1,010 research outputs found
Neutrino cross-section measurement with neutrinos from muon decay
In this paper we stress the idea that new, more precise neutrino
cross-sections measurements at low energies will be necessary to improve the
results of future big neutrino detectors, which will be dominated by the
contribution of the systematic errors. The use of a muon beam instead of the
traditional pion beams is proposed. This choice allows the simultaneous
measurement of both, numu and nue interactions and the two helicities, in a
clean environment and with a precise knowledge of the beam flux. We show that
with approx 10^{15} mu's/year and a moderate mass detector (approx 100 tons)
placed close to the muon storage ring, precisions of the order of 10% in
sigma(nu) (E_nu bin size of 100 MeV) can be reached for neutrino energies below
2 GeV.Comment: 4 pages, proceeding to NUFACT0
Search for uncharged faster than light particles
Searching for uncharged particles with spacelike four momentum traveling faster than ligh
The Mass-Richness Relation of MaxBCG Clusters from Quasar Lensing Magnification using Variability
Accurate measurement of galaxy cluster masses is an essential component not
only in studies of cluster physics, but also for probes of cosmology. However,
different mass measurement techniques frequently yield discrepant results. The
SDSS MaxBCG catalog's mass-richness relation has previously been constrained
using weak lensing shear, Sunyaev-Zeldovich (SZ), and X-ray measurements. The
mass normalization of the clusters as measured by weak lensing shear is >~25%
higher than that measured using SZ and X-ray methods, a difference much larger
than the stated measurement errors in the analyses. We constrain the
mass-richness relation of the MaxBCG galaxy cluster catalog by measuring the
gravitational lensing magnification of type I quasars in the background of the
clusters. The magnification is determined using the quasars' variability and
the correlation between quasars' variability amplitude and intrinsic
luminosity. The mass-richness relation determined through magnification is in
agreement with that measured using shear, confirming that the lensing strength
of the clusters implies a high mass normalization, and that the discrepancy
with other methods is not due to a shear-related systematic measurement error.
We study the dependence of the measured mass normalization on the cluster halo
orientation. As expected, line-of-sight clusters yield a higher normalization;
however, this minority of haloes does not significantly bias the average
mass-richness relation of the catalog.Comment: 9 pages. Accepted for publication in Ap
The QUEST Data Processing Software Pipeline
A program that we call the QUEST Data Processing Software Pipeline has been
written to process the large volumes of data produced by the QUEST camera on
the Samuel Oschin Schmidt Telescope at the Palomar Observatory. The program
carries out both aperture and PSF photometry, combines data from different
repeated observations of the same portion of sky, and produces a Master Object
Catalog. A rough calibration of the data is carried out. This program, as well
as the calibration procedures and quality checks on the output are described.Comment: 17 pages, 1 table, 8 figure
Blazar Optical Variability in the Palomar-QUEST Survey
We study the ensemble optical variability of 276 FSRQs and 86 BL Lacs in the
Palomar-QUEST Survey with the goal of searching for common fluctuation
properties, examining the range of behavior across the sample, and
characterizing the appearance of blazars in such a survey so that future work
can more easily identify such objects. The survey, which covers 15,000 square
degrees multiple times over 3.5 years, allows for the first ensemble blazar
study of this scale. Variability amplitude distributions are shown for the FSRQ
and BL Lac samples for numerous time lags, and also studied through structure
function analyses. Individual blazars show a wide range of variability
amplitudes, timescales, and duty cycles. Of the best sampled objects, 35% are
seen to vary by more than 0.4 magnitudes; for these, the fraction of
measurements contributing to the high amplitude variability ranges constantly
from about 5% to 80%. Blazar variability has some similarities to that of type
I quasars but includes larger amplitude fluctuations on all timescales. FSRQ
variability amplitudes are particularly similar to those of QSOs on timescales
of several months, suggesting significant contributions from the accretion disk
to the variable flux at these timescales. Optical variability amplitudes are
correlated with the maximum apparent velocities of the radio jet for the subset
of FSRQs with MOJAVE VLBA measurements, implying that the optically variable
flux's strength is typically related to that of the radio emission. We also
study CRATES radio-selected FSRQ candidates, which show similar variability
characteristics to known FSRQs; this suggests a high purity for the CRATES
sample.Comment: 29 pages, 12 figures. Accepted for publication in Ap
A Possible Origin of Dark Energy
We discuss the possibility that the existence of dark energy may be due to
the presence of a spin zero field , either elementary or composite. In
the presence of other matter field, the transformation
constant can generate a negative pressure, like the cosmological constant. In
this picture, our universe can be thought as a very large bag, similar to the
much smaller MIT bag model for a single nucleon.Comment: 4 pages, no figure, typos correcte
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