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Isola del Gran Sasso d'Italia, Italy

Vissani F.,Laboratori Nazionali Del Gran Sasso | Aharonian F.,Dublin Institute for Advanced Studies | Sahakyan N.,University of Rome La Sapienza
Astroparticle Physics | Year: 2011

With the arrival of km3 volume scale neutrino detectors the chances to detect the first astronomical sources of TeV neutrinos will be dramatically increased. While the theoretical estimates of the neutrino fluxes contain large uncertainties, we can formulate the conditions for the detectability of certain neutrino sources phenomenologically. In fact, since most galactic neutrino sources are transparent for TeV γ-rays, their detectability implies a minimum flux of the accompanying γ-rays. For a typical energy-dependence of detection areas of km3 volume neutrino detectors, we obtain the quantitative condition Iγ(20TeV) >2×10-15ph/cm2s, that thanks to the normalization of the γ-ray spectrum at 20 TeV appears to be quite robust, i.e. almost independent of the shape of energy spectrum of neutrinos. We remark that this condition is satisfied by the young supernova remnants RX J1713.7-3946 and RX J0852.0-4622 (Vela Jr) - two of the strongest galactic γ-ray sources. The preliminary condition for the detectability of high energy neutrinos is that the bulk of γ-rays has a hadronic origin: A new way to test this hypothesis for RX J1713.7-3946 is proposed. Finally, we assess the relevance of a neutrino detector located in the Northern hemisphere for the search for galactic neutrino sources. In particular, we argue that if the TeV neutrino sources correlate with the galactic mass distribution, the probability that some of them will be observed by a detector in the Mediterranean Sea is larger by a factor of 1.4-2.9 compared to the one of IceCube. © 2011 Elsevier B.V. All rights reserved.

Addazi A.,University of LAquila | Addazi A.,Laboratori Nazionali Del Gran Sasso | Bianchi M.,University of Rome Tor Vergata
Journal of High Energy Physics | Year: 2015

Abstract: We show how exotic stringy instantons can generate an effective interaction between color diquark sextets in a Pati-Salam model, inducing a Majorana mass term for the neutron. In particular, we discuss a simple quiver theory for a Pati-Salam like model, as an example in which the calculations of exotic instanton effects are simple and controllable. We discuss some different possibilities in order to generate n−n¯$$ n-\overline{n} $$ oscillations testable in the next generation of experiments, Majorana mass matrices for neutrini and a Post-Sphaleron Baryogenesis scenario. Connections with Dark Matter issues and the Higgs mass Hierarchy problem are discussed, in view of implications for LHC and rare processes physics. The model may be viewed as a completion of a Left-Right symmetric extension of the Standard Model, alternative to a GUT-inspired scenario. Combined measures in Neutron-Antineutron physics, FCNC, LHC, Dark Matter could rule out the proposed model or uncover aspects of physics at the Planck scale! © 2015, The Author(s).

Addazi A.,University of LAquila | Addazi A.,Laboratori Nazionali Del Gran Sasso
Journal of High Energy Physics | Year: 2015

Abstract: We propose a minimal extension of Standard Model, generating a Majorana mass for neutron, connected with a mechanism of Post-Sphaleron Baryogenesis. We consider an ‘exotic vector-like pair’ of color-triplet scalars, an extra Majorana fermion ψ, and a scalar field ϕ, giving mass to ψ. The vector-like pair is defined ‘exotic’ because of a peculiar mass term of the color-triplet scalars, violating Baryon number as ΔB = 1. Such a mass term could be generated by exotic instantons in a class of string-inspired completions of the Standard Model: open (un-)oriented strings attached between D-brane stacks and Euclidean D-branes. A Post-Sphaleron Baryogenesis is realized through ϕ-decays into six quarks (antiquarks), or through ψ-decays into three quarks (antiquarks). This model suggests some intriguing B-violating signatures, testable in the next future, in Neutron-Antineutron physics and LHC. We also discuss limits from FCNC. Sterile fermion can also be light as 1 − 100GeV. In this case, the sterile fermion could be (meta)-stable and n − n¯$$ \overline{n} $$ oscillation can be indirectly generated by two n − ψ, ψ − n¯$$ \overline{n} $$ oscillations, without needing of an effective Majorana mass for neutron. Majorana fermion ψ can be a good candidate for WIMP-like dark matter. © 2015, The Author(s).

Addazi A.,University of LAquila | Addazi A.,Laboratori Nazionali Del Gran Sasso | Bianchi M.,University of Rome Tor Vergata
Journal of High Energy Physics | Year: 2014

Abstract: We show how a Majorana mass for the neutron could result from non-perturbative quantum gravity effects peculiar to string theory. In particular, “exotic instantons” in un-oriented string compactifications with D-branes extending the (supersymmetric) standard model could indirectly produce an effective operator δm ntn + h.c. In a specific model with an extra vector-like pair of ‘quarks’, acquiring a large mass proportional to the string mass scale (exponentially suppressed by a function of the string moduli fields), δm can turn out to be as low as 10−24-10−25 eV.The induced neutron-antineutron oscillations could take place with a time scale τnn> 108 s that could be tested by the next generation of experiments. On the other hand, proton decay and FCNC’s are automatically strongly suppressed and are compatible with the current experimental limits.Depending on the number of brane intersections, the model may also lead to the generation of Majorana masses for R-handed neutrini. Our proposal could also suggest neutron-neutralino or neutron-axino oscillations, with implications in UCN, Dark Matter Direct Detection, UHECR and Neutron-Antineutron oscillations.This suggests to improve the limits on neutron-antineutron oscillations, as a possible test of string theory and quantum gravity. © 2014, The Author(s).

Addazi A.,University of LAquila | Addazi A.,Laboratori Nazionali Del Gran Sasso
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2016

We discuss a new mechanism in which non-perturbative quantum gravity effects directly generate a Majorana mass for the neutron. In particular, in string theory, exotic instantons can generate an effective six quark operator by calculable mixed disk amplitudes. In a low string scale scenario, with MS≃10÷105 TeV, a neutron-antineutron oscillation can be reached in the next generation of experiments. We argue that protons and neutralinos are not destabilized and that dangerous FCNCs are not generated. We show an example of quiver theories, locally free by tadpoles and anomalies, reproducing MSSM plus a Majorana neutron and a Majorana neutrino. These models naturally provide a viable baryogenesis mechanism by resonant RH neutrino decays, as well as a stable WIMP-like dark matter. © 2016 The Author.

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