103 research outputs found
Measurement of the open-charm contribution to the diffractive proton structure function
Production of D*+/-(2010) mesons in diffractive deep inelastic scattering has
been measured with the ZEUS detector at HERA using an integrated luminosity of
82 pb^{-1}. Diffractive events were identified by the presence of a large
rapidity gap in the final state. Differential cross sections have been measured
in the kinematic region 1.5 < Q^2 < 200 GeV^2, 0.02 < y < 0.7, x_{IP} < 0.035,
beta 1.5 GeV and |\eta(D*+/-)| < 1.5. The measured cross
sections are compared to theoretical predictions. The results are presented in
terms of the open-charm contribution to the diffractive proton structure
function. The data demonstrate a strong sensitivity to the diffractive parton
densities.Comment: 35 pages, 11 figures, 6 table
Isolated tau leptons in events with large missing transverse momentum at HERA
A search for events containing isolated tau leptons and large missing
transverse momentum, not originating from the tau decay, has been performed
with the ZEUS detector at the electron-proton collider HERA, using 130 pb^-1 of
integrated luminosity. A search was made for isolated tracks coming from
hadronic tau decays. Observables based on the internal jet structure were
exploited to discriminate between tau decays and quark- or gluon-induced jets.
Three tau candidates were found, while 0.40 +0.12 -0.13 were expected from
Standard Model processes, such as charged current deep inelastic scattering and
single W-boson production. To search for heavy-particle decays, a more
restrictive selection was applied to isolate tau leptons produced together with
a hadronic final state with high transverse momentum. Two candidate events
survive, while 0.20 +-0.05 events are expected from Standard Model processes.Comment: 28 pages, 4 figures, 3 tables, accepted by Phys. Lett. B. Updated
with minor changes to the text requested by the journal refere
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
Dexamethasone intravitreal implant in previously treated patients with diabetic macular edema : Subgroup analysis of the MEAD study
Background: Dexamethasone intravitreal implant 0.7 mg (DEX 0.7) was approved for treatment of diabetic macular edema (DME) after demonstration of its efficacy and safety in the MEAD registration trials. We performed subgroup analysis of MEAD study results to evaluate the efficacy and safety of DEX 0.7 treatment in patients with previously treated DME. Methods: Three-year, randomized, sham-controlled phase 3 study in patients with DME, best-corrected visual acuity (BCVA) of 34.68 Early Treatment Diabetic Retinopathy Study letters (20/200.20/50 Snellen equivalent), and central retinal thickness (CRT) 65300 \u3bcm measured by time-domain optical coherence tomography. Patients were randomized to 1 of 2 doses of DEX (0.7 mg or 0.35 mg), or to sham procedure, with retreatment no more than every 6 months. The primary endpoint was 6515-letter gain in BCVA at study end. Average change in BCVA and CRT from baseline during the study (area-under-the-curve approach) and adverse events were also evaluated. The present subgroup analysis evaluated outcomes in patients randomized to DEX 0.7 (marketed dose) or sham based on prior treatment for DME at study entry. Results: Baseline characteristics of previously treated DEX 0.7 (n = 247) and sham (n=261) patients were similar. In the previously treated subgroup, mean number of treatments over 3 years was 4.1 for DEX 0.7 and 3.2 for sham, 21.5 % of DEX 0.7 patients versus 11.1 % of sham had 6515-letter BCVA gain from baseline at study end (P = 0.002), mean average BCVA change from baseline was +3.2 letters with DEX 0.7 versus +1.5 letters with sham (P = 0.024), and mean average CRT change from baseline was -126.1 \u3bcm with DEX 0.7 versus -39.0 \u3bcm with sham(P < 0.001). Cataract-related adverse events were reported in 70.3 % of baseline phakic patients in the previously treated DEX 0.7 subgroup; vision gains were restored following cataract surgery. Conclusions: DEX 0.7 significantly improved visual and anatomic outcomes in patients with DME previously treated with laser, intravitreal anti-vascular endothelial growth factor, intravitreal triamcinolone acetonide, or a combination of these therapies. The safety profile of DEX 0.7 in previously treated patients was similar to its safety profile in the total study population
TRANSPORT THEORY AND SPECTRAL PROBLEMS
A simple model of time-independent neutron transport on a line as a stochastic process, using the method of invariant imbedding, is considered. Non- linear equations for the expected values (flux) are also obtained and solved, the results are compared with the ordinary linear theory, and possible advantages of the new formulation are cited. Generalizations to a large class of transport problems are discussed. The nonlinear timedependent operator for transport in one dimension is considered in detail. It has a pure point spectrum, and expansion theorems can be proved. These results contrast with those for isotropic one-velocity neutron transport in the infinite slab. Here there are only a finite number of points in the point spectrum, with a halfplane in the continuous spectrum. Approximations to the eigenvalues and eigenfunctions for the slab case, as well as extensions to the multivelocity problem, are mentioned. There is a brief discussion of recent spectral and expansion theorems for very general geometries. (auth
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Invariant imbedding in two dimensions
J. Corones has noted that the doubling and addition formulas of invariant imbedding can be extended conceptually to very general situations. All that is needed is a black box ''process'' with n ''ports.'' The /ital i/th port has vector input I/sub i/ and vector output J/sub i/. Addition formulas result when two or more of these processes are joined together to form a new process in some regular way. For example, four congruent squares can be juxtaposed to form a larger square. At each join, the output of one process becomes the input of the other and vice versa. (We always suppose the join to occur at one or more ports.) Addition formulas result from the combination of these shared quantities. Corones has thus pointed out that invariant imbedding is not, as is sometimes asserted, an inherently one-dimensional (1-D) method, but works conceptually in any number of dimensions; some previous work that is conceptually along these lines, with references to other such works, can be found in Refs. 2-4. The details can, of course, become very complicated. We shall show that the method is computationally feasible for certain two-dimensional (2-D) problems. To conform to the thrust of these proceedings, we shall usually phrase our discussions in terms of transport theory rather than speaking of more abstract processes. 7 refs., 13 figs
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Inverse problems SVD and pseudo SVD
Physical experiments often gives rise to integral equations of the first kind. If the detection equipment can be adjusted that fact can lead to a kernel function that depends on one or more parameters. We address the general question of how to choose those parameters in such a way as to make the integral operator as well-conditioned as possible, thus optimizing the experiment. Attention is focused on the condition number of the discretized kernel and on its principal singular vector. Several examples are given and some preliminary general results are obtained
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