14,014 research outputs found
On the gravitational wave background from compact binary coalescences in the band of ground-based interferometers
This paper reports a comprehensive study on the gravitational wave (GW)
background from compact binary coalescences. We consider in our calculations
newly available observation-based neutron star and black hole mass
distributions and complete analytical waveforms that include post-Newtonian
amplitude corrections. Our results show that: (i) post-Newtonian effects cause
a small reduction in the GW background signal; (ii) below 100 Hz the background
depends primarily on the local coalescence rate and the average chirp
mass and is independent of the chirp mass distribution; (iii) the effects of
cosmic star formation rates and delay times between the formation and merger of
binaries are linear below 100 Hz and can be represented by a single parameter
within a factor of ~ 2; (iv) a simple power law model of the energy density
parameter up to 50-100 Hz is sufficient to be used
as a search template for ground-based interferometers. In terms of the
detection prospects of the background signal, we show that: (i) detection (a
signal-to-noise ratio of 3) within one year of observation by the Advanced LIGO
detectors (H1-L1) requires a coalescence rate of for binary neutron stars (binary black holes); (ii) this limit on
could be reduced 3-fold for two co-located detectors, whereas the
currently proposed worldwide network of advanced instruments gives only ~ 30%
improvement in detectability; (iii) the improved sensitivity of the planned
Einstein Telescope allows not only confident detection of the background but
also the high frequency components of the spectrum to be measured. Finally we
show that sub-threshold binary neutron star merger events produce a strong
foreground, which could be an issue for future terrestrial stochastic searches
of primordial GWs.Comment: A few typos corrected to match the published version in MNRA
SUSY-Breaking Parameters from RG Invariants at the LHC
We study Renormalization Group invariant (RGI) quantities in the Minimal
Supersymmetric Standard Model and show that they are a powerful and simple
instrument for testing high scale models of supersymmetry (SUSY)-breaking. For
illustration, we analyze the frameworks of minimal and general gauge mediated
(MGM and GGM) SUSY-breaking, with additional arbitrary soft Higgs mass
parameters at the messenger scale. We show that if a gaugino and two first
generation sfermion soft masses are determined at the LHC, the RGIs lead to MGM
sum rules that yield accurate predictions for the other gaugino and first
generation soft masses. RGIs can also be used to reconstruct the fundamental
MGM parameters (including the messenger scale), calculate the hypercharge
D-term, and find relationships among the third generation and Higgs soft
masses. We then study the extent to which measurements of the full first
generation spectrum at the LHC may distinguish different SUSY-breaking
scenarios. In the case of MGM, although most deviations violate the sum rules
by more than estimated experimental errors, we find a 1-parameter family of GGM
models that satisfy the constraints and produce the same first generation
spectrum. The GGM-MGM degeneracy is lifted by differences in the third
generation masses and the messenger scales.Comment: (v1) 30 pages; (v2) mislabeling in figs 2 and 3 corrected, version
accepted for publication in Phys. Rev.
The use of ERTS-1 multispectral imagery for crop identification in a semi-arid climate
Crop identification using multispectral satellite imagery and multivariate pattern recognition was used to identify wheat accurately in Greeley County, Kansas. A classification accuracy of 97 percent was found for wheat and the wheat estimate in hectares was within 5 percent of the USDA's Statistical Reporting Service estimate for 1973. The multispectral response of cotton and sorghum in Texas was not unique enough to distinguish between them nor to separate them from other cultivated crops
Determining the Structure of Supersymmetry-Breaking with Renormalization Group Invariants
If collider experiments demonstrate that the Minimal Supersymmetric Standard
Model (MSSM) is a good description of nature at the weak scale, the
experimental priority will be the precise determination of superpartner masses.
These masses are governed by the weak scale values of the soft supersymmetry
(SUSY)-breaking parameters, which are in turn highly dependent on the
SUSY-breaking scheme present at high scales. It is therefore of great interest
to find patterns in the soft parameters that can distinguish different high
scale SUSY-breaking structures, identify the scale at which the breaking is
communicated to the visible sector, and determine the soft breaking parameters
at that scale. In this work, we demonstrate that 1-loop Renormalization
Group~(RG) invariant quantities present in the MSSM may be used to answer each
of these questions. We apply our method first to generic flavor-blind models of
SUSY-breaking, and then examine in detail the subset of these models described
by General Gauge Mediation and the constrained MSSM with non-universal Higgs
masses. As RG invariance generally does not hold beyond leading-log order, we
investigate the magnitude and direction of the 2-loop corrections. We find that
with superpartners at the TeV scale, these 2-loop effects are either
negligible, or they are of the order of optimistic experimental uncertainties
and have definite signs, which allows them to be easily accounted for in the
overall uncertainty.Comment: v2 -- references added, version to be published in PRD; 40 page
Isotopic composition of Murchison organic compounds: Intramolecular carbon isotope fractionation of acetic acid. Simulation studies of cosmochemical organic syntheses
Recently, in our laboratories, samples of Murchison acetic acid were decarboxylated successfully and the carbon isotopic composition was measured for the methane released by this procedure. These analyses showed significant differences in C-13/C-12 ratios for the methyl and carboxyl carbons of the acetic acid molecule, strongly suggesting that more than one carbon source may be involved in the synthesis of the Murchison organic compounds. On the basis of this finding, laboratory model systems simulating cosmochemical synthesis are being studied, especially those processes capable of involving two or more starting carbon sources
Search for bursts in air shower data
There have been reports in recent years of the possible observation of bursts in air shower data. If such events are truly of an astrophysical nature then, they represent an important new class of phemonenon since no other bursts have been observed above the MeV level. The spectra of conventional gamma ray bursts are unknown at higher energies but their observed spectra at MeV energies appear generally to exhibit a steepening in the higher MeV range and are thus unlikely to extrapolate to measurable fluxes at air shower energies. An attempt has been made to look for deviations from randomness in the arrival times of air showers above approx. 10 to the 14th power eV with a number of systems and results so far are presented here. This work will be continued for a substantial period of ime with a system capable of recording bursts with multiple events down to a spacing of 4 microns. Earlier data have also been searched for the possible association of air shower events with a glitch of the Vela pulsar
The pMSSM Interpretation of LHC Results Using Rernormalization Group Invariants
The LHC has started to constrain supersymmetry-breaking parameters by setting
bounds on possible colored particles at the weak scale. Moreover, constraints
from Higgs physics, flavor physics, the anomalous magnetic moment of the muon,
as well as from searches at LEP and the Tevatron have set additional bounds on
these parameters. Renormalization Group Invariants (RGIs) provide a very useful
way of representing the allowed parameter space by making direct connection
with the values of these parameters at the messenger scale. Using a general
approach, based on the pMSSM parametrization of the soft supersymmetry-breaking
parameters, we analyze the current experimental constraints to determine the
probability distributions for the RGIs. As examples of their application, we
use these distributions to analyze the question of Gaugino Mass Unification and
to probabilistically determine the parameters of General and Minimal Gauge
Mediation with arbitrary Higgs mass parameters at the Messenger Scale.Comment: 38 pages, 10 figure
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