2,441 research outputs found
A new numerical method for obtaining gluon distribution functions , from the proton structure function
An exact expression for the leading-order (LO) gluon distribution function
from the DGLAP evolution equation for the proton structure
function for deep inelastic scattering has
recently been obtained [M. M. Block, L. Durand and D. W. McKay, Phys. Rev.
D{\bf 79}, 014031, (2009)] for massless quarks, using Laplace transformation
techniques. Here, we develop a fast and accurate numerical inverse Laplace
transformation algorithm, required to invert the Laplace transforms needed to
evaluate , and compare it to the exact solution. We obtain accuracies
of less than 1 part in 1000 over the entire and spectrum. Since no
analytic Laplace inversion is possible for next-to-leading order (NLO) and
higher orders, this numerical algorithm will enable one to obtain accurate NLO
(and NNLO) gluon distributions, using only experimental measurements of
.Comment: 9 pages, 2 figure
Large Rapidity Gaps in PP Collisions
The survival probability of large rapidity gaps in pp collisions is
calculated for several different eikonal models of the Gaussian form. Results
obtained for models based on partonic interactions are quite similar. The
Regge-pole model predicts a higher value of .Comment: 11 pages, TAUP 2030-93 (LaTeX, two figures not attached, available
from authors
Improving parsing by incorporating "prosodic clause boundaries" into a grammar
In written language, punctuation is used to separate main and subordinate clause. In spoken language, ambiguities arise due to missing punctuation, but clause boundaries are often marked prosodically and can be used instead. We detect PCBs (Prosodically markedClauseBoundaries) by using prosodic features (duration, intonation, energy, and pause information) with a neural network, achieving a recognition rate of 82%. PCBs are integrated into our grammar using a special syntactic category "break" that can be used in the phrase-structure rules of the grammar in a similar way as punctuation is used in grammars for written language. Whereas punctuation in most cases is obligatory, PCBs are sometimes optional. Moreover, they can in principle occur everywhere in the sentence due e.g. to hesitations or misrecognition. To cope with these problems we tested two different approaches: A slightly modified parser for word chains containing PCBs and a word graph parser that takes the probabilities of PCBs into account. Tests were conducted on a subset of infinitive subordinate clauses from a large speech database containing sentences from the domain of train table inquiries. The average number of syntactic derivations could be reduced by about 70 % even when working on recognized word graphs
Analytic models and forward scattering from accelerator to cosmic-ray energies
Analytic models for hadron-hadron scattering are characterized by analytical
parametrizations for the forward amplitudes and the use of dispersion relation
techniques to study the total cross section and the
parameter. In this paper we investigate four aspects related to the application
of the model to and scattering, from accelerator to cosmic-ray
energies: 1) the effect of different estimations for from
cosmic-ray experiments; 2) the differences between individual and global
(simultaneous) fits to and ; 3) the role of the
subtraction constant in the dispersion relations; 4) the effect of distinct
asymptotic inputs from different analytic models. This is done by using as a
framework the single Pomeron and the maximal Odderon parametrizations for the
total cross section. Our main conclusions are the following: 1) Despite the
small influence from different cosmic-ray estimations, the results allow us to
extract an upper bound for the soft pomeron intercept: ;
2) although global fits present good statistical results, in general, this
procedure constrains the rise of ; 3) the subtraction constant as
a free parameter affects the fit results at both low and high energies; 4)
independently of the cosmic-ray information used and the subtraction constant,
global fits with the odderon parametrization predict that, above GeV, becomes greater than , and
this result is in complete agreement with all the data presently available. In
particular, we infer at GeV and
at 500 GeV (BNL RHIC energies).Comment: 16 pages, 7 figures, aps-revtex, wording changes, corrected typos, to
appear in Physical Review
An effective field theory approach to two trapped particles
We discuss the problem of two particles interacting via short-range
interactions within a harmonic-oscillator trap. The interactions are organized
according to their number of derivatives and defined in truncated model spaces
made from a bound-state basis. Leading-order (LO) interactions are iterated to
all orders, while corrections are treated in perturbation theory. We show
explicitly that next-to-LO and next-to-next-to-LO interactions improve
convergence as the model space increases. In the large-model-space limit we
regain results from a pseudopotential. Arbitrary scattering lengths are
considered, as well as a generalization to include the non-vanishing range of
