54 research outputs found
D* Production in Deep Inelastic Scattering at HERA
This paper presents measurements of D^{*\pm} production in deep inelastic
scattering from collisions between 27.5 GeV positrons and 820 GeV protons. The
data have been taken with the ZEUS detector at HERA. The decay channel
(+ c.c.) has been used in the study. The
cross section for inclusive D^{*\pm} production with
and is 5.3 \pms 1.0 \pms 0.8 nb in the kinematic region
{ GeV and }. Differential cross
sections as functions of p_T(D^{*\pm}), and are
compared with next-to-leading order QCD calculations based on the photon-gluon
fusion production mechanism. After an extrapolation of the cross section to the
full kinematic region in p_T(D^{*\pm}) and (D^{*\pm}), the charm
contribution to the proton structure function is
determined for Bjorken between 2 10 and 5 10.Comment: 17 pages including 4 figure
Observation of Scaling Violations in Scaled Momentum Distributions at HERA
Charged particle production has been measured in deep inelastic scattering
(DIS) events over a large range of and using the ZEUS detector. The
evolution of the scaled momentum, , with in the range 10 to 1280
, has been investigated in the current fragmentation region of the Breit
frame. The results show clear evidence, in a single experiment, for scaling
violations in scaled momenta as a function of .Comment: 21 pages including 4 figures, to be published in Physics Letters B.
Two references adde
Observation of hard scattering in photoproduction events with a large rapidity gap at HERA
Events with a large rapidity gap and total transverse energy greater than 5
GeV have been observed in quasi-real photoproduction at HERA with the ZEUS
detector. The distribution of these events as a function of the
centre of mass energy is consistent with diffractive scattering. For total
transverse energies above 12 GeV, the hadronic final states show predominantly
a two-jet structure with each jet having a transverse energy greater than 4
GeV. For the two-jet events, little energy flow is found outside the jets. This
observation is consistent with the hard scattering of a quasi-real photon with
a colourless object in the proton.Comment: 19 pages, latex, 4 figures appended as uuencoded fil
Observation of Events with an Energetic Forward Neutron in Deep Inelastic Scattering at HERA
In deep inelastic neutral current scattering of positrons and protons at the center of mass energy of 300 GeV, we observe, with the ZEUS detector, events with a high energy neutron produced at very small scattering angles with respect to the proton direction. The events constitute a fixed fraction of the deep inelastic, neutral current event sample independent of Bjorken x and Q2 in the range 3 · 10-4 \u3c xBJ \u3c 6 · 10-3 and 10 \u3c Q2 \u3c 100 GeV2
Acoustical Characterization of the Columbia River Estuary
Investigations of near-shore and in-shore environments have, rightly, focused on geological, thermodynamic
and hydrodynamic parameters. A complementary acoustical characterization of the estuarine environment
provides another layer of information to facilitate a more complete understanding of the physical
environment. Relatively few acoustical studies have been carried out in rivers, estuaries or other energetic
environments; nearly all acoustical work in such environments has been done at high acoustic frequencies—
in the 10’s and 100’s of kHz. To this end, within the context of a larger hydrodynamic field experiment
(RIVET II), a small acoustic field experiment was carried out in the Columbia River Estuary (CRE), the
acoustic objective of which was to characterize the acoustic environment in the CRE in terms of ambient
noise field statistics and acoustic propagation characteristics at low-to-mid-frequencies. Acoustically, the
CRE salt wedge consists of two isospeed layers separated by a thin, three-dimensional high-gradient layer.
Results demonstrate that (1) this stratification supports ducting of low-angle acoustic energy in the upper
layer and the creation of an acoustic shadow zone in the lower layer; (2) the spatiotemporal dynamics of the
salt wedge structure during the very energetic flood and ebb tides induce significant variability in the acoustic
environment, as well as significant flow noise across the acoustic transducer; and (3) this flow noise
correlates to current velocity and complicates acoustical observations at low frequencies
Quantitative ocean characterisation: Acoustically analogous environments
Characterisation of the oceanic environment is of interest to many different scientific and
engineering disciplines, including geologists, fisheries managers, marine mammal biologists,
ocean resource managers, conservationists and ocean acousticians. Quantitative environmental
characterisation requires a robust and efficient methodology to evaluate vast
amounts of spatiotemporal environmental data. Presented here is such a methodology –
flexible and robust enough to be used in multiple applications.The case presented is the
determination of acoustically analogous environments in the ocean. A key element of this
work is the construction of a set of acoustically relevant parameters which characterise
acoustical properties of the water column, based on the sound speed profile. Results
of this methodology demonstrate that this set of acoustically significant parameters
accurately represent the acoustic propagation characteristics of the ocean environment
Comparisons among ten models of acoustic backscattering used in aquatic ecosystem research
The article of record may be found at http://dx.doi.org/10.1121/1.4937607Analytical and numerical scattering models with accompanying digital representations are used increasingly to predict acoustic backscatter by fish and zooplankton in research and ecosystem monitoring applications. Ten such models were applied to targets with simple geometric shapes and parameterized (e.g., size and material properties) to represent biological organisms such as zooplankton and fish, and their predictions of acoustic backscatter were compared to those from exact or approximate analytical models, i.e., benchmarks. These comparisons were made for a sphere, spherical shell, prolate spheroid, and finite cylinder, each with homogeneous composition. For each shape, four target boundary conditions were considered: rigid-fixed, pressure-release, gas-filled, and weakly scattering. Target strength (dB re 1 m2) was calculated as a function of insonifying frequency (f 1⁄4 12 to 400 kHz) and angle of incidence...This work was supported by the NOAA Fisheries Advanced Sampling Technologies Working Group, the Office of Naval Research, and the National Oceanic Partnership Progra
(2009)" GPU Parallelization of Algebraic Dynamic Programming
Abstract. Algebraic Dynamic Programming (ADP) is a framework to encode a broad range of optimization problems, including common bioinformatics problems like RNA folding or pairwise sequence alignment. The ADP compiler translates such ADP programs into C. As all the ADP problems have similar data dependencies in the dynamic programming tables, a generic parallelization is possible. We updated the compiler to include a parallel backend, launching a large number of independent threads. Depending on the application, we report speedups ranging from 6.1 × to 25.8 × on a Nvidia GTX 280 through the CUDA libraries.
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