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![Mattias Blennow, Enrique Fernandez-Martínez and Bryan Zaldívar The popular freeze-out paradigm for Dark Matter (DM) production, relies on DM-baryon couplings of the order of the weak interactions. However, different search strategies for DM have failed to provide a conclusive evidence of such (non-gravitational) interactions, while greatly reducing the parameter space of many representative models. This motivates the study of alternative mechanisms for DM genesis. In the freeze-in framework, the DM is slowly populated from the thermal bath while never reaching equilibrium. In this work, we analyse in detail the possibility of producing a frozen-in DM via a mediator particle which acts as a portal. We give analytical estimates of different freeze-in regimes and support them with full numerical analyses, taking into account the proper distribution functions of bath particles. Finally, we constrain the parameter space of generic models by requiring agreement with DM relic abundance observations. JCAP 1401 (2013) 003 arXiv:1309.7348 [hep-ph]](images/u683-10.png)
![Mattias Blennow, Pilar Coloma and Enrique Fernandez-Martinez The ESSνSB project is a proposed neutrino oscillation experiment based on the European Spallation Source with the search for leptonic CP as its main aim. In this letter we show that a near detector at around 1 km distance from the beamline is not only very desirable for keeping the systematic errors affecting the CP search under control, but would also provide a significant sensitivity probe for sterile neutrino oscillations in the region of the parameter space favored by the long-standing LSND anomaly. We find that the effective mixing angle θμe can be probed down to sin2(2θμe)≃2(8)⋅10−3 at 5σ assuming 15% bin-to-bin (un)correlated systematics. JHEP 1412 (2014) 120 arXiv:1407.1317 [hep-ph]](images/u689-18.png)
![Mattias Blennow, Pilar Coloma and Enrique Fernandez-Martinez We address the validity of the usual procedure to determine the sensitivity of neutrino oscillation experiments to CP violation. An explicit calibration of the test statistic is performed through Monte Carlo simulations for several experimental setups. We find that significant deviations from a χ2 distribution with one degree of freedom occur for experimental setups with low sensitivity to δ. In particular, when the allowed region to which δ is constrained at a given confidence level is comparable to the whole allowed range, the cyclic nature of the variable manifests and the premises of Wilk's theorem are violated. This leads to values of the test statistic significantly lower than a χ2 distribution at that confidence level. On the other hand, for facilities which can place better constraints on δ the cyclic nature of the variable is hidden and, as the potential of the facility improves, the values of the test statistics first become slightly higher than and then approach asymptotically a χ2 distribution. The role of sign degeneracies is also discussed. JHEP 1503 (2015) 005 arXiv:1407.3274 [hep-ph]](images/u692-16.png)
![Aaron C. Vincent, Enrique Fernandez-Martinez, Pilar Hernandez, Massimiliano Lattanzi and Olga Mena We employ state-of-the art cosmological observables including supernova surveys and BAO information to provide constraints on the mass and mixing angle of a non-resonantly produced sterile neutrino species, showing that cosmology can effectively rule out sterile neutrinos which decay between BBN and the present day. The decoupling of an additional heavy neutrino species can modify the time dependence of the Universe's expansion between BBN and recombination and, in extreme cases, lead to an additional matter-dominated period; while this could naively lead to a younger Universe with a larger Hubble parameter, it could later be compensated by the extra radiation expected in the form of neutrinos from sterile decay. However, recombination-era observables including the Cosmic Microwave Background (CMB), the shift parameter RCMB and the sound horizon rs from Baryon Acoustic Oscillations (BAO) severely constrain this scenario. We self-consistently include the full time-evolution of the coupled sterile neutrino and standard model sectors in an MCMC, showing that if decay occurs after BBN, the sterile neutrino is essentially bounded by the constraint sin2θ≲0.026(ms/eV)−2. JCAP 1504 (2015) 006 arXiv:1408.1956 [astro-ph.CO]](images/u697-20.png)
