Light sterile neutrinos and inflationary freedom

We perform a cosmological analysis in which we allow the primordial power spectrum of scalar perturbations to assume a shape that is different from the usual power-law predicted by the simplest models of cosmological inflation. We parameterize the free primordial power spectrum with a ``piecewise cubic Hermite interpolating polynomial'' (PCHIP). We consider a 3+1 neutrino mixing model with a sterile neutrino having a mass at the eV scale, which can explain the anomalies observed in short-baseline neutrino oscillation experiments. We find that the freedom of the primordial power spectrum allows to reconcile the cosmological data with a fully thermalized sterile neutrino in the early Universe. Moreover, the cosmological analysis gives us some information on the shape of the primordial power spectrum, which presents a feature around the wavenumber k=0.002 Mpc 121

Light Sterile Neutrinos and Inflationary Freedom

We perform a cosmological analysis in which we allow the primordial power spectrum of scalar perturbations to assume a shape that is different from the usual power-law predicted by the simplest models of cosmological inflation. We parameterize the free primordial power spectrum with a "piecewise cubic Hermite interpolating polynomial" (PCHIP). We consider a 3+1 neutrino mixing model with a sterile neutrino having a mass at the eV scale, which can explain the anomalies observed in short-baseline neutrino oscillation experiments. We find that the freedom of the primordial power spectrum allows to reconcile the cosmological data with a fully thermalized sterile neutrino in the early Universe. Moreover, the cosmological analysis gives us some information on the shape of the primordial power spectrum, which presents a feature around the wavenumber $k=0.002\,\text{Mpc}^{-1}$.Comment: 19 pages; corrected Fig.4 and added Ref.[35

Light Sterile Neutrinos in Cosmology and Short-Baseline Oscillation Experiments

We analyze the most recent cosmological data, including Planck, taking into account the possible existence of a sterile neutrino with a mass at the eV scale indicated by short-baseline neutrino oscillations data in the 3+1 framework. We show that the contribution of local measurements of the Hubble constant induces an increase of the value of the effective number of relativistic degrees of freedom above the Standard Model value, giving an indication in favor of the existence of sterile neutrinos and their contribution to dark radiation. Furthermore, the measurements of the local galaxy cluster mass distribution favor the existence of sterile neutrinos with eV-scale masses, in agreement with short-baseline neutrino oscillations data. In this case there is no tension between cosmological and short-baseline neutrino oscillations data, but the contribution of the sterile neutrino to the effective number of relativistic degrees of freedom is likely to be smaller than one. Considering the Dodelson-Widrow and thermal models for the statistical cosmological distribution of sterile neutrinos, we found that in the Dodelson-Widrow model there is a slightly better compatibility between cosmological and short-baseline neutrino oscillations data and the required suppression of the production of sterile neutrinos in the early Universe is slightly smaller.Comment: 12 pages; final version published in JHEP 1311 (2013) 21

Updated Global 3+1 Analysis of Short-BaseLine Neutrino Oscillations

We present the results of an updated fit of short-baseline neutrino oscillation data in the framework of 3+1 active-sterile neutrino mixing. We first consider $\nu_e$ and $\bar\nu_e$ disappearance in the light of the Gallium and reactor anomalies. We discuss the implications of the recent measurement of the reactor $\bar\nu_e$ spectrum in the NEOS experiment, which shifts the allowed regions of the parameter space towards smaller values of $|U_{e4}|^2$. The beta-decay constraints allow us to limit the oscillation length between about 2 cm and 7 m at $3\sigma$ for neutrinos with an energy of 1 MeV. We then consider the global fit of the data in the light of the LSND anomaly, taking into account the constraints from $\nu_e$ and $\nu_\mu$ disappearance experiments, including the recent data of the MINOS and IceCube experiments. The combination of the NEOS constraints on $|U_{e4}|^2$ and the MINOS and IceCube constraints on $|U_{\mu4}|^2$ lead to an unacceptable appearance-disappearance tension which becomes tolerable only in a pragmatic fit which neglects the MiniBooNE low-energy anomaly. The minimization of the global $\chi^2$ in the space of the four mixing parameters $\Delta{m}^2_{41}$, $|U_{e4}|^2$, $|U_{\mu4}|^2$, and $|U_{\tau4}|^2$ leads to three allowed regions with narrow $\Delta{m}^{2}_{41}$ widths at $\Delta m^2_{41} \approx 1.7$ (best-fit), 1.3 (at $2\sigma$), 2.4 (at $3\sigma$) eV$^2$. The restrictions of the allowed regions of the mixing parameters with respect to our previous global fits are mainly due to the NEOS constraints. We present a comparison of the allowed regions of the mixing parameters with the sensitivities of ongoing experiments, which show that it is likely that these experiments will determine in a definitive way if the reactor, Gallium and LSND anomalies are due to active-sterile neutrino oscillations or not.Comment: 39 pages; improved treatment of the reactor flux uncertainties and other minor correction

Light sterile neutrinos

The theory and phenomenology of light sterile neutrinos at the eV mass scale is reviewed. The reactor, Gallium and LSND anomalies are briefly described and interpreted as indications of the existence of short-baseline oscillations which require the existence of light sterile neutrinos. The global fits of short-baseline oscillation data in 3+1 and 3+2 schemes are discussed, together with the implications for beta-decay and neutrinoless double-beta decay. The cosmological effects of light sterile neutrinos are briefly reviewed and the implications of existing cosmological data are discussed. The review concludes with a summary of future perspectives.Comment: 41 pages; final version to be published as a Topical Review in Journal of Physics

