Anisotropic Ginzburg-Landau and Lawrence-Doniach Models for Layered Ultracold Fermi Gases

We study the anisotropic Ginzburg-Landau and Lawrence-Doniach models describing a layered superfluid ultracold Fermi gas in optical lattices. We derive the coefficients of the anisotropic Ginzburg-Landau and the mass tensor as a function of anisotropy, filling and interaction, showing that near the unitary limit the effective anisotropy of the masses is significantly reduced. The anisotropy parameter is shown to vary in realistic setups in a wide range of values. We also derive the Lawrence-Doniach model - often used to describe the 2D-3D dimensional crossover in layered superconductors - for a layered ultracold Fermi gas, obtaining a relation between the interlayer Josephson couplings and the Ginzburg-Landau masses. Comparing to the Ginzburg-Landau description, we find that the region of validity of the Lawrence-Doniach model is near the unitary limit.Comment: 15 pages, 4 figure

Strangeness production at finite temperature and baryon density in an effective relativistic mean field model

We study the strangeness production in hot and dense nuclear medium, by requiring the conservation of the baryon density, electric charge fraction and zero net strangeness. The hadronic equation of state is investigated by means of an effective relativistic mean field model, with the inclusion of the full octet of baryons and kaon mesons. Kaons are considered taking into account of an effective chemical potential depending on the self-consistent interaction between baryons. The obtained results are compared with a minimal coupling scheme, calculated for different values of the anti-kaon optical potential and with non-interacting kaon particles. In this context, we also consider the possible onset of the kaon condensation for a wide range of temperatures and baryon densities.Comment: 13 pages, 6 figure

The role of gender diversity on tax aggressiveness and corporate social responsibility: Evidence from Italian listed companies

The paper aims to examine the moderating role of gender diversity within a corporate board on the relationship between tax aggressiveness and a firm's corporate social responsibility (CSR) approach. This analysis was conducted using a set of indicators of financial statements of 168 Italian listed firms between 2011 and 2018. In addition, the sustainability reports of the same companies were observed. To perform the analysis a logit regression model is used. This paper shows different empirical results. First, this study notes that there is not a direct relationship between tax aggressiveness and CSR reporting. Second, gender diversity in a board of directors increases the orientation of companies to CSR disclosure, but does not have an impact on the relationship between tax aggressiveness and CSR disclosure. Instead, CEO gender has a positive influence on the relationship between corporate tax planning and CSR reporting in accordance with Global Reporting Initiative (GRI) standards. This study emphasizes the key role of gender diversity in the growth of the CSR approach and the reputation of companies. Therefore, governments and policymakers of major countries should promote gender diversity in corporate decision-making bodies, which contributes to achieving the Sustainable Development Goals (SDGs)

FIRST experiment: Fragmentation of Ions Relevant for Space and Therapy

Nuclear fragmentation processes are relevant in different fields of basic research and applied physics and are of particular interest for tumor therapy and for space radiation protection applications. The FIRST (Fragmentation of Ions Relevant for Space and Therapy) experiment at SIS accelerator of GSI laboratory in Darmstadt, has been designed for the measurement of different ions fragmentation cross sections at different energies between 100 and 1000 MeV/nucleon. The experiment is performed by an international collaboration made of institutions from Germany, France, Italy and Spain. The experimental apparatus is partly based on an already existing setup made of the ALADIN magnet, the MUSIC IV TPC, the LAND2 neutron detector and the TOFWALL scintillator TOF system, integrated with newly designed detectors in the interaction Region (IR) around the carbon removable target: a scintillator Start Counter, a Beam Monitor drift chamber, a silicon Vertex Detector and a Proton Tagger for detection of light fragments emitted at large angles (KENTROS). The scientific program of the FIRST experiment started on summer 2011 with the study of the 400 MeV/nucleon 12C beam fragmentation on thin (8mm) carbon targe

Thickness and uniformity characterization of thin targets for intense ion beam experiments

The NUMEN Experiment aims to get information on the Nuclear Matrix Elements of the Neutrinoless Double Beta Decay, by measuring heavyion induced Double Charge Exchange (DCE) reactions cross sections. A good energy resolution is needed to clearly distinguish energy states of DCE products. To measure the energy of reaction products with the required resolution, the target must be thin and uniform to minimise dispersion and straggling effects on the ejectile energy. Few hundreds of nanometers of the target isotope are deposited on a Highly Oriented Pyrolytic Graphite substrate a few micrometers thick. The results of the characterisation of the first target prototypes of tin and tellurium are presented. The Scanning Electron Microscopy was used to qualitatively analyse the samples surface. A setup to study Alpha Particle Transmission has been assembled to measure thickness and uniformity of the targets; the thickness results have been verified by the Rutherford Backscattering measurements. To evaluate the effects of the thickness on the resolution of the DCE products energy, a Monte Carlo code has been implemented, using the measured thickness and uniformity as input data for the simulation

