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Edgecock, T. R. et al, Agarwalla, S. K., Cervera-Villanueva, A., Donini, A., Ghosh, T., Gomez-Cadenas, J. J., et al. (2013). High intensity neutrino oscillation facilities in Europe. Phys. Rev. Spec. Top.-Accel. Beams, 16(2), 021002–18pp.
Abstract: The EUROnu project has studied three possible options for future, high intensity neutrino oscillation facilities in Europe. The first is a Super Beam, in which the neutrinos come from the decay of pions created by bombarding targets with a 4 MW proton beam from the CERN High Power Superconducting Proton Linac. The far detector for this facility is the 500 kt MEMPHYS water Cherenkov, located in the Frejus tunnel. The second facility is the Neutrino Factory, in which the neutrinos come from the decay of mu(+) and mu(-) beams in a storage ring. The far detector in this case is a 100 kt magnetized iron neutrino detector at a baseline of 2000 km. The third option is a Beta Beam, in which the neutrinos come from the decay of beta emitting isotopes, in particular He-6 and Ne-18, also stored in a ring. The far detector is also the MEMPHYS detector in the Frejus tunnel. EUROnu has undertaken conceptual designs of these facilities and studied the performance of the detectors. Based on this, it has determined the physics reach of each facility, in particular for the measurement of CP violation in the lepton sector, and estimated the cost of construction. These have demonstrated that the best facility to build is the Neutrino Factory. However, if a powerful proton driver is constructed for another purpose or if the MEMPHYS detector is built for astroparticle physics, the Super Beam also becomes very attractive.
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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. (2013). Measurement of the Azimuthal Angle Dependence of Inclusive Jet Yields in Pb plus Pb Collisions at root s(NN)=2.76 TeV with the ATLAS Detector. Phys. Rev. Lett., 111(15), 152301–18pp.
Abstract: Measurements of the variation of inclusive jet suppression as a function of relative azimuthal angle, Delta phi, with respect to the elliptic event plane provide insight into the path-length dependence of jet quenching. ATLAS has measured the Delta phi dependence of jet yields in 0.14 nb(-1) of root s(NN) = 2.76 TeV Pb + Pb collisions at the LHC for jet transverse momenta p(T) > 45 GeV in different collision centrality bins using an underlying event subtraction procedure that accounts for elliptic flow. The variation of the jet yield with Delta phi was characterized by the parameter, nu(jet)(2), and the ratio of out-of-plane (Delta phi similar to pi/2) to in-plane (Delta phi similar to 0) yields. Nonzero nu(jet)(2) values were measured in all centrality bins for p(T) < 160 GeV. The jet yields are observed to vary by as much as 20% between in-plane and out-of-plane directions.
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Emmanuel-Costa, D., Simoes, C., & Tortola, M. (2013). The minimal adjoint-SU (5) x Z(4) GUT model. J. High Energy Phys., 10(10), 054–30pp.
Abstract: An extension of the adjoint SU (5) model with a flavour symmetry based on the Z(4) group is investigated. The Z(4) symmetry is introduced with the aim of leading the up-and down-quark mass matrices to the Nearest-Neighbour-Interaction form. As a consequence of the discrete symmetry embedded in the SU (5) gauge group, the charged lepton mass matrix also gets the same form. Within this model, light neutrinos get their masses through type-I, type-III and one-loop radiative seesaw mechanisms, implemented, respectively, via a singlet, a triplet and an octet from the adjoint fermionic 24 fields. It is demonstrated that the neutrino phenomenology forces the introduction of at least three 24 fermionic multiplets. The symmetry SU (5) x Z(4) allows only two viable zero textures for the effective neutrino mass matrix. It is showed that one texture is only compatible with normal hierarchy and the other with inverted hierarchy in the light neutrino mass spectrum. Finally, it is also demonstrated that Z(4) freezes out the possibility of proton decay through exchange of coloured Higgs triplets at tree-level.
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Gonzalez Felipe, R., Serodio, H., & Silva, J. P. (2013). Neutrino masses and mixing in A(4) models with three Higgs doublets. Phys. Rev. D, 88(1), 015015–10pp.
Abstract: We study neutrino masses and mixing in the context of flavor models with A(4) symmetry, three scalar doublets in the triplet representation, and three lepton families. We show that there is no representation assignment that yields a dimension-5 mass operator consistent with experiment. We then consider a type-I seesaw with three heavy right-handed neutrinos, explaining in detail why it fails, and allowing us to show that agreement with the present neutrino oscillation data can be recovered with the inclusion of dimension-3 heavy neutrino mass terms that break softly the A(4) symmetry.
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Forero, D. V., Morisi, S., Romao, J. C., & Valle, J. W. F. (2013). Neutrino mixing with revamped A(4) flavor symmetry. Phys. Rev. D, 88(1), 016003–7pp.
Abstract: We suggest a minimal extension of the simplest A(4) flavor model that can induce a nonzero theta(13) value, as required by recent neutrino oscillation data from reactors and accelerators. The predicted correlation between the atmospheric mixing angle theta(23) and the magnitude of theta(13) leads to an allowed region substantially smaller than indicated by neutrino-oscillation global fits. Moreover, the scheme correlates CP violation in neutrino oscillations with the octant of the atmospheric mixing parameter theta(23) in such a way that, for example, maximal mixing necessarily violates CP. We briefly comment on other phenomenological features of the model.
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