20179156
One-loop corrections, uncertainties and approximations in neutralino annihilations: Examples
The extracted value of the relic density has reached the few per-cent level precision. One can therefore no longer content oneself with calculations of this observable where the annihilation processes are computed at tree-level, especially in supersymmetry where radiative corrections are usually large. Implementing full one-loop corrections to all annihilation processes that would be needed in a scan over parameters is a daunting task. On the other hand one may ask whether the bulk of the corrections are taken into account through effective couplings of the neutralino that improve the tree-level calculation and would be easy to implement. We address this issue by concentrating in this first study on the neutralino coupling to i) fermions and sfermions and ii) Z. After constructing the effective couplings we compare their efficiency compared to the full one-loop calculation and comment on the failures and success of the approach. As a bonus we point out that large non decoupling effects of heavy sfermions could in principle be measured in the annihilation process, a point of interest in view of the latest limit on the squark masses from the LHC. We also comment on the scheme dependencies of the one-loop corrected results.
119250843
Top Polarization in Sbottom Decays at the LHC
We perform a comprehensive analysis of the polarization of the top quarks originating from sbottom-pair production at the LHC, followed by sbottom decays to top+chargino. We study moreover the expected net polarization of top quarks produced in sbottom-to-chargino and stop-to-neutralino decays in scenarios with small chargino - neutralino mass difference, where these decays may be hard to distinguish. We show that, in contrast to top quarks produced via the Standard Model processes, the average polarization of top quarks originating from these SUSY decays can obtain any value between +1 and -1. We further study the effect of this polarization on the top quark decay kinematics. On the one hand this may be used to construct measures of this polarization, on the other hand it may be used to enhance the search reach in certain scenarios. Exploiting top polarization may also prove useful for searches for "natural" SUSY with light higgsinos, which is typically very difficult to detect at the LHC.
118523006
Modelling the clustering of dark matter haloes in resummed perturbation theories
We address the issue of the cosmological bias between matter and galaxy distributions, looking at dark matter haloes as a first step to characterize galaxy clustering. Starting from the linear density field at high redshift, we follow the centre-of-mass trajectory of the material that will form each halo at late times (protohalo). We adopt a fluid-like description for the evolution of perturbations in the protohalo distribution, which is coupled to the matter density field via gravity. We present analytical solutions for the density and velocity fields, in the context of renormalized perturbation theory. We start from the linear solution, then compute one-loop corrections for the propagator and the power spectrum. Finally, we analytically resum the propagator, and we use a suitable extension of the time-renormalization-group method to resum the power spectrum. For halo masses M < 1014 h−1 M⊙, our results at z= 0 are in good agreement with N-body simulations. Our model is able to predict the halo–matter cross-spectrum with an accuracy of 5 per cent up to k≈ 0.1 h Mpc−1 approaching the requirements of future galaxy redshift surveys.
116599063
Hawking fluxes and covariant anomalies
A non-destructive, direct method and apparatus for producing stretch blow molded articles having at least one physical dimension within a preselected range. The apparatus includes an injection mold defining an injection mold interior surface having a first differentially dimensioned portion disposed at a preselected location thereon and capable of producing a parison having a parison exterior surface including a first marker formed by contact with the first differentially dimensioned portion, and a stretch blow mold defining a stretch blow mold interior surface having a second differentially dimensioned portion disposed at a predetermined location thereon and capable of producing the article from the parison including a second marker formed by contact with the second differentially dimensioned portion. Relative position of the first marker with respect to the second marker indicates whether a dimension is within a preselected range. The method includes injection molding a parison so that a parison exterior surface includes a first marker disposed at a preselected position thereon and formed by contact with a first differentially dimensioned portion disposed at a preselected location on an injection mold interior surface, and stretch blow molding an article from the parison so that an article exterior surface includes a second marker disposed at a predetermined position thereon and formed by contact with a second differentially dimensioned portion disposed at a predetermined location on a stretch blow mold interior surface.
