No abstract

The MEG experiment, designed to search for the µ + → e + γ decay at a 10 −13 sensitivity level, completed datataking in 2013. In order to increase the sensitivity reach of the experiment by an order of magnitude to the level of 6 × 10 −14 for the branching ratio, a total upgrade, involving substantial changes to the experiment, has been undertaken, known as MEG II. We present both the motivation for the upgrade and a detailed overview of the design of the experiment and of the expected detector performance.

The PTOLEMY project aims to develop a scalable design for a Cosmic Neutrino Background (CNB) detector, the first of its kind and the only one conceived that can look directly at the image of the Universe encoded in neutrino background produced in the first second after the Big Bang. The scope of the work for the next three years is to complete the conceptual design of this detector and to validate with direct measurements that the nonneutrino backgrounds are below the expected cosmological signal. In this paper we discuss in details the theoretical aspects of the experiment and its physics goals. In particular, we mainly address three issues. First we discuss the sensitivity of PTOLEMY to the standard neutrino mass scale. We then study the perspectives of the experiment to detect the CNB via neutrino capture on tritium as a function of the neutrino mass scale and the energy resolution of the apparatus. Finally, we consider an extra sterile neutrino with mass in the eV range, coupled to the active states via oscillations, which has been advocated in view of neutrino oscillation anomalies. This extra state would contribute to the tritium decay spectrum, and its properties, mass and mixing angle, could be studied by analyzing the features in the beta decay electron spectrum.

Two-terminal multistate memory elements based on VO(2)/TiO(2) thin film microcantilevers are reported. Volatile and non-volatile multiple resistance states are programmed by current pulses at temperatures within the hysteretic region of the metal-insulator transition of VO(2). The memory mechanism is based on current-induced creation of metallic clusters by self-heating of micrometric suspended regions and resistive reading via percolation.

The MEG experiment makes use of one of the world's most intense low energy muon beams, in order to search for the lepton flavour violating process μ + → e + γ . We determined the residual beam polarization at the thin stopping target, by measuring the asymmetry of the angular distribution of Michel decay positrons as a function of B. I. Khazin Deceased. a e-mail: fabrizio.cei@pi.infn.it energy. The initial muon beam polarization at the production is predicted to be P μ = −1 by the Standard Model (SM) with massless neutrinos. We estimated our residual muon polarization to be P μ = −0.86 ± 0.02 (stat) +0.05 −0.06 (syst) at the stopping target, which is consistent with the SM predictions when the depolarizing effects occurring during the muon production, propagation and moderation in the target are taken into account. The knowledge of beam polarization is of fundamental importance in order to model the background of our μ + → e + γ search induced by the muon radiative decay: μ + → e +ν μ ν e γ .

The European Research Council has recently funded HOLMES, a new experiment to directly measure the neutrino mass. HOLMES will perform a calorimetric measurement of the energy released in the decay of Ho. The calorimetric measurement eliminates systematic uncertainties arising from the use of external beta sources, as in experiments with beta spectrometers. This measurement was proposed in 1982 by A. De Rujula and M. Lusignoli, but only recently the detector technological progress allowed to design a sensitive experiment. HOLMES will deploy a large array of low temperature microcalorimeters with implanted Ho nuclei. The resulting mass sensitivity will be as low as 0.4 eV. HOLMES will be an important step forward in the direct neutrino mass measurement with a calorimetric approach as an alternative to spectrometry. It will also establish the potential of this approach to extend the sensitivity down to 0.1 eV. We outline here the project with its technical challenges and perspectives.

We present a detailed description of the electromagnetic filter for the PTOLEMY project to directly detect the Cosmic Neutrino Background (CNB). Starting with an initial estimate for the orbital magnetic moment, the higher-order drift process of E × B is configured to balance the gradient-B drift motion of the electron in such a way as to guide the trajectory into the standing voltage potential along the mid-plane of the filter. As a function of drift distance along the length of the filter, the filter zooms in with exponentially increasing precision on the transverse velocity component of the electron kinetic energy. This yields a linear dimension for the total filter length that is exceptionally compact compared to previous techniques for electromagnetic filtering. The parallel velocity component of the electron kinetic energy oscil-arXiv:1810.06703v1 [astro-ph.IM]

Transition-Metal Oxides (TMO) are of great technological impact due to the numerous properties they exhibit, like superconductivity, ferroelectricity and piezoelectricity, dielectricity, semiconductivity, orbital and spin ordered phases, and fully spin-polarized current. Their rich phase diagrams are determined by coupling of spin, charge, and lattice degrees of freedom, whose interplay can be modified by doping, external fields and lattice strain. In TMO, the transition-metal d-orbitals play the game; as a consequence of the strong local interactions, the phase diagrams strongly depend on the overlapping, the occupancy, and the fluctuations of the atomic orbitals.[1] In this scenario, lattice strain is one of the most powerful parameters to achieve control of TMO functionalities. Biaxial strains up to a few percent have been achieved on TMO thin films by changing the substrate lattice constant or by chemical doping, triggering phase transitions and modulating transition temperatures. [2][3][4][5][6][7][8][9] The real contribution of strain is often hindered by spurious effects arising from the growth mechanisms, and is not reversible. [10,11] In order to clarify these issues and move toward applications, active modulation of strain in crystalline TMOs thin films has been achieved by mechanical apparata [12] or by epitaxial locking with ferropiezoelectric substrates [13][14][15][16][17][18] or thin films. [19,20] The maximum attained voltage-assisted biaxial in-plane strain modulation, mainly compressive, is currently limited to about À0.25%. [21] Different approaches for strain manipulation of oxides also exploit the mechanical coupling between oxide nanocomposites [22,23] or the bending of oxide nanobeams and nanowires. [24,25] Nevertheless, bending of thin epitaxial TMO films is still an unexplored terrain. The objective of this work is to produce strain on TMO films by combining crystalline TMO thin films with microelectromechanical systems (MEMS) concepts. In particular, we show a MEMS device that employs mechanical deformations to induce tensile strain on a functional oxide film. So far, despite the enormous strategic interest of smart devices, few works on functional oxide MEMS and free-standing oxide structures have been reported, [26][27][28][29][30] mainly for applications as bolometers, mostly grown on buffer silicon substrates. Employment of piezoelectric ZnO or ferroelectric Pb(Zr 1 Ti)O 3 films for sensing or actuation of silicon cantilevers for atomic force microscopy (AFM) [31] and resistive strain gauges based on polycrystalline binary oxide films have been also reported.[32]Here, we show micro-electromechanical structures entirely based on crystalline perovskites that can be employed as ''strain-generator devices'' for a wide class of epitaxial oxide films. A crystalline suspended bridge of the most common substrate for TMOs deposition, SrTiO 3 (STO), is used as flexible substrate for the deposition of functional epitaxial TMO thin films. This element is bent both mechanically by an AFM tip and...