Double Chooz collaboration(de Kerret, H. et al), & Novella, P. (2018). Yields and production rates of cosmogenic Li-9 and He-8 measured with the Double Chooz near and far detectors. J. High Energy Phys., 11(11), 053–20pp.
Abstract: The yields and production rates of the radioisotopes Li-9 and He-8 created by cosmic muon spallation on C-12, have been measured by the two detectors of the Double Chooz experiment. The identical detectors are located at separate sites and depths, which means that they are subject to different muon spectra. The near (far) detector has an overburden of approximate to 120 m.w.e. (approximate to 300 m.w.e.) corresponding to a mean muon energy of 32.1 +/- 2.0 GeV (63.7 +/- 5.5 GeV). Comparing the data to a detailed simulation of the Li-9 and He-8 decays, the contribution of the He-8 radioisotope at both detectors is found to be compatible with zero. The observed Li-9 yields in the near and far detectors are 5.51 +/- 0.51 and 7.90 +/- 0.51, respectively, in units of 10(-8-1)g(-1)cm(2). The shallow overburdens of the near and far detectors give a unique insight when combined with measurements by KamLAND and Borexino to give the first multi-experiment, data driven relationship between the Li-9 yield and the mean muon energy according to the power law and Y-0 = (0.43 +/- 0.11) x 10(-8-1)g(-1)cm(2). This relationship gives future liquid scintillator based experiments the ability to predict their cosmogenic Li-9 background rates.
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ANTARES and IceCube Collaborations(Albert, A. et al), Barrios-Marti, J., Coleiro, A., Colomer, M., Hernandez-Rey, J. J., Illuminati, G., et al. (2018). Joint Constraints on Galactic Diffuse Neutrino Emission from the ANTARES and IceCube Neutrino Telescopes. Astrophys. J. Lett., 868(2), L20–7pp.
Abstract: The existence of diffuse Galactic neutrino production is expected from cosmic-ray interactions with Galactic gas and radiation fields. Thus, neutrinos are a unique messenger offering the opportunity to test the products of Galactic cosmic-ray interactions up to energies of hundreds of TeV. Here we present a search for this production using ten years of Astronomy with a Neutrino Telescope and Abyss environmental RESearch (ANTARES) track and shower data, as well as seven years of IceCube track data. The data are combined into a joint likelihood test for neutrino emission according to the KRA(gamma) model assuming a 5 PeV per nucleon Galactic cosmic-ray cutoff. No significant excess is found. As a consequence, the limits presented in this Letter start constraining the model parameter space for Galactic cosmic-ray production and transport.
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Anamiati, G., Castillo-Felisola, O., Fonseca, R. M., Helo, J. C., & Hirsch, M. (2018). High-dimensional neutrino masses. J. High Energy Phys., 12(12), 066–26pp.
Abstract: For Majorana neutrino masses the lowest dimensional operator possible is the Weinberg operator at d = 5. Here we discuss the possibility that neutrino masses originate from higher dimensional operators. Specifically, we consider all tree-level decompositions of the d = 9, d = 11 and d = 13 neutrino mass operators. With renormalizable interactions only, we find 18 topologies and 66 diagrams for d = 9, and 92 topologies plus 504 diagrams at the d = 11 level. At d = 13 there are already 576 topologies and 4199 diagrams. However, among all these there are only very few genuine neutrino mass models: At d = (9, 11, 13) we find only (2,2,2) genuine diagrams and a total of (2,2,6) models. Here, a model is considered genuine at level d if it automatically forbids lower order neutrino masses without the use of additional symmetries. We also briefly discuss how neutrino masses and angles can be easily fitted in these high-dimensional models.
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Escudero, M., Rius, N., & Sanz, V. (2017). Sterile neutrino portal to Dark Matter I: the U(1)(B-L) case. J. High Energy Phys., 02(2), 045–27pp.
Abstract: In this paper we explore the possibility that the sterile neutrino and Dark Matter sectors in the Universe have a common origin. We study the consequences of this assumption in the simple case of coupling the dark sector to the Standard Model via a global U(1)(B-L), broken down spontaneously by a dark scalar. This dark scalar provides masses to the dark fermions and communicates with the Higgs via a Higgs portal coupling. We find an interesting interplay between Dark Matter annihilation to dark scalars – the CP-even that mixes with the Higgs and the CP-odd which becomes a Goldstone boson, the Majoron and heavy neutrinos, as well as collider probes via the coupling to the Higgs. Moreover, Dark Matter annihilation into sterile neutrinos and its subsequent decay to gauge bosons and quarks, charged leptons or neutrinos lead to indirect detection signatures which are close to current bounds on the gamma ray flux from the galactic center and dwarf galaxies.
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Bonilla, C., Krauss, M. E., Opferkuch, T., & Porod, W. (2017). Perspectives for detecting lepton flavour violation in left-right symmetric models. J. High Energy Phys., 03(3), 027–50pp.
Abstract: We investigate lepton flavour violation in a class of minimal left-right symmetric models where the left-right symmetry is broken by triplet scalars. In this context we present a method to consistently calculate the triplet-Yukawa couplings which takes into account the experimental data while simultaneously respecting the underlying symmetries. Analysing various scenarios, we then calculate the full set of tree-level and one-loop contributions to all radiative and three-body flavour-violating fully leptonic decays as well as well as μ- e conversion in nuclei. Our method illustrates how these processes depend on the underlying parameters of the theory. To that end we observe that, for many choices of the model parameters, there is a strong complementarity between the different observables. For instance, in a large part of the parameter space, lepton flavour violating T-decays have a large enough branching ratio to be measured in upcoming experiments. Our results further show that experiments coming online in the immediate future, like Mu3e and BELLE II, or longer-term, such as PRISM/PRIME, will probe significant portions of the currently allowed parameter space.
