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BABAR Collaboration(Lees, J. P. et al), Lopez-March, N., Martinez-Vidal, F., & Oyanguren, A. (2011). Study of radiative bottomonium transitions using converted photons. Phys. Rev. D, 84(7), 072002–17pp.
Abstract: We use (111 +/- 1) million Gamma(3S) and (89 +/- 1) million Gamma(2S) events recorded by the BABAR detector at the PEP-II B-factory at SLAC to perform a study of radiative transitions between bottomonium states using photons that have been converted to e(+)e(-) pairs by the detector material. We observe Gamma(3S) -> gamma chi b(0,2)(1P) decay, make precise measurements of the branching fractions for chi b(1,2)(1P, 2P) -> gamma Gamma(1S) and chi b(1,2)(2P) -> gamma Gamma(2S) decays, and search for radiative decay to the eta(b)(1S) and eta(b)(2S) states.
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Gonzalez, P., Mathieu, V., & Vento, V. (2011). Heavy meson interquark potential. Phys. Rev. D, 84(11), 114008–7pp.
Abstract: The resolution of Dyson-Schwinger equations leads to the freezing of the QCD running coupling (effective charge) in the infrared, which is best understood as a dynamical generation of a gluon mass function, giving rise to a momentum dependence which is free from infrared divergences. We calculate the interquark static potential for heavy mesons by assuming that it is given by a massive One Gluon Exchange interaction and compare with phenomenologyical fits inspired by lattice QCD. We apply these potential forms to the description of quarkonia and conclude that, even though some aspects of the confinement mechanism are absent in the Dyson-Schwinger formalism, the spectrum can be reasonably reproduced. We discuss possible explanations for this outcome.
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BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., & Oyanguren, A. (2011). Observation of the rare decay B(+) -> K(+) pi(0)pi(0) and measurement of the quasi-two-body contributions B(+) -> K* (892)(+) pi(0), B(+) -> f(0)(980)K(+), and B(+) -> chi(c0)K(+). Phys. Rev. D, 84(9), 092007–11pp.
Abstract: We report an analysis of charmless hadronic decays of charged B mesons to the final state K(+) pi(0)pi(0), using a data sample of (470.9 +/- 2.8) x 10(6) B (B) over bar events collected with the BABAR detector at the Y(4S) resonance. We observe an excess of signal events, with a significance above 10 standard deviations including systematic uncertainties, and measure the branching fraction and CP asymmetry to be B(B(+) -> K(+) pi(0)pi(0)) = (16.2 +/- 1.2 +/- 1.5) x 10(-6) and A(CP)(B(+) -> K(+) pi(0)pi(0)) = -0.06 +/- 0.06 +/- 0.04, where the uncertainties are statistical and systematic, respectively. Additionally, we study the contributions of the B(+) -> K*(892)(+) pi(0), B(+) -> f(0)(980)K(+), and B(+) -> chi(c0)K(+) quasi-two-body decays. We report the world's best measurements of the branching fraction and CP asymmetry of the B(+) -> K(+) pi(0)pi(0) and B(+) -> K(+)(892)(+) pi(0) channels.
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Gamermann, D., Garcia-Recio, C., Nieves, J., & Salcedo, L. L. (2011). Odd-parity light baryon resonances. Phys. Rev. D, 84(5), 056017–30pp.
Abstract: We use a consistent SU(6) extension of the meson-baryon chiral Lagrangian within a coupled channel unitary approach in order to calculate the T matrix for meson-baryon scattering in the s wave. The building blocks of the scheme are the pi and N octets, the rho nonet and the UDELTA; decuplet. We identify poles in this unitary T matrix and interpret them as resonances. We study here the nonexotic sectors with strangeness S = 0, -1, -2, -3 and spin J = 1/2, 3/2 and 5/2. Many of the poles generated can be asociated with known N, UDELTA;, sigma, Lambda, Xi and Omega resonances with negative parity. We show that most of the low-lying three and four star odd-parity baryon resonances with spin 1/2 and 3/2 can be related to multiplets of the spin-flavor symmetry group SU(6). This study allows us to predict the spin-parity of the Xi (1620), Xi (1690), Xi (1950), Xi (2250), Omega (2250) and Omega (2380) resonances, which have not been determined experimentally yet.
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Boito, D., Cata, O., Golterman, M., Jamin, M., Maltman, K., Osborne, J., et al. (2011). New determination of alpha(s) from hadronic tau decays. Phys. Rev. D, 84(11), 113006–19pp.
Abstract: We present a new framework for the extraction of the strong coupling from hadronic tau decays through finite-energy sum rules. Our focus is on the small, but still significant nonperturbative effects that, in principle, affect both the central value and the systematic error. We employ a quantitative model in order to accommodate violations of quark-hadron duality, and enforce a consistent treatment of the higher-dimensional contributions of the operator product expansion to our sum rules. Using 1998 OPAL data for the nonstrange isovector vector and axial-vector spectral functions, we find the n(f) = 3 values alpha(s)(m(tau)(2)) = 0.307 +/- 0.019 in fixed-order perturbation theory, and 0.322 +/- 0.026 in contour-improved perturbation theory. For comparison, the original OPAL analysis of the same data led to the values 0.324 +/- 0.014 (fixed order) and 0.348 +/- 0.021 (contour improved).
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