10,531 research outputs found
On the asymmetry of Gamow-Teller beta-decay rates in mirror nuclei in relation with second-class currents
The theoretical evaluation of major nuclear structure effects on the
asymmetry of allowed Gamow-Teller beta-decay rates in light mirror nuclei is
presented. The calculations are performed within the shell model, using
empirical isospin-nonconserving interaction and realistic Woods-Saxon radial
wave functions. The revised treatment of p-shell nuclei is supplemented by
systematic calculations for sd-shell nuclei and compared to experimental
asymmetries when available. The results are important in connection with the
possible existence of second-class currents in the weak interaction.Comment: 16 pages, 6 figure
Untangling supernova-neutrino oscillations with beta-beam data
Recently, we suggested that low-energy beta-beam neutrinos can be very useful
for the study of supernova neutrino interactions. In this paper, we examine the
use of a such experiment for the analysis of a supernova neutrino signal. Since
supernova neutrinos are oscillating, it is very likely that the terrestrial
spectrum of supernova neutrinos of a given flavor will not be the same as the
energy distribution with which these neutrinos were first emitted. We
demonstrate the efficacy of the proposed method for untangling multiple
neutrino spectra. This is an essential feature of any model aiming at gaining
information about the supernova mechanism, probing proto-neutron star physics,
and understanding supernova nucleosynthesis, such as the neutrino process and
the r-process. We also consider the efficacy of different experimental
approaches including measurements at multiple beam energies and detector
configurations.Comment: 13 pages, 11 figures, accepted for publication in Phys. Rev.
A dynamical collective calculation of supernova neutrino signals
We present the first calculations with three flavors of collective and shock
wave effects for neutrino propagation in core-collapse supernovae using
hydroynamical density profiles and the S matrix formalism. We explore the
interplay between the neutrino-neutrino interaction and the effects of multiple
resonances upon the time signal of positrons in supernova observatories. A
specific signature is found for the inverted hierarchy and a large third
neutrino mixing angle and we predict, in this case, a dearth of lower energy
positrons in Cherenkov detectors midway through the neutrino signal and the
simultaneous revelation of valuable information about the original fluxes. We
show that this feature is also observable with current generation neutrino
detectors at the level of several sigmas.Comment: 4 pages, 5 figure
What about a beta-beam facility for low energy neutrinos?
A novel method to produce neutrino beams has recently been proposed : the
beta-beams. This method consists in using the beta-decay of boosted radioactive
nuclei to obtain an intense, collimated and pure neutrino beam. Here we propose
to exploit the beta-beam concept to produce neutrino beams of low energy. We
discuss the applications of such a facility as well as its importance for
different domains of physics. We focus, in particular, on neutrino-nucleus
interaction studies of interest for various open issues in astrophysics,
nuclear and particle physics. We suggest possible sites for a low energy
beta-beam facility.Comment: 4 pages, 1 figur
VHE gamma-ray observations of the young synchrotron-dominated SNRs G1.9+0.3 and G330.2+1.0 with H.E.S.S
Supernova remnants (SNRs) are widely considered to be accelerators of cosmic
rays (CR). They are also expected to produce very-high-energy (VHE;
GeV) gamma rays through interactions of high-energy particles with the
surrounding medium and photon fields. They are, therefore, promising targets
for observations with ground-based imaging atmospheric Cherenkov telescopes
like the H.E.S.S. telescope array. VHE gamma-ray emission has already been
discovered from a number of SNRs, establishing them as a prominent source class
in the VHE domain. Of particular interest are the handful of SNRs whose X-ray
spectra are dominated by non-thermal synchrotron emission, such as the VHE
gamma-ray emitters RX J0852.0-4622 (Vela Jr.) and RX J1713-3946. The shell-type
SNRs G1.9+0.3 and G330.2+1.0 also belong to this subclass and are further
notable for their young ages ( kyr), especially G1.9+0.3, which was
recently determined to be the youngest SNR in the Galaxy ( yr). These
unique characteristics motivated investigations with H.E.S.S. to search for VHE
gamma rays. The results of the H.E.S.S. observations and analyses are
presented, along with implications for potential particle acceleration
scenarios.Comment: ICRC 2011 proceedings, 4 pages, 2 figures, 3 table
Influence of Noise on Force Measurements
We demonstrate how the ineluctable presence of thermal noise alters the
measurement of forces acting on microscopic and nanoscopic objects. We quantify
this effect exemplarily for a Brownian particle near a wall subjected to
gravitational and electrostatic forces. Our results demonstrate that the force
measurement process is prone to artifacts if the noise is not correctly taken
into account.Comment: 4 Pages, 4 Figures, Accepte
Microscopic description of Coulomb and nuclear excitation of multiphonon states in Ca + Ca collisions
We calculate the inelastic scattering cross sections to populate one- and
two-phonon states in heavy ion collisions with both Coulomb and nuclear
excitations. Starting from a microscopic approach based on RPA, we go beyond it
in order to treat anharmonicities and non-linear terms in the exciting field.
These anharmonicities and non-linearities are shown to have important effects
on the cross sections both in the low energy part of the spectrum and in the
energy region of the Double Giant Quadrupole Resonance. By properly introducing
an optical potential the inelastic cross section is calculated semiclassically
by integrating the excitation probability over all impact parameters. A
satisfactory agreement with the experimental results is obtained.Comment: 20 pages, 2 figures, revtex, to be published in Phys. Rev.
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