Bulava, J., Della Morte, M., Heitger, J., & Wittemeier, C. (2016). Nonperturbative renormalization of the axial current in N-f=3 lattice QCD with Wilson fermions and a tree-level improved gauge action. Phys. Rev. D, 93(11), 114513–7pp.
Abstract: We nonperturbatively determine the renormalization factor of the axial vector current in lattice QCD with N-f = 3 flavors of Wilson-clover fermions and the tree-level Symanzik-improved gauge action. The (by now standard) renormalization condition is derived from the massive axial Ward identity, and it is imposed among Schrodinger functional states with large overlap on the lowest lying hadronic state in the pseudoscalar channel, in order to reduce kinematically enhanced cutoff effects. We explore a range of couplings relevant for simulations at lattice spacings of approximate to 0.09 fm and below. An interpolation formula for Z(A)(g(0)(2)) , smoothly connecting the nonperturbative values to the 1-loop expression, is provided together with our final results.
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Fonseca, R. M., & Hirsch, M. (2016). Lepton number violation in 331 models. Phys. Rev. D, 94(11), 115003–16pp.
Abstract: Different models based on the extended SU(3)(C) x SU(3)(L) x U(1)(X) (331) gauge group have been proposed over the past four decades. Yet, despite being an active research topic, the status of lepton number in 331 models has not been fully addressed in the literature, and furthermore many of the original proposals can not explain the observed neutrino masses. In this paper we review the basic features of various 331 models, focusing on potential sources of lepton number violation. We then describe different modifications which can be made to the original models in order to accommodate neutrino (and charged lepton) masses.
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Olmo, G. J., Rubiera-Garcia, D., & Sanchez-Puente, A. (2016). Impact of curvature divergences on physical observers in a wormhole space-time with horizons. Class. Quantum Gravity, 33(11), 115007–12pp.
Abstract: The impact of curvature divergences on physical observers in a black hole space-time, which, nonetheless, is geodesically complete is investigated. This space-time is an exact solution of certain extensions of general relativity coupled to Maxwell's electrodynamics and, roughly speaking, consists of two Reissner-Nordstrom (or Schwarzschild or Minkowski) geometries connected by a spherical wormhole near the center. We find that, despite the existence of infinite tidal forces, causal contact is never lost among the elements making up the observer. This suggests that curvature divergences may not be as pathological as traditionally thought.
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Boucenna, S. M., Morisi, S., & Vicente, A. (2016). LHC diphoton resonance from gauge symmetry. Phys. Rev. D, 93(11), 115008–8pp.
Abstract: Motivated by what is possibly the first sign of new physics seen at the LHC, the diphoton excess at 750 GeV in ATLAS and CMS, we present a model that provides naturally the necessary ingredients to explain the resonance. The simplest phenomenological explanation for the diphoton excess requires a new scalar state, X(750), as well as additional vectorlike (VL) fermions introduced in an ad-hoc way in order to enhance its decays into a pair of photons and/or increase its production cross section. We show that the necessary VL quarks and their couplings can emerge naturally from a complete framework based on the SU(3)(L) circle times U(1)(X) gauge symmetry.
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Botella, F. J., Branco, G. C., Rebelo, M. N., & Silva-Marcos, J. I. (2016). What if the masses of the first two quark families are not generated by the standard model Higgs boson? Phys. Rev. D, 94(11), 115031–6pp.
Abstract: We point out that in the standard model there is meaningful quark mixing even in the extreme chiral (EC) limit, where only the third generation of quarks acquires mass. This mixing is in general expected to be of order 1 and the fact that |V-13|(2) + |V-23|(2) approximate to 1.6 x 10(-3) implies a novel fine-tuning problem in the SM which we point out for the first time. We propose a possible way of avoiding this fine-tuning by introducing a symmetry S which leads to V-CKM = 1, with only the third generation of quarks acquiring mass. We consider two scenarios for generating the mass of the first two quark generations and full quark mixing based on the assumption that the masses of the first two quark families are not generated by the standard Higgs. One consists of the introduction of a second Higgs doublet which is neutral under S. The second scenario consists of assuming new physics at a high energy scale, contributing to the masses of light quark generations, in an effective field theory approach. This last scenario leads to couplings of the Higgs particle to s (s) over bar and c (c) over tilde which are significantly enhanced with respect to those of the SM. In both schemes, one has scalar-mediated flavor-changing neutral currents which are naturally suppressed. Flavor-violating top decays are predicted in the second scenario at the level Br(t -> hc) >= 5 x 10(-5).
