High-energy Data Research Articles

High temperature stress-induced “double loop-like” phase transitions in Bi-based perovskites

Polycrystalline 0.94(Bi1/2Na1/2)TiO3–0.06BaTiO3 samples were tested under uniaxial mechanical compression at various temperatures in the vicinity of the polar tetragonal to nonpolar tetragonal phase boundary. They are shown to display double loop-like stress-strain behavior, marked by a closed ferroelastic hysteresis loop. Thus, it forms a mechanical analog to the polarization-electric field hysteresis behavior of barium titanate above the Curie temperature. As temperature is increased there is an apparent loss of macroscopically observable ferroelasticity, despite the persistence of tetragonality. Macroscopic experimental results are discussed in conjunction with temperature-dependent and stress-dependent high-energy x-ray diffraction data. This reveals a phase transition below the Curie temperature, marked by a discontinuous change in lattice parameters and octahedral tilting during compressive mechanical loading.

Λ(1520)photoproduction off a proton target with Regge contributions

We investigate the $\ensuremath{\Lambda}(1520,3/{2}^{\ensuremath{-}})\ensuremath{\equiv}{\ensuremath{\Lambda}}^{*}$ photoproduction off the proton target beyond the resonance region within a model including the Regge contributions, the tree-level diagrams with the nucleon and the certain resonance intermediate states, and one contact term. The Reggeized propagators for the $K$ and ${K}^{*}$ exchanges in the $t$ channel are employed in a gauge-invariant manner. We compute the angular and energy dependences of the cross section and some polarization observables, such as the photon-beam asymmetry and the polarization-transfer coefficients. Our results qualitatively agree with the current experimental data. We find that the Regge contributions are necessary to explain the high-energy data beyond ${E}_{\ensuremath{\gamma}}\ensuremath{\approx}4$ GeV, especially for the angular dependences in the forward region. On the contrary, the polarization observables are insensitive to the Regge contributions due to the contact-term dominance, which is a consequence of gauge invariance. We also calculate the ${K}^{\ensuremath{-}}$-angle distribution function in the Gottfried-Jackson frame, using the polarization-transfer coefficients in the $z$ direction. We find that it owns a complicated angle and energy dependences in the forward ${K}^{+}$ scattering region.

Strangeness enhancements at central rapidity in 40 A GeV/c Pb–Pb collisions

Results are presented on the production of K0S, hyperons and antihyperons in Pb–Pb and p–Be interactions at 40 GeV/c per nucleon. The enhancement pattern follows the same hierarchy as seen in the higher energy data—the enhancement increases with the strangeness content of the hyperons and with the centrality of collision. The centrality dependence of the Pb–Pb yields and enhancements is steeper at 40 than at 158 A GeV/c. The energy dependence of strangeness enhancements at mid-rapidity is discussed.

Real-time compression system research based on DMD hadamard transform spectrometer

We propose a new lossy compression approach for hyperspectral images which comes from hadamard transform (HT) spectral imager for space-based surveillance that uses the Digital Micro-mirror Device (DMD) as the programmable mask other than the conventional mechanical mask. This paper firstly introduces that the DMD Hadamard spectrometer described in this paper is good at obtaining multi-channel high-energy high-SNR spectral data, which is superior to traditional ones. And then,based on the hardware platform composed of Xilinx FPGA and ADV212 (a codec chip for special JPEG2000), the sampled image data was then compressed with high SNR,high-resolution compression ratio. Last, we show the experimental results which demonstrate that the PSNR is up to 47.3dB and make no significant distortion for vision. Obviously, this approach takes distinguished advantages on real-time ability, image distortion and the practical value. The design can be utilized in national defense, earth resource survey aerospace, environmental disaster monitoring and other fields.

GRB 090426: the farthest short gamma-ray burst?

Aims. With an observed and rest-frame duration of < 2s and < 0.5s, respectively, GRB090426 could be classified as a short GRB. The prompt detection, both from space and ground-based telescopes, of a bright optical counterpart to this GRB offered a unique opportunity to complete a detailed study. Methods. Based on an extensive ground-based observational campaign, we obtained the spectrum of the optical afterglow of GRB090426, measuring its redshift and obtaining information about the medium in which the event took place. We completed follow-up observation of the afterglow optical light curve down to the brightness level of the host galaxy that we firmly identified and studied. We also retrieved and analyzed all the available high-energy data of this event, and compared the results with our findings in the optical. This represents one of the most detailed studies of a short-duration event presented so far. Results. The time properties qualify GRB090426 as a short burst. In this case, its redshift of z = 2.61 would be the highest yet found for a GRB of this class. On the other hand, the spectral and energy properties are more similar to those of long bursts. LBT late-time deep imaging identifies a star-forming galaxy at a redshift consistent with that of the GRB. The afterglow lies within the light of its host and shows evidence of local absorption.

