14,831 research outputs found
Three body systems with strangeness and exotic systems
Get PDFWe report on four 's and three 's, in the 1500 - 1800 MeV
region, as two meson - one baryon S-wave resonances found by solving
the Faddeev equations in the coupled channel approach, which can be associated
to the existing = -1, low lying baryon resonances. On the
other hand we also report on a new, hidden strangeness state, mostly made
of , with mass around 1920 MeV, which we think could be
responsible for the peak seen in the around this
energy. Finally we address a very novel topic in which we show how few body
systems of several mesons can be produced, with their spins aligned up
to J=6, and how these states found theoretically can be associated to several
known mesons with spins J=2,3,4,5,6.Comment: Talk at the 21st European Conference on Few Body Problems in Physics,
Salamanca, Sep. 201
A new perspective on the Faddeev equations and the system from chiral dynamics and unitarity in coupled channels
Full text linkWe review recent work concerning the interaction and Faddeev
equations with chiral dynamics which allow us to look at the from a
different perspective and pay attention to problems that have been posed in
previous studies on the subject. We show results which provide extra
experimental evidence on the existence of two states. We then
show the findings of a recent approach to Faddeev equations using chiral
unitary dynamics, where an explicit cancellation of the two body off shell
amplitude with three body forces stemming from the same chiral Lagrangians
takes place. This removal of the unphysical off shell part of the amplitudes is
most welcome and renders the approach unambiguous, showing that only on shell
two body amplitudes need to be used. With this information in mind we use an
approximation to the Faddeev equations within the fixed center approximation to
study the system, providing answers within this approximation to
questions that have been brought before and evaluating binding energies and
widths of this three body system. As a novelty with respect to recent work on
the topic we find a bound state of the system with spin S=1, like a bound state
of -deuteron, less bound that the one of S=0, where all recent efforts
have been devoted. The width is relatively large in this case, suggesting
problems in a possible experimental observation.Comment: 18 pages, 7 figures, one misprint corrected, Nuclear Physics A in
pres
Molecular evolution of aphids and their primary ( Buchnera sp.) and secondary endosymbionts: implications for the role of symbiosis in insect evolution.
Get PDFAphids maintain an obligate, endosymbiotic association with Buchnera sp., a bacterium closely related to Escherichia coli. Bacteria are housed in specialized cells of organ-like structures called bacteriomes in the hemocoel of the aphid and are maternally transmitted. Phylogenetic studies have shown that the association had a single origin, dated about 200-250 million years ago, and that host and endosymbiont lineages have evolved in parallel since then. However, the pattern of deepest branching within the aphid family remains unsolved, which thereby hampers tin appraisal of, for example, the role played by horizontal gene transfer in the early evolution of Buchnera. The main role of Buchnera in this association is the biosynthesis and provisioning of essential amino acids to its aphid host. Physiological and metabolic studies have recently substantiated such nutritional role. In addition, genetic studies of Buchnera from several aphids have shown additional modifications, such as strong genome reduction, high A+T content compared to free-living bacteria, differential evolutionary rates, a relative increase in the number of non-synonymous substitutions, and gene amplification mediated by plasmids. Symbiosis is an active process in insect evolution cis revealed by the intermediate values of the previous characteristics showed by secondary symbionts compared to free-living bacteria and Buchnera
Interpreting the peak structures around 1800 MeV in the BES data on ,
Full text linkIn this talk we present an interpretation for the experimental data available
on two different processes, namely, , , which seem to indicate existence of two new resonances
with the same quantum numbers () and very similar mass
(~1800 MeV) but with very different decay properties. However, our studies show
that the peak structure found in the invariant mass, in , is a manifestation of the well known while
the cross section enhancement found in is indeed
a new resonance with mass near 1800 MeV. We present an explanation for
the different decay properties of these two scalar resonances.Comment: Proceedings for the nuclear physics meeting ("XXXVI Reuni\~ao de
trabalho sobre f\'isica nuclear no Brasil") held in Maresias during Sept.
1-5. To be published as AIP proceeding
Delta rho pi interaction leading to N* and Delta* resonances
Full text linkWe have performed a calculation for the three body system
by using the fixed center approximation to Faddeev equations, taking the
interaction between and , and, and and
from the chiral unitary approach. We find several peaks in the modulus
squared of the three-body scattering amplitude, indicating the existence of
resonances, which can be associated to known and and baryon states.Comment: Presented at the 21st European Conference on Few-Body Problems in
Physics, Salamanca, Spain, 30 August - 3 September 201
Letter to Colonel William Card: 1998-06-02
Get PDFLetter to Colonel William Card from the officers of Harlingen Obstetrics and Gynecology Associates, P.A. (HOGA) regarding their support for the Regional Academic Health Center (RAHC).https://scholarworks.utrgv.edu/hcard/1225/thumbnail.jp
Recent Developments in Chiral Unitary Dynamics of Resonances
Get PDFIn this talk I summarize recent findings made on the description of axial
vector mesons as dynamically generated states from the interaction of
peseudoscalar mesons and vector mesons, dedicating some attention to the two
states. Then I review the generation of open and hidden charm
scalar and axial states. Finally, I present recent results showing that the low
lying baryon resonances for S=-1 can be obtained as bound states or
resonances of two mesons and one baryon in coupled channels dynamics.Comment: Talk at the International Conference on Hadron Physics, Troia07,
Canakkale, Turkey, Sep. 2007 and at the Chiral Symmetry in Hadron and Nuclear
Physics Workshop, Chiral07, Osaka, November 200
High frequency mechanical excitation of a silicon nanostring with piezoelectric aluminum nitride layers
Get PDFA strong trend for quantum based technologies and applications follows the
avenue of combining different platforms to exploit their complementary
technological and functional advantages. Micro and nano-mechanical devices are
particularly suitable for hybrid integration due to the easiness of fabrication
at multi-scales and their pervasive coupling with electrons and photons. Here,
we report on a nanomechanical technological platform where a silicon chip is
combined with an aluminum nitride layer. Exploiting the AlN piezoelectricity,
Surface Acoustic Waves are injected in the Si layer where the material has been
localy patterned and etched to form a suspended nanostring. Characterizing the
nanostring vertical displacement induced by the SAW, we found an external
excitation peak efficiency in excess of 500 pm/V at 1 GHz mechanical frequency.
Exploiting the long term expertise in silicon photonic and electronic devices
as well as the SAW robustness and versatility, our technological platform
represents a strong candidate for hybrid quantum systems
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