Physics reach of CERN-based SuperBeam neutrino oscillation experiments

We compare the physics potential of two representative options for a SuperBeam in Europe, studying the achievable precision at 1\sigma with which the CP violation phase (\delta) could be measured, as well as the mass hierarchy and CP violation discovery potentials. The first setup corresponds to a high energy beam aiming from CERN to a 100 kt liquid argon detector placed at the Pyh\"asalmi mine (2300 km), one of the LAGUNA candidate sites. The second setup corresponds to a much lower energy beam, aiming from CERN to a 500 kt water \v{C}erenkov detector placed at the Gran Sasso underground laboratory (730 km). This second option is also studied for a baseline of 650 km, corresponding to the LAGUNA candidate sites of Umbria and the Canfranc underground laboratory. All results are presented also for scenarios with statistics lowered by factors of 2, 4, 8 and 16 to study the possible reductions of flux, detector mass or running time allowed by the large value of \theta_{13} recently measured.Comment: 15 pages, 4 figure

Reassessing the sensitivity to leptonic CP violation

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 $\chi^2$ distribution with one degree of freedom occur for experimental setups with low sensitivity to $\delta$. In particular, when the allowed region to which $\delta$ 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 $\chi^2$ distribution at that confidence level. On the other hand, for facilities which can place better constraints on $\delta$ 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 $\chi^2$ distribution. The role of sign degeneracies is also discussed.Comment: 14 pages, 5 figures, RevTeX4. The discussion of the results has been improved and considerably extended. Version accepted for publication in JHE

Freeze-in through portals

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.Comment: 18 pages, 6 figure

Optimization of neutrino oscillation facilities for large \theta_{13}

Up to now, future neutrino beam experiments have been designed and optimized in order to look for CP violation, \theta_{13} and the mass hierarchy under the conservative assumption that \theta_{13} is very small. However, the recent results from T2K and MINOS favor a \theta_{13} which could be as large as 8^{\circ}. In this work, we propose a re-optimization for neutrino beam experiments in case this hint is confirmed. By switching from the first to the second oscillation peak, we find that the CP discovery potential of future oscillation experiments would not only be enhanced, but it would also be less affected by systematic uncertainties. In order to illustrate the effect, we present our results for a Super-Beam experiment, comparing the results obtained at the first and the second oscillation peaks for several values of the systematic errors. We also study its combination with a \beta-beam facility and show that the synergy between both experiments would also be enhanced due to the larger L/E. Moreover, the increased matter effects at the larger L/E also significantly improves the sensitivity to the mass hierarchy.Comment: Discussion and references expanded. Matches version accepted in JHE

Atmospheric neutrinos in ice and measurement of neutrino oscillation parameters

The main goal of the IceCube Deep Core Array is to search for neutrinos of astrophysical origins. Atmospheric neutrinos are commonly considered as a background for these searches. We show that the very high statistics atmospheric neutrino data can be used to obtain precise measurements of the main oscillation parameters.Comment: expanded discussion of systematic uncertainties, 8 pages, 4 figure

Non-Unitarity, sterile neutrinos, and Non-Standard neutrino Interactions

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.Comment: 19 pages, 2 figures: minor changes and references added, version published in JHE