Design and Evaluation of an Energy-Delay-Area Efficient Datapath for Coarse-Grain Reconfigurable Computing Systems

This paper presents the architecture and complete VLSI implementation of a high data throughput, energy and area efficient data path targeted for DSP and multimedia applications. The architecture presented here is extremely flexible and can be easily extended to process 8-16-32 bit operands. For the initial analysis and design, three different implementations of the reconfigurable data path using static, dynamic domino and D3L logic styles were implemented to evaluate the performance of the proposed architecture in static as well as dynamic design domains. This paper presents complete evaluations of the architecture, along with an analysis of every design decision from the lowermost level. The proposed architecture can be easily extended to generalized N-bit operations. This is demonstrated through the custom implementation of 8-16 and 32 bit versions.

Optimizing experimental design, overcoming challenges, and gaining valuable information from the Sb K-edge XANES region

There are many challenges associated with collecting, processing, and interpreting high-energy XAS data. The most significant of these are broad spectra, minimal separation of edge positions, and high background owing to the Compton tail. Studies of the Sb system are a particular challenge owing to its complex bonding character and formation of mixed oxidation-state minerals. Furthermore, in environmental samples such as stream sediment containing mine waste, different Sb phases may coexist. Ways to overcome these challenges and achieve accurate and useful information are presented. Our investigations used Sb K -edge X-ray absorption near-edge spectroscopy (XANES) to elucidate Sb geochemical behavior. Several Sb mineral spectra are presented, including Sb sulfosalts, and contrasted based on the different hosting and coordination environments around the Sb atom in the crystal structure. These comparisons lead to the recognition of how the different hosting and coordination environments are manifested in the shape of the Sb mineral spectra. In fact from the shape of the spectra, the occupation of the Sb atom in a single or in multiple crystallographic sites, regardless of whether multiple phases are present in the sample, is discernible. Furthermore, we demonstrate that quantitative information can be derived from the XANES region using linear combination fitting of the derivative spectra, rather than the energy spectra. Particularly useful to the advancement of Sb research is the demonstration that a significant amount of information can be gained from the Sb K -edge XANES region.

Charge Density Study on Phase Transition in BaTi2O5 Ferroelectric

The accurate crystal structure of BaTi2O5 ferroelectric has been derived at the charge density levels from 100 to 900 K in both the paraelectric and ferroelectric phases. High-energy synchrotron-radiation powder-diffraction data were taken and analyzed by the maximum entropy method (MEM)/Rietveld method. Three independent Ti–O6 octahedra in the structure of BaTi2O5 are distorted, two of which can be regarded as having five-oxygen coordination in both phases. The structural change associated with the ferroelectric phase transition is characterized by the occurrence of extra distortion in Ti1–O6, which is the least distorted octahedron above TC. The spontaneous polarization calculated from the determined crystal structure is Ps = 15 µC/cm2 at room temperature. The contribution of the distortion of Ti1–O6 to Ps is about 80%.

Measurement of semi-inclusiveπ+electroproduction off the proton

Semi-inclusive pi+ electroproduction on protons has been measured with the CLAS detector at Jefferson Lab. The measurement was performed on a liquid-hydrogen target using a 5.75 GeV electron beam. The complete five-fold differential cross sections were measured over a wide kinematic range including the complete range of azimuthal angles between hadronic and leptonic planes, phi, enabling us to separate the phi-dependent terms. Our measurements of phi-independent term of the cross section at low Bjorken x were found to be in fairly good agreement with pQCD calculations. Indeed, the conventional current fragmentation calculation can account for almost all of the observed cross section, even at small pi+ momentum. The measured center-of-momentum spectra are in qualitative agreement with high energy data, which suggests a surprising numerical similarity between the spectator diquark fragmentation in the present reaction and the anti-quark fragmentation measured in e+e- collisions. We have observed that the two phi-dependent terms of the cross section are small. Within our precision the cos(2phi) term is compatible with zero, except for low-z region, and the measured cos(phi) term is much smaller in magnitude than the sum of the Cahn and Berger effects.

X-ray evidence for a mildly relativistic and variable outflow in the luminous Seyfert 1 galaxy Mrk 509

There is growing evidence for the presence of blueshifted Fe K absorption lines in a number of radio-quiet AGNs and QSOs. These may be fundamental to probe flow dynamics near supermassive black holes. Here we aim at verifying and better characterising the existence of such Fe K absorption at ~8-10 keV in the luminous Seyfert 1 galaxy Mrk509, one of the most promising target for these studies. We present a comprehensive spectral analysis of the six XMM-Newton observations of the source (for a total of ~200 ks), focusing on the detailed and systematic search for absorption features in the high-energy data. We detect several absorption features at rest-frame energies ~8-8.5 keV and ~9.7 keV. The lines are consistent with being produced by H-like iron Ka and Kb shell absorptions associated with an outflow with mildly relativistic velocity of ~0.14-0.2 c. The lines are found to be variable in energy and, marginally in intensity, implying that variations in either the column density, geometry and/or ionization structure of the outflow are common in this source.

