Global relativistic folding optical potential and the relativistic Green's function model

Optical potentials provide critical input for calculations on a wide variety of nuclear reactions, in particular, for neutrino-nucleus reactions, which are of great interest in the light of the new neutrino oscillation experiments. We present the global relativistic folding optical potential (GRFOP) fits to elastic proton scattering data from C-12 nucleus at energies between 20 and 1040 MeV. We estimate observables, such as the differential cross section, the analyzing power, and the spin rotation parameter, in elastic proton scattering within the relativistic impulse approximation. The new GRFOP potential is employed within the relativistic Green's function model for inclusive quasielastic electron scattering and for (anti) neutrino-nucleus scattering at MiniBooNE kinematics.

Measuring the $^{127}$I, $\nu_{e}$ Charged-Current Cross-Section of NaI[Tl]

The primary objective of this experiment is to measure the cross-section of $\nu_{e}$ charged-current neutrino interactions on $^{127}$I. To measure this interaction, an array of twenty-four, 7.7 kg sodium iodide (NaI[Tl]) scintillating detectors will be deployed to the Spallation Neutron Source at Oak Ridge National Laboratory. The design of the detector array is presented here along with preliminary characterization and background measurements conducted at Duke University.

Background Measurement Techniques and Sensitivity Studies for the SNO+ Neutrinoless Double Beta Decay Search

The control of radioactive backgrounds will be key in the search for neutrinoless double beta decay at the SNO+ experiment. Several aspects of the SNO+ back- grounds have been studied. The SNO+ tellurium purification process may require ultra low background ethanol as a reagent. A low background assay technique for ethanol was developed and used to identify a source of ethanol with measured 238U and 232Th concentrations below 2.8 10^-13 g/g and 10^-14 g/g respectively. It was also determined that at least 99:997% of the ethanol can be removed from the purified tellurium using forced air ow in order to reduce 14C contamination. In addition, a quality-control technique using an oxygen sensor was studied to monitor 222Rn contamination due to air leaking into the SNO+ scintillator during transport. The expected sensitivity of the technique is 0.1mBq/L or better depending on the oxygen sensor used. Finally, the dependence of SNO+ neutrinoless double beta decay sensitivity on internal background levels was studied using Monte Carlo simulation. The half-life limit to neutrinoless double beta decay of 130Te after 3 years of operation was found to be 4.8 1025 years under default conditions.

A simple approach to the supernova progenitor–explosion connection

We present a new approach to understand the landscape of supernova explosion energies, ejected nickel masses, and neutron star birth masses. In contrast to other recent parametric approaches, our model predicts the properties of neutrino-driven explosions based on the pre-collapse stellar structure without the need for hydrodynamic simulations. The model is based on physically motivated scaling laws and simple differential equations describing the shock propagation, the contraction of the neutron star, the neutrino emission, the heating conditions, and the explosion energetics. Using model parameters compatible with multi-D simulations and a fine grid of thousands of supernova progenitors, we obtain a variegated landscape of neutron star and black hole formation similar to other parametrized approaches and find good agreement with semi-empirical measures for the ‘explodability’ of massive stars. Our predicted explosion properties largely conform to observed correlations between the nickel mass and explosion energy. Accounting for the coexistence of outflows and downflows during the explosion phase, we naturally obtain a positive correlation between explosion energy and ejecta mass. These correlations are relatively robust against parameter variations, but our results suggest that there is considerable leeway in parametric models to widen or narrow the mass ranges for black hole and neutron star formation and to scale explosion energies up or down. Our model is currently limited to an all-or-nothing treatment of fallback and there remain some minor discrepancies between model predictions and observational constraints.

