arXiv subjects

Marco Chianese

Publications and source records attributed to Marco Chianese.

53 records · Page 3Linked to original sources

arXiv2019

Potential Dark Matter Signals at Neutrino Telescopes

Recent analyses of the diffuse TeV-PeV neutrino flux highlight a tension between different Ice-Cube data samples that strongly suggests a two-component scenario rather than a single steep power-law flux. Such a tension is further strengthened once the latest ANTARES data are also taken into account. Remarkably, both experiments show an excess in the same energy range (40-200 TeV), whose origin could intriguingly be related to dark matter. In this paper, I discuss the combined analysis of IceCube and ANTARES data, highlighting the presence of the low-energy excess. Moreover, I update the results of the angular analysis for potential dark matter signals, previously obtained with the 4-year High-Energy Starting Events data. In particular, I statistically compare the distribution of the arrival directions of 6-year IceCube events belonging to the low-energy excess with the angular distributions expected in case of different dark matter neutrino signals.

hep-ph↗

arXiv2018

Investigating two heavy neutral leptons neutrino seesaw mechanism at SHiP

One of the main purposes of SHiP experiment is to shed light on neutrino mass generation mechanisms like the so-called seesaw. We consider a minimal type-I seesaw neutrino mass mechanism model with two heavy neutral leptons (right-handed or sterile neutrinos) with arbitrary masses. Extremely high active-sterile mixing angle requires a correlation between the phases of the Dirac neutrino couplings. Actual experimental limits on the half-life of neutrinoless double beta decay $0νββ$-rate on the active-sterile mixing angle are not significative for SHiP.

hep-ph↗

arXiv2018

Neutrinophilic Dark Matter in the epoch of IceCube and Fermi-LAT

The recent observation of the blazar TXS 0506+056 suggests the presence of a hard power-law component in the extraterrestrial TeV-PeV neutrino flux, in agreement with the IceCube analysis on the 8-year through-going muon neutrinos from the Northern Sky. This is slightly in tension with the soft power-law neutrino flux deduced by the IceCube 6-year High Energy Starting Events data. A possible solution to such a puzzle is assuming a two-component neutrino flux. In this paper, we focus on the case where, in addition to an astrophysical power-law, the second component is a pure neutrino line produced by decaying Dark Matter particles. We investigate how to realize a neutrinophilic decaying Dark Matter in an extension of the Standard Model. The main features of the model are: i) the requirement of a new symmetry like a global $U(1)$ charge; ii) the Dirac nature of active neutrinos; iii) a low-reheating temperature of the Universe of about 1 TeV. We perform a likelihood statistical analysis to fit the IceCube data according to the present Fermi-LAT gamma-rays constraints.

hep-ph↗

arXiv2018

Probing relic neutrino decays with 21 cm cosmology

We show how 21 cm cosmology can test relic neutrino radiative decays into sterile neutrinos. Using recent EDGES results, we derive constraints on the lifetime of the decaying neutrinos. If the EDGES anomaly will be confirmed, then there are two solutions, one for much longer and one for much shorter lifetimes than the age of the universe, showing how relic neutrino radiative decays can explain the anomaly in a simple way. We also show how to combine EDGES results with those from radio background observations, showing that potentially the ARCADE 2 excess can be also reproduced together with the EDGES anomaly within the proposed non-standard cosmological scenario. Our calculation of the specific intensity at the redshifts probed by EDGES can be also applied to the case of decaying dark matter and it also corrects a flawed expression appeared in previous literature.

hep-ph↗

arXiv2018

The Dark Side of the Littlest Seesaw: freeze-in, the two right-handed neutrino portal and leptogenesis-friendly fimpzillas

We propose a minimal model to simultaneously account for a realistic neutrino spectrum through a type-I seesaw mechanism and a viable dark matter relic density. The model is an extension of the Littlest Seesaw model in which the two right-handed neutrinos of the model are coupled to a $Z_2$-odd dark sector via right-handed neutrino portal couplings. In this model, a highly constrained and direct link between dark matter and neutrino physics is achieved by considering the freeze-in production mechanism of dark matter. We show that the neutrino Yukawa couplings which describe neutrino mass and mixing may also play a dominant role in the dark matter production. We investigate the allowed regions in the parameter space of the model that provide the correct neutrino masses and mixing and simultaneously give the correct dark matter relic abundance. In certain cases the right-handed neutrino mass may be arbitrarily large, for example in the range $10^{10}-10^{11}$ GeV required for vanilla leptogenesis, with a successful relic density arising from frozen-in dark matter particles with masses around this scale, which we refer to as "fimpzillas".

hep-ph↗

arXiv2018

Strong thermal $SO(10)$-inspired leptogenesis in the light of recent results from long-baseline neutrino experiments

