A key component of the phase diagram of many iron-based superconductors and electron-doped cuprates is believed to be a quantum critical point (QCP), delineating the onset of antiferromagnetic ...spin-density wave order in a quasi-two-dimensional metal. The universality class of this QCP is believed to play a fundamental role in the description of the proximate non-Fermi liquid behavior and superconducting phase. A minimal model for this transition is the O(3) spin-fermion model. Despite many efforts, a definitive characterization of its universal properties is still lacking. Here, we numerically study the O(3) spin-fermion model and extract the scaling exponents and functional form of the static and zero-momentum dynamical spin susceptibility. We do this using a Hybrid Monte Carlo (HMC) algorithm with a novel auto-tuning procedure, which allows us to study unprecedentedly large systems of 80 × 80 sites. We find a strong violation of the Hertz-Millis form, contrary to all previous numerical results. Furthermore, the form that we do observe provides good evidence that the universal scaling is actually governed by the analytically tractable fixed point discovered near perfect "hot-spot'" nesting, even for a larger nesting window. Our predictions can be directly tested with neutron scattering. Additionally, the HMC method we introduce is generic and can be used to study other fermionic models of quantum criticality, where there is a strong need to simulate large systems.
In this paper, we present the extensive characterization of large-area silicon carbide-based UV sensors candidate for outdoors spectroscopic applications of gas or liquid. The proposed SiC Schottky ...devices exhibit a dark current density of 0.12 nA/cm 2 at 15 V, a 0.12-A/W responsivity at 300 nm, optimal visible blindness, and a switching time of ~190 ns. Effects of temperature on the sensor performance, of crucial interest for outdoors applications, are also examined in the range from -20 °C to 90 °C.
We report on the structure and performance of 4H-SiC p + -n APDs fabricated in a fully planar technology. A dark current density lower than 10 nA/cm 2 at 30-V reverse bias and a breakdown voltage of ...88 V were observed. A gain as high as 10 5 was measured at 94-V reverse bias, confirming the avalanche multiplication working condition. The maximum responsivity value was measured at 270 nm, increasing from 0.06 A/W (QE = 29%) at 0-V bias to 0.10 A/W (QE of about 45%) at 30-V reverse bias.
In the direct searches for Weakly Interacting Massive Particles (WIMPs) as Dark Matter candidates, the sensitivity of the detector to the incom- ing particle direction could provide a smoking gun ...signature for an interesting event. The SCENE collaboration firstly suggested the possible directional de- pendence of a dual-phase argon Time Projection Chamber through the columnar recombination effect. The Recoil Directionality project (ReD) within the Global Argon Dark Matter Collaboration aims to characterize the light and charge re- sponse of a liquid Argon dual-phase TPC to neutron-induced nuclear recoils to probe for the hint by SCENE. In this work, the directional sensitivity of the de- tector in the energy range of interest for WIMPs (20-100 keV) is investigated with a data-driven analysis involving a Machine Learning algorithm.
A compton spectrometer to monitor the ELI-NP gamma beam energy Borgheresi, R.; Adriani, O.; Albergo, S. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
08/2019, Letnik:
936
Journal Article
Recenzirano
The ELI-NP facility (Extreme Light Infrastructure-Nuclear Physics) will deliver an intense and almost monochromatic gamma beam for frontier research in nuclear physics. Peculiar devices and ...techniques have been developed to measure and monitor the beam parameters during the commissioning and the operational phase. In this work we will present the Compton Spectrometer, designed to reconstruct the γ beam energy spectrum, by measuring the energy and the position of Compton scattered electrons. The energy and the angle of the scattered electron are measured by a High Purity Germanium detector and a double sided silicon strip detector. The associated photon is detected in coincidence with the electron by barium fluoride (BaF2) crystals for trigger purpose. In this work we report the status of the characterization carried out on the detectors composing the spectrometer.
•Compton spectrometer, designed to reconstruct the ELI-NP γ beam energy spectrum.•Energy of the scattered e− measured with a High Purity Germanium detector.•Scattered angle determined by a double sided silicon strip detector.•Scattered photon detected in coincidence by BaF2 crystals for trigger purpose.•Tests carried out on the components of the spectrometer are presented.
Abstract
Directional sensitivity to nuclear recoils would provide a smoking gun for a possible discovery of dark matter in the form of WIMPs (Weakly Interacting Massive Particles). A hint of ...directional dependence of the response of a dual-phase argon Time Projection Chamber (TPC) was found in the SCENE experiment. Given the potential importance of such a capability in the framework of dark matter searches, a new dedicated experiment, ReD (Recoil Directionality), was designed by the Global Argon Dark Matter Collaboration, in order to scrutinise this hint. A small dual-phase argon TPC was irradiated with neutrons produced by the p(
7
Li,
7
Be)n reaction using the 15 MV TANDEM accelerator of the INFN - Laboratori Nazionali del Sud, Catania, Italy, so as to produce argon nuclear recoils in the range (20 - 100) keV of interest for dark matter searches. Energy and direction of nuclear recoils are inferred by the detection of the elastically-scattered neutron by a set of scintillation detectors. Events were selected by gating of the associated
7
Be, which is detected by a telescope of Si detectors.
Aria is a plant hosting a Formula omitted cryogenic isotopic distillation column, the tallest ever built, which is being installed in a mine shaft at Carbosulcis S.p.A., Nuraxi-Figus (SU), Italy. ...Aria is one of the pillars of the argon dark-matter search experimental program, lead by the Global Argon Dark Matter Collaboration. It was designed to reduce the isotopic abundance of Formula omitted in argon extracted from underground sources, called Underground Argon (UAr), which is used for dark-matter searches. Indeed, Formula omitted is a Formula omitted-emitter of cosmogenic origin, whose activity poses background and pile-up concerns in the detectors. In this paper, we discuss the requirements, design, construction, tests, and projected performance of the plant for the isotopic cryogenic distillation of argon. We also present the successful results of the isotopic cryogenic distillation of nitrogen with a prototype plant.
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