Searching for sterile neutrinos from π\pi and KK decays

The production of heavy sterile neutrinos from $\pi^-,K^-$ decay at rest yields charged leptons with negative helicity (positive for $\pi^+,K^+$). We obtain the branching ratio for this process and argue that a Stern-Gerlach filter leads to spatially separated domains of both helicity components with abundances determined by the branching ratio. Complemented with a search of monochromatic peaks, this setup can yield both the mass and mixing angles for sterile neutrinos with masses in the range $3 MeV \lesssim m_s \lesssim 414 MeV$ in next generation high intensity experiments. We also study oscillations of light Dirac and Majorana sterile neutrinos with $m_s \simeq eV$ produced in meson decays including decoherence aspects arising from lifetime effects of the decaying mesons and the stopping distance of the charged lepton in short baseline experiments. We obtain the transition probability from production to detection via charged current interactions including these decoherence effects for 3+1 and 3+2 scenarios, also studying $|\Delta L|=2$ transitions from $\bar{\nu} \leftrightarrow \nu$ oscillations for Majorana neutrinos and the impact of these effects on the determination of CP-violating amplitudes. We argue that decoherence effects are important in current short baseline accelerator experiments, leading to an underestimate of masses, mixing and CP-violating angles. At MiniBooNE/SciBooNE we estimate that these effects lead to an $\sim 15$ underestimate for sterile neutrino masses $m_s \gtrsim 3 \,\mathrm{eV}$. We argue that reactor and current short baseline accelerator experiments are fundamentally different and suggest that in future high intensity experiments with neutrinos produced from $\pi,K$ decay at rest, stopping the charged leptons on distances much smaller than the decay length of the parent meson suppresses considerably these decoherence effects.Comment: 42 pages, 16 figures. To appear in Phys. Rev.

Pre-slow roll initial conditions: large scale power suppression and infrared aspects during inflation

If the large scale anomalies in the temperature power spectrum of the cosmic microwave background are of primordial origin, they may herald modifications to the slow roll inflationary paradigm on the largest scales. We study the possibility that the origin of the large scale power suppression is a modification of initial conditions during slow roll as a result of a pre-slow roll phase during which the inflaton evolves rapidly. This stage is manifest in a potential in the equations for the Gaussian fluctuations during slow roll and modify the power spectra of scalar perturbations via an initial condition transfer function $\mathcal{T}(k)$. We provide a general analytical study of its large and small scale properties and analyze the impact of these initial conditions on the infrared aspects of typical test scalar fields. The infrared behavior of massless minimally coupled test scalar field theories leads to the dynamical generation of mass and anomalous dimensions, both depend non-analytically on $\mathcal{T}(0)$. During inflation all quanta decay into many quanta even of the same field because of the lack of kinematic thresholds. The decay leads to a quantum entangled state of sub and superhorizon quanta with correlations across the horizon. We find the modifications of the decay width and the entanglement entropy from the initial conditions. In all cases, initial conditions from a ``fast-roll'' stage that lead to a suppression in the scalar power spectrum at large scales also result in a suppression of the dynamically generated masses, anomalous dimensions and decay widths.Comment: expanded discussion on fast-slow roll stage. version to appear in PR

LA CONFISCA DI PREVENZIONE EX ART. 24 D. LGS. 6 SETTEMBRE 2011 N. 159. LA 'SFIDA' DEL PRINCIPIO DI PROPORZIONE

Il lavoro concerne il tema del contrasto patrimoniale alla criminalità organizzata e la confisca di prevenzione ante delictum (art. 24, d.lgs. n. 159/2011). Lo spregiudicato ricorso a questo strumento ha creato una confusione tra i piani della prevenzione (ante delictum) e della repressione (post delictum) della criminalità. Si nota, inoltre, la tendenza della confisca a sconfinare verso settori d’intervento della giustizia penale differenti da quelli per i quali è espressamente prevista. La Parte prima della tesi è dedicata alla ricostruzione delle origini storiche delle misure di prevenzione patrimoniali, nonché ai presupposti e alle finalità di sequestro e confisca. La Parte seconda affronta il problema della natura giuridica della confisca. Alla dottrina che si è espressa per la sostanziale natura sanzionatoria della misura (formalmente) di “prevenzione”, si oppone la giurisprudenza che la estromette dalla materia penale e dalle garanzie (costituzionali e convenzionali). La Parte terza è dedicata alla ‘sfida’ del principio di proporzione: la verifica della ragionevolezza della confisca secondo il modello del giudizio trilaterale. Nelle conclusioni si espongono delle considerazioni sui rapporti tra prevenzione ante delictum e principio di sussidiarietà, nell’ottica di una valorizzazione dell’idea di gradualità e di promozione dell’uguaglianza tra cittadini.The work concerns the contrast against organized crime and the preventive confiscation (art. 24, d.lgs. n. 159/2011). The use of confiscation has created a confusion between the plans of crime prevention (ante delictum) and crime repression (post delictum). The first part of the thesis concerns: reconstruction of the historical origins of the preventive system; conditions and purposes of seizure and confiscation. The second part deals with the problem of the legal nature of confiscation. The doctrine has been expressed for substantial punitive measure; jurisprudence excludes confiscation from criminal law and its guarantees. The third part concerns the 'challenge' of the principle of proportionality: the verification of the reasonableness of confiscatione. The conclusions expose the considerations on the relationship between prevention ante delictum and the principle of subsidiarity, to valorize the idea of gradually and of equality between citizens