15519228
PRECISION ASTROMETRY WITH ADAPTIVE OPTICS
We investigate the limits of ground-based astrometry with adaptive optics using the core of the Galactic globular cluster M5. Adaptive optics systems provide near diffraction-limit imaging with the world's largest telescopes. The substantial improvement in both resolution and signal-to-noise ratio enables high-precision astrometry from the ground. We describe the dominant systematic errors that typically limit ground-based differential astrometry, and enumerate observational considerations for mitigating their effects. After implementing these measures, we find that the dominant limitation on astrometric performance in this experiment is caused by tilt anisoplanatism. We then present an optimal estimation technique for measuring the position of one star relative to a grid of reference stars in the face of this correlated random noise source. Our methodology has the advantage of reducing the astrometric errors to and faster than the square root of the number of reference stars, effectively eliminating noise caused by atmospheric tilt to the point that astrometric performance is limited by centering accuracy. Using 50 reference stars, we demonstrate a single-epoch astrometric precision of ≈1 mas in 1 s, decreasing to 100 μas in 2 minutes of integration time at the Hale 200 inch telescope. We also show that our astrometry is accurate to 100 μas for observations separated by 2 months. Finally, we discuss the limits and potential of differential astrometry with current and next-generation large-aperture telescopes. At this level of accuracy, numerous astrometric applications become accessible, including planet detection, astrometric microlensing signatures, and kinematics of distant Galactic stellar populations.
20207808
DISCOVERY OF A COSMOLOGICAL, RELATIVISTIC OUTBURST VIA ITS RAPIDLY FADING OPTICAL EMISSION
We report the discovery by the Palomar Transient Factory (PTF) of the transient source PTF11agg, which is distinguished by three primary characteristics: (1) bright (Rpeak = 18.3mag), rapidly fading (ΔR = 4mag in Δt = 2 days) optical transient emission; (2) a faint (R = 26.2 ± 0.2mag), blue (g � − R = 0.17 ± 0.29mag) quiescent optical counterpart; and (3) an associated year-long, scintillating radio transient. We argue that these observed properties are inconsistent with any known class of Galactic transients (flare stars, X-ray binaries, dwarf novae), and instead suggest a cosmological origin. The detection of incoherent radio emission at such distances implies a large emitting region, from which we infer the presence of relativistic ejecta. The observed properties are allconsistentwiththepopulationoflong-durationgamma-raybursts(GRBs),markingthefirsttimesuchanoutburst has been discovered in the distant universe independent of a high-energy trigger. We searched for possible highenergy counterparts to PTF11agg, but found no evidence for associated prompt emission. We therefore consider three possible scenarios to account for a GRB-like afterglow without a high-energy counterpart: an “untriggered” GRB (lack of satellite coverage), an “orphan” afterglow (viewing-angle effects), and a “dirty fireball” (suppressed high-energy emission). The observed optical and radio light curves appear inconsistent with even the most basic predictions for off-axis afterglow models. The simplest explanation, then, is that PTF11agg is a normal, on-axis long-durationGRBforwhichtheassociatedhigh-energyemissionwassimplymissed.However,wehavecalculated the likelihood of such a serendipitous discovery by PTF and find that it is quite small (≈2.6%). While not definitive, we nonetheless speculate that PTF11agg may represent a new, more common (>4 times the on-axis GRB rate at 90% confidence) class of relativistic outbursts lacking associated high-energy emission. If so, such sources will be uncovered in large numbers by future wide-field optical and radio transient surveys.
118374860
Real-time Detection and Rapid Multiwavelength Follow-up Observations of a Highly Subluminous Type II-P Supernova from the Palomar Transient Factory Survey
The Palomar Transient Factory (PTF) is an optical wide-field variability survey carried out using a camera with a 7.8 deg^2 field of view mounted on the 48 inch Oschin Schmidt telescope at Palomar Observatory. One of the key goals of this survey is to conduct high-cadence monitoring of the sky in order to detect optical transient sources shortly after they occur. Here, we describe the real-time capabilities of the PTF and our related rapid multiwavelength follow-up programs, extending from the radio to the γ-ray bands. We present as a case study observations of the optical transient PTF10vdl (SN 2010id), revealed to be a very young core-collapse (Type II-P) supernova having a remarkably low luminosity. Our results demonstrate that the PTF now provides for optical transients the real-time discovery and rapid-response follow-up capabilities previously reserved only for high-energy transients like gamma-ray bursts.
14169943
Precision astrometry of a sample of speckle binaries and multiples with the adaptive optics facilities at the Hale and Keck II telescopes
Using the adaptive optics facilities at the 200-in Hale and 10-m Keck II, we observed in 
the near-infrared a sample of 12 binary and multiple stars and one open cluster. We used 
the near diffraction limited images of these systems to measure the relative separations and 
position angles between their components. In this paper, we investigate and correct for the 
influence of the differential chromatic refraction and chip distortions on our relative astrometric 
measurements. Over one night, we achieve an astrometric precision typically well below 1mas 
and occasionally as small as 40 μas. Such a precision is in principle sufficient to astrometrically 
detect planetary mass objects around the components of nearby binary and multiple stars. Since 
we have not had sufficiently large data sets for the observed sample of stars to detect planets, 
we provide the limits to planetary mass objects based on the obtained astrometric precision.