![Sven Heinemeyer, Josu Hernandez-Garcia, Maria Jose Herrero, Xabier Marcano, Ana Maria Rodriguez-Sanchez In this work we study the radiative corrections to the mass of the lightest Higgs boson of the MSSM from three generations of Majorana neutrinos and sneutrinos. The spectrum of the MSSM is augmented by three right handed neutrinos and their supersymmetric partners. A seesaw mechanism of type I is used to generate the physical neutrino masses and oscillations that we require to be in agreement with present neutrino data. We present a full one-loop computation of these Higgs mass corrections, and analyze in full detail their numerical size in terms of both the MSSM and the new (s)neutrino parameters. A critical discussion on the different possible renormalization schemes and their implications is included. Adv. High Energy Phys. 2015, 152394 (2015) arXiv:1407.1083 [hep-ph]](images/u702-14.png)
![Enrique Fernandez-Martinez, Josu Hernandez-Garcia, Jacobo Lopez-Pavon and Michele Lucente We perform a detailed study of the importance of loop corrections when deriving bounds on heavy-active neutrino mixing in the context of general Seesaw mechanisms with extra heavy right-handed neutrinos. We find that, for low-scale Seesaws with an approximate B−L symmetry characterized by electroweak scale Majorana masses and large Yukawas, loop corrections could indeed become relevant in a small part of the parameter space. Previous results in the literature showed that a partial cancellation between these important loop corrections and the tree level contributions could relax some constraints and lead to qualitatively different results upon their inclusion. However, we find that this cancellation can only take place in presence of large violations of the B−L symmetry, that lead to unacceptably large contributions to the light neutrino masses at loop level. Thus, when we restrict our analysis of the key observables to an approximate B−L symmetry so as to recover the correct values for neutrino masses, we always find loop corrections to be negligible in the regions of the parameter space preferred by data. arXiv:1508.03051 [hep-ph]](images/u712-11.png)
![Mattias Blennow, Pilar Coloma, Enrique Fernandez-Martinez, Pedro A. N. Machado and Bryan Zaldivar In this work we combine information from relic abundance, direct detection, cosmic microwave background, positron fraction, gamma rays, and colliders to explore the existing constraints on effective couplings between Dark Matter and Standard Model constituents when no underlying model or correlation is assumed. Our results show that Dark Matter masses below 20 GeV are disfavoured at the 3σ level by tension between the relic abundance requirement and upper constraints on the Dark Matter couplings. Furthermore, large couplings are typically only allowed in combinations which avoid effective couplings to the nuclei used in direct detection experiments. arXiv:1509.01587 [hep-ph]](images/u717-11.png)
![E.Baussan, M.Blennow, M.Bogomilov, E.Bouquerel, J.Cederkall, P.Christiansen, P.Coloma, P.Cupial, H.Danared, C.Densham, M.Dracos, T.Ekelof, M.Eshraqi, E.Fernandez Martinez, G.Gaudiot, R.Hall-Wilton, J.-P.Koutchouk, M.Lindroos, R.Matev, D.McGinnis, M.Mezzetto, R.Miyamoto, L.Mosca, T.Ohlsson, H.Ohman, F.Osswald, S.Peggs, P.Poussot, R.Ruber, J.Y.Tang, R.Tsenov, G.Vankova-Kirilova, N.Vassilopoulos, E.Wildner, J.Wurtz Very intense neutrino beams and large neutrino detectors will be needed in order to enable the discovery of CP violation in the leptonic sector. We propose to use the proton linac of the European Spallation Source currently under construction in Lund, Sweden to deliver, in parallel with the spallation neutron production, a very intense, cost effective and high performance neutrino beam. The baseline program for the European Spallation Source linac is that it will be fully operational at 5 MW average power by 2022, producing 2 GeV 2.86 ms long proton pulses at a rate of 14 Hz. Our proposal is to upgrade the linac to 10 MW average power and 28 Hz, producing 14 pulses/s for neutron production and 14 pulses/s for neutrino production. Furthermore, because of the high current required in the pulsed neutrino horn, the length of the pulses used for neutrino production needs to be compressed to a few μs with the aid of an accumulator ring. A long baseline experiment using this Super Beam and a megaton underground Water Cherenkov detector located in existing mines 300-600 km from Lund will make it possible to discover leptonic CP violation at 5 σ significance level in up to 50% of the leptonic Dirac CP-violating phase range. This experiment could also determine the neutrino mass hierarchy at a significance level of more than 3 σ if this issue will not already have been settled by other experiments by then. The mass hierarchy performance could be increased by combining the neutrino beam results with those obtained from atmospheric neutrinos detected by the same large volume detector. This detector will also be used to measure the proton lifetime, detect cosmological neutrinos and neutrinos from supernova explosions. Results on the sensitivity to leptonic CP violation and the neutrino mass hierarchy are presented. Nuclear Physics B, Volume 885, August 2014, Pages 127-149 arXiv:1309.7022 [hep-ex]](images/u971-11.png)
