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BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., & Oyanguren, A. (2017). Search for Invisible Decays of a Dark Photon Produced in e(+)e(-) Collisions at BABAR. Phys. Rev. Lett., 119(13), 131804–7pp.
Abstract: We search for single-photon events in 53 fb(-1) of e(+)e(-) collision data collected with the BABAR detector at the PEP-II B-Factory. We look for events with a single high-energy photon and a large missing momentum and energy, consistent with production of a spin-1 particle A' through the process e(+)e(-) -> gamma A'; A' -> invisible. Such particles, referred to as “dark photons,” are motivated by theories applying a U(1) gauge symmetry to dark matter. We find no evidence for such processes and set 90% confidence level upper limits on the coupling strength of A' to e(+)e(-) in the mass range m(A') <= 8 GeV. In particular, our limits exclude the values of the A' coupling suggested by the dark-photon interpretation of the muon (g – 2)(mu) anomaly, as well as a broad range of parameters for the dark-sector models.
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T2K Collaboration(Abe, K. et al), Cervera-Villanueva, A., Izmaylov, A., Novella, P., & Sorel, M. (2017). Combined Analysis of Neutrino and Antineutrino Oscillations at T2K. Phys. Rev. Lett., 118(15), 151801–9pp.
Abstract: T2K reports its first results in the search for CP violation in neutrino oscillations using appearance and disappearance channels for neutrino-and antineutrino-mode beams. The data include all runs from January 2010 to May 2016 and comprise 7.482 x 10(20) protons on target in neutrino mode, which yielded in the far detector 32 e-like and 135 mu-like events, and 7.471 x 10(20) protons on target in antineutrino mode, which yielded 4 e-like and 66 mu-like events. Reactor measurements of sin(2) 2 theta(13) have been used as an additional constraint. The one-dimensional confidence interval at 90% for the phase delta(CP) spans the range (-3.13,-0.39) for normal mass ordering. The CP conservation hypothesis (delta(CP) = 0, pi) is excluded at 90% C.L.
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Dudouet, J. et al, Domingo-Pardo, C., Gadea, A., & Perez-Vidal, R. M. (2017). Kr-96(36)60-Low-Z Boundary of the Island of Deformation at N=60. Phys. Rev. Lett., 118(16), 162501–6pp.
Abstract: Prompt.-ray spectroscopy of the neutron-rich Kr-96, produced in transfer-and fusion-induced fission reactions, has been performed using the combination of the Advanced Gamma Tracking Array and the VAMOS + +spectrometer. A second excited state, assigned to J pi = 4(+), is observed for the first time, and a previously reported level energy of the first 2+ excited state is confirmed. The measured energy ratio R-4/2 = E(4(+))/E(2(+)) = 2.12(1) indicates that this nucleus does not show a well-developed collectivity contrary to that seen in heavier N = 60 isotones. This new measurement highlights an abrupt transition of the degree of collectivity as a function of the proton number at Z = 36, of similar amplitude to that observed at N = 60 at higher Z values. A possible reason for this abrupt transition could be related to the insufficient proton excitations in the g(9/2), d(5/2), and s(1/2) orbitals to generate strong quadrupole correlations or to the coexistence of competing different shapes. An unexpected continuous decrease of R-4/2 as a function of the neutron number up to N = 60 is also evidenced. This measurement establishes the Kr isotopic chain as the low-Z boundary of the island of deformation for N = 60 isotones. A comparison with available theoretical predictions using different beyond mean-field approaches shows that these models fail to reproduce the abrupt transitions at N = 60 and Z = 36.
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LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Henry, L., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., et al. (2017). Observation of Five New Narrow Omega(0)(c) States Decaying to Xi K-+(c)-. Phys. Rev. Lett., 118(18), 182001–10pp.
Abstract: The Xi K-+(c)- mass spectrum is studied with a sample of pp collision data corresponding to an integrated luminosity of 3.3 fb(-1), collected by the LHCb experiment. The Xi(+)(c) is reconstructed in the decay mode pK(-)pi(vertical bar) . Five new, narrow excited Omega(0)(c) states are observed: the Omega(c)(3000)(0), Omega(c)(3050)(0), Omega(c)(3066)(0), Omega(c) (3090)(0), and Omega(c)(3119)(0). Measurements of their masses and widths are reported.
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Muñoz, E., Barrio, J., Etxebeste, A., Ortega, P. G., Lacasta, C., Oliver, J. F., et al. (2017). Performance evaluation of MACACO: a multilayer Compton camera. Phys. Med. Biol., 62(18), 7321–7341.
Abstract: Compton imaging devices have been proposed and studied for a wide range of applications. We have developed a Compton camera prototype which can be operated with two or three detector layers based on monolithic lanthanum bromide (LaBr3) crystals coupled to silicon photomultipliers (SiPMs), to be used for proton range verification in hadron therapy. In this work, we present the results obtained with our prototype in laboratory tests with radioactive sources and in simulation studies. Images of a Na-22 and an Y-88 radioactive sources have been successfully reconstructed. The full width half maximum of the reconstructed images is below 4 mm for a Na-22 source at a distance of 5 cm.
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