7,187 research outputs found
Hadron Collider Sensitivity to Fat Flavourful s for
We further investigate the case where new physics in the form of a massive
particle explains apparent measurements of lepton flavour
non-universality in decays. Hadron collider
sensitivities for direct production of such s have been previously
studied in the narrow width limit for a final state. Here, we
extend the analysis to sizeable decay widths and improve the sensitivity
estimate for the narrow width case. We estimate the sensitivities of the high
luminosity 14 TeV Large Hadron Collider (HL-LHC), a high energy 27 TeV LHC
(HE-LHC), as well as a potential 100 TeV future circular collider (FCC). The
HL-LHC has sensitivity to narrow resonances consistent with the
anomalies. In one of our simplified models the FCC could probe 23 TeV
particles with widths of up to 0.35 of their mass at 95\% confidence
level (CL). In another model, the HL-LHC and HE-LHC cover sizeable portions of
parameter space, but the whole of perturbative parameter space can be covered
by the FCC.Comment: 24 pages, 11 figures; v2 Reference
On the "Universal" Quantum Area Spectrum
There has been much debate over the form of the quantum area spectrum for a
black hole horizon, with the evenly spaced conception of Bekenstein having
featured prominently in the discourse. In this letter, we refine a very
recently proposed method for calibrating the Bekenstein form of the spectrum.
Our refined treatment predicts, as did its predecessor, a uniform spacing
between adjacent spectral levels of in Planck units; notably, an outcome
that already has a pedigree as a proposed ``universal'' value for this
intrinsically quantum-gravitational measure. Although the two approaches are
somewhat similar in logic and quite agreeable in outcome, we argue that our
version is conceptually more elegant and formally simpler than its precursor.
Moreover, our rendition is able to circumvent a couple of previously unnoticed
technical issues and, as an added bonus, translates to generic theories of
gravity in a very direct manner.Comment: 7 Pages; (v2) now 9 full pages, significant changes to the text and
material added but the general theme and conclusions are unchange
LANDSAT application of remote sensing to shoreline-form analysis
The author has identified the following significant results. LANDSAT imagery of the southern end of Assateague Island, Virginia, was enlarged to 1:80,000 and compared with high altitude (1:130,000) and low altitude (1:24,000) aerial photography in an attempt to quantify change in land area over a nine month period. Change in area and configuration was found with LANDSAT and low altitude photography. Change in configuration, but no change in area was found with high altitude photography. Due to tidal differences at time of image obtention and lack of baseline data, the accuracy of the LANDSAT measurements could not be determined. They were consistent with the measurements from the low altitude photography
Attentional load and sensory competition in human vision: Modulation of fMRI responses by load fixation during task-irrelevant stimulation in the peripheral visual field.
Perceptual suppression of distractors may depend on both endogenous and exogenous factors, such as attentional load of the current task and sensory competition among simultaneous stimuli, respectively. We used functional magnetic resonance imaging (fMRI) to compare these two types of attentional effects and examine how they may interact in the human brain. We varied the attentional load of a visual monitoring task performed on a rapid stream at central fixation without altering the central stimuli themselves, while measuring the impact on fMRI responses to task-irrelevant peripheral checkerboards presented either unilaterally or bilaterally. Activations in visual cortex for irrelevant peripheral stimulation decreased with increasing attentional load at fixation. This relative decrease was present even in V1, but became larger for successive visual areas through to V4. Decreases in activation for contralateral peripheral checkerboards due to higher central load were more pronounced within retinotopic cortex corresponding to 'inner' peripheral locations relatively near the central targets than for more eccentric 'outer' locations, demonstrating a predominant suppression of nearby surround rather than strict 'tunnel vision' during higher task load at central fixation. Contralateral activations for peripheral stimulation in one hemifield were reduced by competition with concurrent stimulation in the other hemifield only in inferior parietal cortex, not in retinotopic areas of occipital visual cortex. In addition, central attentional load interacted with competition due to bilateral versus unilateral peripheral stimuli specifically in posterior parietal and fusiform regions. These results reveal that task-dependent attentional load, and interhemifield stimulus-competition, can produce distinct influences on the neural responses to peripheral visual stimuli within the human visual system. These distinct mechanisms in selective visual processing may be integrated within posterior parietal areas, rather than earlier occipital cortex