![M. Blennow, P. Coloma and E. Fernández-Martinez In this letter, we analyze for the first time the physics reach in terms of sensitivity to leptonic CP violation of the proposed MuOn-decay MEdium baseline NeuTrino beam (MOMENT) experiment, a novel neutrino oscillation facility that would operate with neutrinos from muon decay. Apart from obtaining a sufficiently intense flux, the bottlenecks to the physics reach of this experiment will be achieving a high enough suppression of the atmospheric background and, particularly, attaining a sufficient level of charge identification. We thus present our results as a function of these two factors. As for the detector, we consider a very massive Gd-doped Water Cherenkov detector. We find that MOMENT will be competitive with other currently planned future oscillation experiments if a charge identification of at least 80 % can be achieved at the same time that the atmospheric background can be suppressed by at least a factor of ten. We also find a large synergy of MOMENT with the current generation of neutrino oscillation experiments, T2K and NOvA, which significantly enhances its final sensitivity. JHEP 1603 (2016) 197 arXiv:1511.02859 [hep-ex]](images/u1162-12.png)
![E. Fernandez-Martinez, J. Hernandez-Garcia and J. Lopez-Pavon We derive general constraints on the mixing of heavy Seesaw neutrinos with the SM fields from a global fit to present flavour and electroweak precision data. We explore and compare both a completely general scenario, where the heavy neutrinos are integrated out without any further assumption, and the more constrained case were only 3 additional heavy states are considered. The latter assumption implies non-trivial correlations in order to reproduce the correct neutrino masses and mixings as observed by oscillation data and thus some qualitative differences can be found with the more general scenario. The relevant processes analyzed in the global fit include searches for Lepton Flavour Violating (LFV) decays, probes of the universality of weak interactions, CKM unitarity bounds and electroweak precision data. In particular, a comparative and detailed study of the present and future sensitivity of the different LFV experiments is performed. We find a mild 1−2σ preference for non-zero heavy neutrino mixing of order 0.03-0.04 in the electron and tau sectors. At the 2σ level we derive bounds on all mixings ranging from 0.1 to 0.01 with the notable exception of the e−μ sector with a more stringent bound of 0.005 from the μ→eγ process. JHEP 1608 (2016) 033 arXiv:1605.08774 [hep-ex]](images/u1176-12.png)
![DUNE Collaboration The LBNF/DUNE CDR describes the proposed physics program and experimental design at the conceptual design phase. Volume 2, entitled The Physics Program for DUNE at LBNF, outlines the scientific objectives and describes the physics studies that the DUNE collaboration will perform to address these objectives. The long-baseline physics sensitivity calculations presented in the DUNE CDR rely upon simulation of the neutrino beam line, simulation of neutrino interactions in the far detector, and a parameterized analysis of detector performance and systematic uncertainty. The purpose of this posting is to provide the results of these simulations to the community to facilitate phenomenological studies of long-baseline oscillation at LBNF/DUNE. Additionally, this posting includes GDML of the DUNE single-phase far detector for use in simulations. DUNE welcomes those interested in performing this work as members of the collaboration, but also recognizes the benefit of making these configurations readily available to the wider community. arXiv:1606.09550 [hep-ex]](images/u1193-12.png)