Experimentally constrained density-functional calculations of the amorphous structure of the prototypical phase-change materialGe2Sb2Te5

Phase change materials involve the rapid and reversible transition between nanoscale amorphous $(a\text{\ensuremath{-}})$ and crystalline $(c\text{\ensuremath{-}})$ spots in a polycrystalline film and play major roles in the multimedia world, including nonvolatile computer memory. The materials of choice are alloys of Ge, Sb, and Te, e.g., ${\text{Ge}}_{2}{\text{Sb}}_{2}{\text{Te}}_{5}$ (GST) in digital versatile disk--random access memory. There has been much speculation about the structure of $a\text{\ensuremath{-}}$ GST, but no model has yet received general acceptance. Here we optimize the structure by combining the results of density-functional calculations with high-energy x-ray diffraction data and x-ray photoelectron spectroscopy (XPS) measurements of the electronic densities of states to determine the structure. The structure agrees very well with available experimental data, including the differences in the XPS data between the amorphous and crystalline structures.

Future Prospects of B Physics

In recent years, the CKM picture of flavor and CP violation has been confirmed, mainly due to B decay data. Yet, it is likely that there are small corrections to this picture. We expect to find new physics not much above the weak scale. This new physics could modify flavor changing processes compared to their SM expectations. Much larger B decay data sets, which are expected from LHCb and super-B-factories, will be used to search for these deviations with much improved sensitivity. The combination of low and high energy data will be particularly useful to probe the structure of new physics.

Indications of a shallow potential inCa48+Zr96fusion reactions

Fusion data for $^{48}\mathrm{Ca}+^{96}\mathrm{Zr}$ are analyzed by coupled-channels calculations. Puzzling features of a previous analysis are eliminated by applying a potential that has a shallow pocket in the entrance channel. Thus the observed $S$ factor for fusion, which develops a maximum at low energy, can be reproduced fairly well. The high-energy data can also be accounted for but that requires the use of a weak, short-ranged imaginary potential that absorbs the incoming flux near the location of the minimum of the potential pocket. Predictions of the fusion hindrance in other $\mathrm{Ca}+\mathrm{Zr}$ systems are made and are compared with the systematics that has been developed previously.

On the measurement of the proton-air cross section using air shower data

The analysis of high-energy air shower data allows one to study the proton-air cross section at energies beyond the reach of fixed target and collider experiments. The mean depth of the first interaction point and its fluctuations are a measure of the proton-air particle production cross section. Since the first interaction point in air cannot be measured directly, various methods have been developed in the past to estimate the depth of the first interaction from air shower observables in combination with simulations. As the simulations depend on assumptions made for hadronic particle production at energies and phase space regions not accessible in accelerator experiments, the derived cross sections are subject to significant systematic uncertainties. The focus of this work is the development of an improved analysis technique that allows a significant reduction of the model dependence of the derived cross section at very high energy. Performing a detailed Monte Carlo study of the potential and the limitations of different measurement methods, we quantify the dependence of the measured cross section on the hadronic interaction model used. Based on these results, a general improvement of the analysis methods is proposed by introducing the actually derived cross section already in the simulation of reference showers. The reduction of the model dependence is demonstrated for one of the measurement methods.

The Time-Series Link Prediction Problem with Applications in Communication Surveillance

The ability to predict linkages among data objects is central to many data mining tasks, such as product recommendation and social network analysis. Substantial literature has been devoted to the link prediction problem either as an implicitly embedded problem in specific applications or as a generic data mining task. This literature has mostly adopted a static graph representation where a snapshot of the network is analyzed to predict hidden or future links. However, this representation is only appropriate to investigate whether a certain link will ever occur and does not apply to many applications for which the prediction of the repeated link occurrences are of primary interest (e.g., communication network surveillance). In this paper, we introduce the time-series link prediction problem, taking into consideration temporal evolutions of link occurrences to predict link occurrence probabilities at a particular time. Using Enron e-mail data and high-energy particle physics literature coauthorship data, we have demonstrated that time-series models of single-link occurrences achieve comparable link prediction performance with commonly used static graph link prediction algorithms. Furthermore, a combination of static graph link prediction algorithms and time-series models produced significantly better predictions over static graph link prediction methods, demonstrating the great potential of integrated methods that exploit both interlink structural dependencies and intralink temporal dependencies.

