32 research outputs found
Tetraquarks in a chiral constituent quark model
We analyze the possibility of heavy-light tetraquark bound states by means of
a chiral constituent quark model. The study is done in a variational approach.
Special attention is paid to the contribution given by the different terms of
the interacting potential and also to the role played by the different color
channels. We find a stable state for both and
configurations. Possible decay modes of these structures are
analyzed.Comment: 13 pages, no figures. Accepted for publication in European Journal of
Physics
Four-quark stability
The physics of charm has become one of the best laboratories exposing the
limitations of the naive constituent quark model and also giving hints into a
more mature description of meson spectroscopy, beyond the simple
quark--antiquark configurations. In this talk we review some recent studies of
multiquark components in the charm sector and discuss in particular exotic and
non-exotic four-quark systems, both with pairwise and many-body forces.Comment: 6 pages. Article based on the presentations by J. Vijande and J.-M.
Richard at the Fifth Workshop on Critical Stability, Erice, Sicil
Pentaquark baryons in SU(3) quark model
We study the SU(3) group structure of pentaquark baryons which are made of
four quarks and one antiquark. The pentaquark baryons form {1}, {8}, {10},
{10}-bar, {27}, and {35} multiplets in SU(3) quark model. First, the flavor
wave functions of all the pentaquark baryons are constructed in SU(3) quark
model and then the flavor SU(3) symmetry relations for the interactions of the
pentaquarks with three-quark baryons and pentaquark baryons are obtained.Comment: REVTeX, 36 pages, 8 figures, references added, section for mass sum
rules is added, to appear in Phys. Rev.
Charmed Exotics in Heavy Ion Collisions
Based on the color-spin interaction in diquarks, we argue that charmed
multiquark hadrons are likely to exist. Because of the appreciable number of
charm quarks produced in central nucleus-nucleus collisions at
ultrarelativistic energies, production of charmed multiquark hadrons is
expected to be enhanced in these collisions. Using both the quark coalescence
model and the statistical hadronization model, we estimate the yield of charmed
tetraquark meson and pentaquark baryon in heavy ion
collisions at RHIC and LHC. We further discuss the decay modes of these charmed
exotic hadrons in order to facilitate their detections in experiments
Search for a strongly decaying neutral charmed pentaquark
We present a search for a charmed pentaquark decaying strongly to
. Finding no evidence for such a state, we set limits on the cross
section times branching ratio relative to and under particular
assumptions about the production mechanism.Comment: To be published in Physics Letters
An integrated approach to control soil-transmitted helminthiasis, schistosomiasis, intestinal protozoa infection, and diarrhea : protocol for a cluster randomized trial
Background: The global strategy to control helminthiases (schistosomiasis and soil-transmitted helminthiasis) emphasizes preventive chemotherapy. However, in the absence of access to clean water, improved sanitation, and adequate hygiene, reinfection after treatment can occur rapidly. Integrated approaches might be necessary to sustain the benefits of preventive chemotherapy and make progress toward interruption of helminthiases transmission.
Objective: The aim of this study was to assess and quantify the effect of an integrated control package that consists of preventive chemotherapy, community-led total sanitation, and health education on soil-transmitted helminthiasis, schistosomiasis, intestinal protozoa infection, and diarrhea in rural Côte d’Ivoire.
Methods: In a first step, a community health education program was developed that includes an animated cartoon to promote improved hygiene and health targeting school-aged children, coupled with a health education theater for the entire community. In a second step, a cluster randomized trial was implemented in 56 communities of south-central Côte d’Ivoire with 4 intervention arms: (1) preventive chemotherapy; (2) preventive chemotherapy plus community-led total sanitation; (3) preventive chemotherapy plus health education; and (4) all 3 interventions combined. Before implementation of the aforementioned interventions, a baseline parasitologic, anthropometric, and hygiene-related knowledge, attitudes, practices, and beliefs survey was conducted. These surveys were repeated 18 and 39 months after the baseline cross-sectional survey to determine the effect of different interventions on helminth and intestinal protozoa infection, nutritional indicators, and knowledge, attitudes, practices, and beliefs. Monitoring of diarrhea was done over a 24-month period at 2-week intervals, starting right after the baseline survey.
