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Armillis, R., Lazarides, G., & Pallis, C. (2014). Inflation, leptogenesis, and Yukawa quasiunification within a supersymmetric left-right model. Phys. Rev. D, 89(6), 065032–22pp.
Abstract: A simple extension of the minimal left-right symmetric supersymmetric grand unified theory model is constructed by adding two pairs of superfields. This naturally violates the partial Yukawa unification predicted by the minimal model. After including supergravity corrections, we find that this extended model naturally supports hilltop F-term hybrid inflation along its trivial inflationary path with only a very mild tuning of the initial conditions. With a convenient choice of signs of the terms in the Kahler potential, we can reconcile the inflationary scale with the supersymmetric grand unified theory scale. All the current data on the inflationary observables are readily reproduced. Inflation is followed by nonthermal leptogenesis via the decay of the right-handed neutrinos emerging from the decay of the inflaton, and any possible washout of the lepton asymmetry is avoided thanks to the violation of partial Yukawa unification. The extra superfields also assist us in reducing the reheat temperature so as to satisfy the gravitino constraint. The observed baryon asymmetry of the universe is naturally reproduced consistently with the neutrino oscillation parameters.
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Beltran Jimenez, J., Heisenberg, L., & Olmo, G. J. (2014). Infrared lessons for ultraviolet gravity: the case of massive gravity and Born-lnfeld. J. Cosmol. Astropart. Phys., 11(11), 004–26pp.
Abstract: We generalize the ultraviolet sector of gravitation via a Born-Infeld action using lessons from massive gravity. The theory contains all of the elementary symmetric polynomials and is treated in the Palatini formalism. We show how the connection can be solved algebraically to be the Levi-Civita connection of an effective metric. The non-linearity of the algebraic equations yields several branches, one of which always reduces to General Relativity at low curvatures. We explore in detail a minimal version of the theory, for which we study solutions in the presence of a perfect fluid with special attention to the cosmological evolution. In vacuum we recover Ricci-flat solutions, but also an additional physical solution corresponding to an Einstein space. The existence of two physical branches remains for non-vacuum solutions and, in addition, the branch that connects to the Einstein space in vacuum is not very sensitive to the specific value of the energy density. For the branch that connects to the General Relativity limit we generically find three behaviours for the Hubble function depending on the equation of state of the fluid, namely: either there is a maximum value for the energy density that connects continuously with vacuum, or the energy density can be arbitrarily large but the Hubble function saturates and remains constant at high energy densities, or the energy density is unbounded and the Hubble function grows faster than in General Relativity. The second case is particularly interesting because it could offer an interesting inflationary epoch even in the presence of a dust component. Finally, we discuss the possibility of avoiding certain types of singularities within the minimal model.
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Di Mauro, M., Donato, F., Fornengo, N., Lineros, R. A., & Vittino, A. (2014). Interpretation of AMS-02 electrons and positrons data. J. Cosmol. Astropart. Phys., 04(4), 006–33pp.
Abstract: We perform a combined analysis of the recent AMS-02 data on electrons, positrons, electrons plus positrons and positron fraction, in a self-consistent framework where we realize a theoretical modeling of all the astrophysical components that can contribute to the observed fluxes in the whole energy range. The primary electron contribution is modeled through the sum of an average flux from distant sources and the fluxes from the local supernova remnants in the Green catalog. The secondary electron and positron fluxes originate from interactions on the interstellar medium of primary cosmic rays, for which we derive a novel determination by using AMS-02 proton and helium data. Primary positrons and electrons from pulsar wind nebulae in the ATNF catalog are included and studied in terms of their most significant (while loosely known) properties and under different assumptions (average contribution from the whole catalog, single dominant pulsar, a few dominant pulsars). We obtain a remarkable agreement between our various modeling and the AMS-02 data for all types of analysis, demonstrating that the whole AMS-02 leptonic data admit a self-consistent interpretation in terms of astrophysical contributions.
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Deppisch, F. F., Desai, N., & Valle, J. W. F. (2014). Is charged lepton flavor violation a high energy phenomenon? Phys. Rev. D, 89(5), 051302–5pp.
Abstract: Searches for rare processes such as μ-> e gamma put stringent limits on lepton flavor violation expected in many beyond-the-Standard-Model physics scenarios. This usually precludes the observation of flavor violation at high energy colliders such as the LHC. We here discuss a scenario where right-handed neutrinos are produced via a Z' portal but which can only decay via small flavor violating couplings. Consequently, the process rate is unsuppressed by the small couplings and can be visible despite unobservably small μ-> e gamma rates.
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Gottardo, A. et al, Gadea, A., & Algora, A. (2014). Isomeric decay spectroscopy of the Bi-217 isotope. Phys. Rev. C, 90(3), 034317–6pp.
Abstract: The structure of the neutron-rich bismuth isotope Bi-217 has been studied for the first time. The fragmentation of a primary U-238 beam at the FRS-RISING setup at GSI was exploited to perform gamma-decay spectroscopy, since μs isomeric states were expected in this nucleus. Gamma rays following the decay of a t(1/2) = 3 μs isomer were observed, allowing one to establish the low-lying structure of Bi-217. The level energies and the reduced electric quadrupole transition probability B(E2) from the isomeric state are compared to large-scale shell-model calculations.
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