169 research outputs found
Evaluation of Stakeholders’ Roles in the Management of Artisanal and Small-Scale Gold Mining in Anka, Zamfara State, Nigeria
This paper evaluates the roles of stakeholders in the management of Artisanal and Small-scale Gold Mining (ASGM) in Anka, a typical ASGM town in Zamfara State, North-western Nigeria, dominated by sporadic and mostly unlicenced ASGM activities. Conceptual, SWOT, PESTLE, MOTAP and SELOP analyses were used to evaluate stakeholders’ roles in the management of ASGM in the area. From the evaluation, weak legislation, poor policy implementation, stringent licencing procedures, centralised government functions and poor government attention were identified to be the major factors militating against the effective functioning of ASGM regulators. Lack of management skills by the ASGM operators in the area was identified as a major barrier to their economic prosperity. Child labour, poor environmental management and cultural practices contribute to the environmental, health and safety hazards ravaging the sporadic ASGM activities by the local miners. Community leaders are thus left to grapple with the control of ASGM activities in their domain. Relief agencies and international organisations were identified as the main anchors of intervention programmes, the success of which is linked to the support and cooperation of the community leaders. Decentralisation of government functions on ASGM and organisation of miners into cooperative groups and their full integration into the formal licenced mining sector are recommended for sustainable, effective and efficient ASGM in Anka. Keywords: Artisanal and small-scale gold mining, Management functions, Environmental degradation, Rural development, Regulators, Stakeholders, Community leaders
On the observability of the neutrino charge radius
It is shown that the probe-independent charge radius of the neutrino is a
physical observable; as such, it may be extracted from experiment, at least in
principle. This is accomplished by expressing a set of experimental
neutrino-electron cross-sections in terms of the finite charge radius and two
additional gauge- and renormalization-group-invariant quantities, corresponding
to the electroweak effective charge and mixing angle.Comment: 10 pages, 1 figure; a typo in Eq.1 corrected, some comments adde
Self-Lensing Models of the LMC
All of the proposed explanations for the microlensing events observed towards
the LMC have difficulties. One of these proposed explanations, LMC
self-lensing, which invokes ordinary LMC stars as the long sought-after lenses,
has recently gained considerable popularity as a possible solution to the
microlensing conundrum. In this paper, we carefully examine the set of LMC
self-lensing models. In particular, we review the pertinent observations made
of the LMC, and show how these observations place limits on such self-lensing
models. We find that, given current observational constraints, no purely LMC
disk models are capable of producing optical depths as large as that reported
in the MACHO collaboration 2-year analysis. Besides pure disk, we also consider
alternate geometries, and present a framework which encompasses the previous
studies of LMC self-lensing. We discuss which model parameters need to be
pushed in order for such models to succeed. For example, like previous workers,
we find that an LMC halo geometry may be able to explain the observed events.
However, since all known LMC tracer stellar populations exhibit disk-like
kinematics, such models will have difficulty being reconciled with
observations. For SMC self-lensing, we find predicted optical depths differing
from previous results, but more than sufficient to explain all observed SMC
microlensing. In contrast, for the LMC we find a self-lensing optical depth
contribution between 0.47e-8 and 7.84e-8, with 2.44e-8 being the value for the
set of LMC parameters most consistent with current observations.Comment: 20 pages, Latex, 14 figures, submitted to Ap
On the Importance of Electroweak Corrections for Majorana Dark Matter Indirect Detection
Recent analyses have shown that the inclusion of electroweak corrections can
alter significantly the energy spectra of Standard Model particles originated
from dark matter annihilations. We investigate the important situation where
the radiation of electroweak gauge bosons has a substantial influence: a
Majorana dark matter particle annihilating into two light fermions. This
process is in p-wave and hence suppressed by the small value of the relative
velocity of the annihilating particles. The inclusion of electroweak radiation
eludes this suppression and opens up a potentially sizeable s-wave contribution
to the annihilation cross section. We study this effect in detail and explore
its impact on the fluxes of stable particles resulting from the dark matter
annihilations, which are relevant for dark matter indirect searches. We also
discuss the effective field theory approach, pointing out that the opening of
the s-wave is missed at the level of dimension-six operators and only encoded
by higher orders.Comment: 25 pages, 6 figures. Minor corrections to match version published in
JCA
Z', new fermions and flavor changing processes, constraints on E models from --> eee
We study a new class of flavor changing interactions, which can arise in
models based on extended gauge groups (rank 4) when new charged fermions are
present together with a new neutral gauge boson. We discuss the cases in which
the flavor changing couplings in the new neutral current coupled to the
are theoretically expected to be large, implying that the observed
suppression of neutral flavor changing transitions must be provided by heavy
masses together with small - mixing angles.