Evaluation of target non-uniformity and dispersion effects on energy measurement resolution in NUMEN experiment

In the NUMEN Experiment, Double Charge Exchange (DCE) reactions will be studied to get very precise measurements of their cross sections and final state levels. The interest for these reactions lies in the possibility for some nuclides to have DCE with initial and final states identical to those of the Neutrinoless Double β-Decay. To reach a good precision in the energy measurements, high statistics is needed and severe constraints about the target thickness must be satisfied. A 50 μA intense ion beam will provide the desired statistics, while posing the problem of dissipating the massive heat generated in the target. It is therefore necessary to design a suitable cooling system, which must affect the particles' energy as little as possible. Said energy is already influenced by the current setup. The Superconducting Cyclotron (SC) and the MAGNEX Spectrometer introduce an error on the particles' energy by 1/1000th (FWHM value) of its average energy. In the target, the main sources of error are straggling of projectiles and reaction products, and the dispersion effect. Both closely depend on the target thickness, which must be of the order of few hundred nanometres. In addition, the two effects are worsened if the target thickness is not uniform. The solution to these problems has been found by backing the target isotope with relatively thin substrate of Highly Oriented Pyrolytic Graphite (HOPG). Its thermodynamic properties fit the cooling requirements and can be as thin as 450 μg cm-2. The further straggling suffered by the ejectiles is tolerable, falling within the resolution requirements. Samples are deposited by using Electron Beam Evaporation: results obtained for Sn and Te are checked by Scanning Electron Microscopy (SEM). A quantitative evaluation of the samples' thickness has been performed by Alpha-Particle Transmission (APT) and Rutherford Backscattering Spectrometry (RBS) measurements. A Monte Carlo code has been implemented to estimate the ejectiles energy distribution using the experimental measurements as input. Results from characterization and simulations help in optimizing the target thickness and the energy resolution of reaction products

Tests of a cooling system for thin targets submitted to intense ion beams for the numen experiment

The NUMEN experiment, hosted at LNS (Catania, Italy), aims to determine the Nuclear Matrix Elements (NMEs) involved in 0β β decay via heavy-ion induced Double Charge Exchange (DCE) reactions. High intensity beams of about 50 μA and of energies ranging from 15 to 60 MeV/u are necessary, due to the low DCE cross sections and the use of very thin targets (several hundreds of nm) needed to reach the required energy resolution. These intense beams produce a considerable amount of heat inside the target, which can be dissipated by depositing the targets on a highly thermally conductive substrate, HOPG (Highly Oriented Pyrolytic Graphite), and coupling it with a suitable designed target-cooler system. The heat transfer from the beam spot to the cold region has been studied by solving numerically the heat equation to determine the evolution in space and time of the temperature inside the target. According to calculations, the temperatures of most of the target isotopes remain under the melting points. Experimental tests with a laser were initiated to validate the whole cooling system and the calculations

Performance of HPGe Detectors in High Magnetic Fields

A new generation of high-resolution hypernuclear gamma$-spectroscopy experiments with high-purity germanium detectors (HPGe) are presently designed at the FINUDA spectrometer at DAPhiNE, the Frascati phi-factory, and at PANDA, the antiproton proton hadron spectrometer at the future FAIR facility. Both, the FINUDA and PANDA spectrometers are built around the target region covering a large solid angle. To maximise the detection efficiency the HPGe detectors have to be located near the target, and therefore they have to be operated in strong magnetic fields B ~ 1 T. The performance of HPGe detectors in such an environment has not been well investigated so far. In the present work VEGA and EUROBALL Cluster HPGe detectors were tested in the field provided by the ALADiN magnet at GSI. No significant degradation of the energy resolution was found, and a change in the rise time distribution of the pulses from preamplifiers was observed. A correlation between rise time and pulse height was observed and is used to correct the measured energy, recovering the energy resolution almost completely. Moreover, no problems in the electronics due to the magnetic field were observed.Comment: submitted to Nucl. Instrum. Meth. Phys. Res. A, LaTeX, 19 pages, 9 figure