Evaluation of the structural model for ferrihydrite derived from real-space modelling of high-energy X-ray diffraction data

AbstractA new structural model for ferrihydrite that challenges the standard ferrihydrite model established by X-ray diffraction and confirmed by neutron diffraction and single-crystal electron nanodiffraction was recently proposed by Michel et al. (2007a) from the simulation of the pair distribution function obtained by Fourier transformation of diffraction data measured at λ = 0.137 Å. The new ferrihydrite model is isostructural to akdalaite (Al10O14(OH)2), a mineral having the Baker-Figgis δ-isomer of the Al13-Keggin structure as its structural motif. The new model is unrealistic because: (1) it is completely periodic (i.e. defect-free); (2), it has 20% tetravalent octahedral iron (VIFe4+), 20% divalent tetrahedral iron (IVFe2+), and some IVFe–O distances equal to or larger than the VIFe3+–O distances, thus violating Pauling's 2nd rule; (3) it does not describe X-ray diffraction and EXAFS spectroscopic data; and, (4) it is inconsistent with electron microscopy results and contradicts previous X-ray scattering studies.

The underlying event and the total cross section from Tevatron to the LHC

Multiple partonic interactions are widely used to simulate the hadronic final state in high energy hadronic collisions, and successfully describe many features of the data. It is important to make maximum use of the available physical constraints on such models, particularly given the large extrapolation from current high energy data to LHC energies. In eikonal models, the rate of multiparton interactions is coupled to the energy dependence of the total cross section. Using a Monte Carlo implementation of such a model, we study the connection between the total cross section, the jet cross section, and the underlying event. By imposing internal consistency on the model, we derive constraints on its parameters at the LHC. By imposing internal consistency on the model and comparing to current data we constrain the allowed range of its parameters. We show that measurements of the total proton-proton cross-section at the LHC are likely to break this internal consistency, and thus to require an extension of the model. Likely such extensions are that hard scatters probe a denser matter distribution inside the proton in impact parameter space than soft scatters, a conclusion also supported by Tevatron data on double-parton scattering, and/or that the basic parameters of the model are energy dependent.

On the mistake in the implementation of the minimal model of the dual parametrization and resulting inability to describe the high-energy deeply virtual Compton data

We correct the mistaken claim made by Guzey and Polyakov [Eur. Phys. J. C 46, 151 (2006) ] and Guzey and Teckentrup [Phys. Rev. D 74, 054027 (2006)] that the minimal model of the dual parametrization of nucleon generalized parton distributions gives a good, essentially model-independent description of high-energy data on deeply virtual Compton scattering (DVCS). In the implementation of the dual parametrization by Guzey-Polyakov and Guzey-Teckentrup (see above), the numerical prefactor of two in front of the DVCS amplitude was missing. We show that the corrected minimal model of the dual parametrization significantly overestimates the Hadron Electron Ring Accelerator data (H1 and ZEUS experiments) on the DVCS cross section.

Aspirations and Outlook for NASA Cosmic Ray Research on Balloons and in Space

The cosmic-ray community has produced a steady stream of science results with both space-based and balloon-borne experiments. Low-energy cosmic rays have been studied with satellites since the dawn of the space age, but stratospheric balloons have provided all of the direct high-energy data. Results extending beyond 10 14 eV from balloon flights in Antarctica now overlap indirect ground based observations in the energy range below the knee (∼3 ×10 15 eV). Ultra long-duration balloon flights with super-pressure balloons might allow direct observations to reach 10 15 eV within the next decade, but larger aperture space missions with longer exposures may be needed to connect cosmic ray composition to supernovae. Space instruments looking down on the Earth's atmosphere, creating a detector as wide as the Earth, could provide information about astrophysical accelerators involving the intense gravity around black holes, neutron stars, and the largest electromagnetic fields known.

Exclusive ρ0 electroproduction on the proton at CLAS

The $e p\to e^\prime p \rho^0$ reaction has been measured, using the 5.754 GeV electron beam of Jefferson Lab and the CLAS detector. This represents the largest ever set of data for this reaction in the valence region. Integrated and differential cross sections are presented. The $W$, $Q^2$ and $t$ dependences of the cross section are compared to theoretical calculations based on $t$-channel meson-exchange Regge theory on the one hand and on quark handbag diagrams related to Generalized Parton Distributions (GPDs) on the other hand. The Regge approach can describe at the $\approx$ 30% level most of the features of the present data while the two GPD calculations that are presented in this article which succesfully reproduce the high energy data strongly underestimate the present data. The question is then raised whether this discrepancy originates from an incomplete or inexact way of modelling the GPDs or the associated hard scattering amplitude or whether the GPD formalism is simply inapplicable in this region due to higher-twists contributions, incalculable at present.