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ATLAS Collaboration(Aad, G. et al), Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Fassi, F., Ferrer, A., et al. (2012). ATLAS search for a heavy gauge boson decaying to a charged lepton and a neutrino in pp collisions at root s=7 TeV. Eur. Phys. J. C, 72(12), 2241–23pp.
Abstract: The ATLAS detector at the LHC is used to search for high-mass states, such as heavy charged gauge bosons (W'), decaying to a charged lepton (electron or muon) and a neutrino. Results are presented based on the analysis of pp collisions at a center-of-mass energy of 7 TeV corresponding to an integrated luminosity of 4.7 fb(-1). No excess beyond Standard Model expectations is observed. A W' with Sequential Standard Model couplings is excluded at the 95 % credibility level for masses up to 2.55 TeV. Excited chiral bosons (W*) with equivalent coupling strength are excluded for masses up to 2.42 TeV.
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Bolle, E., Casella, C., Chesi, E., De Leo, R., Dissertori, G., Fanti, V., et al. (2012). AX-PET: A novel PET concept with G-APD readout. Nucl. Instrum. Methods Phys. Res. A, 695, 129–134.
Abstract: The AX-PET collaboration has developed a novel concept for high resolution PET imaging to overcome some of the performance limitations of classical PET cameras, in particular the compromise between spatial resolution and sensitivity introduced by the parallax error. The detector consists of an arrangement of long LYSO scintillating crystals axially oriented around the field of view together with arrays of wave length shifter strips orthogonal to the crystals. This matrix allows a precise 3D measurement of the photon interaction point. This is valid both for photoelectric absorption at 511 key and for Compton scattering down to deposited energies of about 100 keV. Crystals and WLS strips are individually read out using Geiger-mode Avalanche Photo Diodes (G-APDs). The sensitivity of such a detector can be adjusted by changing the number of layers and the resolution is defined by the crystal and strip dimensions. Two AX-PET modules were built and fully characterized in dedicated test set-ups at CERN, with point-like Na-22 sources. Their performance in terms of energy (Renew approximate to 11.8% (FWMH) at 511 key) and spatial resolution was assessed (sigma(axial) approximate to 0.65 mm), both individually and for the two modules in coincidence. Test campaigns at ETH Zurich and at the company AAA allowed the tomographic reconstructions of more complex phantoms validating the 3D reconstruction algorithms. The concept of the AX-PET modules will be presented together with some characterization results. We describe a count rate model which allows to optimize the planing of the tomographic scans.
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BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., & Oyanguren, A. (2012). B-0 meson decays to rho K-0*(0), f(0)K*(0), and rho K-*(+), including higher K* resonances. Phys. Rev. D, 85(7), 072005–16pp.
Abstract: We present branching fraction measurements for the decays B-0 -> rho K-0*(0), B-0 -> f(0)K*(0), and B-0 -> rho K-*(+), where K* is an S-wave (K pi)*(0) or a K*(892) meson; we also measure B-0 -> f(0)K*(2)(1430)(0). For the K*(892) channels, we report measurements of longitudinal polarization fractions (for rho final states) and direct CP violation asymmetries. These results are obtained from a sample of (471.0 +/- 2.8) X 10(6) B (B) over bar pairs collected with the BABAR detector at the PEP-II asymmetric-energy e(+)e(-) collider at the SLAC National Accelerator Laboratory. We observe rho K-0*(892)(0), rho(0)(K pi)*(0)(0), f(0)K*(892)(0), and rho K-*(892)(+) with greater than 5 sigma significance, including systematics. We report first evidence for f(0)(K pi)*(0)(0) and f(0)K*(2)(1430)(0), and place an upper limit on rho(-)(K pi)*(+)(0). Our results in the K*(892) channels are consistent with no direct CP violation.
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Li, X. Q., Li, Y. M., Lu, G. R., & Su, F. (2012). B-s(0)-(B)over-bar(s)(0) mixing in a family non-universal Z ' model revisited. J. High Energy Phys., 05(5), 049–27pp.
Abstract: Motivated by the very recent measurements performed at the LHCb and the Tevatron of the B-s(0) – (B) over bar (0)(s) mixing, in this paper we revisit it in a family non-universal Z' model, to check if a simultaneous explanation for all the mixing observables, especially for the like-sign dimuon charge asymmetry observed by the D0 collaboration, could be made in such a specific model. In the first scenario where the Z' boson contributes only to the off-diagonal element M-12(s), it is found that, once the combined constraints from Delta M-s, phi(s) and Delta Gamma(s) are imposed, the model could not explain the measured flavour-specific CP asymmetry a(fs)(s), at least within its 1 sigma ranges. In the second scenario where the NP contributes also to the absorptive part Gamma(s)(12) via tree-level Z'-induced b -> c (c) over bars operators, we find that, with the constraints from Delta M-s, phi(s) and the indirect CP asymmetry in (B) over bar (d) -> J/psi K-S taken into account, the present measured 1 sigma experimental ranges for a(fs)(s) could not be reproduced too. Thus, such a specific Z' model with our specific assumptions could not simultaneously reconcile all the present data on B-s(0) – B-s(0) mixing. Future improved measurements from the LHCb and the proposed superB experiments, especially of the flavour-specific CP asymmetries, are expected to shed light on the issue.
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Chen, H. X., Dmitrasinovic, V., & Hosaka, A. (2012). Baryon fields with U-L(3) x U-R(3) chiral symmetry. IV. Interactions with chiral (8,1) circle plus (1,8) vector and axial-vector mesons and anomalous magnetic moments. Phys. Rev. C, 85(5), 055205.
Abstract: We construct all SUL(3) x SUR(3) chirally invariant anomalous magnetic, i.e., involving a Pauli tensor and one-derivative, interactions of one chiral [(8, 1) circle plus (1, 8)] meson fieldwith chiral [(6, 3) circle plus (3, 6)], [(3, (3) over bar) circle plus ((3) over bar), 3], and [(8, 1) circle plus (1, 8)] baryon fields and their “mirror” images. We find strong chiral selection rules; e. g., there is only one off-diagonal chirally symmetric anomalous magnetic interaction between J = 1/2 fields belonging to the [(6, 3) circle plus (3, 6)] and the [(3, (3) over bar) circle plus ((3) over bar), 3] chiral multiplets. We also study the chiral selection rules for the anomalous magnetic interactions of the [(3, (3) over bar) circle plus ((3) over bar), 3] and the [(8, 1) circle plus (1, 8)] baryon fields. Again, no diagonal and only one off-diagonal chiral SUL(3) x SUR(3) interaction of this type is allowed, that turns out also to conserve the U-A(1) symmetry. We calculate the F/D ratios for the baryons' anomalous magnetic moments predicted by these interactions in the SU(3) symmetry limit and find that only the [(6, 3) circle plus (3, 6)]-[(3, (3) over bar) circle plus ((3) over bar), 3] one reproduces F/D = 1/3, in close proximity to the value extracted from experiment.
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