Scientific Open-access Literature Archive and Repository
Not a member yet
16397 research outputs found
Sort by
Imaging of the solar atmosphere in the centimetre-millimetre band through single-dish observations
Get PDFSolar observations offer both a rich interdisciplinary laboratory on fundamental astrophysics and precious tools for Space Weather applications. The involved plasma processes determine a complex radio emission picture that could be efficiently explored through single-dish imaging at high frequencies. In particular, mapping the brightness temperature of the free-free radio emission in the centimetre and millimetre range is an effective tool to characterise the vertical structure of the solar atmosphere. We are performing continuum imaging of the solar chromosphere in K-band (18-26.5 GHz, spatial resolution ∼1 arcmin) with the 32-m diameter Medicina radio telescope and with the 64-m diameter Sardinia Radio Telescope (SRT), as a first scientific demonstration test for the potentialities of Italian single-dish antennas in this field. This will also be useful for the assessment of observation parameters aiming at studying in detail the chromospheric brightness temperature of the quiet Sun, the solar flares, active regions and the sunspots, at high radio frequencies. These early observations proved that our antennas and Kband receivers are stable during solar pointing and could provide full mapping of the solar disk in ∼1 hour exposure using state-of-the-art imaging techniques
Isospin-symmetry breaking in nuclear structure
Get PDFThe breaking of the isospin symmetry is discussed from the point of view of the nuclear shell-model. The accuracy of the theoretical framework is demonstrated on the description of the isobaric multiplet splittings. The use of phenomenological versus realistic interactions is discussed. We demonstrate the relevance of the theoretical description for isospin-forbidden processes. The developed formalism is important for the calculation of isospin-symmetry breaking corrections to the weak-interaction process on nuclei, and it can provide missing information on the structure of proton-rich nuclei relevant for astrophysics applications
The NUMEN Project @ LNS: Status and perspectives
Get PDFThe NUMEN project aims at accessing experimentally driven information on Nuclear Matrix Elements (NME) involved in the half-life of the neutrinoless double beta decay (0νββ), by high-accuracy measurements of the cross sections of Heavy Ion (HI) induced Double Charge Exchange (DCE) reactions. Particular attention is given to the (18O,18Ne) and (20Ne,20O) reactions as tools for β+β+ and β−β− decays, respectively. First evidence about the possibility to get quantitative information about NME from experiments is found for both kind of reactions. In the experiments, performed at INFN - Laboratory Nazionali del Sud (LNS) in Catania, the beams are accelerated by the Superconducting Cyclotron (CS) and the reaction products are detected by the MAGNEX magnetic spectrometer. The measured cross sections are challengingly low, limiting the present exploration to few selected isotopes of interest in the context of typically low-yield experimental runs. A major upgrade of the LNS facility is foreseen in order to increase the experimental yield of at least two orders of magnitude, thus making feasible a systematic study of all the cases of interest. Frontiers technologies are going to be developed, to this purpose, for the accelerator and the detection systems. In parallel, advanced theoretical models will be developed in order to extract the nuclear structure information from the measured cross sections
Time of flight identification with FAZIA
Get PDFThis contribution reports on the time of flight implementation in the FAZIA Si-Si-CsI(Tl) telescopes, focusing on the basic ideas of the method and on some preliminary results from recent experiments at LNS
Charge Symmetry Breaking in strange nuclei
Get PDFCharge symmetry breaking in Λ-hypernuclei manifests in a difference between the Λ separation energies in mirror hypernuclei. For the s−shell this difference appears to be sizeable, while for p−shell experimental results suggest a
much weaker effect. In this paper an updated experimental review is given
Study of multi-neutron emission in the β-decay of 11Li
Get PDFThe kinematics of two-neutron emission following the β-decay of 11Li was investigated for the first time by detecting the two neutrons in coincidence and by measuring their angle and energy. An array of liquid-scintillator neutron detectors was used to reject cosmic-ray and γ-ray backgrounds by pulse-shape discrimination. Cross-talk events in which two detectors are fired by a single neutron
were rejected using a filter tested on the β-1n emitter 9Li. A large cross-talk rejection rate is obtained (> 95%) over most of the energy range of interest. Application
to 11Li data leads to a significant number of events interpreted as β-2n decay. A discrete neutron line at ≈ 2 MeV indicates sequential two-neutron emission, possibly
from the unbound state at 10.6 MeV excitation energy in 11Be
New results on 13C structure from α + 9Be low energy reactions
Get PDFIn the framework of clustering in light nuclei, 13C plays a crucial role since it can show a pronounced 3α + n structure. Several theoretical models predicted the existence of molecular rotational bands characterized by large moment of inertia, typical of highly clusterized structures. In this paper, we investigated α + 9Be reactions at low incident energies with the aim of improving our knowledge of 13C spectroscopy by means of a comprehensive R-matrix fit of several reaction channels. Such procedure leads to a firmer determination of Jπ assignments for several states and to a better determination of the branching ratio of each reaction
channel
Recent results on charmed meson decays at BESIII
Get PDFThe BESIII Experiment at the Beijing Electron Positron Collider (BEPCII) has accumulated the world largest e+e− annihilation samples at 3.773 GeV with 2.93 fb−1 for D0(±) and 4.178 GeV with 3.19 fb−1 for D± s , which provide a clean background to study charmed meson decays. In this proceeding, we present the recent results of the study of D meson decays at BESII
First measurements of the analyzing powers of the proton-deuteron break-up reaction at large proton scattering angles
Get PDFA measurement of the analyzing powers for the 2H(p, pp )n break-up reaction was carried out at KVI exploiting a polarized-proton beam at 135 MeV. In this work, we extended the earlier measurements that were done for kinematical
configurations at small proton scattering angles to large angles. The results are compared with theoretical calculations based on a two-nucleon (NN) potential alone or
combined with a three-nucleon (3N) potential. The theoretical calculations describe the main features of the measured distributions, but none of them can reproduce
the details. This indicates the need for further development of the 3N force models
Achievements and challenges in understanding nucleon-deuteron reactions
Get PDFResults on three-nucleon (3N) elastic scattering below the pion production threshold are discussed with an emphasis on a need for a three-nucleon force (3NF). The large discrepancies found between a theory based on numerical
solutions of 3N Faddeev equations with (semi) phenomenological nucleon-nucleon (NN) potentials only and data point to the need for 3NF’s. This notion is supported by the fact that another possible reason for the discrepancies in elastic nucleondeuteron (Nd) scattering, relativistic effects, turned out to be small. Results based
on a new generation of chiral NN forces (up to N4LO) alone or combined with N2LO 3NF support predictions found with standard interactions. To resolve higher energy discrepancies found in nucleon-deuteron (Nd) reactions requires application of a chiral 3NF up to at least N3LO order of chiral expansion