27 research outputs found
Adapting Clinical Images to Appear with Different Noise and Sharpness to Model a Different Detector
Precision Measurement of the p(e,e ' p)pi(0) Reaction at Threshold
New results are reported from a measurement of electroproduction near
threshold using the reaction. The experiment was
designed to determine precisely the energy dependence of and wave
electromagnetic multipoles as a stringent test of the predictions of Chiral
Perturbation Theory (ChPT). The data were taken with an electron beam energy of
1192 MeV using a two-spectrometer setup in Hall A at Jefferson Lab. For the
first time, complete coverage of the and angles
in the center-of-mass was obtained for invariant energies above
threshold from 0.5 MeV up to 15 MeV. The 4-momentum transfer coverage
ranges from 0.05 to 0.155 (GeV/c) in fine steps. A simple phenomenological
analysis of our data shows strong disagreement with wave predictions from
ChPT for (GeV/c), while the wave predictions are in
reasonable agreement.Comment: 5 pages, 6 figure
Large expert-curated database for benchmarking document similarity detection in biomedical literature search
Document recommendation systems for locating relevant literature have mostly relied on methods developed a decade ago. This is largely due to the lack of a large offline gold-standard benchmark of relevant documents that cover a variety of research fields such that newly developed literature search techniques can be compared, improved and translated into practice. To overcome this bottleneck, we have established the RElevant LIterature SearcH consortium consisting of more than 1500 scientists from 84 countries, who have collectively annotated the relevance of over 180 000 PubMed-listed articles with regard to their respective seed (input) article/s. The majority of annotations were contributed by highly experienced, original authors of the seed articles. The collected data cover 76% of all unique PubMed Medical Subject Headings descriptors. No systematic biases were observed across different experience levels, research fields or time spent on annotations. More importantly, annotations of the same document pairs contributed by different scientists were highly concordant. We further show that the three representative baseline methods used to generate recommended articles for evaluation (Okapi Best Matching 25, Term Frequency-Inverse Document Frequency and PubMed Related Articles) had similar overall performances. Additionally, we found that these methods each tend to produce distinct collections of recommended articles, suggesting that a hybrid method may be required to completely capture all relevant articles. The established database server located at https://relishdb.ict.griffith.edu.au is freely available for the downloading of annotation data and the blind testing of new methods. We expect that this benchmark will be useful for stimulating the development of new powerful techniques for title and title/abstract-based search engines for relevant articles in biomedical research.Peer reviewe
Variabilidade genética em tambaquis (Teleostei: Characidae) de diferentes regiões do Brasil
First measurement of the polarization observable E in the p→(γ→,π<sup>+</sup>)n reaction up to 2.25 GeV
First results from the longitudinally polarized frozen-spin target (FROST)
program are reported. The double-polarization observable E, for the reaction
, has been measured using a circularly polarized
tagged-photon beam, with energies from 0.35 to 2.37 GeV. The final-state pions
were detected with the CEBAF Large Acceptance Spectrometer in Hall B at the
Thomas Jefferson National Accelerator Facility. These polarization data agree
fairly well with previous partial-wave analyses at low photon energies. Over
much of the covered energy range, however, significant deviations are observed,
particularly in the high-energy region where high-L multipoles contribute. The
data have been included in new multipole analyses resulting in updated nucleon
resonance parameters. We report updated fits from the Bonn-Gatchina, J\"ulich,
and SAID groups.Comment: 6 pages, 3 figure
Beam-target helicity asymmetry e in K0 Λ and K0 Σ0 photoproduction on the neutron
We report the first measurements of the E beam-target helicity asymmetry for the γ - n - →K0Λ and K0Σ0 channels in the energy range 1.70≤W≤2.34 GeV. The CLAS system at Jefferson Lab uses a circularly polarized photon beam and a target consisting of longitudinally polarized solid molecular hydrogen deuteride with low background contamination for the measurements. The multivariate analysis method boosted decision trees is used to isolate the reactions of interest. Comparisons with predictions from the KaonMAID, SAID, and Bonn-Gatchina models are presented. These results will help separate the isospin I=0 and I=1 photocoupling transition amplitudes in pseudoscalar meson photoproduction
First measurement of the helicity asymmetry E in eta photoproduction on the proton
Results are presented for the first measurement of the double-polarization
helicity asymmetry E for the photoproduction reaction . Data were obtained using the FROzen Spin Target (FROST)
with the CLAS spectrometer in Hall B at Jefferson Lab, covering a range of
center-of-mass energy W from threshold to 2.15 GeV and a large range in
center-of-mass polar angle. As an initial application of these data, the
results have been incorporated into the J\"ulich model to examine the case for
the existence of a narrow resonance between 1.66 and 1.70 GeV. The
addition of these data to the world database results in marked changes in the
predictions for the E observable using that model. Further comparison with
several theoretical approaches indicates these data will significantly enhance
our understanding of nucleon resonances
Photon beam asymmetry Sigma for eta and eta ' photoproduction from the proton
Measurements of the linearly-polarized photon beam asymmetry for
photoproduction from the proton of and mesons are
reported. A linearly-polarized tagged photon beam produced by coherent
bremsstrahlung was incident on a cryogenic hydrogen target within the CEBAF
Large Acceptance Spectrometer. Results are presented for the reaction for incident photon energies from 1.070 to 1.876 GeV, and from
1.516 to 1.836 GeV for the reaction. For , the data reported here considerably extend the range of
measurements to higher energies, and are consistent with the few previously
published measurements for this observable near threshold. For , the results obtained are consistent with the few previously
published measurements for this observable near threshold, but also greatly
expand the incident photon energy coverage for that reaction. Initial analysis
of the data reported here with the Bonn-Gatchina model strengthens the evidence
for four nucleon resonances -- the , ,
and resonances -- which presently lack the
"four-star" status in the current Particle Data Group compilation, providing
examples of how these new measurements help refine models of the
photoproduction process.Comment: 10 pages, 3 figure