We confront recent experimental results on neutrino mixing parameters with the requirements from strong thermal $SO(10)$-inspired leptogenesis, where the asymmetry is produced from next-to-lightest right-handed neutrinos $N_2$ independently of the initial conditions. There is a nice agreement with latest global analyses supporting $\sinδ< 0$ and normal ordering at $ \sim 95\%$ C.L. On the other hand, the more stringent experimental lower bound on the atmospheric mixing angle starts to corner strong thermal $SO(10)$-inspired leptogenesis. Prompted and encouraged by this rapid experimental advance, we obtain a precise determination of the allowed region in the plane $δ$ versus $θ_{23}$. We confirm that for the benchmark case $α_2 \equiv m_{D2} / m_{\rm charm}= 5 \, $, where $m_{D2}$ is the intermediate neutrino Dirac mass setting the $N_2$ mass, and initial pre-existing asymmetry $N_{B-L}^{\rm p, i} = 10^{-3}$, the bulk of solutions lies in the first octant. Though most of the solutions are found outside the $95\%$ C.L. experimental region, there is still a big allowed fraction that does not require a too fine-tuned choice of the Majorana phases so that the neutrinoless double beta decay effective neutrino mass allowed range is still $m_{ee}\simeq [10,30]\,{\rm meV}$. We also show how the constraints depend on $N_{B-L}^{\rm p, i}$ and $α_2$. In particular, we show that the current best fit, ($θ_{23},δ)\simeq (47^{\circ}, -130^{\circ})$, can be reproduced for $N_{B-L}^{\rm p, i} = 10^{-3}$ and $α_2 = 6$. Such large values for $α_2$ have been recently obtained in a few realistic fits within $SO(10)$-inspired models. Finally, we also obtain that current neutrino data rule out $N_{B-L}^{\rm p, i} \gtrsim 0.1$ for $α_2 \lesssim 4.7$.

hep-ph↗

arXiv2018

Use of ANTARES and IceCube data to constrain a single power-law neutrino flux

We perform the first statistical combined analysis of the diffuse neutrino flux observed by ANTARES (nine-year) and IceCube (six-year) by assuming a single astrophysical power-law flux. The combined analysis reduces by a few percent the best-fit values for the flux normalization and the spectral index. Both data samples show an excess in the same energy range (40--200 TeV), suggesting the presence of a second component. We perform a goodness-of-fit test to scrutinize the null assumption of a single power-law, scanning different values for the spectral index. The addition of the ANTARES data reduces the $p$-value by a factor 2$÷$3. In particular, a single power-law component in the neutrino flux with the spectral index deduced by the six-year up-going muon neutrinos of IceCube is disfavored with a $p$-value smaller than $10^{-2}$.

hep-ph↗

arXiv2017

Interpreting IceCube 6-year HESE data as an evidence for hundred TeV decaying Dark Matter

The assumption of a single astrophysical power-law flux to explain the IceCube 6-year HESE extraterrestrial events yields a large spectral index that is in tension with gamma-ray observations and the 6-year up-going muon neutrinos data. Adopting a spectral index belonging to the range $\left[2.0,2.2\right]$, which is compatible with the one deduced by the analysis performed on the 6-year up-going muon neutrinos data and with $p$-$p$ astrophysical sources, the latest IceCube data show an up to $2.6\,σ$ excess in the number of events in the energy range 40--200 TeV. We interpret such an excess as a decaying Dark Matter signal and we perform a likelihood-ratio statistical test to compare the two-component scenario with respect to the single-component one.

hep-ph↗

arXiv2017

The IceCube low-energy excess: a Dark Matter interpretation

The recent study on the the 6-year up-going muon neutrinos by the IceCube Collaboration support the hypothesis of a two-component scenario explaining the diffuse TeV-PeV neutrino flux. Once a hard astrophysical power-law is considered, an excess in the IceCube data is shown in the energy range 10-100 TeV (low-energy excess}). By means of a statistical analysis on the neutrino energy spectrum and on the angular distribution of neutrino arrival directions, we characterize a two-component neutrino flux where decaying/annihilating Dark Matter particles provide a contribution to the IceCube observations.

hep-ph↗

arXiv2017

Characterising exotic matter driving wormhole

In this paper, we develop an iterative approach to span the whole set of exotic matter models able to drive a traversable wormhole. The method, based on a Taylor expansion of metric and stress-energy tensor components in a neighbourhood of the wormhole throat, reduces the Einstein equations to an infinite set of algebraic conditions, which can be satisfied order by order. The approach easily allows the implementation of further conditions linking the stress-energy tensor components among each other, like symmetry conditions or equations of state. The method is then applied to some relevant examples of exotic matter characterised by a constant energy density and that also show an isotropic behaviour in the stress-energy tensor or obeying to a quintessence-like equation of state.

gr-qc↗

arXiv2017

A Consistent Theory of Decaying Dark Matter Connecting IceCube to the Sesame Street

The high energy events observed at the IceCube Neutrino Observatory have triggered many investigations interpreting the highly energetic neutrinos detected as decay products of heavy unstable Dark Matter particles. However, while very detailed treatments of the IceCube phenomenology exist, only a few references focus on the (non-trivial) Dark Matter production part -- and all of those rely on relatively complicated new models which are not always testable directly. We instead investigate two of the most minimal scenarios possible, where the operator responsible for the IceCube events is directly involved in Dark Matter production. We show that the simplest (four-dimensional) operator is not powerful enough to accommodate all constraints. A more non-minimal setting (at mass dimension six), however, can do both fitting all the data and also allowing for a comparatively small parameter space only, parts of which can be in reach of future observations. We conclude that minimalistic approaches can be enough to explain all data required, while complicated new physics seems not to be required by IceCube.