DEFINITION OF NOVEL HEALTH AND AIR POLLUTION INDEX BASED ON SHORT TERM EXPOSURE AND AIR CONCENTRATION LEVELS

Health impact assessment has become important in the development of air quality policies and in finding the relationships between pollutants concentration and health effects. In our work we presented a novel index able to evaluate the effects on the human exposure caused by ambient air pollution in urban areas. The index is able to link both health risk factors and pollutants levels. The indexes is of additive type and is composed by two terms: the former is based on pollutants concentration and is connected with EPA air quality index (AQI), while the latter is composed by an adimensional term based on the exposure levels. We tested the methodology using PM10 as studied pollutants. The spatial and temporal variation of its health impact was evaluated by means of index maps applying the above methodology in the city of Rome during three selected episodes. Our study shows index maps for all episodes linked to population and to pollutants

Thermalisation of sterile neutrinos in the early universe in the 3+1 scheme with full mixing matrix

In the framework of a 3+1 scheme with an additional inert state, we consider the thermalisation of sterile neutrinos in the early Universe taking into account the full 4×4 mixing matrix. The evolution of the neutrino energy distributions is found solving the momentum-dependent kinetic equations with full diagonal collision terms, as in previous analyses of flavour neutrino decoupling in the standard case. The degree of thermalisation of the sterile state is shown in terms of the effective number of neutrinos, Neff, and its dependence on the three additional mixing angles (θ_14, θ_24, θ_34) and on the squared mass difference Δm^2_41 is discussed. Our results are relevant for fixing the contribution of a fourth light neutrino species to the cosmological energy density, whose value is very well constrained by the final Planck analysis. For the preferred region of active-sterile mixing parameters from short-baseline neutrino experiments, we find that the fourth state is fully thermalised (Neff≃4)

Neutrino masses and their ordering: global data, priors and models

We present a full Bayesian analysis of the combination of current neutrino oscillation, neutrinoless double beta decay and Cosmic Microwave Background observations. Our major goal is to carefully investigate the possibility to single out one neutrino mass ordering, namely Normal Ordering or Inverted Ordering, with current data. Two possible parametrizations (three neutrino masses versus the lightest neutrino mass plus the two oscillation mass splittings) and priors (linear versus logarithmic) are exhaustively examined. We find that the preference for NO is only driven by neutrino oscillation data. Moreover, the values of the Bayes factor indicate that the evidence for NO is strong only when the scan is performed over the three neutrino masses with logarithmic priors; for every other combination of parameterization and prior, the preference for NO is only weak. As a by-product of our Bayesian analyses, we are able to (a) compare the Bayesian bounds on the neutrino mixing parameters to those obtained by means of frequentist approaches, finding a very good agreement; (b) determine that the lightest neutrino mass plus the two mass splittings parametrization, motivated by the physical observables, is strongly preferred over the three neutrino mass eigenstates scan and (c) find that logarithmic priors guarantee a weakly-to-moderately more efficient sampling of the parameter space. These results establish the optimal strategy to successfully explore the neutrino parameter space, based on the use of the oscillation mass splittings and a logarithmic prior on the lightest neutrino mass, when combining neutrino oscillation data with cosmology and neutrinoless double beta decay. We also show that the limits on the total neutrino mass ∑ mν can change dramatically when moving from one prior to the other. These results have profound implications for future studies on the neutrino mass ordering, as they crucially state the need for self-consistent analyses which explore the best parametrization and priors, without combining results that involve different assumptions

Short-term effects of air pollution on cardiovascular hospitalizations in the pisan longitudinal study

Air pollution effects on cardiovascular hospitalizations in small urban/suburban areas have been scantly investigated. Such effects were assessed among the participants in the analytical epidemiological survey carried out in Pisa and Cascina, Tuscany, Italy (2009-2011). Cardiovascular hospitalizations from 1585 subjects were followed up (2011-2015). Daily mean pollutant concentrations were estimated through random forests at 1 km (particulate matter: PM10, 2011-2015; PM2.5, 2013-2015) and 200 m (PM10, PM2.5, NO2, O3, 2013-2015) resolutions. Exposure effects were estimated using the case-crossover design and conditional logistic regression (odds ratio-OR-and 95% confidence interval-CI-for 10 μg/m3 increase; lag 0-6). During the period 2011-2015 (137 hospitalizations), a significant effect at lag 0 was observed for PM10 (OR = 1.137, CI: 1.023-1.264) at 1 km resolution. During the period 2013-2015 (69 hospitalizations), significant effects at lag 0 were observed for PM10 (OR = 1.268, CI: 1.085-1.483) and PM2.5 (OR = 1.273, CI: 1.053-1.540) at 1 km resolution, as well as for PM10 (OR = 1.365, CI: 1.103-1.690), PM2.5 (OR = 1.264, CI: 1.006-1.589) and NO2 (OR = 1.477, CI: 1.058-2.061) at 200 m resolution; significant effects were observed up to lag 2. Larger ORs were observed in males and in subjects reporting pre-existent cardiovascular/respiratory diseases. Combining analytical and routine epidemiological data with high-resolution pollutant estimates provides new insights on acute cardiovascular effects in the general population and in potentially susceptible subgroups living in small urban/suburban areas