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Barenboim, G., & Bosch, C. (2016). Composite states of two right-handed neutrinos. Phys. Rev. D, 94(11), 116019–10pp.
Abstract: In this work, we develop a model for Higgs-like composites based on two generations of right-handed neutrinos that condense. We analyze the spontaneous symmetry breaking of the theory with two explicit breakings, setting the different scales of the model and obtaining massive bosons as a result. Finally, we calculate the gravitational wave imprint left by the phase transition associated with the symmetry breaking of a generic potential dictated by the symmetries of the composites.
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ANTARES, I. C., LIGO and Virgo Collaborations(Adrian-Martinez, S. et al), Barrios-Marti, J., Hernandez-Rey, J. J., Sanchez-Losa, A., Tönnis, C., Zornoza, J. D., et al. (2016). High-energy neutrino follow-up search of gravitational wave event GW150914 with ANTARES and IceCube. Phys. Rev. D, 93(12), 122010–15pp.
Abstract: We present the high-energy-neutrino follow-up observations of the first gravitational wave transient GW150914 observed by the Advanced LIGO detectors on September 14, 2015. We search for coincident neutrino candidates within the data recorded by the IceCube and ANTARES neutrino detectors. A possible joint detection could be used in targeted electromagnetic follow-up observations, given the significantly better angular resolution of neutrino events compared to gravitational waves. We find no neutrino candidates in both temporal and spatial coincidence with the gravitational wave event. Within +/- 500 s of the gravitational wave event, the number of neutrino candidates detected by IceCube and ANTARES were three and zero, respectively. This is consistent with the expected atmospheric background, and none of the neutrino candidates were directionally coincident with GW150914. We use this nondetection to constrain neutrino emission from the gravitational-wave event.
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de Salas, P. F., Lineros, R. A., & Tortola, M. (2016). Neutrino propagation in the Galactic dark matter halo. Phys. Rev. D, 94(12), 123001–14pp.
Abstract: Neutrino oscillations are a widely observed and well-established phenomenon. It is also well known that deviations with respect to flavor conversion probabilities in vacuum arise due to neutrino interactions with matter. In this work, we analyze the impact of new interactions between neutrinos and the dark matter present in the Milky Way on the neutrino oscillation pattern. The dark matter-neutrino interaction is modeled by using an effective coupling proportional to the Fermi constant GF with no further restrictions on its flavor structure. For the galactic dark matter profile we consider a homogeneous distribution as well as several density profiles, estimating in all cases the size of the interaction required to get an observable effect at different neutrino energies. Our discussion is mainly focused in the PeV neutrino energy range, to be explored in observatories like IceCube and KM3NeT. The obtained results may be interpreted in terms of a light O(sub-eV-keV) or weakly interacting massive particlelike dark matter particle or as a new interaction with a mediator of O(sub-eV-keV) mass.
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Barenboim, G., & Park, W. I. (2016). Small changes to the inflaton potential can result in large changes in observables. Phys. Rev. D, 93(12), 123508–5pp.
Abstract: We show that a tiny correction to the inflaton potential can make critical changes in the inflationary observables for some types of inflation models.
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Alekhin, S. et al, & Hernandez, P. (2016). A facility to search for hidden particles at the CERN SPS: the SHiP physics case. Rep. Prog. Phys., 79(12), 124201–137pp.
Abstract: This paper describes the physics case for a new fixed target facility at CERN SPS. The SHiP (search for hidden particles) experiment is intended to hunt for new physics in the largely unexplored domain of very weakly interacting particles with masses below the Fermi scale, inaccessible to the LHC experiments, and to study tau neutrino physics. The same proton beam setup can be used later to look for decays of tau-leptons with lepton flavour number non-conservation, tau -> 3 μand to search for weakly-interacting sub-GeV dark matter candidates. We discuss the evidence for physics beyond the standard model and describe interactions between new particles and four different portals-scalars, vectors, fermions or axion-like particles. We discuss motivations for different models, manifesting themselves via these interactions, and how they can be probed with the SHiP experiment and present several case studies. The prospects to search for relatively light SUSY and composite particles at SHiP are also discussed. We demonstrate that the SHiP experiment has a unique potential to discover new physics and can directly probe a number of solutions of beyond the standard model puzzles, such as neutrino masses, baryon asymmetry of the Universe, dark matter, and inflation.
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