87 research outputs found
Simple Formula for Nuclear Charge Radius
A new formula for the nuclear charge radius is proposed, dependent on the
mass number (A) and neutron excess (N-Z) in the nucleus. It is simple and it
reproduces all the experimentally available mean square radii and their
isotopic shifts of even--even nuclei much better than other frequently used
relations.Comment: The paper contains 7 pages in LateX and 6 figures (available upon
request) in postscript. Email: [email protected]
Dynamical Dark Energy model parameters with or without massive neutrinos
We use WMAP5 and other cosmological data to constrain model parameters in
quintessence cosmologies, focusing also on their shift when we allow for
non-vanishing neutrino masses. The Ratra-Peebles (RP) and SUGRA potentials are
used here, as examples of slowly or fastly varying state parameter w(a). Both
potentials depend on an energy scale \Lambda. Here we confirm the results of
previous analysis with WMAP3 data on the upper limits on \Lambda, which turn
out to be rather small (down to ~10^{-9} in RP cosmologies and ~10^{-5} for
SUGRA). Our constraints on \Lambda are not heavily affected by the inclusion of
neutrino mass as a free parameter. On the contrary, when the neutrino mass
degree of freedom is opened, significant shifts in the best-fit values of other
parameters occur.Comment: 9 pages, 3 figures, submitted to JCA
Constraints on neutrino masses from WMAP5 and BBN in the lepton asymmetric universe
In this paper, we put constraints on neutrino properties such as mass
and degeneracy parameters from WMAP5 data and light element
abundances by using a Markov chain Monte Carlo (MCMC) approach. In order to
take consistently into account the effects of the degeneracy parameters, we run
the Big Bang Nucleosynthesis code for each value of and the other
cosmological parameters to estimate the Helium abundance, which is then used to
calculate CMB anisotropy spectra instead of treating it as a free parameter. We
find that the constraint on is fairly robust and does not vary very
much even if the lepton asymmetry is allowed, and is given by ().Comment: 19 pages, 7 figures, 5 table
Neutrinos as the messengers of CPT violation
CPT violation has the potential to explain all three existing neutrino anomalies without enlarging the neutrino sector. CPT violation in the Dirac mass terms of the three neutrino flavors preserves Lorentz invariance, but generates independent masses for neutrinos and antineutrinos. This specific signature is strongly motivated by braneworld scenarios with extra dimensions, where neutrinos are the natural messengers for Standard Model physics of CPT violation in the bulk. A simple model of maximal CPT violation is sufficient to explain the exisiting neutrino data quite neatly, while making dramatic predictions for the upcoming KamLAND and MiniBooNE experiments. Furthermore we obtain a promising new mechanism for baryogenesis
Neutrino mass from cosmology: Impact of high-accuracy measurement of the Hubble constant
Non-zero neutrino mass would affect the evolution of the Universe in
observable ways, and a strong constraint on the mass can be achieved using
combinations of cosmological data sets. We focus on the power spectrum of
cosmic microwave background (CMB) anisotropies, the Hubble constant H_0, and
the length scale for baryon acoustic oscillations (BAO) to investigate the
constraint on the neutrino mass, m_nu. We analyze data from multiple existing
CMB studies (WMAP5, ACBAR, CBI, BOOMERANG, and QUAD), recent measurement of H_0
(SHOES), with about two times lower uncertainty (5%) than previous estimates,
and recent treatments of BAO from the Sloan Digital Sky Survey (SDSS). We
obtained an upper limit of m_nu < 0.2eV (95% C.L.), for a flat LambdaCDM model.
This is a 40% reduction in the limit derived from previous H_0 estimates and
one-third lower than can be achieved with extant CMB and BAO data. We also
analyze the impact of smaller uncertainty on measurements of H_0 as may be
anticipated in the near term, in combination with CMB data from the Planck
mission, and BAO data from the SDSS/BOSS program. We demonstrate the
possibility of a 5 sigma detection for a fiducial neutrino mass of 0.1eV or a
95% upper limit of 0.04eV for a fiducial of m_nu = 0eV. These constraints are
about 50% better than those achieved without external constraint. We further
investigate the impact on modeling where the dark-energy equation of state is
constant but not necessarily -1, or where a non-flat universe is allowed. In
these cases, the next-generation accuracies of Planck, BOSS, and 1% measurement
of H_0 would all be required to obtain the limit m_nu < 0.05 - 0.06eV (95%
C.L.) for the fiducial of m_nu = 0eV. The independence of systematics argues
for pursuit of both BAO and H_0 measurements.Comment: 22 pages, 6 figures, 12 table
Effect of a sweeping conductive wire on electrons stored in the Penning trap between the KATRIN spectrometers
The KATRIN experiment is going to search for the mass of the electron
antineutrino down to 0.2 eV/c^2. In order to reach this sensitivity the
background rate has to be understood and minimised to 0.01 counts per second.
One of the background sources is the unavoidable Penning trap for electrons due
to the combination of the electric and magnetic fields between the pre- and the
main spectrometer at KATRIN. In this article we will show that by sweeping a
conducting wire periodically through such a particle trap stored particles can
be removed, an ongoing discharge in the trap can be stopped, and the count rate
measured with a detector looking at the trap is reduced.Comment: Final version published in EPJ A, 14 pages, 19 figures (21 files
Effects of Short Range Correlations on Ca Isotopes
The effect of Short Range Correlations (SRC) on Ca isotopes is studied using
a simple phenomenological model. Theoretical expressions for the charge
(proton) form factors, densities and moments of Ca nuclei are derived. The role
of SRC in reproducing the empirical data for the charge density differences is
examined. Their influence on the depletion of the nuclear Fermi surface is
studied and the fractional occupation probabilities of the shell model orbits
of Ca nuclei are calculated. The variation of SRC as function of the mass
number is also discussed.Comment: 11 pages (RevTex), 6 Postscript figures available upon request at
[email protected] Physical Review C in prin
Neutrinoless double-beta decay and seesaw mechanism
From the standard seesaw mechanism of neutrino mass generation, which is
based on the assumption that the lepton number is violated at a large
(~10exp(+15) GeV) scale, follows that the neutrinoless double-beta decay is
ruled by the Majorana neutrino mass mechanism. Within this notion, for the
inverted neutrino-mass hierarchy we derive allowed ranges of half-lives of the
neutrinoless double-beta decay for nuclei of experimental interest with
different sets of nuclear matrix elements. The present-day results of the
calculation of the neutrinoless double-beta decay nuclear matrix elements are
briefly discussed. We argue that if neutrinoless double-beta decay will be
observed in future experiments sensitive to the effective Majorana mass in the
inverted mass hierarchy region, a comparison of the derived ranges with
measured half-lives will allow us to probe the standard seesaw mechanism
assuming that future cosmological data will establish the sum of neutrino
masses to be about 0.2 eV.Comment: Some changes in sections I, II, IV, and V; two new figures;
additional reference
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