BABAR Collaboration(del Amo Sanchez, P. et al), Azzolini, V., Lopez-March, N., Martinez-Vidal, F., Milanes, D. A., & Oyanguren, A. (2010). Test of Lepton Universality in Y(1S) Decays at BABAR. Phys. Rev. Lett., 104(19), 191801–7pp.
Abstract: The ratio R-tau mu(Y(1S)) = Gamma Y(1S)->tau(+)tau(-)/Gamma(+)(-)(Y(1S)->mu)(mu) is measured using a sample of (121.8 +/- 1.2) x 10(6)Y(3S) events recorded by the BABAR detector. This measurement is intended as a test of lepton universality and as a search for a possible light pseudoscalar Higgs boson. In the standard model (SM) this ratio is expected to be close to 1. Any significant deviations would violate lepton universality and could be introduced by the coupling to a light pseudoscalar Higgs boson. The analysis studies the decays Y(3S) -> Y(1S)pi(+)pi(-), Y(1S) -> l(+)l(-), where l = mu, tau. The result, R-tau μ(Y(1S)) = 1.005 +/- 0.013(stat) +/- 0.022(syst), shows no deviation from the expected SM value, while improving the precision with respect to previous measurements.
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BABAR Collaboration(Lees, J. P. et al), Azzolini, V., Lopez-March, N., Martinez-Vidal, F., Milanes, D. A., & Oyanguren, A. (2010). Search for Charged Lepton Flavor Violation in Narrow Gamma Decays. Phys. Rev. Lett., 104(15), 151802–7pp.
Abstract: Charged-lepton flavor-violating processes are unobservable in the standard model, but they are predicted to be enhanced in several extensions to the standard model, including supersymmetry and models with leptoquarks or compositeness. We present a search for such processes in a sample of 99 x 10(6)Gamma(2S) decays and 117 x 10(6)Gamma(3S) decays collected with the BABAR detector. We place upper limits on the branching fractions B(Gamma(nS) --> e(+/-)tau(-/+)) and B(Gamma(n(S) --> mu(+/-)tau(-/+)) (n = 2, 3) at the 10(-6) level and use these results to place lower limits of order 1 TeV on the mass scale of charged-lepton flavor-violating effective operators.
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BABAR Collaboration(Aubert, B. et al), Azzolini, V., Lopez-March, N., Martinez-Vidal, F., Milanes, D. A., & Oyanguren, A. (2010). Search for B+ -> l(+)nu(l) recoiling against B- -> D(0)l(-)(nu)over-barX. Phys. Rev. D, 81(5), 051101–9pp.
Abstract: We present a search for the decay B+ -> l(+)nu(l) (l = tau, mu, or e) in (458.9 +/- 5.1) x 10(6) B (B) over bar pairs recorded with the BABAR detector at the PEP-II B-factory. We search for these B decays in a sample of B+B- events where one B- meson is reconstructed as B- -> D(0)l(-)(nu) over barX. Using the method of Feldman and Cousins, we obtain B(B+ -> tau(+)nu(tau)) = (1.7 +/- 0.8 +/- 0.2) x 10(-4), which excludes zero at 2.3 sigma. We interpret the central value in the context of the standard model and find the B meson decay constant to be f(B)(2) = (62 +/- 31) x 10(3) MeV2. We find no evidence for B+ -> e(+)nu(e) and B+ -> mu(+)nu(mu) and set upper limits at the 90% C. L. B(B+ -> e(+)nu(e)) < 0.8 x 10(-5) and B(B+ -> mu(+)nu(mu)) < 1.1 x 10(-5).
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BABAR Collaboration(Aubert, B. et al), Azzolini, V., Lopez-March, N., Martinez-Vidal, F., Milanes, D. A., & Oyanguren, A. (2010). Measurement of branching fractions of B decays to K-1(1270)pi and K-1(1400)pi and determination of the CKM angle alpha from B-0 -> a(1)(1260)(+/-)pi(-/+). Phys. Rev. D, 81(5), 052009–16pp.
Abstract: We report measurements of the branching fractions of neutral and charged B meson decays to final states containing a K-1(1270) or K-1(1400) meson and a charged pion. The data, collected with the BABAR detector at the SLAC National Accelerator Laboratory, correspond to 454 x 10(6) B (B) over bar pairs produced in e(+)e(-) annihilation. We measure the branching fractions B(B-0 -> K-1(1270)(+)pi(-) + K-1(1400)(+)pi(-)) = 3.1(-0.7)(+0.8) x 10(-5) and B(B+ -> K-1(1270)(0)pi(+) + K1(1400)(0)pi(+)) = 2.9(-1.7)(+2.9) x 10(-5) (< 8.2 x 10(-5) at 90% confidence level), where the errors are statistical and systematic combined. The B-0 decay mode is observed with a significance of 7.5 sigma, while a significance of 3.2 sigma is obtained for the B+ decay mode. Based on these results, we estimate the weak phase alpha = (79 +/- 7 +/- 11)degrees from the time-dependent CP asymmetries in B-0 -> a(1)(1260)(+/-)pi(-/+) decays.
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BABAR Collaboration(Lees, J. P. et al), Azzolini, V., Lopez-March, N., Martinez-Vidal, F., Milanes, D. A., & Oyanguren, A. (2010). Measurement of the gamma gamma* -> eta c transition form factor. Phys. Rev. D, 81(5), 052010–18pp.
Abstract: We study the reaction e(+)e(-) -> e(+)e(-) eta(c), eta(c) -> KSK +/-pi(-/+) and obtain eta(c) mass and width values 2982.2 +/- 0.4 +/- 1.6 MeV/c(2) and 31.7 +/- 1.2 +/- 0.8 MeV, respectively. We find Gamma(eta(c) -> gamma gamma)B(eta(c) -> KK pi) = 0.374 +/- 0.009 +/- 0.031 keV, and measure the gamma gamma* -> eta(c) transition form factor in the momentum transfer range from 2 to 50 GeV2. The analysis is based on 469 fb(-1) of integrated luminosity collected at PEP-II with the BABAR detector at e(+)e(-) center-of-mass energies near 10.6 GeV.
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