4,126 research outputs found
WIMPs search by scintillators: possible strategy for annual modulation search with large-mass highly-radiopure NaI(Tl)
The DAMA experiments are running deep underground in the Gran Sasso National
Laboratory. Several interesting results have been achieved so far. Here a
maximum likelihood method to search for the WIMP annual modulation signature is
discussed and applied to a set of preliminary test data collected with large
mass highly radiopure NaI(Tl) detectors. Various related technical arguments
are briefly addressed.Comment: 6 pages, 4 figures, LaTex. Contributed paper to TAUP97; to appear in
the Proceeding
New particle detectors (and possible R&D’s) of interest in NON-accelerator physics
This paper shortly summarizes some of the many R&D activities in the field of NON-accelerator physics. New conceptual detectors, read-outs and associated electronics are presented for a wide scenarios of applications in physics, such as rare events (dark matter, double beta decay, . . .) investigations, neutrino physics, cosmic rays experiments (either at ground level and in the space), gravitational waves and general physics studies
A Pilot Survey for CIII] Emission in the Reionization Era: Gravitationally-Lensed z Galaxies in the Frontier Fields Cluster Abell 2744
We report results of a search for CIII] 1907,1909 {\AA}
emission using Keck's MOSFIRE spectrograph in a sample of 7
candidates () lensed by the Hubble Frontier Field cluster Abell 2744.
Earlier work has suggested the promise of using the CIII] doublet for redshift
confirmation of galaxies in the reionization era given
(1216 {\AA}) is likely attenuated by the neutral intergalactic medium.
The primary challenge of this approach is the feasibility of locating CIII]
emission without advanced knowledge of the spectroscopic redshift. With an
integration time of 5 hours in the H-band, we reach a median flux
limit (in between the skylines) of ergs cm
sec but no convincing CIII] emission was found. We also incorporate
preliminary measurements from two other CLASH/HFF clusters in which, similarly,
no line was detected, but these were observed to lesser depth. Using the known
distribution of OH emission and the photometric redshift likelihood
distribution of each lensed candidate, we present statistical upper limits on
the mean total CIII] rest-frame equivalent width for our sample.
For a signal/noise ratio of 5, we estimate the typical CIII] doublet rest-frame
equivalent width is, with 95\% confidence, {\AA}. Although consistent
with the strength of earlier detections in brighter objects at ,
our study illustrates the necessity of studying more luminous or
strongly-lensed examples prior to the launch of the James Webb Space Telescope.Comment: 7 pages, 4 figures, 1 table; accepted for publication in ApJ Letter
MOSFIRE Absorption Line Spectroscopy of z > 2 Quiescent Galaxies: Probing a Period of Rapid Size Growth
Using the MOSFIRE near-infrared multi-slit spectrograph on the Keck 1
Telescope, we have secured high signal-to-noise ratio absorption line spectra
for six massive galaxies with redshift 2 < z < 2.5. Five of these galaxies lie
on the red sequence and show signatures of passive stellar populations in their
rest-frame optical spectra. By fitting broadened spectral templates we have
determined stellar velocity dispersions and, with broad-band HST and Spitzer
photometry and imaging, stellar masses and effective radii. Using this enlarged
sample of galaxies we confirm earlier suggestions that quiescent galaxies at z
> 2 have small sizes and large velocity dispersions compared to local galaxies
of similar stellar mass. The dynamical masses are in very good agreement with
stellar masses (log Mstar/Mdyn = -0.02 +/- 0.03), although the average
stellar-to-dynamical mass ratio is larger than that found at lower redshift
(-0.23 +/- 0.05). By assuming evolution at fixed velocity dispersion, not only
do we confirm a surprisingly rapid rate of size growth but we also consider the
necessary evolutionary track on the mass-size plane and find a slope alpha =
dlogR / dlogM > ~2 inconsistent with most numerical simulations of minor
mergers. Both results suggest an additional mechanism may be required to
explain the size growth of early galaxies.Comment: Updated to match the published versio
Multigap RPC time resolution to 511 keV annihilation photons
The time resolution of Multigap Resistive Plate Counters (MRPCs) to keV
gamma rays has been investigated using a Na source and four detectors.
