4,895 research outputs found
A closer look at string resonances in dijet events at the LHC
The first string excited state can be observed as a resonance in dijet
invariant mass distributions at the LHC, if the scenario of low-scale string
with large extra dimensions is realized. A distinguished property of the dijet
resonance by string excited states from that the other "new physics" is that
many almost degenerate states with various spin compose a single resonance
structure. It is examined that how we can obtain evidences of low-scale string
models through the analysis of angular distributions of dijet events at the
LHC. Some string resonance states of color singlet can obtain large mass shifts
through the open string one-loop effect, or through the mixing with closed
string states, and the shape of resonance structure can be distorted. Although
the distortion is not very large (10% for the mass squared), it might be able
to observe the effect at the LHC, if gluon jets and quark jets could be
distinguished in a certain level of efficiency.Comment: 12 pages, 8 figure
Interaction of reed and acoustic resonator in clarinetlike systems
Sound emergence in clarinetlike instruments is investigated in terms of
instability of the static regime. Various models of reed-bore coupling are
considered, from the pioneering work of Wilson and Beavers ["Operating modes of
the clarinet", J. Acoust. Soc. Am. 56, 653--658 (1974)] to more recent modeling
including viscothermal bore losses and vena contracta at the reed inlet. The
pressure threshold above which these models may oscillate as well as the
frequency of oscillation at threshold are calculated. In addition to Wilson and
Beavers' previous conclusions concerning the role of the reed damping in the
selection of the register the instrument will play on, the influence of the
reed motion induced flow is also emphasized, particularly its effect on playing
frequencies, contributing to reduce discrepancies between Wilson and Beavers'
experimental results and theory, despite discrepancies still remain concerning
the pressure threshold. Finally, analytical approximations of the oscillating
solution based on Fourier series expansion are obtained in the vicinity of the
threshold of oscillation. This allows to emphasize the conditions which
determine the nature of the bifurcation (direct or inverse) through which the
note may emerge, with therefore important consequences on the musical playing
performances
Microwave sensors for in situ monitoring of trace metals in polluted water
Thousands of pollutants are threatening our water supply, putting at risk human and environmental health. Between them, trace metals are of significant concern, due to their high toxicity at low concentrations. Abandoned mining areas are globally one of the major sources of toxic metals. Nowadays, no method can guarantee an immediate response for quantifying these pollutants. In this work, a novel technique based on microwave spectroscopy and planar sensors for in situ real-time monitoring of water quality is described. The sensors were developed to directly probe water samples, and in situ trial measurements were performed in freshwater in four polluted mining areas in the UK. Planar microwave sensors were able to detect the water pollution level with an immediate response specifically depicted at three resonant peaks in the GHz range. To the authors' best knowledge, this is the first time that planar microwave sensors were tested in situ, demonstrating the ability to use this method for classifying more and less polluted water using a multiple-peak approach
Cosmic Rays and Large Extra Dimensions
We have proposed that the cosmic ray spectrum "knee", the steepening of the
cosmic ray spectrum at energy E \gsim 10^{15.5} eV, is due to "new physics",
namely new interactions at TeV cm energies which produce particles undetected
by the experimental apparatus. In this letter we examine specifically the
possibility that this interaction is low scale gravity. We consider that the
graviton propagates, besides the usual four dimensions, into an additional
, compactified, large dimensions and we estimate the graviton
production in collisions in the high energy approximation where graviton
emission is factorized. We find that the cross section for graviton production
rises as fast as , where is the fundamental
scale of gravity in dimensions, and that the distribution of
radiating a fraction of the initial particle's energy into gravitational
energy (which goes undetected) behaves as . The missing
energy leads to an underestimate of the true energy and generates a break in
the {\sl inferred} cosmic ray spectrum (the "kne"). By fitting the cosmic ray
spectrum data we deduce that the favorite values for the parameters of the
theory are TeV and .Comment: 8 pages, 1 figur
TeV Strings and the Neutrino-Nucleon Cross Section at Ultra-high Energies
In scenarios with the fundamental unification scale at the TeV one expects
string excitations of the standard model fields at accessible energies. We
study the neutrino-nucleon cross section in these models. We show that duality
of the scattering amplitude forces the existence of a tower of massive
leptoquarks that mediate the process in the s-channel. Using the narrow-width
approximation we find a sum rule for the production rate of resonances with
different spin at each mass level. We show that these contributions can
increase substantially the standard model neutrino-nucleon cross section,
although seem insufficient in order to explain the cosmic ray events above the
GZK cutoff energy.Comment: 10 pages, 1 figure, version to appear in PR
A non-linear optimal estimation inverse method for radio occultation measurements of temperature, humidity and surface pressure
An optimal estimation inverse method is presented which can be used to
retrieve simultaneously vertical profiles of temperature and specific humidity,
in addition to surface pressure, from satellite-to-satellite radio occultation
observations of the Earth's atmosphere. The method is a non-linear, maximum
{\it a posteriori} technique which can accommodate most aspects of the real
radio occultation problem and is found to be stable and to converge rapidly in
most cases. The optimal estimation inverse method has two distinct advantages
over the analytic inverse method in that it accounts for some of the effects of
horizontal gradients and is able to retrieve optimally temperature and humidity
simultaneously from the observations. It is also able to account for
observation noise and other sources of error. Combined, these advantages ensure
a realistic retrieval of atmospheric quantities.
A complete error analysis emerges naturally from the optimal estimation
theory, allowing a full characterisation of the solution. Using this analysis a
quality control scheme is implemented which allows anomalous retrieval
conditions to be recognised and removed, thus preventing gross retrieval
errors.
The inverse method presented in this paper has been implemented for bending
angle measurements derived from GPS/MET radio occultation observations of the
Earth. Preliminary results from simulated data suggest that these observations
have the potential to improve NWP model analyses significantly throughout their
vertical range.Comment: 18 (jgr journal) pages, 7 figure
Compact Hyperbolic Extra Dimensions: Branes, Kaluza-Klein Modes and Cosmology
We reconsider theories with low gravitational (or string) scale M_* where
Newton's constant is generated via new large-volume spatial dimensions, while
Standard Model states are localized to a 3-brane. Utilizing compact hyperbolic
manifolds (CHM's) we show that the spectrum of Kaluza-Klein (KK) modes is
radically altered. This allows an early universe cosmology with normal
evolution up to substantial temperatures, and completely negates the
constraints on M_* arising from astrophysics. Furthermore, an exponential
hierarchy between the usual Planck scale and the true fundamental scale of
physics can emerge with only order unity coefficients. The linear size of the
internal space remains small. The proposal has striking testable signatures.Comment: 4 pages, no figure
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