Search results for "rex"
showing 10 items of 701 documents
COMPUTER SIMULATION OF PROFILES OF INTERFACES BETWEEN COEXISTING PHASES: DO WE UNDERSTAND THEIR FINITE SIZE EFFECTS?
2000
Interfaces between coexisting phases are very common in condensed matter physics, and thus many simulations attempt to characterize their properties, in particular, the interfacial tension and the interfacial profile. However, while theory usually deals with the "intrinsic profile", the latter is not a straightforward output of a simulation: The actual profile (observed in simulations and/or experiments!) is broadened by lateral fluctuations. Therefore, in the usual simulation geometry of L × L × L (in three dimensions), where one chooses suitable boundary conditions to stabilize one or two interfaces of (minimal) area L × L, the profile (and in particular the interfacial width) depends on…
Magnetism of metallacrown single-molecule magnets: From a simplest model to realistic systems
2018
Electronic and magnetic properties of molecular nanomagnets are determined by competing energy scales due to the crystal field splitting, the exchange interactions between transition metal atoms, and relativistic effects. We present a comprehensive theory embracing all these phenomena based on first-principles calculations. In order to achieve this goal, we start from the ${\mathrm{FeNi}}_{4}$ cluster as a paradigm. The system can be accurately described on the ab initio level yielding all expected electronic states in a range of multiplicities from 1 to 9, with a ferromagnetic ground state. By adding the spin-orbit coupling between them we obtain the zero-field splitting. This allows to in…
Exchange Interactions I: Mechanisms
1996
A most important phenomenon in molecular magnetism is the exchange interaction between magnetic centers. Its relevance as well as the terms and concepts required to its rationalization were stated long ago by physicists working in the quantum-mechanical theory of magnetism (Heisenberg, Dirac, van Vleck, Anderson, Zener, and many others). Depending on the extent of delocalization of the magnetic moments and on the metallic/non-metallic properties of the solid four kinds of exchange coupling were usually distinguished in the physical literature namely direct exchange, superexchange, indirect exchange and itinerant exchange [1]. The relations of these types of couplings are depicted in Figure …
New limits on neutrino magnetic moments from low energy neutrino data
2016
Here we give a brief review on the current bounds on the general Majorana transition neutrino magnetic moments (TNMM) which cover also the conventional neutrino magnetic moments (NMM). Leptonic CP phases play a key role in constraining TNMMs. While the Borexino experiment is the most sensitive to the TNMM magnitudes, one needs complementary information from reactor and accelerator experiments in order to probe the complex CP phases.
Calibration campaign of the Borexino detector for the search of sterile neutrinos with SOX
2020
Abstract The SOX (Short distance Oscillations with boreXino) experiment aims to investigate possible anomalous oscillatory behaviours in neutrinos, including the existence of sterile neutrinos, by exploiting the very low radioactive background of the Borexino detector. A calibration campaign is crucial to achieve a deeper understanding of the energy response and the spatial reconstruction accuracies of the detector. It will be performed with a suite of low-activity radioactive sources which will map the whole active volume, especially nearby the inner vessel. The calibration points at the border of the active zones will be extremely important to study the neutron detection efficiency. The c…
Search for sterile neutrinos with SOX: Monte Carlo studies of the experiment sensitivity and systematic effects
2020
Abstract Some neutrino experiments reveal anomalous results which can make room for new physics beyond the three-flavor neutrino oscillation model. These hints suggest the existence of sterile neutrinos with mass m <eV. SOX will be a short-baseline disappearance experiment aiming to test this hypotesis, performed with the liquid scintillator detector Borexino at Gran Sasso National Laboratory in Italy [1]. Due to the good energy and position resolution, a light sterile neutrino can create an oscillatory pattern in the signal. The SOX sensitivity, the related analysis and systematics will be briefly discussed.
The Neutrino Magnetic Moment Portal: Cosmology, Astrophysics, and Direct Detection
2020
We revisit the physics of neutrino magnetic moments, focusing in particular on the case where the right-handed, or sterile, neutrinos are heavier (up to several MeV) than the left-handed Standard Model neutrinos. The discussion is centered around the idea of detecting an upscattering event mediated by a transition magnetic moment in a neutrino or dark matter experiment. Considering neutrinos from all known sources, as well as including all available data from XENON1T and Borexino, we derive the strongest up-to-date exclusion limits on the active-to-sterile neutrino transition magnetic moment. We then study complementary constraints from astrophysics and cosmology, performing, in particular,…
Low energy reactions with radioactive ions at REX-ISOLDE-the 9Li + 2H case
2005
19 pages, 12 figures, 2 tables.-- PACS nrs.: 25.60.-t; 25.45.-z; 27.20.+n.-- et al. ISOLDE Collaborattion and REX-ISOLDE Collaboration.
Neutrino electron scattering and electroweak gauge structure: Future tests
1997
Low-energy high-resolution neutrino-electron scattering experiments may play an important role in testing the gauge structure of the electroweak interaction. We propose the use of radioactive neutrino sources (e.g. $^{51}$Cr) in underground experiments such as BOREXINO, HELLAZ and LAMA. As an illustration, we display the sensitivity of these detectors in testing the possible existence of extra neutral gauge bosons, both in the framework of E_6 models and of models with left-right symmetry.
XENON1T signal from transition neutrino magnetic moments
2020
The recent puzzling results of the XENON1T collaboration at few keV electronic recoils could be due to the scattering of solar neutrinos endowed with finite Majorana transition magnetic moments (TMMs). Within such general formalism, we find that the observed excess in the XENON1T data agrees well with this interpretation. The required TMM strengths lie within the limits set by current experiments, such as Borexino, specially when one takes into account a possible tritium contamination.