fb(-1) of ATLAS pp collision data collected in 2011 at the LHC center-of-mass energy of 7 TeV. A simultaneous mass and decay time maximum likelihood fit is used to extract the Lambda(0)(b) lifetime and mass. They are measured to be tau(Lambda b) = 1.449 +/- 0.036(stat) +/- 0.017(syst) ps and m(Lambda b) = 5619.7 +/- 0.7(stat) +/- 1.1(syst) MeV.
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Diamanti, R., Giusarma, E., Mena, O., Archidiacono, M., & Melchiorri, A. (2013). Dark radiation and interacting scenarios. Phys. Rev. D, 87(6), 063509–8pp.
Abstract: An extra dark radiation component can be present in the universe in the form of sterile neutrinos, axions or other very light degrees of freedom which may interact with the dark matter sector. We derive here the cosmological constraints on the dark radiation abundance, on its effective velocity and on its viscosity parameter from current data in dark radiation-dark matter coupled models. The cosmological bounds on the number of extra dark radiation species do not change significantly when considering interacting schemes. We also find that the constraints on the dark radiation effective velocity are degraded by an order of magnitude while the errors on the viscosity parameter are a factor of two larger when considering interacting scenarios. If future Cosmic Microwave Background data are analyzed assuming a noninteracting model but the dark radiation and the dark matter sectors interact in nature, the reconstructed values for the effective velocity and for the viscosity parameter will be shifted from their standard 1/3 expectation, namely c(eff)(2) = 0.34(-0.003)(+0.006) and c(vis)(2) = 0.29(-0.001)(+0.002) at 95% C.L. for the future COrE mission data.
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Vijande, J., Valcarce, A., & Richard, J. M. (2013). Adiabaticity and color mixing in tetraquark spectroscopy. Phys. Rev. D, 87(3), 034040–5pp.
Abstract: We revisit the role of color mixing in the quark model calculation of tetraquark states, and compare simple pairwise potentials to more elaborate string models with three-and four-body forces. We attempt to disentangle the improved dynamics of confinement from the approximations made in the treatment of the internal color degrees of freedom.
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BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., & Oyanguren, A. (2013). Measurement of CP asymmetries and branching fractions in charmless two-body B-meson decays to pions and kaons. Phys. Rev. D, 87(5), 052009–16pp.
Abstract: We present improved measurements of CP-violation parameters in the decays B-0 -> pi(+)pi(-), B-0 -> K+pi(-), and B-0 -> pi(0)pi(0), and of the branching fractions for B-0 -> pi(0)pi(0) and B-0 -> K-0 pi(0). The results are obtained with the full data set collected at the Upsilon(4S) resonance by the BABAR experiment at the PEP-II asymmetric-energy B factory at the SLAC National Accelerator Laboratory, corresponding to (467 +/- 5) x 10(6) B (B) over bar pairs. We find the CP-violation parameter values and branching fractions: S pi+pi- = -0.68 +/- 0.10 +/- 0.03, C-pi+pi(-) = -0.25 +/- 0.08 +/- 0.02, A(K+pi-) = -0.107 +/- 0.016(-0.004)(+0.006), C pi(0)pi(0) = -0.43 +/- 0.26 +/- 0.05, B(B-0 -> pi(0)pi(0)) = (1.83 +/- 0.21 +/- 0.13) x 10(-6), B(B-0 -> pi(0)pi(0)) = (10.1 +/- 0.6 +/- 0.4) x 10(-6), where in each case, the first uncertainties are statistical and the second are systematic. We observe CP violation with a significance of 6.7 standard deviations for B-0 -> pi(+)pi(-) and 6.1 standard deviations for B-0 -> K+pi(-), including systematic uncertainties. Constraints on the unitarity triangle angle alpha are determined from the isospin relations among the B -> pi pi rates and asymmetries. Considering only the solution preferred by the Standard Model, we find alpha to be in the range [71 degrees,109 degrees] at the 68% confidence level.
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