5,078 research outputs found
Hybrid meson production by electromagnetic and weak interactions in a flux-tube simulation of lattice QCD
We calculate rates for hybrid meson production by electromagnetic and weak
interactions in the flux-tube model. Applications include photo and
electroproduction at Jefferson Laboratory and HERA, and the production of light
strange and charmed hybrids in the weak decays of heavy flavours.
Photoproduction of some light hybrids is predicted to be prominent in charge
exchange reactions, and accessible in . Production of light or charmed hybrids in and decays may be
feasible with high statistics. Photoproduction of the axial hybrid meson is
predicted to be large courtesy of exchange, and its strange counterpart
is predicted in with . Production
rates for exotic hybrid candidates are given special
attention. Selection rules that can help to distinguish between hybrid and
conventional states with the same are noted.Comment: uses psfrag; One reference correcte
Electroweak production of hybrid mesons in a Flux-Tube simulation of Lattice QCD
We make the first calculation of the electroweak couplings of hybrid mesons
to conventional mesons appropriate to photoproduction and to the decays of
or mesons. amplitudes are found to be large and may contribute in
charge exchange allowing production of (amongst others)
the charged exotic hybrid off exchange. Axial hybrid meson
photoproduction is predicted to be large courtesy of exchange, and its
strange hybrid counterpart is predicted in with . Higher multipoles, and some implications for hybrid charmonium
are briefly discussed.Comment: 4 page
Pentaquark Symmetries, Selection Rules and another potentially Narrow State
We identify essential differences between the pentaquark and chiral soliton
models of \10bar and {\bf 8} pentaquarks and conventional {\bf 8}
states, which are experimentally measurable. We show how the decays of
states in particular can test models of the pentaquarks, recommend study of the
relative branching ratios of e.g. , and
predict that the decay amplitude is zero at leading order
in pentaquark models for any mixture of \10bar and the associated {\bf 8}.
We also include a pedagogic discussion of wavefunctions in the pentaquark
picture and show that pentaquark models have this {\bf 8} with ,
in leading order forbidding . The role of Fermi-Dirac
symmetry in the wavefunction and its implications for the width of
pentaquarks are briefly discussed. The relative couplings for . A further potentially
narrow state in {\bf 8} with is predicted around
1650 MeV.Comment: Revised version, corrects PDF margin problems, minor changes to tex
Hadron Spectroscopy (theory): Diquarks, Tetraquarks, Pentaquarks and no quarks
States beyond those expected in the simple constituent quark model are now
emerging. I focus on the scalar glueball and its mixing with states in the
nonet, and also on correlations in Strong QCD that may form diquarks
and seed states. Some models of the pentaquark candidate
are critically discussed.Comment: Plenary talk at ICHEP0
Production of , , and in hadronic decays
A coherent study of the production of (, 2, 3 corresponding to
, , and ) in is
reported based on a previously proposed glueball and nonet mixing
scheme, and a factorization for the decay of , where
denotes the isoscalar vector mesons and , and denotes
pseudoscalar mesons. The results show that the decays are very
sensitive to the structure of those scalar mesons, and suggest a glueball in
the GeV region, in line with Lattice QCD. The presence of significant
glueball mixings in the scalar wavefunctions produces peculiar patterns in the
branching ratios for , which are in good agreement
with the recently published experimental data from the BES collaboration.Comment: Version accepted by PRD; Numerical results in Tab IV and VI changed
due to correction of an error in quoting an experimental datum; Conclusion is
not change
Charmonium in lattice QCD and the non-relativistic quark-model
We compare the results of a numerical lattice QCD calculation of the
charmonium spectrum with the structure of a general non-relativistic potential
model. To achieve this we form the non-relativistic reduction of
derivative-based fermion bilinear interpolating fields used in lattice QCD
calculations and compute their overlap with c-cbar meson states at rest
constructed in the non-relativistic quark model, providing a bound-state model
interpretation for the lattice data. Essential gluonic components in the
bound-states, usually called hybrids, are identified by considering
interpolating fields that involve the gluonic field-strength tensor and which
have zero overlap onto simple c-cbar model states
Implications of a DK Molecule at 2.32 GeV
We discuss the implications of a possible quasinuclear DK bound state at 2.32
GeV. Evidence for such a state was recently reported in D_s^+pi^o by the BaBar
Collaboration. We first note that a conventional quark model c-sbar assignment
is implausible, and then consider other options involving multiquark systems.
An I=0 c sbar n nbar baryonium assignment is one possibility. We instead favor
a DK meson molecule assignment, which can account for the mass and quantum
numbers of this state. The higher-mass scalar c-sbar state expected at 2.48 GeV
is predicted to have a very large DK coupling, which would encourage formation
of an I=0 DK molecule. Isospin mixing is expected in hadron molecules, and a
dominantly I=0 DK state with some I=1 admixture could explain both the narrow
total width of the 2.32 GeV state as well as the observed decay to D_s^+ pi^o.
Additional measurements that can be used to test this and related scenarios are
discussed.Comment: 6 pages, 1 figur
Dynamics of hadron strong production and decay
We generalize results of lattice QCD to determine the spin-dependent
symmetries and factorization properties of meson production in OZI allowed
processes. This explains some conjectures previously made in the literature
about axial meson decays and gives predictions for exclusive decays of vector
charmonia, including ways of establishing the structure of Y(4260) and Y(4325)
from their S-wave decays. Factorization gives a selection rule which forbids
near threshold with the tensor meson in helicity 2. The
relations among amplitudes for double charmonia production \e^+e^-\to
\psi\chi_{0,1,2} are expected to differ from the analagous relations among
light flavour production such as \e^+e^-\to \omega f_{0,1,2}.Comment: 13 pages; journal versio
CLARK: fast and accurate classification of metagenomic and genomic sequences using discriminative k-mers.
BackgroundThe problem of supervised DNA sequence classification arises in several fields of computational molecular biology. Although this problem has been extensively studied, it is still computationally challenging due to size of the datasets that modern sequencing technologies can produce.ResultsWe introduce CLARK a novel approach to classify metagenomic reads at the species or genus level with high accuracy and high speed. Extensive experimental results on various metagenomic samples show that the classification accuracy of CLARK is better or comparable to the best state-of-the-art tools and it is significantly faster than any of its competitors. In its fastest single-threaded mode CLARK classifies, with high accuracy, about 32 million metagenomic short reads per minute. CLARK can also classify BAC clones or transcripts to chromosome arms and centromeric regions.ConclusionsCLARK is a versatile, fast and accurate sequence classification method, especially useful for metagenomics and genomics applications. It is freely available at http://clark.cs.ucr.edu/
- …