Non-radial instabilities and progenitor asphericities in core-collapse supernovae

Since core-collapse supernova simulations still struggle to produce robust neutrino-driven explosions in 3D, it has been proposed that asphericities caused by convection in the progenitor might facilitate shock revival by boosting the activity of non-radial hydrodynamic instabilities in the post-shock region. We investigate this scenario in depth using 42 relativistic 2D simulations with multigroup neutrino transport to examine the effects of velocity and density perturbations in the progenitor for different perturbation geometries that obey fundamental physical constraints (like the anelastic condition). As a framework for analysing our results, we introduce semi-empirical scaling laws relating neutrino heating, average turbulent velocities in the gain region, and the shock deformation in the saturation limit of non-radial instabilities. The squared turbulent Mach number, 〈Ma2〉, reflects the violence of aspherical motions in the gain layer, and explosive runaway occurs for 〈Ma2〉 ≳ 0.3, corresponding to a reduction of the critical neutrino luminosity by ∼25∼25 per cent compared to 1D. In the light of this theory, progenitor asphericities aid shock revival mainly by creating anisotropic mass flux on to the shock: differential infall efficiently converts velocity perturbations in the progenitor into density perturbations δρ/ρ at the shock of the order of the initial convective Mach number Maprog. The anisotropic mass flux and ram pressure deform the shock and thereby amplify post-shock turbulence. Large-scale (ℓ = 2, ℓ = 1) modes prove most conducive to shock revival, whereas small-scale perturbations require unrealistically high convective Mach numbers. Initial density perturbations in the progenitor are only of the order of Ma2progMaprog2 and therefore play a subdominant role.

The Status of Multi-Dimensional Core-Collapse Supernova Models

Models of neutrino-driven core-collapse supernova explosions have matured considerably in recent years. Explosions of low-mass progenitors can routinely be simulated in 1D, 2D, and 3D. Nucleosynthesis calculations indicate that these supernovae could be contributors of some lighter neutron-rich elements beyond iron. The explosion mechanism of more massive stars remains under investigation, although first 3D models of neutrino-driven explosions employing multi-group neutrino transport have become available. Together with earlier 2D models and more simplified 3D simulations, these have elucidated the interplay between neutrino heating and hydrodynamic instabilities in the post-shock region that is essential for shock revival. However, some physical ingredients may still need to be added/improved before simulations can robustly explain supernova explosions over a wide range of progenitors. Solutions recently suggested in the literature include uncertainties in the neutrino rates, rotation, and seed perturbations from convective shell burning. We review the implications of 3D simulations of shell burning in supernova progenitors for the ‘perturbations-aided neutrino-driven mechanism,’ whose efficacy is illustrated by the first successful multi-group neutrino hydrodynamics simulation of an 18 solar mass progenitor with 3D initial conditions. We conclude with speculations about the impact of 3D effects on the structure of massive stars through convective boundary mixing.

Flavour symmetries in a renormalizable SO(10) model

In the context of a renormalizable supersymmetric SO(10) Grand Unified Theory, we consider the fermion mass matrices generated by the Yukawa couplings to a 10 circle plus 120 circle plus (126) over bar representation of scalars. We perform a complete investigation of the possibilities of imposing flavour symmetries in this scenario; the purpose is to reduce the number of Yukawa coupling constants in order to identify potentially predictive models. We have found that there are only 14 inequivalent cases of Yukawa coupling matrices, out of which 13 cases are generated by 74 symmetries, with suitable n, and one case is generated by a Z(2) x Z(2) symmetry. A numerical analysis of the 14 cases reveals that only two of them-dubbed A and B in the present paper allow good fits to the experimentally known fermion masses and mixings. (C) 2016 The Authors. Published by Elsevier B.V.

Scotogenic model for co-bimaximal mixing

We present a scotogenic model, i.e. a one-loop neutrino mass model with dark right-handed neutrino gauge singlets and one inert dark scalar gauge doublet eta, which has symmetries that lead to co-bimaximal mixing, i.e. to an atmospheric mixing angle theta(23) = 45 degrees and to a CP-violating phase delta = +/-pi/2, while the mixing angle theta(13) remains arbitrary. The symmetries consist of softly broken lepton numbers L-alpha (alpha = e, mu, tau), a non-standard CP symmetry, and three L-2 symmetries. We indicate two possibilities for extending the model to the quark sector. Since the model has, besides eta, three scalar gauge doublets, we perform a thorough discussion of its scalar sector. We demonstrate that it can accommodate a Standard Model-like scalar with mass 125 GeV, with all the other charged and neutral scalars having much higher masses.

