109 research outputs found
Measurement of eta photoproduction on the proton from threshold to 1500 MeV
Beam asymmetry and differential cross section for the reaction gamma+p->eta+p
were measured from production threshold to 1500 MeV photon laboratory energy.
The two dominant neutral decay modes of the eta meson, eta->2g and eta->3pi0,
were analyzed. The full set of measurements is in good agreement with
previously published results. Our data were compared with three models. They
all fit satisfactorily the results but their respective resonance contributions
are quite different. The possible photoexcitation of a narrow state N(1670) was
investigated and no evidence was found.Comment: 18 pages, 14 figures, 4 tables Submitted to EPJ
Neutral pion photoproduction off protons in the energy range 0.3 GeV < E(gamma) < 3 GeV
Single pi0 photoproduction has been studied with the CB-ELSA experiment at
Bonn using tagged photon energies between 0.3 and 3.0 GeV. The experimental
setup covers a very large solid angle of about 98% of 4 pi. Differential cross
sections (d sigma)/(d Omega) have been measured. Complicated structures in the
angular distributions indicate a variety of different resonances being produced
in the s channel intermediate state gamma p --> N* (Delta*) --> p pi0. A
combined analysis including the data presented in this letter along with other
data sets reveals contributions from known resonances and evidence for a new
resonance N(2070)D15.Comment: LaTeX file, 4 pages, 4 encapsulated postscript figures, submitted to
Phys. Rev. Lett. The publication of hep-ex/0407022 is accompanied by
hep-ex/0311045 on photoproduction of eta mesons. Reference [3]: changed,
reference [17]: citation added. Figure 3, 4: SAID added up to 2 GeV for
comparison, update
Do critical thinkers drink too much alcohol, forget to do class assignments, or cheat on exams? Using a critical thinking measure to predict college studentsâ real-world outcomes
Critical thinking is a higher-order way of reasoning composed of the skill and will to use cognitive abilities and knowledge on a daily basis. It is identified as essential by higher education institutions, corporations, and society in general. To analyze whether college students are critical thinkers in their daily lives, the Halpern Critical Thinking Assessment (HCTA; Halpern in Halpern Critical Thinking Assessment (Measurement instrument), Schuhfried, Mödling, 2012) and the real-world outcomes inventory (RWO; Butler in Appl Cogn Psychol 26(5):721â729, 2012) were administered to 238 students. We performed a cluster analysis (K-means-constrained clustering method), and ANOVAs for each cluster solution tested to identify the most suitable clustering solution, taking the RWO inventory dimensions as dependent variables and cluster membership as an independent variable. Four separate clusters emerged, each representing a different profile related to studentsâ everyday negative outcomes resulting from a lack of critical thinking. We performed multinomial logistic regression to examine which dimensions of the HCTA test, as well as gender, age, and disciplinary area, predicted the four singular groups of students that emerged: âMature,â âRisk-taking,â âLost in translation,â and âReflective.â Results indicate that: (1) age is a relevant predictor of slackness, rashness, and health neglect, all characteristics of âMatureâ students; (2) students who are particularly skilled in hypothesis testing tend to be âRisk-taking,â while it is less likely that students who are specifically competent in argument analysis will be in this group; (3) gender is relevant to predict âLost in translationâ students, while argument analysis is negatively related to the chances of being in this group. Our study supports the relevance of critical thinking in daily decisions and everyday outcomes.FCT -Fundação para a CiĂȘncia e a Tecnologia(Advanced Training)info:eu-repo/semantics/publishedVersio
Academic Performance and Behavioral Patterns
Identifying the factors that influence academic performance is an essential
part of educational research. Previous studies have documented the importance
of personality traits, class attendance, and social network structure. Because
most of these analyses were based on a single behavioral aspect and/or small
sample sizes, there is currently no quantification of the interplay of these
factors. Here, we study the academic performance among a cohort of 538
undergraduate students forming a single, densely connected social network. Our
work is based on data collected using smartphones, which the students used as
their primary phones for two years. The availability of multi-channel data from
a single population allows us to directly compare the explanatory power of
individual and social characteristics. We find that the most informative
indicators of performance are based on social ties and that network indicators
result in better model performance than individual characteristics (including
both personality and class attendance). We confirm earlier findings that class
attendance is the most important predictor among individual characteristics.
Finally, our results suggest the presence of strong homophily and/or peer
effects among university students
Photoproduction of eta mesons off protons for photon energies from 0.75 GeV to 3 GeV
Total and differential cross sections for the reaction p(gamma, eta)p have
been measured for photon energies in the range from 750 MeV to 3 GeV. The
low-energy data are dominated by the S11 wave which has two poles in the energy
region below 2 GeV. Eleven nucleon resonances are observed in their decay into
p eta. At medium energies we find evidence for a new resonance N(2070)D15 with
(mass, width) = (2068+-22, 295+-40) MeV. At photon energies above 1.5 GeV, a
strong peak in forward direction develops, signalling the exchange of vector
mesons in the t channel.Comment: LaTeX, 4 pages including 4 eps-figures, submitted to Phys. Rev. Lett.
The publication of hep-ex/0311045 is accompanied by hep-ex/0407022 on
photoproduction of neutral pions, submitted to Phys. Rev. Lett. Fits
published in the latest version are based on additional data, new beam
asymmetry data from GRAAL are included, for instance. The data demanded more
resonant contributions which were studied in detail. PWA reference adde
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
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
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