9,827 research outputs found
A consistent explanation of the Roper phenomenology
We study the electromagnetic transitions of the Roper N(1440) resonance. Our
results, when combined with the previously obtained for the mass and the pionic
strong decay widths of the Roper, show that within a non-relativistic
constituent quark model scheme, a comprehensible understanding of the Roper
phenomenology can be achieved. They also seem to support the view of the Roper
as a radial excitation of the nucleon, though more experimental data are needed
to reach a definitive conclusion.Comment: 14 pages, 4 figures (7 postscript files). Some referencess adde
Community structures and role detection in music networks
We analyze the existence of community structures in two different social
networks obtained from similarity and collaborative features between musical
artists. Our analysis reveals some characteristic organizational patterns and
provides information about the driving forces behind the growth of the
networks. In the similarity network, we find a strong correlation between
clusters of artists and musical genres. On the other hand, the collaboration
network shows two different kinds of communities: rather small structures
related to music bands and geographic zones, and much bigger communities built
upon collaborative clusters with a high number of participants related through
the period the artists were active. Finally, we detect the leading artists
inside their corresponding communities and analyze their roles in the network
by looking at a few topological properties of the nodes.Comment: 14 pages 7 figure
Strong Pionic Decays From a Spectroscopic Quark Model
From a refined non-relativistic quark model that fits the baryonic low-energy
spectrum the study of strong pion decay processes within an elementary emission
model scheme points out the need of incorporating size-contributing components
into the baryon wave functions. In particular the effect of a (qqq qantiq)
component is investigated in the framework of a quark pair creation model.Comment: 26 pages, 9 figures (1 postscript file), LaTe
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