The Askaryan radio array

The Askar'yan Radio Array (ARA), a neutrino detector to be situated at the South Pole next to the IceCube detector, will be sensitive to ultrahigh-energy cosmic neutrinos above 0.1 EeV and will have the greatest sensitivity within the favored energy range from 0.1 EeV up to 10 EeV. Neutrinos of this energy are guaranteed by current observations of the GZK-cutoff by the HiRes and Pierre Auger Observatories. The detection method is based on Cherenkov emission by a neutrino induced cascade in the ice, coherent at radio wavelengths, which was predicted by Askar'yan in 1962 and verified in beam tests at SLAC in 2006. The detector is planned to consist of 37 stations with 16 antennas each, deployed at depths of up to 200 m under the ice surface. During the last two polar seasons (2010-2011, 2011-2012), a prototype station and a first detector station were successfully deployed and are taking data. These data have been and are currently being analyzed to study the ambient noise background and the radio frequency properties of the South Pole ice sheet. A worldwide collaboration is working on the planning, construction and data analysis of the detector array. This article will give a short report on the status of the ARA detector and show recent results from the recorded data. © 2013 AIP Publishing LLC.

Toxicidade de extratos vegetais ao percevejo bronzeado do eucalipto Thaumastocoris peregrinus (hemiptera: heteroptera: thaumastocoridae) e organismos não-alvo

Thaumastocoris peregrinus (Hemiptera: Thaumastocoridae ) is an insect from Australia which is causing severe damage to eucalyptus crops around the world. When feeding from the leaves sap, it causes bronzening, and in extreme cases, may lead to the tree death. Control methods have been studied and the most promising so far is the egg parasitoid Cleruchoides noackae (Hymenoptera: Mymaridae). Alternative products from plants with insecticidal properties could also be a viable option, and they might even be used concomitantly with C. noackae, aiming for a most effective control, but still safe for the environment. Thus, the objective of this work was to verify the action of 5% aqueous plant extracts of Matricaria chamomilla, Echinodorus grandiflorus, Punica granatum, Maytenus ilicifolia a n d Origanum majorana on T. peregrinus. In addition, we aimed to study the extracts potential toxicity to C. noackae and Gallus domesticus L., since the plant compounds might have negative effect upon the non-target organisms. At first, HPLC (High Performance Liquid Chromatography) was used to verify which phenolic compounds would be found in the plant extracts. These were tested on bronze bug adults, in confinement test (to verify the insecticidal action of the extracts) and free-choice test (to verify the repellency). The extracts that showed better results were selected for further tests with non-target organisms. Regarding C. noackae, pre-parasitism and post-parasitism, confinement and free-choice tests were performed to verify if the extracts would affect the host-choosing by the female or the development of the immature stages of the parasitoid. To verify if the extracts would be toxic to G. domesticus, the plant extracts were added to young birds feed for five days. Parameters such as weight gain, food intake, quantification of serum enzymes and histopathological analysis were carried out. HPLC analysis detected gallic, ferulic, vanillic, caffeic and cumaric acid in the extracts samples. All plant extracts tested reduced T. peregrinus survival, but E. grandiflorus, Matricaria chamomilla Maytenus ilicifolia had also a repellent effect, and were tested on the non-target organisms. None of these extracts affected neither the host choice by C. noackae nor adult emergency, when compared to the control group. In addition, the extracts did not cause alterations in any of the studied parameters. Thus, we verified that E. grandiflorus, Matricaria chamomilla and Maytenus ilicifolia have potential to be used to control T. peregrinus and are safe to C. noackae and G. domesticus.

Topological massive Dirac edge modes and long-range superconducting Hamiltonians

We discover novel topological effects in the one-dimensional Kitaev chain modified by long-range Hamiltonian deformations in the hopping and pairing terms. This class of models display symmetry-protected topological order measured by the Berry/Zak phase of the lower-band eigenvector and the winding number of the Hamiltonians. For exponentially decaying hopping amplitudes, the topological sector can be significantly augmented as the penetration length increases, something experimentally achievable. For power-law decaying superconducting pairings, the massless Majorana modes at the edges get paired together into a massive nonlocal Dirac fermion localized at both edges of the chain: a new topological quasiparticle that we call topological massive Dirac fermion. This topological phase has fractional topological numbers as a consequence of the long-range couplings. Possible applications to current experimental setups and topological quantum computation are also discussed.

