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Gomez Dumm, D., Roig, P., Pich, A., & Portoles, J. (2010). Hadron structure in tau -> KK pi nu(tau) decays. Phys. Rev. D, 81(3), 034031–17pp.
Abstract: We analyze the hadronization structure of both vector and axial-vector currents leading to tau -> KK pi nu(tau) decays. At leading order in the 1/N-C expansion, and considering only the contribution of the lightest resonances, we work out, within the framework of the resonance chiral Lagrangian, the structure of the local vertices involved in those processes. The couplings in the resonance theory are constrained by imposing the asymptotic behavior of vector and axial-vector spectral functions ruled by QCD. In this way we predict the hadron spectra and conclude that, contrary to previous assertions, the vector contribution dominates by far over the axial-vector one in all KK pi charge channels.
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BABAR Collaboration(Aubert, B. et al), Azzolini, V., Lopez-March, N., Martinez-Vidal, F., Milanes, D. A., & Oyanguren, A. (2010). Observation of inclusive D*(+/-) production in the decay of Y(1S). Phys. Rev. D, 81(1), 011102–8pp.
Abstract: We present a study of the inclusive D*(+/-) production in the decay of Y(1S) using (98.6 +/- 0.9) X 10(6) Y(2S) mesons collected with the BABAR detector at the Y(2S) resonance. Using the decay chain Y(2S) -> pi(+)pi Y-(1S), Y(1S) -> D*X-+/-, where X is unobserved, we measure the branching fraction B[Y(1S) -> D*X-+/-] = (2.52 +/- 0.13(stat) +/- 0.15(syst)% and the D*(+/-) momentum distribution in the rest frame of the Y(1S). We find evidence for an excess of D*+/- production over the expected rate from the virtual photon annihilation process Y(1S) -> gamma* -> c (c) over bar -> D*X-+/-.
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Roca, L., & Oset, E. (2010). Asymmetry observables in e(+)e(-) -> pi(+) pi(-) gamma in the phi region within a chiral unitary approach. Phys. Rev. D, 81(1), 014010–8pp.
Abstract: We make a theoretical study of the charge and forward-backward pion asymmetries in the e(+)e(-) -> pi(+) pi(-) gamma process on and off the phi resonance energy. These observables are rather sensitive to the inner details of the theoretical models to describe the reaction. In addition to the standard implementation of the initial state radiation and the bremsstrahlung contribution to the final state radiation, we use the techniques of the chiral unitary approach to evaluate the contribution from the mechanisms of phi decay into pi(+) pi(-) gamma. This contribution involves the implementation of final state interaction from direct chiral loops, the exchange of vector and axial-vector resonances and the final state interaction through the consideration of the meson-meson unitarized amplitudes, which were found important in a previous work describing the phi -> pi pi gamma. We find a good reproduction of the experimental data from KLOE for the forward-backward asymmetry, both at the phi peak and away from it. We also make predictions for the angular distributions of the charge asymmetry and show that this observable is very sensitive to the chiral loops involved in phi radiative decay.
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Fernandes, L. M. P., Freitas, E. D. C., Ball, M., Gomez-Cadenas, J. J., Monteiro, C. M. B., Yahlali, N., et al. (2010). Primary and secondary scintillation measurements in a Xenon Gas Proportional Scintillation Counter. J. Instrum., 5, P09006–15pp.
Abstract: NEXT is a new experiment to search for neutrinoless double beta decay using a 100 kg radio-pure high-pressure gaseous xenon TPC. The detector requires excellent energy resolution, which can be achieved in a Xe TPC with electroluminescence readout. Hamamatsu R8520-06SEL photomultipliers are good candidates for the scintillation readout. The performance of this photomultiplier, used as VUV photosensor in a gas proportional scintillation counter, was investigated. Initial results for the detection of primary and secondary scintillation produced as a result of the interaction of 5.9 keV X-rays in gaseous xenon, at room temperature and at pressures up to 3 bar, are presented. An energy resolution of 8.0% was obtained for secondary scintillation produced by 5.9 keV X-rays. No significant variation of the primary scintillation was observed for different pressures (1, 2 and 3 bar) and for electric fields up to 0.8 V cm(-1) torr(-1) in the drift region, demonstrating negligible recombination luminescence. A primary scintillation yield of 81 +/- 7 photons was obtained for 5.9 keV X-rays, corresponding to a mean energy of 72 +/- 6 eV to produce a primary scintillation photon in xenon.
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ATLAS Collaboration(Abat, E. et al), Bernabeu Verdu, J., Castillo Gimenez, V., Costa, M. J., Escobar, C., Ferrer, A., et al. (2010). Combined performance studies for electrons at the 2004 ATLAS combined test-beam. J. Instrum., 5, P11006–68pp.
Abstract: In 2004 at the ATLAS (A Toroidal LHC ApparatuS) combined test beam, one slice of the ATLAS barrel detector (including an Inner Detector set-up and the Liquid Argon calorimeter) was exposed to particles from the H8 SPS beam line at CERN. It was the first occasion to test the combined electron performance of ATLAS. This paper presents results obtained for the momentum measurement p with the Inner Detector and for the performance of the electron measurement with the LAr calorimeter (energy E linearity and resolution) in the presence of a magnetic field in the Inner Detector for momenta ranging from 20 GeV/c to 100 GeV/c. Furthermore the particle identification capabilities of the Transition Radiation Tracker, Bremsstrahlungs-recovery algorithms relying on the LAr calorimeter and results obtained for the E/p ratio and a way how to extract scale parameters will be discussed.
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