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Salvado, J., Mena, O., Palomares-Ruiz, S., & Rius, N. (2017). Non-standard interactions with high-energy atmospheric neutrinos at IceCube. J. High Energy Phys., 01(1), 141–30pp.
Abstract: Non-standard interactions in the propagation of neutrinos in matter can lead to significant deviations from expectations within the standard neutrino oscillation framework and atmospheric neutrino detectors have been considered to set constraints. However, most previous works have focused on relatively low-energy atmospheric neutrino data. Here, we consider the one-year high-energy through-going muon data in IceCube, which has been already used to search for light sterile neutrinos, to constrain new interactions in the μtau-sector. In our analysis we include several systematic uncertainties on both, the atmospheric neutrino flux and on the detector properties, which are accounted for via nuisance parameters. After considering different primary cosmic-ray spectra and hadronic interaction models, we improve over previous analysis by using the latest data and showing that systematics currently affect very little the bound on the off-diagonal epsilon(mu tau), with the 90% credible interval given by -6.0 x 10(-3) < epsilon(mu tau) < 5.4 x 10(-3), comparable to previous results. In addition, we also estimate the expected sensitivity after 10 years of collected data in IceCube and study the precision at which non-standard parameters could be determined for the case of epsilon(mu tau) near its current bound.
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Alcaide, J., Das, D., & Santamaria, A. (2017). A model of neutrino mass and dark matter with large neutrinoless double beta decay. J. High Energy Phys., 04(4), 049–21pp.
Abstract: We propose a model where neutrino masses are generated at three loop order but neutrinoless double beta decay occurs at one loop. Thus we can have large neutrinoless double beta decay observable in the future experiments even when the neutrino masses are very small. The model receives strong constraints from the neutrino data and lepton flavor violating decays, which substantially reduces the number of free parameters. Our model also opens up the possibility of having several new scalars below the TeV regime, which can be explored at the collider experiments. Additionally, our model also has an unbroken Z(2) symmetry which allows us to identify a viable Dark Matter candidate.
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Bellomo, N., Bellini, E., Hu, B., Jimenez, R., Pena-Garay, C., & Verde, L. (2017). Hiding neutrino mass in modified gravity cosmologies. J. Cosmol. Astropart. Phys., 02(2), 043–12pp.
Abstract: Cosmological observables show a dependence with the neutrino mass, which is partially degenerate with parameters of extended models of gravity. We study and explore this degeneracy in Horndeski generalized scalar-tensor theories of gravity. Using forecasted cosmic microwave background and galaxy power spectrum datasets, we find that a single parameter in the linear regime of the effective theory dominates the correlation with the total neutrino mass. For any given mass, a particular value of this parameter approximately cancels the power suppression due to the neutrino mass at a given redshift. The extent of the cancellation of this degeneracy depends on the cosmological large-scale structure data used at different redshifts. We constrain the parameters and functions of the effective gravity theory and determine the influence of gravity on the determination of the neutrino mass from present and future surveys.
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Adhikari, R. et al, Pastor, S., & Valle, J. W. F. (2017). A White Paper on keV sterile neutrino Dark Matter. J. Cosmol. Astropart. Phys., 01(1), 025–247pp.
Abstract: We present a comprehensive review of keV-scale sterile neutrino Dark Matter, collecting views and insights from all disciplines involved – cosmology, astrophysics, nuclear, and particle physics – in each case viewed from both theoretical and experimental/observational perspectives. After reviewing the role of active neutrinos in particle physics, astrophysics, and cosmology, we focus on sterile neutrinos in the context of the Dark Matter puzzle. Here, we first review the physics motivation for sterile neutrino Dark Matter, based on challenges and tensions in purely cold Dark Matter scenarios. We then round out the discussion by critically summarizing all known constraints on sterile neutrino Dark Matter arising from astrophysical observations, laboratory experiments, and theoretical considerations. In this context, we provide a balanced discourse on the possibly positive signal from X-ray observations. Another focus of the paper concerns the construction of particle physics models, aiming to explain how sterile neutrinos of keV-scale masses could arise in concrete settings beyond the Standard Model of elementary particle physics. The paper ends with an extensive review of current and future astrophysical and laboratory searches, highlighting new ideas and their experimental challenges, as well as future perspectives for the discovery of sterile neutrinos.
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Double Chooz collaboration(Abrahao, T. et al), & Novella, P. (2017). Cosmic-muon characterization and annual modulation measurement with Double Chooz detectors. J. Cosmol. Astropart. Phys., 02(2), 017–20pp.
Abstract: A study on cosmic muons has been performed for the two identical near and far neutrino detectors of the Double Chooz experiment, placed at similar to 120 and similar to 300 m. w.e. underground respectively, including the corresponding simulations using the MUSIC simulation package. This characterization has allowed us to measure the muon flux reaching both detectors to be (3.64 +/- 0.04) x 10(-4) cm(-2) s(-1) for the near detector and (7.00 +/- 0.05) x 10(-5) cm(-2) s(-1) for the far one. The seasonal modulation of the signal has also been studied observing a positive correlation with the atmospheric temperature, leading to an effective temperature coefficient of alpha(T) = 0.212 +/- 0.024 and 0.355 +/- 0.019 for the near and far detectors respectively. These measurements, in good agreement with expectations based on theoretical models, represent one of the first measurements of this coefficient in shallow depth installations.
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