Fattibilità della misura di cattura neutronica sugli isotopi dispari del gadolinio

In questo lavoro di tesi ci proponiamo di determinare lo spessore degli isotopi ^155Gd e ^157Gd in vista della misura della sezione d’urto di cattura neutronica presso la facility n_TOF del CERN. La principale motivazione dell’esperimento è legata alla necessità di ottenere misure più accurate per le applicazioni ai reattori nucleari. Inoltre, i nuovi risultati, potranno essere sfruttati anche per applicazioni ai recenti sviluppi nella Terapia di Cattura Neutronica e per costruire nuovi rivelatori nell’ambito della ricerca del neutrino. La misura sarà effettuata nella prima area sperimentale EAR-1 di n TOF, equipaggiata con rivelatori, come per esempio gli scintillatori liquidi al benzene deuterato (C6D6) particolarmente adatti per questi tipi di misura. La sezione d’urto di questi due isotopi cambia di molti ordini di grandezza al variare dell’energia dei neutroni incidenti. Per questo motivo, lo studio effettuato in questa tesi ha mostrato che sono necessari due campioni altamente arricchiti per ogni isotopo da misurare: un campione estremamente sottile per energie del neutrone fino a 100 meV, e uno più spesso per energie maggiori. Inoltre per questi campioni sono stati determinati le densità areali necessarie per lo svolgimento dell’esperimento affinchè avvenga il fenomeno di trasmissione dei neutroni.

Studio di fattibilità della ricostruzione del decadimento $D^0\to K^-\mu^+\nu_{\mu}$ ad LHCb

Il Modello Standard delle particelle elementari prevede l’universalità del sapore leptonico, cioè l’uguaglianza della probabilità di accoppiamento dei bosoni di gauge carichi dell’interazione debole con tutti i leptoni. Recentemente, le Collaborazioni LHCb, BaBar e Belle, misurando il rapporto tra i branching ratio dei decadimenti $B^0\to D^{∗− }\tau^+\nu_{\tau} e $B^0 →D^{∗−}\mu^+\nu_{\mu}, hanno osservato una deviazione dai valori previsti dal Modello Standard di 3.9 deviazioni standard. Questo interessante risultato, se confermato, indicherebbe l’esistenza di nuove particelle, come per esempio il bosone di Higgs carico. Analogamente ai decadimenti del mesone $B^0$ , è possibile cercare effetti analoghi anche nel rapporto di branching ratio dei decadimenti $D^0\to K^ −\mu^+\nu_{\mu}$ e $D^0\to K^−e^+\nu_e$ . In questo lavoro di tesi è stato realizzato uno studio preliminare di questa misura. In particolare, è stato studiata, tramite simulazioni Monte Carlo, la ricostruzione del processo $D^{*\pm}\to D^0 (\to K^− \mu+\nu_{\mu})\pi_s^{\pm}$ nell’esperimento LHCb. Questo canale ha la particolarità di avere una particella invisibile, il neutrino, al rivelatore LHCb. Tuttavia, mediante vincoli cinematici e topologici, è possibile ricavare le componenti dell’impulso del neutrino, con risoluzioni non paragonabili a quelle di una particella visibile, ma comunque accettabili. In questa tesi sono riportati i calcoli che permettono di ottenere queste informazioni ed è stata studiata la risoluzione sulla massa invariante del $D^{∗\pm}$ . La tesi è organizzata nel seguente modo: il primo capitolo riporta le motivazioni della misura dei rapporti dei branching ratio e l’attuale stato sperimentale; il secondo capitolo contiene una breve descrizione del rivelatore LHCb; il terzo capitolo, infine, descrive lo studio di fattibilità della ricostruzione del decadimento $D^0\to K^-\mu^+\nu_{\mu}.