The MRPCs time resolution has been derived from the Time-of-Flight information,
measured from pairs of space correlated triggered events. A GEANT4 simulation
has been performed to analyze possible setup contributions and to support
experimental results. A time resolution (FWHM) of ps and ps has
been measured for a single MRPC with four m gas gaps by considering
respectively one and two independent pairs of detectors.Comment: 25 pages, 14 figure
Pre-implantation mouse embryos cultured In vitro under different oxygen concentrations show altered ultrastructures
Abstract
Assisted Reproductive Technologies routinely utilize different culture media and oxygen (O2) concentrations to culture human embryos. Overall, embryos cultured under physiological O2 tension (5%) have improved development compared to embryos cultured under atmospheric O2 conditions (20%). The mechanisms responsible for this remain unclear. This study aimed to evaluate the effect of physiologic (5%) or atmospheric O2 (20%) tension on the microscopic ultrastructure of pre-implantation mouse embryos using Transmission Electron Microscopy (TEM). Embryos flushed out of the uterus after natural mating were used as the control. For use as the control, 2-cells, 4-cells, morulae, and blastocysts were flushed out of the uterus after natural fertilization. In vitro fertilization (IVF) was performed using potassium simplex optimized medium (KSOM) under different O2 tensions (5% and 20%) until the blastocyst stage. After collection, embryos were subjected to the standard preparative for light microscopy (LM) and TEM. We found that culture in vitro under 5% and 20% O2 results in an increase of vacuolated shaped mitochondria, cytoplasmic vacuolization and presence of multi-vesicular bodies at every embryonic stage. In addition, blastocysts generated by IVF under 5% and 20% O2 showed a lower content of heterochromatin, an interruption of the trophectodermal and inner cell mass cell membranes, an increased density of residual bodies, and high levels of glycogen granules in the cytoplasm. In conclusion, this study suggests that in vitro culture, particularly under atmospheric O2 tension, causes stage-specific changes in preimplantation embryo ultrastructure. In addition, atmospheric (20%) O2 is associated with increased alterations in embryonic ultrastructure; these changes may explain the reduced embryonic development of embryos cultured with 20% O2
DAMA annual modulation effect and asymmetric mirror matter
The long-standing model-independent annual modulation effect measured by DAMA
Collaboration is examined in the context of asymmetric mirror dark matter,
assuming that dark atoms interact with target nuclei in the detector via
kinetic mixing between mirror and ordinary photons, both being massless. The
relevant ranges for the kinetic mixing parameter are obtained taking into
account various existing uncertainties in nuclear and particle physics
quantities as well as characteristic density and velocity distributions of dark
matter in different halo models.Comment: 27 pages, 5 figures, 2 tables; version in publication on Eur. Phys.
J.
Observations of annual modulation in direct detection of relic particles and light neutralinos
The long-standing model-independent annual modulation effect measured by the
DAMA Collaboration, which fulfills all the requirements of a dark matter annual
modulation signature, and the new result by the CoGeNT experiment that shows a
similar behavior are comparatively examined under the hypothesis of a dark
matter candidate particle interacting with the detectors' nuclei by a coherent
elastic process. The ensuing physical regions in the plane of the dark
matter-particle mass versus the dark matter-particle nucleon cross-section are
derived for various galactic halo models and by taking into account the impact
of various experimental uncertainties. It is shown that the DAMA and the CoGeNT
regions agree well between each other and are well fitted by a supersymmetric
model with light neutralinos which satisfies all available experimental
constraints, including the most recent results from CMS and ATLAS at the CERN
Large Hadron Collider.Comment: 13 pages, 7 figure
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