Concentrating on E models, we show how the tight experimental limit on implies serious constraints on the mass and mixing
angle. We conclude that if the value of the flavor changing parameters is
assumed to lie in a theoretically natural range, in most cases the presence of
a much lighter than 1 TeV is unlikely.Comment: plain tex, 22 pages + 2 pages figures in PostScript (appended after
`\bye'), UM-TH 92-1
Status of cosmic-ray antideuteron searches
The precise measurement of cosmic-ray antiparticles serves as important means
for identifying the nature of dark matter. Recent years showed that identifying
the nature of dark matter with cosmic-ray positrons and higher energy
antiprotons is difficult, and has lead to a significantly increased interest in
cosmic-ray antideuteron searches. Antideuterons may also be generated in dark
matter annihilations or decays, offering a potential breakthrough in unexplored
phase space for dark matter. Low-energy antideuterons are an important approach
because the flux from dark matter interactions exceeds the background flux by
more than two orders of magnitude in the low-energy range for a wide variety of
models. This review is based on the "dbar14 - dedicated cosmic-ray antideuteron
workshop", which brought together theorists and experimentalists in the field
to discuss the current status, perspectives, and challenges for cosmic-ray
antideuteron searches and discusses the motivation for antideuteron searches,
the theoretical and experimental uncertainties of antideuteron production and
propagation in our Galaxy, as well as give an experimental cosmic-ray
antideuteron search status update. This report is a condensed summary of the
article "Review of the theoretical and experimental status of dark matter
identification with cosmic-ray antideuteron" (arXiv:1505.07785).Comment: 9 pages, 4 figures, ICRC 2015 proceeding
Kaluza-Klein Dark Matter, Electrons and Gamma Ray Telescopes
Kaluza-Klein dark matter particles can annihilate efficiently into
electron-positron pairs, providing a discrete feature (a sharp edge) in the
cosmic spectrum at an energy equal to the particle's mass (typically
several hundred GeV to one TeV). Although this feature is probably beyond the
reach of satellite or balloon-based cosmic ray experiments (those that
distinguish the charge and mass of the primary particle), gamma ray telescopes
may provide an alternative detection method. Designed to observe very
high-energy gamma-rays, ACTs also observe the diffuse flux of electron-induced
electromagnetic showers. The GLAST satellite, designed for gamma ray astronomy,
will also observe any high energy showers (several hundred GeV and above) in
its calorimeter. We show that high-significance detections of an
electron-positron feature from Kaluza-Klein dark matter annihilations are
possible with GLAST, and also with ACTs such as HESS, VERITAS or MAGIC.Comment: 10 pages, 2 figure
Low energy antideuterons: shedding light on dark matter
Low energy antideuterons suffer a very low secondary and tertiary
astrophysical background, while they can be abundantly synthesized in dark
matter pair annihilations, therefore providing a privileged indirect dark
matter detection technique. The recent publication of the first upper limit on
the low energy antideuteron flux by the BESS collaboration, a new evaluation of
the standard astrophysical background, and remarkable progresses in the
development of a dedicated experiment, GAPS, motivate a new and accurate
analysis of the antideuteron flux expected in particle dark matter models. To
this extent, we consider here supersymmetric, universal extra-dimensions (UED)
Kaluza-Klein and warped extra-dimensional dark matter models, and assess both
the prospects for antideuteron detection as well as the various related sources
of uncertainties. The GAPS experiment, even in a preliminary balloon-borne
setup, will explore many supersymmetric configurations, and, eventually, in its
final space-borne configuration, will be sensitive to primary antideuterons
over the whole cosmologically allowed UED parameter space, providing a search
technique which is highly complementary with other direct and indirect dark
matter detection experiments.Comment: 26 pages, 7 figures; version to appear in JCA
Anomaly mediated SUSY breaking scenarios in the light of cosmology and in the dark (matter)
Anomaly mediation is a popular and well motivated supersymmetry breaking
scenario. Different possible detailed realisations of this set-up are studied
and actively searched for at colliders. Apart from limits coming from flavour,
low energy physics and direct collider searches, these models are usually
constrained by the requirement of reproducing the observations on dark matter
density in the universe. We reanalyse these bounds and in particular we focus
on the dark matter bounds both considering the standard cosmological model and
alternative cosmological scenarios. These scenarios do not change the
observable cosmology but relic dark matter density bounds strongly depend on
them. We consider few benchmark points excluded by standard cosmology dark
matter bounds and suggest that loosening the dark matter constraints is
necessary in order to avoid a too strong (cosmological) model dependence in the
limits that are obtained for these models. We also discuss briefly the
implications for phenomenology and in particular at the Large Hadron Collider.Comment: 37 pages, 20 figures, 1 tabl
Analyzing the discharge regime of a large tropical river through remote sensing, ground-based climatic data, and modeling
This study demonstrates the potential for applying passive microwave satellite sensor data to infer the discharge dynamics of large river systems using the main stem Amazon as a test case. The methodology combines (1) interpolated ground-based meteorological station data, (2) horizontally and vertically polarized temperature differences (HVPTD) from the 37-GHz scanning multichannel microwave radiometer (SMMR) aboard the Nimbus 7 satellite, and (3) a calibrated water balance/water transport model (WBM/WTM). Monthly HVPTD values at 0.25° (latitude by longitude) resolution were resampled spatially and temporally to produce an enhanced HVPTD time series at 0.5° resolution for the period May 1979 through February 1985. Enhanced HVPTD values were regressed against monthly discharge derived from the WBM/WTM for each of 40 grid cells along the main stem over a calibration period from May 1979 to February 1983 to provide a spatially contiguous estimate of time-varying discharge. HVPTD-estimated flows generated for a validation period from March 1983 to February 1985 were found to be in good agreement with both observed arid modeled discharges over a 1400-km section of the main stem Amazon. This span of river is bounded downstream by a region of tidal influence and upstream by low sensor response associated with dense forest canopy. Both the WBM/WTM and HVPTD-derived flow rates reflect the significant impact of the 1982–1983 El Niño-;Southern Oscillation (ENSO) event on water balances within the drainage basin
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