7,184 research outputs found

    Hadron Collider Sensitivity to Fat Flavourful ZZ^\primes for RK()R_{K^{(\ast)}}

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    We further investigate the case where new physics in the form of a massive ZZ^\prime particle explains apparent measurements of lepton flavour non-universality in BK()l+lB \rightarrow K^{(\ast)} l^+ l^- decays. Hadron collider sensitivities for direct production of such ZZ^\primes have been previously studied in the narrow width limit for a μ+μ\mu^+ \mu^- 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 ZZ^\prime resonances consistent with the anomalies. In one of our simplified models the FCC could probe 23 TeV ZZ^\prime 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

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    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 8π8\pi 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

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    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.

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    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

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    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

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    In various statistical-mechanical models the introduction of a metric onto the space of parameters (e.g. the temperature variable, β\beta, and the external field variable, hh, in the case of spin models) gives an alternative perspective on the phase structure. For the one-dimensional Ising model the scalar curvature, R{\cal R}, of this metric can be calculated explicitly in the thermodynamic limit and is found to be R=1+cosh(h)/sinh2(h)+exp(4β){\cal R} = 1 + \cosh (h) / \sqrt{\sinh^2 (h) + \exp (- 4 \beta)}. 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 R{\cal R} for the one-dimensional qq-state Potts model, finding an expression of the form R=A(q,β,h)+B(q,β,h)/η(q,β,h){\cal R} = A(q,\beta,h) + B (q,\beta,h)/\sqrt{\eta(q,\beta,h)}, where η(q,β,h)\eta(q,\beta,h) is the Potts analogue of sinh2(h)+exp(4β)\sinh^2 (h) + \exp (- 4 \beta). 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

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    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

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    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

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    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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