Polarised infrared emission from X-ray binary jets
Near-infrared (NIR) and optical polarimetric observations of a selection of
X-ray binaries are presented. The targets were observed using the Very Large
Telescope and the United Kingdom Infrared Telescope. We detect a significant
level (3 sigma) of linear polarisation in four sources. The polarisation is
found to be intrinsic (at the > 3 sigma level) in two sources; GRO J1655-40 (~
4-7% in H and Ks-bands during an outburst) and Sco X-1 (~ 0.1-0.9% in H and K),
which is stronger at lower frequencies. This is likely to be the signature of
optically thin synchrotron emission from the collimated jets in these systems,
whose presence indicates a partially-ordered magnetic field is present at the
inner regions of the jets. In Sco X-1 the intrinsic polarisation is variable
(and sometimes absent) in the H and K-bands. In the J-band (i.e. at higher
frequencies) the polarisation is not significantly variable and is consistent
with an interstellar origin. The optical light from GX 339-4 is also polarised,
but at a level and position angle consistent with scattering by interstellar
dust. The other polarised source is SS 433, which has a low level (0.5-0.8%) of
J-band polarisation, likely due to local scattering. The NIR counterparts of
GRO J0422+32, XTE J1118+480, 4U 0614+09 and Aql X-1 (which were all in or near
quiescence) have a linear polarisation level of < 16% (3 sigma upper limit,
some are < 6%). We discuss how such observations may be used to constrain the
ordering of the magnetic field close to the base of the jet in such systems.Comment: Accepted to be published in MNRAS; 13 pages, 6 figure
The Information Geometry of the One-Dimensional Potts Model
In various statistical-mechanical models the introduction of a metric onto
the space of parameters (e.g. the temperature variable, , and the
external field variable, , in the case of spin models) gives an alternative
perspective on the phase structure. For the one-dimensional Ising model the
scalar curvature, , of this metric can be calculated explicitly in
the thermodynamic limit and is found to be . This is positive definite and, for
physical fields and temperatures, diverges only at the zero-temperature,
zero-field ``critical point'' of the model.
In this note we calculate for the one-dimensional -state Potts
model, finding an expression of the form , where is the Potts
analogue of . This is no longer positive
definite, but once again it diverges only at the critical point in the space of
real parameters. We remark, however, that a naive analytic continuation to
complex field reveals a further divergence in the Ising and Potts curvatures at
the Lee-Yang edge.Comment: 9 pages + 4 eps figure
Study of thermal protection requirements for a lifting body entry vehicle suitable for near-earth missions Final report
Reentry and abort trajectory analyses, and thermal protection requirements for lifting body entry vehicle
High energy X-ray spectra of cygnus XR-1 observed from OSO-8
X-ray spectra of Cygnus XR-1 were measured with the scintillation spectrometer on board the OSO-8 satellite during a period of one and one-half to three weeks in each of the years from 1975 to 1977. Observations were made when the source was both in a high state and in a low state. Typical spectra of the source between 15 and 250 keV are presented. The observed pivoting effect is consistent with two temperature accretion disk models of the X-ray emitting region. No significant break in the spectrum occurred at energies up to 150 keV. The high state as defined in the 3 to 6 keV bandwidth was found to be the higher luminosity state of the X-ray source. One transition from a low to a high state occurred during observations. The time of occurrence of this and other transitions is consistent with the hypothesis that all intensity transitions occur near periastron of the binary system, and that such transitions are caused by changes in the mass transfer rate between the primary and the accretion disk around the secondary
The Administration\u27s Program for Economic Recovery : Theory and Evidence
The economic recovery program proposes to inject about $100 billion into the aggregate spending stream while simultaneously reducing the inflation rate. Careful analysis of estimates of the supply response to tax rate reductions and deregulation show that output increases will not balance the increased demand. Savings rates several times historic levels are thus necessary not only to reduce inflation, but even to prevent the program from worsening inflation. Recent evidence indicates that none of the scenarios most often mentioned as producing the requisite savings hold much promise
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