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CDF Collaboration(Aaltonen, T. et al), & Cabrera, S. (2010). Search for Supersymmetry with Gauge-Mediated Breaking in Diphoton Events with Missing Transverse Energy at CDF II. Phys. Rev. Lett., 104(1), 011801–8pp.
Abstract: We present the results of a search for supersymmetry with gauge-mediated breaking and (chi) over tilde (1)(0) -> gamma(G) over tilde in the gamma gamma + missing transverse energy final state. In 2.6 +/- 0.2 fb(-1) of p (p) over bar collisions at root s 1.96 TeV recorded by the CDF II detector we observe no candidate events, consistent with a standard model background expectation of 1.4 +/- 0.4 events. We set limits on the cross section at the 95% C.L. and place the world's best limit of 149 GeV/c(2) on the (chi) over tilde (1)(0) mass at tau((chi) over tilde 01) << 1 ns. We also exclude regions in the (chi) over tilde (1)(0) mass-lifetime plane for tau((chi) over tilde 01) less than or similar to 2 ns.
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BABAR Collaboration(Aubert, B. et al), Azzolini, V., Lopez-March, N., Martinez-Vidal, F., Milanes, D. A., & Oyanguren, A. (2010). Measurements of Charged Current Lepton Universality and vertical bar V-us vertical bar Using Tau Lepton Decays to e(-)(nu)over-bar(e)nu(tau), mu(-)(nu)over-bar(mu)nu(tau), pi(-)nu(tau), and K-nu(tau). Phys. Rev. Lett., 105(5), 051602–8pp.
Abstract: Using 467 fb(-1) of e(+)e(-) annihilation data collected with the BABAR detector, we measure B(tau(-)->mu(-)(nu) over bar (mu)nu(tau))/B(tau(-)-> e(-)(nu) over bar (e)nu(tau)) = (0.9796 +/- 0.0016 +/- 0.0036), B(tau(-)->pi(-)nu(tau))/B(tau(-)-> e(-)nu(e)nu(tau)) = (0.5945 +/- 0.0014 +/- 0.0061), and B(tau(-)-> K-nu(tau))/B(tau(-)-> e(-)nu(e)nu(tau)) = (0.03882 +/- 0.00032 +/- 0.00057), where the uncertainties are statistical and systematic, respectively. From these precision similar to measurements, we test the standard model assumption of μ- e and tau – μcharge current lepton universality and provide determinations of vertical bar V-us vertical bar experimentally independent of the decay of a kaon.
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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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Catford, W. N. et al, Caballero, L., & Rubio, B. (2010). Migration of Nuclear Shell Gaps Studied in the d(Ne-24, p gamma)Ne-25 Reaction. Phys. Rev. Lett., 104(19), 192501–4pp.
Abstract: The transfer of neutrons onto Ne-24 has been measured using a reaccelerated radioactive beam of Ne-24 to study the (d, p) reaction in inverse kinematics. The unusual raising of the first 3/2(+) level in Ne-25 and its significance in terms of the migration of the neutron magic number from N = 20 to N = 16 is put on a firm footing by confirmation of this state's identity. The raised 3/2(+) level is observed simultaneously with the intruder negative parity 7/2(-) and 3/2(-) levels, providing evidence for the reduction in the N = 20 gap. The coincident gamma-ray decays allowed the assignment of spins as well as the transferred orbital angular momentum. The excitation energy of the 3/2(+) state shows that the established USD shell model breaks down well within the sd model space and requires a revised treatment of the proton-neutron monopole interaction.
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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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