![V. De Romeri, E. Fernandez-Martinez and M. Sorel We study the physics reach of the long-baseline oscillation analysis of the DUNE experiment when realistic simulations are used to estimate its neutrino energy reconstruction capabilities. Our studies indicate that significant improvements in energy resolution compared to what is customarily assumed are plausible. This improved energy resolution can increase the sensitivity to leptonic CP violation in two ways. On the one hand, the CP-violating term in the oscillation probability has a characteristic energy dependence that can be better reproduced. On the other hand, the second oscillation maximum, especially sensitive to δCP, is better reconstructed. These effects lead to a significant improvement in the fraction of values of δCP for which a 5σ discovery of leptonic CP-violation would be possible. The precision of the δCP measurement could also be greatly enhanced, with a reduction of the maximum uncertainties from 26∘ to 18∘ for a 300~MW⋅kt⋅yr exposure. We therefore believe that this potential gain in physics reach merits further investigations of the detector performance achievable in DUNE. JHEP 1609 (2016) 030 arXiv:1607.00293 [hep-ex]](images/u1207-12.png)
![R. Alonso, E. Fernandez Martinez, M.B. Gavela, B. Grinstein, L. Merlo and P. Quilez The gauging of the lepton flavour group is considered in the Standard Model context and in its extension with three right-handed neutrinos. The anomaly cancellation conditions lead to a Seesaw mechanism as underlying dynamics for all leptons; requiring in addition a phenomenologically viable setup leads to Majorana masses for the neutral sector: the type I Seesaw Lagrangian in the Standard Model case and the inverse Seesaw in the extended model. Within the minimal extension of the scalar sector, the Yukawa couplings are promoted to scalar fields in the bifundamental of the flavour group. The resulting low-energy Yukawa couplings are proportional to inverse powers of the vacuum expectation values of those scalars; the protection against flavour changing neutral currents differs from that of Minimal Flavor Violation. In all cases, the μ−τ flavour sector exhibits rich and promising phenomenological signals. JHEP 1612 (2016) 119 arXiv:1609.05902 [hep-ex]](images/u1221-12.png)
![M. Blennow, P. Coloma, E. Fernandez-Martinez, J. Hernandez-Garcia and J. Lopez-Pavon The simplest Standard Model extension to explain neutrino masses involves the addition of right-handed neutrinos. At some level, this extension will impact neutrino oscillation searches. In this work we explore the differences and similarities between the case in which these neutrinos are kinematically accessible (sterile neutrinos) or not (mixing matrix non-unitarity). We clarify apparent inconsistencies in the present literature when using different parametrizations to describe these effects and recast both limits in the popular neutrino non-standard interaction (NSI) formalism. We find that, in the limit in which sterile oscillations are averaged out at the near detector, their effects at the far detector coincide with non-unitarity at leading order, even in presence of a matter potential. We also summarize the present bounds existing in both limits and compare them with the expected sensitivities of near future facilities taking the DUNE proposal as a benchmark. We conclude that non-unitarity effects are too constrained to impact present or near future neutrino oscillation facilities but that sterile neutrinos can play an important role at long baseline experiments. The role of the near detector is also discussed in detail. JHEP 1704 (2017) 153 arXiv:1609.08637 [hep-ex]](images/u1235-11.png)
![V. De Romeri, E. Fernandez-Martinez, J. Gehrlein, P. A. N. Machado and V. Niro The Inverse Seesaw naturally explains the smallness of neutrino masses via an approximate B−L symmetry broken only by a correspondingly small parameter. In this work the possible dynamical generation of the Inverse Seesaw neutrino mass mechanism from the spontaneous breaking of a gauged U(1) B−L symmetry is investigated. Interestingly, the Inverse Seesaw pattern requires a chiral content such that anomaly cancellation predicts the existence of extra fermions belonging to a dark sector with large, non-trivial, charges under the U(1) B−L. We investigate the phenomenology associated to these new states and find that one of them is a viable dark matter candidate with mass around the TeV scale, whose interaction with the Standard Model is mediated by the Z′ boson associated to the gauged U(1) B−L symmetry. Given the large charges required for anomaly cancellation in the dark sector, the B−L Z′ interacts preferentially with this dark sector rather than with the Standard Model. This suppresses the rate at direct detection searches and thus alleviates the constraints on Z′-mediated dark matter relic abundance. The collider phenomenology of this elusive Z′ is also discussed. arXiv:1707.08606 [hep-ex]](images/u1249-11.png)