Results: Key results from this cluster randomized trial will shed light on the effect of integrated approaches consisting of preventive chemotherapy, community-led total sanitation, and health education against infections with soil-transmitted helminths, schistosomes, an intestinal protozoa and prevention of diarrhea in a rural part of Côte d’Ivoire.
Conclusions: The research provided new insights into the acceptability, strengths, and limitations of an integrated community-based control package targeting helminthiases, intestinal protozoa infections, and diarrhea in rural communities of Côte d’Ivoire. In the longer term, the study will allow determining the effect of the integrated control approach on infection patterns with parasitic worms and intestinal protozoa, diarrheal incidence, anthropometric measures, and hygiene-related knowledge, attitudes, practices, and beliefs
Dark matter with invisible light from heavy double charged leptons of almost-commutative geometry?
A new candidate of cold dark matter arises by a novel elementary particle
model: the almostcommutative AC-geometrical framework. Two heavy leptons are
added to the Standard Model, each one sharing a double opposite electric charge
and an own lepton flavor number The novel mathematical theory of
almost-commutative geometry [1] wishes to unify gauge models with gravity. In
this scenario two new heavy (m_L>100GeV), oppositely double charged leptons
(A,C),(A with charge -2 and C with charge +2), are born with no twin quark
companions. The model naturally involves a new U(1) gauge interaction,
possessed only by the AC-leptons and providing a Coulomblike attraction between
them. AC-leptons posses electro-magnetic as well as Z-boson interaction and,
according to the charge chosen for the new U(1) gauge interaction, a new
"invisible light" interaction. Their final cosmic relics are bounded into
"neutral" stable atoms (AC) forming the mysterious cold dark matter, in the
spirit of the Glashow's Sinister model. An (AC) state is reached in the early
Universe along a tail of a few secondary frozen exotic components. They should
be now here somehow hidden in the surrounding matter. The two main secondary
manifest relics are C (mostly hidden in a neutral (Cee) "anomalous helium"
atom, at a 10-8 ratio) and a corresponding "ion" A bounded with an ordinary
helium ion (4He); indeed the positive helium ions are able to attract and
capture the free A fixing them into a neutral relic cage that has nuclear
interaction (4HeA).Comment: This paper has been merged with [astro-ph/0603187] for publication in
Classical and Quantum Gravit
Heavy Quark Symmetry and the Skyrme Model
We present a consistent way of describing heavy baryons containing a heavy
quark as bound states of an soliton and heavy mesons. The resulting
mass formula reveals the heavy quark symmetry explicitly. By extending the
model to the orbitally excited states, we establish the generic structure of
the heavy baryon spectrum. As anticipated from the heavy quark spin symmetry,
the -factor denoting the hyperfine splitting constant {\em vanishes} and the
baryons with the same angular momentum of light degrees of freedom form
degenerate doublets. This approach is also applied to the pentaquark exotic
baryons, where the conventional -factor plays no more a role of the
hyperfine constant. After diagonalizing the Hamiltonian of order , we
get the degenerate doublets, which implies the vanishing of genuine hyperfine
splitting.Comment: REVTeX, 33 pages, 3 figures included, SNUTP-94/13 (revised
Search for the pentaquark via the P^0_{{c bar}s} --> phi,pi,p decay
We report results of the first search for the pentaquark P_{{c bar}s} which
is predicted to be a doublet of states: P^0_{{c bar}s}=({c bar} s u u d) and
P^-_{{c bar}s}=({c bar} s d d u). A search was made for the decay P^0_{{c
bar}s} --> phi,pi,p in data from Fermilab experiment E791, in which 500 GeV/c
pi^- beam interacted with nuclear targets. We present upper limits at 90%
confidence level for the ratio of cross section times branching fraction of
this decay to that for the decay D_s --> phi,pi. The upper limits are 0.031 and
0.063 for M(P^0_{{c bar}s}) = 2.75 and 2.86 GeV/c^2, respectively, assuming a
P^0_{{c bar}s} lifetime of 0.4 ps.Comment: 9 pages postscript file, 11 pages Latex file, one Figure. Submitted
to Physical Review Letter