A study of the relativistic corrections to tritium β\beta-decay

Forthcoming experiments like Project8 and Ptolemy aim at investigating with high precision the end-point of the tritium $\beta$-decay spectrum sensitive to the neutrino mass. In light of this, using the standard parametrization in terms of nuclear polar form factors, we analyze the complete relativistic expression for the spectrum of the $\beta$-electron emitted by a tritium nucleus. Given the small parameters in the problem, we discuss the approximations that can be made, and present the first two corrections to the standard lowest order formula, improving on the few results available in the literature.Comment: 5 pages, 1 figure, 1 tabl

Relativistic corrections to polarized-tritium β decay

Forthcoming experiments such as Project 8 and Ptolemy aim at investigating with high precision the end point of the tritium β-decay spectrum sensitive to the neutrino mass. In light of this, using the standard parametrization in terms of nuclear polar form factors, we analyze the complete relativistic expression for the spectrum of the β electron emitted by a tritium nucleus. Given the small parameters in the problem, we systematically discuss the approximations that can be made, and present the first two corrections to the standard lowest-order formula. We particularly discuss the case of an initially polarized target, and the consequences on the spectrum as a function of the neutrino mass. We show that, while it induces an angular anisotropy that can be measured by future experiments, such anisotropy cannot be used as an additional handle to constrain the neutrino mass

Neurobiological underpinnings of reward anticipation and outcome evaluation in gambling disorder

Gambling disorder is characterized by persistent and recurrent maladaptive gambling behavior, which leads to clinically significant impairment or distress. The disorder is associated with dysfunctions in the dopamine system. The dopamine system codes reward anticipation and outcome evaluation. Reward anticipation refers to dopaminergic activation prior to reward, while outcome evaluation refers to dopaminergic activation after reward. This article reviews evidence of dopaminergic dysfunctions in reward anticipation and outcome evaluation in gambling disorder from two vantage points: a model of reward prediction and reward prediction error by Wolfram Schultz et al. and a model of “wanting” and “liking” by Terry E. Robinson and Kent C. Berridge. Both models offer important insights on the study of dopaminergic dysfunctions in addiction, and implications for the study of dopaminergic dysfunctions in gambling disorder are suggested

Carbon nanostructures for directional light dark matter detection

Carbon nanostructures offer exciting new possibilities in the detection of light dark matter. A darkmatter particle with mass between 1 MeV and 1 GeV scattering off an electron in the carbon wouldtransfer sufficient energy to extract the electron from the lattice. In 2D materials, such as grapheneor carbon nanotubes, these electrons would be released directly into the vacuum, avoiding theirre-absorption in the medium. We present two novel detector concepts: a ’Graphene-FET’ design,based on graphene sheets, developed at Princeton University; and a ’Dark-PMT’ based on alignedcarbon nanotubes, developed in University of Rome Sapienza. We discuss their light dark matterdiscovery potential, the status of the RD, and the recent commissioning of a state-of-the-art carbonnanotube growing facility in Rome

Searching for Light Dark Matter with Aligned Carbon Nanotubes: The ANDROMeDa Project

The ANDROMeDa (Aligned Nanotube Detector for Research On MeV Dark matter) project aims to develop a novel Dark Matter detector based on carbon nanotubes: the “Dark-PMT”. The detector is designed to be sensitive to dark matter particles with mass between 1 MeV and 1 GeV. The detection scheme is based on dark matter-electron scattering inside a target made of vertically-aligned carbon nanotubes. Vertically-aligned carbon nanotubes have reduced density in the direction of the tube axis, therefore the scattered electrons are expected to leave the target without being re-absorbed only if their momentum has a small enough angle with that direction, which is what happens when the tubes are parallel to the dark matter wind. This grants directional sensitivity to the detector, a unique feature in this dark matter mass range

Transmission through graphene of electrons in the 30 – 900 eV range

Here, we report on accurate transmission measurements of electrons below 1 keV through suspended monolayer graphene. Monolayer graphene was grown via chemical vapor deposition and transferred onto transmission electron microscopy (TEM) grids. A monochromatic electron gun has been employed to perform the measurements in the 30 – 900 eV range in ultra-high vacuum. The graphene transparency is obtained from the absolute measurement of the direct beam current and the transmitted one, by means of a Faraday cup. We observed a transmission going from 20 to 80% for monolayer graphene within the experimental electron energy range. The high quality and the grid coverage of the suspended graphene has been proved via micro-Raman, X-ray photoemission, electron energy loss spectroscopies and field-emission scanning electron microscopy. After a 550 °C in-vacuum annealing of the samples, the main contribution to the C 1s spectrum is due to the component and the evidence of suspended monolayer graphene has been observed through the -plasmon excitation

Next-generation ultra-compact calorimeters based on oriented crystals

Calorimeters based on oriented crystals provide unparalleled compactness and resolution in measuring the energy of electromagnetic particles. Recent experiments performed at CERN and DESY beamlines by the AXIAL/ELIOT experiments demonstrated a significant reduction in the radiation length inside tungsten and PbWO4, the latter being the scintillator used for the CMS ECAL, observed when the incident particle trajectory is aligned with a lattice axis within ∼1∘. This remarkable effect, being observed over the wide energy range from a few GeV to 1 TeV or higher, paves the way for the development of innovative calorimeters based on oriented crystals, featuring a design significantly more compact than currently achievable while rivaling the current state of the art in terms of energy resolution in the range of interest for present and future forward detectors (such as the KLEVER Small Angle Calorimeter at CERN SPS) and source-pointing space-borne γ-ray telescopes