hep-ph↗

arXiv2017

Dark Matter scenarios at IceCube

The recent study on the the 6-year up-going muon neutrinos by the IceCube Collaboration and the multi-messenger analyses support the hypothesis of a two-component scenario explaining the diffuse TeV-PeV neutrino flux. Depending on the steepness of the astrophysical power-law, an excess in the IceCube data is shown in the energy range 10-100 TeV (low-energy excess) or at PeV (high-energy excess). In both cases, we characterize a two-component neutrino flux where decaying Dark Matter particles provide a contribution to the IceCube observations.

hep-ph↗

arXiv2016

IceCube PeV Neutrinos and Leptophilic Dark Matter

We analyze the scenario where the IceCube high energy neutrino events are explained in terms of an extraterrestrial flux due to two different components: a contribution coming from know astrophysical sources for energies up to few hundreds TeV and a top-down contribution originated by the decay of heavy dark matter particles with a mass of few PeV. Contrary to previous approaches, we consider a leptophilic three-body decay that dominates at PeV energies due to the absence of quarks in the final state. We find that the theoretical predictions of such a scenario are in a slightly better agreement with the IceCube data if the astrophysical component has a cut-off at about 100 TeV. This interpretation of IceCube data can be easily tested in the near future since the decaying dark matter scenario predicts a sharp cut-off at PeV energy scale and the observation of an anisotropy towards Galactic Center of our Galaxy in contrast with the isotropic astrophysical flux.

hep-ph↗

arXiv2016

Low energy IceCube data and a possible Dark Matter related excess

In this Letter we focus our attention on the IceCube events in the energy range between 60 and 100 TeV, which show an order 2-sigma excess with respect to a power-law with spectral index 2. We analyze the possible origin of such an excess by comparing the distribution of the arrival directions of IceCube events with the angular distributions of simply distributed astrophysical galactic/extragalactic sources, as well as with the expected flux coming from DM interactions (decay and annihilation) for different DM profiles. The statistical analysis performed seems to disfavor the correlation with the galactic plane, whereas rules out the DM annihilation scenario only in case of small clumpiness effect. The small statistics till now collected does not allow to scrutinize the cases of astrophysical isotropic distribution and DM decay scenarios. For this reason we perform a forecast analysis in order to stress the role of future Neutrino Telescopes.

hep-ph↗

arXiv2016

Decaying Leptophilic Dark Matter at IceCube

We present a novel interpretation of IceCube high energy neutrino events (with energy larger than 60 TeV) in terms of an extraterrestrial flux due to two different contributions: a flux originated by known astrophysical sources and dominating IceCube observations up to few hundreds TeV, and a new flux component where the most energetic neutrinos come from the leptophilic three-body decays of dark matter particles with a mass of few PeV. Differently from other approaches, we provide two examples of elementary particle models that do not require extremely tiny coupling constants. We find the compatibility of the theoretical predictions with the IceCube results when the astrophysical flux has a cutoff of the order of 100 TeV (broken power law). In this case the most energetic part of the spectrum (PeV neutrinos) is due to an extra component such as the decay of a very massive dark matter component. Due to the low statistics at our disposal we have considered for simplicity the equivalence between deposited and neutrino energy, however such approximation does not affect dramatically the qualitative results. Of course, a purely astrophysical origin of the neutrino flux (no cutoff in energy below the PeV scale - unbroken power law) is still allowed. If future data will confirm the presence of a sharp cutoff above few PeV this would be in favor of a dark matter interpretation.

hep-ph↗

arXiv2015

Viability of SUSY-GUT paradigm after LHC

The SUSY-GUT paradigm is the most promising scenario for the physics beyond the Standard Model. After the LHC run I, it is of interest to reanalyze the room still remaining for SUSY-GUT inspired models and to study the limits on the SUSY mass spectrum. Assuming one step unification of gauge couplings, under some natural requirements we have obtained the energy upper bound for the observation of SUSY phenomenology. We found that in the SUSY-GUT framework the mass of lightest gluino or Higgsino cannot be larger than about 20 TeV.

hep-ph↗

arXiv2015

Chances for SUSY-GUT in the LHC Epoch

The magic couple of SUSY and GUT still appears the most elegant and predictive physics concept beyond the Standard Model. Since up to now LHC found no evidence for supersymmetric particles it becomes of particular relevance to determine an upper bound of the energy scale they have to show up. In particular, we have analyzed a generic SUSY-GUT model assuming one step unification like in SU(5), and adopting naturalness principles, we have obtained general bounds on the mass spectrum of SUSY particles. We claim that if a SUSY gauge coupling unification takes place, the lightest gluino or Higgsino cannot have a mass larger than about 20 TeV. Such a limit is of interest for planning new accelerator machines.

hep-ph↗