the interaction.Comment: 27 pages, 12 figure
A Parallel SSOR Preconditioner for Lattice QCD
A parallelizable SSOR preconditioning scheme for Krylov subspace iterative
solvers in lattice QCD applications involving Wilson fermions is presented. In
actual Hybrid Monte Carlo and quark propagator calculations it helps to reduce
the number of iterations by a factor of 2 compared to conventional odd-even
preconditioning. This corresponds to a gain in cpu-time of 30\% - 70\% over
odd-even preconditioning.Comment: Talk presented at LATTICE96(algorithms), 3 pages, LaTeX file, 3
epsf-files include
Improving parsing of spontaneous speech with the help of prosodic boundaries
Parsing can be improved in automatic speech understanding if prosodic boundary marking is taken into account, because syntactic boundaries are often marked by prosodic means. Because large databases are needed for the training of statistical models for prosodic boundaries, we developed a labeling scheme for syntactic-prosodic boundaries within the German VERBMOBIL project (automatic speech-to-speech translation). We compare the results of classifiers (multi-layer perceptrons and language models) trained on these syntactic-prosodic boundary labels with classifiers trained on perceptual-prosodic and purely syntactic labels. Recognition rates of up to 96% were achieved. The turns that we need to parse consist of 20 words on the average and frequently contain sequences of partial sentence equivalents due to restarts, ellipsis, etc. For this material, the boundary scores computed by our classifiers can successfully be integrated into the syntactic parsing of word graphs; currently, they improve the parse time by 92% and reduce the number of parse trees by 96%. This is achieved by introducing a special Prosodic Syntactic Clause Boundary symbol (PSCB) into our grammar and guiding the search for the best word chain with the prosodic boundary scores
Regional climate model simulations as input for hydrological applications: evaluation of uncertainties
International audienceThe ERA15 Reanalysis (1979-1993) has been dynamically downscaled over Central Europe using 4 different regional climate models. The regional simulations were analysed with respect to 2m temperature and total precipitation, the main input parameters for hydrological applications. Model results were validated against three reference data sets (ERA15, CRU, DWD) and uncertainty ranges were derived. For mean annual 2 m temperature over Germany, the simulation bias lies between -1.1°C and +0.9°C depending on the combination of model and reference data set. The bias of mean annual precipitation varies between -31 and +108 mm/year. Differences between RCM results are of the same magnitude as differences between the reference data sets
Localization of a 64-kDa phosphoprotein in the lumen between the outer and inner envelopes of pea chloroplasts
The identification and localization of a marker protein for the intermembrane space between the outer and inner chloroplast envelopes is described. This 64-kDa protein is very rapidly labeled by [γ-32P]ATP at very low (30 nM) ATP concentrations and the phosphoryl group exhibits a high turnover rate. It was possible to establish the presence of the 64-kDa protein in this plastid compartment by using different chloroplast envelope separation and isolation techniques. In addition comparison of labeling kinetics by intact and hypotonically lysed pea chloroplasts support the localization of the 64-kDa protein in the intermembrane space. The 64-kDa protein was present and could be labeled in mixed envelope membranes isolated from hypotonically lysed plastids. Mixed envelope membranes incorporated high amounts of 32P from [γ-32P]ATP into the 64-kDa protein, whereas separated outer and inner envelope membranes did not show significant phosphorylation of this protein. Water/Triton X-114 phase partitioning demonstrated that the 64-kDa protein is a hydrophilic polypeptide. These findings suggest that the 64-kDa protein is a soluble protein trapped in the space between the inner and outer envelope membranes. After sonication of mixed envelope membranes, the 64-kDa protein was no longer present in the membrane fraction, but could be found in the supernatant after a 110000 × g centrifugation
Survival probability for exclusive central diffractive production of colorless states at the LHC
In this paper we discuss the survival probability for exclusive central
diffractive production of a colorless small size system at the LHC. This
process has a clear signature of two large rapidity gaps. Using the eikonal
approach for the description of soft interactions, we predict the value of the
survival probability to be about 5~6% for single channel models, while for a
two channel model the survival probability is about 3%. The dependence of the
survival probability factor (damping factor) on the transverse momenta of the
recoiled protons is discussed, and we suggest it be measured at the Tevatron so
as to minimize the possible ambiguity in the calculation of survival
probability at the LHC.Comment: 33 pages, 26 figure
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